Record Low Lightning Deaths in 2011; What about 2012?

A horrific weather year. I'm sure that you are aware of how bad 2011 was overall in terms of severe weather, with more than a dozen billion-dollar weather disasters and a record 99 Presidential disaster declarations. With 552 tornado fatalities, the year tied with 1936 for second-most tornado deaths on record, trailing only 1925 which had 794. April alone brought 748 tornadoes, a record for any month of any year. May brought the tornado at Joplin, Missouri that killed at least 158 people (with additional indirect deaths), most for a single tornado in the United States since 1947.

The listing of severe events could go on and on! You can refresh your memory about 2011 in Stu Ostro's blog and images of 2011 and my blog on the 2011 tornadoes.

Record-low lightning fatalities. Despite all of the severe thunderstorm and tornado activity, there were only 26 confirmed lightning fatalities in 2011, a record low. While this is still too many, it's gratifying that the trend has been downward for decades. We've been helping spread the message "when thunder roars, go (stay) indoors" and hopefully that has been a contributing factor. (Read more about this slogan below.) The safest places to be are inside a building with plumbing and wiring or inside a metal-bodied and metal-roofed vehicle. Keep away from electrical appliances, corded telephones, and plumbing during a thunderstorm, as lightning can travel into and through the house in wires and pipes. Avoid contact with metal inside vehicles. Stay in these safe places for at least 30 minutes after the last thunder or lightning has ended to allow storm clouds to clear the area.

Practice lightning safety in 2012. Even one lightning death is too many, and about 10 times as many people are injured as are killed. Most of the casualties are people caught outside during a thunderstorm. Monitor the weather and avoid outside activities as much as possible when thunderstorms are predicted, particularly activities in remote areas where a shelter would not be within quick reach. Many of the fatalities are from the first strike of a thunderstorm. Thus, it's best to seek shelter when the skies start to darken on a day when thunderstorms are predicted. Certainly practice another safety rule "Use your brain, don't wait for the rain!" And don't let sports activities delay your response. Remember more lightning safety slogans: "Don't be lame, end the game! Don't be a fool, get out of the pool!"

Miss America Contestant a Lightning Safety Spokesperson. Lightning safety advocates will be rooting for Ellen Bryan, Miss Ohio (right above) to win the Miss America Pageant on 14 January. She has been a
spokesperson for lightning safety for several years. Her sister Christina (left above) was struck by lightning in 2000 and suffered permanent brain damage. Ellen has made lightning safety and "when thunder roars, go indoors" her Miss America platform issue. You can read Christina's story and watch their lightning safety video clips at the link above.

What about 2012? About this time each year, people wonder how bad the new year will be. In reality, the skill in predicting that is quite low. When it comes to anticipating tornadoes, many researchers have examined potential links to El Nino and La Nina. Results have varied depending upon geographical region and how the studies were conducted. Results are a bit more robust for tropical cyclones, with El Nino conditions tending to reduce the threat of tropical cyclones for the United States. The current La Nina conditions are predicted to persist at least into the spring, and if they persisted beyond that then there would not be a suppressing factor for at least the start of the tropical cyclone season.

El Nino is a phenomenon in which surface and near-surface waters in the eastern and central portions of the equatorial Pacific Ocean are warmer than average. By contrast, La Nina episodes have below-average water temperatures there. The warm or cold waters can impact the formation and location of thunderstorm clusters and rising motions in these areas that, in turn, can affect the strength and location of the jet stream in subtropical and middle latitudes. The jet stream influences weather systems that sometimes produce tornadoes.

There has been a tendency for large tornado outbreaks during La Nina episodes during the January through April months. The record numbers of tornadoes in each of those months occurred during La Nina conditions, including April 2011. Of the eleven largest and most impactful tornado outbreaks since 1950 in those months, six were during La Nina, 3 during El Nino, and 2 during neutral conditions. These statistics suggest, but don't guarantee, above-average tornado activity in January-April 2012. Historically this activity occurs mainly in the Gulf Coast (excluding the Florida Peninsula), Southeast, Mississippi Valley, and Tennessee Valley states.

El Nino conditions have tended to exist during large tornado outbreaks from May through December in the past, but we can't predict with certainty what the conditions will be during these months in 2012.

Tornado outbreaks are mainly driven by travelling weather systems (low pressure systems, fronts, and upper-air disturbances) operating on much shorter time scales than El Nino or La Nina. It's whether or not those factors become favorable that ultimately determine whether or not and how bad an outbreak will be. But factors like La Nina can impact the configuration of those travelling weather systems, and thus exert some influence, but aren't the dominant factor.

Another phenomenon that can potentially influence weather patterns is the North Atlantic Oscillation (NAO). An index of this oscillation is positive when there is a strong upper low over or near the Greenland area (as in the figures below). The index is negative when there is relatively high pressure over this region. The nature of the NAO tends to influence the location and intensity of the jet stream pattern over the Northeast, and the temperature pattern over the central and eastern United States.

Positive NAO conditions were present during the record-tornado April 2011. Of the 27 largest and most impactful tornado outbreaks since 1950, 14 were during positive NAO, 8 during negative NAO, and 5 during near-zero periods. Thus, positive NAO tends to favor tornado outbreaks, but it's far from a foolproof indicator. NAO is much more variable and on shorter time scales than El Nino/La Nina, so it can't be predicted far enough in advance to use it in forecasts of tornado activity in 2012.

Another large-scale potential influencing factor is the Arctic Oscillation (AO). This is positive when there is colder-than-average air over the North Pole region at the upper-level jet stream altitudes. Positive NAO tends to mean a stronger-than-average polar jet stream, which can influence possible tornado-producing weather systems. AO was positive during April 2011 and was positive in 16 of the 27 largest and most impactful tornado outbreaks since 1950. Again, though, it is rather variable and can't be predicted far enough in advance to use in forecasts of tornado activity in 2012.

The bottom line is that La Nina conditions may lead to an active January-to-April period for tornadoes in 2012, but that can't be predicted with total certainty. We can all hope that the death toll in 2012 will be way below that of 2011.

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The ridge, heat, humidity, drought, and Dust Bowl

Here come da ridge!

[ECMWF model forecast; image source: wright-weather.com]

For extremity of summertime ridges of high pressure aloft over the United States, meteorologists look at "500 millibar heights" -- in non-technical terms, that represents how high the pressure is a few miles above the Earth's surface -- and in particular how close those heights get to 600 decameters (19,685 feet). That's the benchmark, as it's about as high as those "heights" ever get.

And they're gonna get pretty close to that in a few days. [July 17 update: The 500 mb height reached 600 dm this evening over Omaha. Preliminary data suggests that's a record for that location and the farthest north 600 dm has been reached in the central states.]

Translation of all of that into what it means for people: The extreme heat of 2011, which has already been remarkable in parts of the country during the early part of the season including before summer officially even started, is about to expand as we enter into the next phase of the pattern.

[July 18 addendum: Wichita's # of 100+ degree days up through this point in the season and the average temp since June 1 have exceeded that of any year of the 1930s, and each is just shy of the highest, which occurred during the extreme heat wave of 1980.]

In the southern states, particularly the southern Plains, afternoon high temperatures have consistently been particularly extreme, assisted by how dry the soil is. Rather than some of the sun's energy going into evaporating soil moisture, it gets efficiently converted into quickly-rising temperatures each day.

And in turn, the soil dries out even more, worsening the drought.

Immediately adjacent, it's been the opposite, with exceptionally wet conditions including record flooding.

As the uber ridge expands and the heat surges north during the coming days, the atmosphere will have to work harder there than farther south for each degree of the afternoon high temperature, but any limitation in that department will be made up for in the heat index, a measure which is an attempt at quantifying the combination of heat and humidity.

Soil and crop moisture evaporating will boost the dewpoint, which translates to how humid the air feels. Dewpoints and heat indices are expected to rise to exceptionally high levels as far north as parts of the Dakotas and Minnesota this weekend into early next week.

What's more, overnight low temperatures will be quite high along with oppressive humidity.

Please be careful and take precautions! Heat (including the effects of humidity) nowadays is typically the #1 weather-related killer in the U.S. (other than vehicular accidents due to wet, snowy, or icy roads), with an estimated 1,500 each year dying on average.

This season is shaping up to be a memorable hot summer along with those such as the ones in 1930, 1934, 1936, 1954, 1980, and 1988.

We'll have to see when all is said and done, looking back from the vantage point of when we get to September and October, exactly how 2011 ends up stacking up.

There are various ways of comparing the heat, including the persistence, expanse and extremity of it.

In regard to the latter, many state high temperature records were set in the 1930s during the peak of the Dust Bowl, especially in 1936.

A significant contributor to that was the expanse of the drought.

You might be familiar with Drought Monitor maps that appear on The Weather Channel and weather.com. The Drought Monitor is a great initiative and set of products, however a significant limitation for historical perspective is that the maps and data that we have become so accustomed to and reliant upon exist only back to 2000.

The Palmer Drought Severity Index (PDSI), one of the inputs to the Drought Monitor product, is available back more than a century.

It focuses on long-term water levels rather than short-term moisture (though is at least partly also reflective of the latter).

The map plots below represent, as best as I can tell, a reasonable apples-to-apples comparison between the current drought and that during the peak of the Dust Bowl, in particular 1936, when 14 states set record high temperatures that still stand. (There were other factors that made the Dust Bowl what it was; here I'm referring specifically to meteorological and hydrological ones.)

These are maps for June since that's the latest month for which one is available for in 2011, and there haven't been any huge changes during the first couple weeks of July.

You can see the extraordinary dichotomy of extreme wet/dry that exists in such close juxtaposition to each other this spring & summer in the U.S., as well as the much greater expanse of drought in the mid-1930s. That helped boost temps in many states to values that have not been exceeded since.

Although the current drought is not as expansive, by this measure the driest categories are actually more prevalent than in June 1936. [July 17 addendum: A 9-month lack of precipitation in Midland shattered the previous record.]

The combination of expanse and severity stands out more in 1934. In both of those 1930s Junes, the focus was farther north than in 2011.

[PDSI images source: NOAA/ESRL Physical Sciences Division.]

What happened in the 1930s and other decades reinforces that there have always been extremes in weather, and there is always natural variability at play. What's changing now is the nature of those extremes, and also what's important is the context.

This time, the extreme drought, heat, and wildfires are occurring along with U.S. extremes this year in rainfall, snowfall, flooding, and tornadoes, and many other stunning temperature and precipitation extremes elsewhere in the world in recent years as well as, as I posted on my TWC Facebook "fan" page, record-shattering 500 millibar heights in high latitudes. And all of this is happening while there's an alarming drop in the amount of Arctic sea ice.

The nature and context of the extremes is the difference between the 1930s and now.

[Source: Polar Science Center; click on image for full-sized version.]

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Climate Dice- The Sixth Roll: Lottery Numbers For Summer 2012

The Power Ball (or overall National Climatic Data Center Ranking) number for summer 2012 came up as 116, the third warmest ranking on record for the lower 48 states for any summer. A ranking of 1 would have been the coldest possible ranking. The National Climatic Data Center has been ranking months, seasons and years from 1 to 118 since 1895 with 1 being the coldest possible temperature average ranking and 118 being the warmest possible temperature average. In the Climate Lottery game, I've defined each individual lottery number as rankings for each month for the lower 48 states, Power Ball numbers as those for each season, and Mega Ball numbers as those for each year. As we keep seeing over and over again the Climate Lottery game is rigged towards those higher number rankings. For everyone who participated in my fourth lottery contest, the numbers were: 105/118/103 for JUN/JUL/AUG 2012 with an overall Power Ball ranking for the season of 116. Just like summer and fall 2011, winter 2012, and spring 2012 not even one month was below average. Above average rankings have occurred for every month since (and including) June 2011. In fact, the lower 48 states have never had 15 straight months of above average temperatures since records have been kept in 1895... a phenomenon that I HIGHLY think is due to man induced global warming.

The winner was Buzz Bernard (again!) who came closest to picking the correct numbers. His picks were 118/115/100 with a "power ball" ranking of 114 for JUN/JUL/AUG 2012. Good going Buzz, we'll all have to look a little closer at the data to beat you next time. Buzz had previously won the contest for winter 2011/2012.

Well, let's play the lottery again. I wonder if we will ever see in the future a "gotcha" set of three months when temperatures are below average for an entire season across the lower 48 states. Just like last time pick three numbers between 1 and 118 (with one representing the coldest possible ranking and 118 being the highest possible ranking) for SEP/AUG/SEP 2012. Also pick a "Power Ball" or overall ranking number for fall 2012 between 1 and 118. Please give your picks in the reply section to this blog by October 1st. As usual, if you wait until just before October 1st to make your picks, you can get an educated guess as to what the ranking for September will be. I'll announce another winner shortly after the National Climatic Data Center processes fall averages and rankings on my next post around December the 10th, 2012. I won't be shocked, at all though again, if just like last summer, fall, winter, and this spring and summer not one single month of fall is below average.

For reference the following are links to my first five posts:

http://www.weather.com/blog/weather/8_26573.html?from=blog_permalink_mainindex">http://www.weather.com/outlook/weather-news/news/articles/climate-dice-fifth-roll-blog_2012-06-25

http://www.weather.com/blog/weather/8_26573.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_26573.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_26102.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_25602.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_23192.html?from=blog_permalink_month

Once again, the summer season, as a whole, was above long term averages with no individual month below average; and thus, having above average rankings. I'll reiterate once more (I know that this is getting repetitive) that due to climate change it is unlikely for a land area the size of the contiguous United States to have below average temperatures for an entire season. I'm not going to state that there will NEVER AGAIN be another below average season for the United States, but due to man induced global warming, the chances for an entire season of below average conditions is becoming much less likely. The whole point of these posts is to demonstrate how skewed temperatures have become towards warmth due to climate change...and they were very skewed towards warmth this summer. As stated in my fourth post, only an increase in volcanic activity from what is presently occurring at the moment can significantly slow the overall warming trend of the planet. What has happened so far this year is yet more proof of the climate dice being loaded for warmth in the United States.

The summer heat got deadly this season. Over one hundred people were killed due to heat related issues in the United States. If this summer is any indication of what is to happen in the future, we will all be dreading the advent of the summer solstice and yearning for fall to come quickly. Going back to my first blog, I've been looking closely at temperature averages since my career began at TWC in the 1980s and record temperature data since the late 1990s. In fact, a log of record data that I started on 1/1/2000 led to a peer review science paper indicating that the ratio of record highs to record lows will increase with time during the 21st century should the pace of global warming continue as predicted by climate science's current models. For an overview and summary please see: http://www.agu.org/pubs/crossref/2009/2009GL040736.shtml
The public doesn't mind if there is a record high of say 70 in New York City during the middle of January...in fact it may be welcome, but people do feel uncomfortable, and actually can die if a record high of over 100 occurs in that same city during the summer. Such was the case during the summer of 2012 when 9685 daily records were set, 358 of which were all-time records. For a horrifying preview of a world to come see the Rolling Stones post at: http://www.rollingstone.com/politics/news/global-warmings-terrifying-new-math-20120719

Here's a breakdown of the National Climatic Center's ranking numbers for each month of the summer:

In June the overall ranking for the lower 48 states was 105 (out of 118):

The historic early heat wave of late spring/early summer started in the Inter-Mountain West. Colorado had its warmest June in recorded history. You can pick out the individual rankings for each state from each map that I will present. The devastating fires in Colorado were a direct result of the early season heat accompanied by drought. The Southeast started out the month on a cool note, but Atlanta, where I live, had an all-time record high of 106 on the last day of June. The heat from the Plains spread east by the end of the month. 343 all-time records were set from late June into July across the U.S.

In July the overall ranking for the lower 48 states was 118 (out of 118).

Oh my! July was the hottest July in recorded history for the lower 48 states. Not only that, it was THE WARMEST MONTH in recorded history. The previous warmest month was July 1936 during the height of the Dust Bowl.
It was only a few months ago that March 2012 also ranked at 118...remarkable! Again, the ranking for each month is not an average of the rankings for each individual state, but a comparison of the averages of all prior years since 1895 for the entire lower 48 states.

In August the overall ranking for the lower 48 states was 103 (out of 118).

In August the jet stream dipped southward into the eastern U.S. allowing cooler than average air masses to penetrate deep into the South; but high pressure aloft continued to cook the West and much of the Plains. It was still warm enough from coast to coast for August to be the 16th warmest August (out of 118) on record.

The overall ranking for summer 2012 was 116 (out of 118)...The third hottest summer on record.

Again, I am getting all of my ranking numbers from the National Climatic Data Center.
The link for the National Climatic Data Center's Climate at a Glance Site where the rankings are archived is: http://www.ncdc.noaa.gov/oa/climate/research/cag3/cag3.html

I'm keeping the format on all of my charts the same as on the last three posts. The average ranking for 2012 is
59 since the coldest ranking would be 1 and the hottest would be 118. I have color coded all rankings for this post at or below 38 blue and all those at or above 79 red with rankings + or -- 19 from the median value of 59 black.

The following are the rankings so far for the 2010's:

Also, for reference, the following are "Power-Ball" and "Mega-Ball" ranking numbers for 2000 to the present.
Please see my prior posts for more charts dating back to 1900. Seasonal or Power-Ball rankings for winter are those for DEC/JAN/FEB, spring are those for MAR/APR/MAY, summer is JUN/JUL/AUG, and fall is SEP/OCT/NOV. Also, keep in mind that NCDC rankings for seasons compare seasons and are not merely an average of rankings of individual months of a season or year.

Notice that since the start of 2000 only five out of fifty-one seasons have been below average or "blue". Thirty-six out of the fifty-one seasons since 2000 have been "red" or above average. Indeed, as stated in the last post, the climate dice are very much loaded for above average temperatures for the lower 48 states looking at recent history.
I hope that everyone will have a pleasant fall. Even if fall ends up being well above average, at least it will be cooler than what has occurred during this torrid summer.

Click here to leave a comment and play the climate lottery.

Guy Walton
Lead Forecaster, the Weather Channel

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Climate Lottery- Ranking For October 2012

The lottery pick (or overall National Climatic Data Center Ranking) number for October 2012 came up as 44, the 44th coldest ranking on record for the lower 48 states for any October since 1895. A ranking of 1 would have been the coldest possible ranking. The National Climatic Data Center has been ranking months, seasons and years from 1 to 118 since 1895 with 1 being the coldest possible temperature average ranking and 118 being the warmest possible temperature average. In the Climate Lottery game, I've defined each individual lottery number as rankings for each month for the lower 48 states, Power Ball numbers as those for each season, and Mega Ball numbers as those for each year. As we keep seeing over and over again the Climate Lottery game is rigged towards those higher number rankings due to global warming, but October was a "gotcha" month since below average temperature rankings occurred for most of the lower 48 states. Some contrarians will point to the cool month as proof that global warming may not be occurring, yet I will contend that due to the warming an overall cool season across the U.S. will be a rare event. So far, for the contest of fall 2012 Dr. Jeff Masters and I tied for the best picks for October, which was 85...good going, Jeff! Our picks were too warm, overall, for the month, but they were the lowest of everyone who played.

October 2012 was a good example of how the atmosphere can line up to produce cooler than average conditions for a large geographical area, such as the continental U.S. despite an overall warming trend across the planet due to man induced climate change. One huge event did occur at the end of the month, which many climatologists attribute to climate change: Hurricane Sandy. For more on Sandy see Andrew Freedman's post from Climate Central at:
http://www.climatecentral.org/news/how-global-warming-made-hurricane-sandy-worse-15190

In October the overall ranking for the lower 48 states was 44 (out of 118):

The jet stream was oriented such that cool air masses penetrated through the nation's mid-section with warmer than average temperatures occurring in the West and Northeast. The overall raking for the U.S. came up as 44...slightly below the average of 59... and a "black" or neutral number as rankings go. Looking at the map you can pick out each individual state ranking. Again the overall ranking of 44 is not an average of the 48 individual state rankings; rather the ranking is a comparison of temperature averages for the lower 48 states for each October since 1895.

Again, I am getting all of my ranking numbers from the National Climatic Data Center.
The link for the National Climatic Data Center's Climate at a Glance Site where the rankings are archived is: http://www.ncdc.noaa.gov/oa/climate/research/cag3/cag3.html

I'm keeping the format on all of my charts the same as on my previous posts.
The average ranking for 2012 is 59 since the coldest ranking would be 1 and the hottest would be 118. I have color coded all rankings for this post at or below 38 blue and all those at or above 79 red with rankings + or -- 19 from the median value of 59 black.

For a reference to my last "Climate Dice" post see: http://www.weather.com/news/climate-dice-sixth-roll-20120912

November 2012 has started out on the warm side, despite winter storms occurring in the West and in the Northeast. As of this writing across the U.S. 725 daily record highs have been either set or tied while only 148 stations have set or tied daily record lows for the month of November. We'll see if this trend goes on for the rest of the fall, or if the overall warmth of this year continues.

Guy Walton...."That Climate Guy"
Lead Forecaster, the Weather Channel

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A tornado-producing machine

Tonight at 8pm EDT, TWC will be airing a special program on the recent historic tornado outbreak, called "Twisters: Trail of Destruction." Here are some additional reflections on the three-day onslaught, and we'd be interested in yours via comments to this entry. Our thoughts are with those who have experienced the wrath of the atmosphere.

The outbreak on Thursday, Friday and Saturday, April 14-16, 2011 from Tushka, Oklahoma to Askewville, North Carolina left many memorable images. Here are a couple: this photo of schoolchildren looking out the window at a tornado in Clinton, Mississippi (why were they not taking shelter?), and a man sitting in his car and calmly observing as a vicious tornado races in his direction (those are not leaves as he says, they're pieces of buildings!).

Source: http://yfrog.com/hsvctwhj

This outbreak didn't match the most intense one on record, the Superoutbreak of April 3-4, 1974. That produced numbers which no outbreak in recorded history before or since has come close to rivaling: of the 148 tornadoes within 24 hours, 30 were of at least F4 on the Fujita Scale (now known as the Enhanced Fujita Scale, with EF instead of F ratings), including six F5s.

What made the recent one so notable was the way it was so potent and tragic three days in a row, culminating in one of the deadliest tornado outbreaks in the history of North Carolina along with destruction that was extraordinarily widespread for that part of the country.

And what occurred meteorologically to result in that was the nature of a sharp dip in a strong jet stream, which took the shape of what meteorologists call a "negatively tilted trough," and how that plowed east like a machine, producing spinning, deadly tornadic supercells day after day.

This set of maps illustrates what I'm talking about. The way the dashed line representing the trough axis extends from northwest to southeast is the "negative tilt," as opposed to a positive tilt, which would be from northeast to southwest, or a neutral one, which is due north-south. All kinds of troughs can be associated with thunderstorm outbreaks, snowstorms, and other hazardous weather, but on average the negative tilts tend to have a little extra oomph, and this was an exceptionally strong and persistent one.

Those upper-level jet stream maps, by the way, have some similarities to the pattern present for big outbreaks last May in Oklahoma, April 1998 in the Deep South, and March 1984 in the Carolinas ... except this time it happened on three consecutive days.

With this kind of dip, the jet stream energy tends to really punch over the warm, humid, unstable air ahead of it, conducive to severe storms. Also, the air ahead of the trough spreads widely apart in upper levels of the atmosphere (a particularly vivid example of which is above, as I illustrated on the Friday map with the arrows that follow along with the wind flags), which helps lead to thunderstorm development as air rises to take the place of the air evacuated above.

[There's a whole separate technical topic of "diffluence" vs. "divergence," but that's beyond the scope of this blog! Readers who are interested in learning more about that can find a quick tutorial here.]

Then, with the right combination of other ingredients such as winds at different levels of the atmosphere blowing in different directions, tornadoes can form. Those ingredients were also strongly present on Thursday, Friday, and Saturday.

It's not uncommon to get this kind of trough. What's unusual is the way it kept its form, and kept slamming nearly due east day after day. As a friend of a friend on Facebook (you can sign up for my weather posts on my TWC Facebook fan page) noted, these troughs often either lift quickly to the northeast and become somewhat disconnected to the most explosive instability, or they become "cutoff lows," in which, as the name sounds, they cut off from the main jet stream and grind to a halt, and can still produce very inclement weather but generally not bad tornado outbreaks.

There's no rest for the weary, with, per the graphics below, another such trough coming, which is going to bring about another collision with warm, moist, unstable air tomorrow (Tuesday) and Tuesday night. The main threat area will be in the Mid-Mississippi Valley into the Ohio Valley.

Source of images: wright-weather.com

This time, though, the system will swing northeast rather than crashing over the Carolinas and Virginia. It'll be a two-day outbreak, not three, and tornado-producing ingredients on Wednesday are not expected to be present to the degree they were on Saturday when that system came east. There will be a lot of wind energy, though, so a threat for damaging storms will exist in places such as PA, NY, and New England, and at least some risk of energetic thunderstorms into the Deep South.

It's been a wild month, starting with what was, by the standards of straight-line wind damage events rather than tornadoes, a superoutbreak on April 4; then a destructive evening in Iowa on April 9 and the following day an outbreak in Wisconsin which was record-setting for that state; then the most recent siege last Thursday, Friday, and Saturday, and now the upcoming system ... And looking ahead, the pattern will stay active this weekend and into next week with the potential for additional severe thunderstorms as well as flooding rains in the nation's midsection.

Stay safe, everyone!

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Meteorological perfection

INFRARED SATELLITE IMAGE - OCTOBER 30, 1991

Hard to believe it's been 20 years since the Perfect Storm. And, just as it represented a meteorological event unique up until that point in the historical record, there has been nothing like it since.

[UPDATE FRI AM: Though amazingly, on the 20th anniversary, even though it'll be of a different nature it looks like there's going to be another wild and highly unusual (for October) storm in the northeast U.S.!]

[ADDENDUM FRI NOV 4: For in-depth scientific analyses of the weather situation in late October and early November 1991, see these papers by Jason Cordeira and Lance Bosart of SUNY Albany, one on the development of the storms and one on the large-scale pattern associated with their formation, which includes not only the two I highlight in my blog, but also one over the northeast Atlantic near Europe.]

This is a repost and update of previous blogs I've written about the 1991 Perfect Storm.

Tropical cyclones have official numbers and names, but not other kinds of weather systems. Sometimes, though, one will be exceptional enough to come to be known informally by name, such as the "Blizzard of 1888" or 1962's "Ash Wednesday Storm" in the Mid-Atlantic and "Big Blow" in the Pacific Northwest.

Until today when TWC severe weather expert Dr. Greg Forbes and I unofficially categorized what happened in late April 2011 as a tornado "superoutbreak," there had only been one outbreak known as that, in April 1974. There still is only one storm that has gained acceptance as a "superstorm," in March 1993. And there is still only one known as the "Perfect Storm." There have been other contendas, but none ended up rivaling the atmospheric process which unfolded this final week of October in 1991.

For a while it was known as the "Halloween Storm" (even though it was past its peak by October 31), until Bob Case of the National Weather Service coined it "The Perfect Storm," and then came the book & movie which chronicled the plight of the Andrea Gail and escalated this weather event's legacy into popular culture.

Mr. Case was not engaging in hyperbole. This was a truly extraordinary confluence of atmospheric ingredients. Although other East Coast cyclones (e.g. hurricanes and snowstorms) have been "worse" in terms of severity of wind and precipitation, and overall impact to people and/or property, this one was unique in its evolution, and per these NCDC and NWS reports it was no slouch in its atmospheric and oceanic statistics either. And of course there were the tragedies at sea for which the storm is [in]famous.

For all of these reasons, the event is more well-known than many of those in recent decades which have made the official billion dollar disaster list (this one's cost was in the hundreds of millions of dollars).

This is a great sequence of satellite images showing the life cycle of the storm; this is an animation of the evolution at the surface and aloft.

And here are a meteorological analysis; a video clip of me on The Weather Channel during the Perfect Storm, showing a rare satellite loop of it; and a look at another lesser known but also whopper storm walloping North America at the same time.

IT ALL BEGAN ...

... on the 28th and 29th of October 1991 with a cold front and burgeoning non-tropical storm over the northwest Atlantic eating Hurricane Grace for breakfast. We'll never know exactly what the outcome would have been without Grace; the situation was already potent, but the hurricane did play a key role by providing extra moisture & energy and influencing the overall configuration of weather systems.

Meanwhile, there was also a strong high pressure system over eastern Canada to the northwest of the developing storm which helped develop a steep "pressure gradient" and long fetch of wind. This already caused waves to build, and it was during this phase that the Andrea Gail met its fate. (The exact time of the vessel's and its crew's loss is unknown but the final reported contact was on the 28th).

Ultimately the developing storm became quite a formidable one in strength and a behemoth in size, and it backed toward the U.S. coast rather than move away as most storms which are already at sea do.

The most significant impacts on land were felt in the northeast U.S. where damage was widespread, including, as you might recall, to then-President George H. W. Bush's house in Kennebunkport, Maine, but effects in the form of high waves were felt all the way from Newfoundland to Florida and Puerto Rico.

Although the storm was officially "extratropical" at its peak and it certainly did have non-tropical aspects, near its center the cyclone also had some characteristics of a tropical or at least subtropical cyclone.

It's not easy to find radar imagery of the Perfect Storm, but I have this screen shot from TWC's coverage, as the cyclone moved westward near southeast New England. Sure looks like an eyewall on the north side of the center, doesn't it? (The south "eyewall" may have been too far away from the radar to show up, or the rain might have not completely surrounded the center.)

After whacking the coast on October 30 -- its estimated lowest pressure of 972 millibars was that day and its closest approach to land was that night -- the storm rapidly wound down on Halloween itself.

However, in a bizarre (yet fitting) final chapter ...

Within the weakening larger overall circulation, a small circulation (see below) that was decidedly "warm-core," indicative of a tropical cyclone, spun up on November 1 and became an unnamed hurricane!

Thus, the "unnamed hurricane" wasn't The Perfect Storm per se, but it was a component of the evolution of the system, one which ironically did not produce the significant damage.

[Click on image for close-up of the unnamed hurricane.]

VISIBLE SATELLITE IMAGE - NOVEMBER 1, 1991

The hurricane was not named because it was feared that would confuse people. Given how bad the original storm was, there was the potential for undue alarm if residents along the coast heard a hurricane with a traditional "name" had now developed. But ironically the hurricane was so tiny that it was relatively harmless, especially given that it was heading away from the U.S. coast, not toward it like the parent storm a couple days prior. Landfall was eventually made, but as a rapidly waning tropical storm in Nova Scotia on November 2 with little impact.

A non-tropical system absorbing a tropical one is not unprecedented, nor is a tropical cyclone developing from a non-tropical system. But for both processes to occur with the same system, not to mention one of this magnitude, is what made the cyclone so amazing. In fact, Grace even started as a subtropical storm. This weather system was an ultimate hybrid!

MEMORIES ...

I have vivid memories of that whole situation as it unfolded. I had been at The Weather Channel for only a couple of years, and was in the midst of a few days off. Upon briefly stopping by the office to attend a meeting, my colleague Tony Fulkerson, who was working the shift on the other side of the week, popped his head in the room and said, "Stu, have you looked at the weather situation?"

Upon doing so shortly thereafter, I thought, "Oh, my!"

Next thing I knew, I found myself on the air the following evening, with Jeff Morrow, whom I've known for -- gasp! we're not as young as we once were! -- 35 years now since our first math class together in our freshman year in college.

This was the second weather event during which I made cameo on-camera appearances. The first was Hurricane Bob a couple months prior. The next ones after The Perfect Storm included Hurricane Andrew and the severe nor'easter in December 1992, then the Superstorm in March 1993 [video clip of that is here]. Ahh, those were the days ...

And, as much as it makes me wince to go back and look (for example, my not-ready-for-primetime eyeglasses!), here is a video of one of my Perfect Storm segments.

I can't definitively lay claim to that being the first time water vapor imagery was ever shown on television because I don't know for sure what else might have taken place before that, but at least to the best of my knowledge it was the first time on TWC and elsewhere. In any event, I couldn't resist displaying and talking about that water vapor loop, as it seemed if ever there was a time to spring it on the masses, this was it -- what a sight! And now that clip is the only easily accessible satellite loop that I know of which shows the development of the storm including the ingestion of Grace.

THE OTHER STORM

Not having received the worldwide notoriety that its cousin to the east did but remembered vividly by those who were in Minnesota and thereabouts at the time was another extreme storm concurrent with the latter part of the Perfect Storm.

Portions of the Upper Midwest were being affected by another powerful cyclone and an unusually cold arctic outbreak for so early in the season, the combination of which resulted in a record early-season snowstorm. It was dubbed by some the "Great Halloween Megastorm" and set the record for the largest single-storm snowfall (28.4") in Minneapolis history for any month of the year! Likewise, the 37.9" snowfall in Duluth was the largest on record at that time for the state of Minnesota, beating any storm in the middle of winter. (It was exceeded in January 1994.) On the southern fringe of the wintry precipitation was a severe ice storm in Iowa.

And the two atmospheric explosions were connected, as can be seen by the pattern aloft (first map below), in an exceptionally "high-amplitude" pattern: a big-time trough over all of western North America with a strong disturbance about to swing from the southwest U.S. toward the Great Lakes, which led to the intense cyclone centered near Lake Superior a few days later (second map below, and note the relatively benign unnamed tropical storm in Nova Scotia); a mammoth cutoff low in the western Atlantic, associated with the Perfect Storm which was blocked from a rapid exit out to sea; and a ridge in between waaay up across eastern Canada.

If you remember either one of these storms, submit a comment!

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Tornado Outbreaks Then and Now - Apples and Oranges?

Early in my graduate school experience I had the privilege of surveying the damage from many of the April 3-4, 1974 Superoutbreak tornadoes as part of Dr. Fujita's team. 148 tornadoes struck in 48 hours. Six of the tornadoes in that outbreak were rated F5 (on the original Fujita Scale) and 30 were rated F4 or stronger. There were more than 300 fatalities, over 5000 injuries, and the sum of tornado path lengths exceeded 2500 miles. The Superoutbreak has been the benchmark for all tornado outbreaks since.

I always thought that there was a chance that some future tornado outbreak might be worse. The most recent one could be, at least in some respects. Damage surveys are still in progress that will bring us the true count of the number of tornadoes, their EF-Scale ratings, path lengths and widths, and other measures of the outbreak's fury. The National Weather Service, using preliminary data, has already indicated that its tornado count might exceed the number of tornadoes in the Superoutbreak.

Once Doppler radars were deployed across the United States in the early 1990s, though, I never thought I'd see a tornado outbreak kill hundreds of people again. How sad that it has happened on Wednesday. More than 200 people were killed in Alabama alone and more than 300 in total, according to news reports! The Doppler radars allow us to see tornadoes and their parent thunderstorms' rotating updrafts like never before, and the National Weather Service issues tornado warnings with an average of 13 minutes of lead time (in advance of the tornado), and often much more than that. Combine that with so many more - and more efficient - ways of getting the warnings in this internet era and it's a "different world" relative to the 80-character-per-second teletypes that gave warnings to the media (and not directly to the public) back in 1974. People can get timely and effective warnings on NOAA Weather Radio, on The Weather Channel, from services like TWC's "Nofify!" that can personally send you a message that a tornado is coming, and in many other ways.

It's apples versus oranges in the relative ability for people to know a tornado was coming in the two eras. Yet so many died in 2011. That must be a function of the violence of the tornadoes, combined with the fact that so many took aim on communities rather than rural areas. And when tornadoes are violent, even being warned and taking proper safety measures is no guarantee of survival. Finding proper shelter improves your odds, but only being in an underground shelter or specially designed in-home shelter can ensure your survival.

But it's also a "different world" in the way that tornadoes get rated. The mainstay of the original Fujita Scale used to rate tornadoes was that a home crushed into small pieces and blown away would earn an F5 rating, with wind speeds estimated at 261-318 mph. Engineers surveying the tornado damage back in 1974 began to tell meteorologists that it didn't take 300 mph winds to turn homes into piles of rubble and cast the pieces to the wind. Even well constructed concrete block and brick school buildings could fail in 220 mph winds, they said. And homes with damage apparently fitting an F5 description often happened because the house was not properly secured to its foundation in winds less than 150 mph.

In the years since, these engineering analyses began to work their way into damage assessments, and in 2007 an Enhanced Fujita Scale (EF Scale) system was officially implemented. An EF5 tornado has winds estimated as low as 201 mph. And it's difficult to rate a tornado as EF5 based upon it just demolishing a house.

Statistically, the number of tornadoes being rated 2-5 have been decreasing since the 1970s, despite the total number of tornadoes being recorded showing a dramatic increase. This is at least partly a consequence of the introduction of engineering concepts into the rating process. I was part of the team that developed the EF Scale, and it's a system that more accurately estimates tornado wind speeds. But it troubled me then (and still does) that it might be hard to compare past tornado outbreaks with future ones and determine which was worst. It's apples and oranges, to some extent, in the rating systems then and now.

April outbreak versus Superoutbreak?It will be interesting to see just how many tornadoes were in this April's outbreak, and how many get rated EF5. But the death toll, the number of tornadoes in a 24-hour period, and the total path length of the tornadoes may be more appropriate measures by which to compare it to the Superoutbreak than the number rated EF5. Amazingly, the April 2011 death toll already appears to be worse!

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Climate Dice- The Seventh Roll: Lottery Numbers For Fall 2012

Blog: Climate Dice- The Seventh Roll: Lottery Numbers For Fall 2012

The winning Climate Lottery numbers for fall (SEP/OCT/NOV) 2012 were 101/44/99, and the Power Ball number was 98

The Power Ball (or overall National Climatic Data Center Ranking) number for fall 2012 came up as 98, which was the 21st warmest for any fall on record for the lower 48 states. A ranking of 1 would have been the coldest possible ranking. The National Climatic Data Center has been ranking months, seasons and years from 1 to 118 since 1895 with 1 being the coldest possible temperature average ranking and 118 being the warmest possible temperature average. In the Climate Lottery game, I've defined each individual lottery number as rankings for each month for the lower 48 states, Power Ball numbers as those for each season, and Mega Ball numbers as those for each year. As we keep seeing over and over again the Climate Lottery game is rigged towards those higher number rankings. Above average rankings have occurred for every month since (and including) June 2011 up until October 2012 when near normal conditions occurred.

There was no clear winner for fall 2012. If I can get a consensus who the winner was, I will post an update.

Well, let's play the lottery again. I wonder if we will ever see in the future a "gotcha" set of three months when temperatures are below average for an entire season across the lower 48 states. Pick three numbers between 1 and 118 (with one representing the coldest possible ranking and 118 being the highest possible ranking) for DEC 2012. The highest possible ranking will be 119 for JAN and FEB 2013. Also pick a "Power Ball" or overall ranking number for winter 2012 between 1 and 118. Please give your picks in the reply section to this blog by January 5th, 2013...I'm giving folks a bit more time this go round due to the holidays. As usual, if you wait until just before January 5th to make your picks, you can get an educated guess as to what the ranking for December will be (and also a heads-up guess for January). I'll announce another winner shortly after the National Climatic Data Center processes fall averages and rankings on my next post around March 10th, 2012. Just for kicks and grins, pick the "Mega-ball" number for 2012...if you've been following along, this should be easy.

Here's a hint for December 2012: up to this writing 1,220 daily record highs have either been tied or set while only 6 daily record lows have either been tied or set.
See: http://www.ncdc.noaa.gov/extremes/records/daily/maxt/2012/12/00?sts[]=US#records_look_up for the latest update.

For reference the following are links to my first six posts:

http:// http://www.weather.com/blog/weather/8_28110.html?from=blog_permalink_mainindex

http://www.weather.com/outlook/weather-news/news/articles/climate-dice-fifth-roll-blog_2012-06-25

http://www.weather.com/blog/weather/8_26573.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_26102.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_25602.html?from=blog_permalink_mainindex

http://www.weather.com/blog/weather/8_23192.html?from=blog_permalink_month

Once again, the fall season, as a whole, was above long term averages, but we finally saw one month below average for the first time since June 2011...October 2012. I'll reiterate once more (I know that this is getting repetitive) that due to climate change it is unlikely for a land area the size of the contiguous United States to have below average temperatures for an entire season. I'm not going to state that there will NEVER AGAIN be another below average season for the United States, but due to man induced global warming, the chances for an entire season of below average conditions is becoming much less likely. The whole point of these posts is to demonstrate how skewed temperatures have become towards warmth due to climate change...and they were much skewed towards warmth again this fall. As stated in my fourth post, only an increase in volcanic activity from what is presently occurring at the moment can significantly slow the overall warming trend of the planet. What has happened so far this year is yet more proof of the climate dice being loaded for warmth in the United States.

Here's a breakdown of the National Climatic Center's ranking numbers for each month of the fall:

In September the overall ranking for the lower 48 states was 101 (out of 118):

The jet stream was oriented such that very warm weather persisted in the West with cooler than average temperatures occurring in the Midwest. Nevertheless the overall raking for the U.S. came up as 101...well above the average of 59 and very much in the red as far as rankings go. Looking at the map you can pick out each individual state ranking. Again the overall ranking of 101 is not an average of the 48 individual state rankings; rather the ranking is a comparison of temperature averages for the lower 48 states for September since 1895.

In the last couple of months NCDC revised September's ranking from 96 to 101, so Eric Fisher with his guess of 100 was the winner for that month...good going Eric! From January to September 2012 there were 10 consecutive months having rankings above 100...a phenomena that had never occurred, so far, since 1895.

In October the overall ranking for the lower 48 states was 44 (out of 118):

October 2012 was a good example of how the atmosphere can line up to produce cooler than average conditions for a large geographical area, such as the continental U.S., despite an overall warming trend across the planet due to man induced climate change. One huge event did occur at the end of the month, which many climatologists attribute to climate change: Hurricane Sandy. Meteorologist Stu Ostro of The Weather Channel has written an in depth article relating Sandy to global warming. Please see:
http://www.wunderground.com/blog/stuostro/show.html?entrynum=18

For the contest of fall 2012 Dr. Jeff Masters and I tied for the best picks for October, which was 85...good going, Jeff! Our picks were too warm, overall, for the month but they were the lowest of everyone who played.

In November the overall ranking for the lower 48 states was 99 (out of 118):

The jet stream was oriented such that there was a ridge keeping conditions very warm in the West while during the early part of November cold conditions were prevalent in the East.

Our old friend Buzz Bernard was dead on target with a prediction of 99 as his pick for November...way to go Buzz for the best pick for November!

The overall ranking for fall 2012 was 98 (out of 118)...The 21st warmest fall on record.

Nevada had its warmest fall on record. Despite cold conditions in the East, the overall ranking reflecting average temperatures was well above average for the lower 48 states.

Buzz Bernard did it again...his guess of 100 for the "Power-Ball" was closest to the ranking of 98.

I am getting all of my ranking numbers from the National Climatic Data Center.
The link for the National Climatic Data Center's Climate at a Glance Site where the rankings are archived is: http://www.ncdc.noaa.gov/oa/climate/research/cag3/cag3.html

I'm keeping the format on all of my charts the same as on the last three posts. The average ranking for 2012 is
59 since the coldest ranking would be 1 and the hottest would be 118. I have color coded all rankings for this post at or below 38 blue and all those at or above 79 red with rankings + or -- 19 from the median value of 59 black.

The following are the rankings so far for the 2010's:

Also, for reference, the following are "Power-Ball" and "Mega-Ball" ranking numbers for 2000 to the present.
Please see my prior posts for more charts dating back to 1900. Seasonal or Power-Ball rankings for winter are those for DEC/JAN/FEB, spring are those for MAR/APR/MAY, summer is JUN/JUL/AUG, and fall is SEP/OCT/NOV. Also, keep in mind that NCDC rankings for seasons compare seasons and are not merely an average of rankings of individual months of a season or year.

Notice that since the start of 2000 only five out of fifty-two seasons have been below average or "blue". Thirty-seven out of the fifty-two seasons since 2000 have been "red" or above average. Indeed, as stated in the last post, the climate dice are very much loaded for above average temperatures for the lower 48 states looking at recent history.

I hope that everyone will have a great winter. We'll see if this winter turns out to be colder and snowier than that of 2011/2012, which was very mild, despite December 2012 starting out so warm.

Click here to leave a comment and play the climate lottery.

Guy Walton
Lead Forecaster, the Weather Channel
"That Climate Guy"

View the original article here

This Year's Tornadoes Some of the Worst

This is the second in a series of articles that seek to quantify just how bad this year's tornadoes were in a historical context. It wasn't just media hype!

In a previous article I wrote that the late April tornado outbreak was so severe that it merited the special name "Superoutbreak 2011." That's just the second time that a tornado outbreak has earned that title, the first being on April 3-4, 1974.

This article focuses on three of the individual tornadoes from the spring of 2011 that rank among the worst on record in the United States. Two of them came on April 27 during that Superoutbreak 2011: an EF4 tornado that hit Tuscaloosa and Birmingham AL along an 80-mile path, and an EF5 tornado that hit Phil Campbell and Hackleburg AL along a path that was over 106 miles long and continued into Tennessee. The third was an EF5 tornado that hit Joplin Missouri on May 22.

These were the three deadliest tornadoes in the United States since 1957, when radars began to be widely used for storm detection in the United States. At that time the National Weather Service was called the Weather Bureau, and the radars did not have any Doppler wind information. The Joplin tornado caused at least 159 deaths. The Hackleburg tornado killed at least 72, and the Tuscaloosa tornado killed at least 64. The Joplin tornado was the deadliest since a tornado hit Woodward, Oklahoma in 1947.The table below lists the 20 deadliest tornadoes on record in the United States. Joplin stands as the only tornado on the list since 1953, the year that the Weather Bureau began to issue tornado forecasts. The worst was the Tri-State (MO, IL, IN) tornado on March 18, 1925 that killed 695 along a 219-mile path, the longest on record.

In raw dollars (i.e., costs at the time that they occurred), these were also the three costliest tornadoes on record in the United States. Estimated costs from the Joplin tornado are $2.8 B (billion), $2.2 B from the Tuscaloosa tornado and $1.25B from the Hackleburg tornado. The previous record holder in raw dollars (not adjusted for inflation), was the F5 tornado that hit Moore, Oklahoma and Oklahoma City on May 3, 1999, with loss of $1 B.

Of course, because of inflation it isn't fair to compare raw costs from a tornado today to one that occurred decades ago. For that reason, I've attempted to "normalize" the costs into 2011 dollars. To do that I've used economic statistical measures called "Fixed Reproducible Tangible Wealth" or "wealth" from 1929 to 1995, and "Gross Domestic Product" for years when "wealth" data weren't available. This is just one way to do it, but follows in the tracks of a
http://www.nssl.noaa.gov/users/brooks/public_html/papers/damage.pdf previous study by colleagues Harold Brooks and Chuck Doswell. Results are in the table below.

Even with the adjustment for inflation of older tornadoes, Joplin still ranks as the costliest tornado. With the dramatic effects of the adjustment for inflation, the St. Louis tornado of 1896 zooms from a raw cost of $12 million to $2.558 billion to take second place. The Tuscaloosa and Hackleburg tornadoes from Superoutbreak 2011 take third and thirteenth places, respectively. From the 1974 Superoutbreak, only the F5 Xenia, Ohio tornado cracks the top 25.

Combining deaths and damage to come up with a ranking of worst tornadoes is definitely a very subjective and arbitrary process. What I've done is to give the deadliest tornado (Tri-State tornado of 1925) 50 points and then scale other tornadoes on their percentage of that tornado's death toll. Similarly, I've given 50 points to the Joplin tornado for its 2.8 billion dollars in damage, and then scaled other tornadoes based on their adjusted damage cost values. There would be a maximum score of 100 if a single tornado had highest values in each category, which wasn't the case. Values and rankings are shown in the table below.

Using that ranking scheme, the Joplin tornado of 2011 winds up third-worst tornado on record in the United States. It follows the Tri-State tornado of 1925 and the St. Louis tornado of 1896. The Tuscaloosa tornado comes in fourth and the Hackleburg tornado comes in eighth.

An interesting result is that, despite earning the first classification as a "Superoutbreak", none of its tornadoes on April 3-4, 1974 ranked in the top 25 individual worst ones. By contrast, the 2011 Superoutbreak had two of the top 25 worst tornadoes. The 1974 Superoutbreak had more killer tornadoes, but the most deaths from an individual tornado were 34 from the Xenia, OH tornado. That death toll was so far down on the list (and not on the top table) that it kept it (and other tornadoes from 1974) off the "worst tornado" list.

In summary, 2011 brought one of the two worst tornado outbreaks on record in the United States and three of the worst individual tornadoes. It also brought six tornadoes (thus far) given the top rating of EF5. The only other year which had that many was 1974. 2011 truly was a remarkable year!

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The Katrina of tornado outbreaks

Our thoughts at TWC are with those who have been affected by the recent siege of severe weather including twisters, wind/hail damage, and flooding.

Here are some thoughts about last week's catastrophic tornado outbreak ...

Terrible perfection

I posted that graphic last Wednesday afternoon on my TWC Facebook page. The ingredients were "textbook." I mean, literally what I learned from a textbook more than 30 years ago. The atmosphere was explosively unstable with summerlike heat and humidity, interacting with a classic wind shear setup as a strong jet stream and upper-level trough crashed overhead. Also, dry air aloft (dark red shades on the left image below) put a lid on things and allowed the energy to build up until it blew sky high.

[Image source: NCAR/UCAR]

Not only were the elements perfect for a tornado outbreak, they were present to an extreme degree. The observed EHI ("Energy Helicity Index"), a measure which represents a combination of instability and wind shear, was extraordinary, higher than during the time of two notorious [E]F5s, the Moore, Oklahoma and Greensburg, Kansas tornadoes on May 3, 1999 and May 4, 2007, respectively.

Such a set of combustible ingredients, plus a remarkable number of supercells with hook echoes on radar and "ground-truth" observations of tornadoes, led Dr. Forbes and me to decide to up TWC's "TOR:CON" index to a 10 for northern Alabama, meaning a 100% chance of a tornado within 50 miles, the first time that's been done since the product was developed a couple of years ago.

Capricious

Many counties have been affected by the calamity, with the effects extending beyond just those people and locations struck directly by the tornadoes. Yet even with this widespread an outbreak, an extremely small percentage of the land area of northern and central AL was actually hit.

Above are screen captures from a video taken from a helicopter during Dr. Forbes' aerial survey of the damage. Tornadoes never cease to amaze me in their capriciousness, even in a situation such as this with relatively widespread devastation, leaving one part of a neighborhood unscathed while an adjacent one is in ruins.

Tornado Alley?

Last week's outbreak, and the past month of tornadoes, reinforce that "Tornado Alley" is *not* just in the Great Plains.

The first map below is one that in the past TWC has shown, and NOAA has graphics online depicting a similar area.

The second map plots all tornadoes in the official database which are [E]F 3 and higher on the [Enhanced] Fujita scale, those which account for approximately 3/4 of all tornado fatalities. IMO, true Tornado Alley is represented by the much broader area in which all those red lines are concentrated.

What about climate change / global warming?

What's needed relative to this question is an apolitical, non-reactionary, objective assessment. However, as soon as the extremity of last week's outbreak became apparent, there were, as is usually the case, reactions on two extremes. One headline on the web blared that hundreds were killed in "states represented by climate pollution deniers," while a high-ranking federal government official was reported to have dismissed climate change as a factor, quoted as saying, "Actually what we're seeing is springtime."

The former is obscene and the latter fails to represent what's happened weatherwise recently, which actually, no, has not been a typical month in spring.

On the one hand there is no decisive trend in overall tornado occurrences, and while in recent years there's been a rash of outbreaks which have been unusually far north and intense for the time of year (including the one in Wisconsin last month), the one last Wednesday was geographically consistent with April climatology.

On the other hand, this event needs to be considered in the *context* of the relentless series of severe thunderstorm and tornado outbreaks which started on April 4 and culminated on the 27th. The number of severe weather reports and confirmed tornadoes has been atypical even by April standards, shattering the previous records. Even taking into account limitations of the historical record, the numbers have been stunning.

As noted above, the combination of instability and wind shear was extreme even by classic tornado setup standards. The temperature in Laredo reached 111 degrees the day prior to the peak outbreak, the hottest on record at that location for so early in the season. Precipitation extremes have been extreme even by extreme precipitation standards, with April rainfall upwards of 20" in Arkansas and record levels on some rivers in the central U.S., juxtaposed with an exceptionally large amount of Texas being classified in extreme or exceptional drought. [Tue May 3 addendum: And the warmest April on record in the UK.]

And all of this is in the context of a relentless series of extreme weather events in the U.S. and other countries during the months preceding April, and many others worldwide during recent years which I've documented and which have had apparent a physical connection with a warmer atmosphere.

I've also read categorical statements assigning a one-to-one cause-effect attribution to La Nina. But while La Nina is present now as it was during the 1974 Superoutbreak, it was not during some of the other most notorious outbreaks of all time, such as the 2002 Van Wert / Mossy Grove, 1999 Oklahoma, 1991 Andover KS, 1984 Carolinas, and 1965 Palm Sunday outbreaks.

The atmosphere is extraordinarily complex, and ultimately what's happened the past month is probably a combination of influences, including La Nina, other natural variability, and anthropogenic global warming.

Bigger than the Superoutbreak?

Hanging on the wall of my office at TWC (low-res cellphone pic above) is an original map of the April 3-4, 1974 Superoutbreak, which I've had since the '70s (a high-res online map can be seen via this link). As Dr. Forbes said a few days ago in his blog about it, that event is the benchmark for tornado outbreaks.

As soon as the number of tornado reports from last Wednesday exceeded 148, the number of tornadoes within 24 hours in the 1974 Superoutbreak, there was talk about this outbreak being bigger than that one. I sent an email to the staff at TWC on this topic and provided commentary about it on camera, as I wanted to make sure that there was awareness of how extreme The Superoutbreak was and that the proper perspective is being applied in comparing the two.

That one had *thirty* F4 or higher tornadoes on the original Fujita scale. Communities were reeling from that level of damage in Alabama, Georgia, Tennessee, North Carolina, Kentucky, Indiana, and Ohio. Among those 30, six F5s occurred across five of those states. Tornadoes struck along a total path length of more than *2500* miles.

We'll need to await the final numbers before doing a final comparison, but with the latest information as of this writing, and even accounting for subjectivity and changes in tornado assessments over the years and decades as the Fujita Scale evolved into the Enhanced Fujita Scale, it looks like the April 27, 2011 outbreak will fall far short of some of those '74 numbers.

It's not just all about the total number of tornadoes, plus, despite definitive official statements about a total of 211 having occurred (and a report today that it's been raised to 312!), any such estimates are premature, as those are just preliminary *reports*, some of which were duplicates of the same long-track tornadoes.

That all having been said, no matter how this all shakes out in the end, the April 27, 2011 outbreak will go down as one of the biggest and worst on record. The amount of energy it unleashed is hard to comprehend.

By why do any of these such statistics even matter? Well, scientific assessments of ingredients and results help meteorologists understand the phenomena and factors and climatology involved, and apply that to forecasting future events.

But to people who have lost their lives, and their surviving family, friends, and colleagues, the meteorological statistics don't matter. Those folks are gone. And the latest death toll is now well over 300 and higher than that of the Superoutbreak and among the few highest on record in the U.S. from a tornado outbreak, and with many other people still unaccounted for.

The Katrina of tornado outbreaks

So that makes this the Katrina of tornado outbreaks, in the sense that it's a vivid and tragic reminder that although high death tolls from tornadoes and hurricanes are much less common than they were in the 19th and first part of the 20th centuries, we are not immune to them, even in this era of modern meteorological and communication technology.

Timely and accurate outlooks were disseminated in the hours and days leading up to the outbreak as well as short-term warnings once the supercells formed. This included "tornado emergency" level warnings by the National Weather Service; in fact, there were so many of those issued that it was mind-boggling.

I think I speak for all meteorologists/forecasters when I say that I/we are at peace with feeling like we did everything we could while also being heartbroken that it still wasn't enough. My heart sank as more and more reports of extreme damage came in that evening with a fatality count that has kept rising since then.

The power of the atmosphere is overwhelming, and how vulnerable we are to it has been reinforced yet again. Weather is as awe-inspiring, fascinating, mysterious, fearsome, and humbling as when I first became obsessed with it as a child. I wish it didn't have to have such tragic consequences.

[Image source: http://bit.ly/jlOpvd]

ADDENDUM 3PM EDT TUESDAY MAY 3, 2011

To follow up on some of the comments received so far ...

For those who do not understand why I chose Katrina as the hurricane to highlight, perhaps this will help. It illustrates what I was referring to in that portion of the blog entry, which is the death toll of tornado outbreaks and hurricanes in the era of modern technology vs. prior to that.

View the original article here

The Climate Lottery- Ranking Numbers of Boreal Fall 2011

The National Climatic Data Center has finished processing the rankings for Boreal Fall 2011 for the lower 48 states. So, for everyone who participated in my little contest, the lottery numbers were: 97/85/93 with an overall "power-ball" ranking for the season of 102. The data can be found at: http://www.ncdc.noaa.gov/sotc/national/2011/11

The winner was Florida Girl, who came closest to picking the correct numbers. Her picks were 90/86/94.

Well, my picks were too low. I wasn't trying to "sand-bag", but truly trying to make a forecast, which underestimated the overall warmth of the season. My ranking climate lottery forecast picks were 75/68/32 for SEP/OCT/NOV. What's alarming is that everyone who played the Climate Lottery (just for fun) had picks that were lower than what verified. Not even my predicted "cooling trend" verified. The season, as a whole, was above long term averages with no individual months below average; and thus, having above average rankings. I'll stress again that for an area of the globe the size of the continental United States it is becoming unlikely that temperature averages for an entire season will be below average, although at a state level there remains a lot of variability. In the future only volcanic eruptions might cool the planet off enough in order for entire seasons or years to be below average. I'll have more about that later in this post.

Here's a breakdown of the National Climatic Center's ranking numbers for each month of the fall:

In September the overall ranking for the lower 48 states was 97 (out of 117):

The ridge that produced the extensive heat wave in the Southern Plains and Texas over the summer retrograded to the West Coast during September, which allowed the heat wave to break. Those of you living in Mississippi and Missouri saw some relatively cool weather, while those of you living in Portland and Seattle had a toasty late summer, even though the bulk of the Pacific Northwest's conditions during the summer were cool. Overall though, September was much warmer than average for the entire contiguous United States.

In October the overall ranking for the lower 48 states was 85 (out of 117).

In October the western upper ridge remained in place from September. Colder than average air masses continued to penetrate the Southeast where below average temperatures were predominant, but the air masses weren't cold enough to give the northern tier of states colder than average conditions for the lower 48 states. Once again, the Climate Dice came up red in October.

In November the overall ranking for the lower 48 states was 93 (out of 117).
The overall ranking for boreal fall was 102 (the 16th warmest fall out of 117 on record).

The pattern reversed in November with the jet stream digging into the West where below average temperatures occurred. There was a lot of warmth in the East, however. The climate dice came up very red in the Northeast. The Hudson Bay low, which typically starts to form during the middle of the fall, is only now beginning to form in early December, but this feature is still centered, for the most part, north of the bay. The Hudson Bay low funnels polar air masses southward into the lower 48 states from mid-fall into winter. Another reason why the fall was mild was the fact that the North Atlantic Oscillation has been in a positive phase since August. Of course, the warming trend is due to increasing carbon dioxide interacting with the overall weather pattern to produce above average conditions. The warming trend has been so stark over the last decade that weather patterns have to be in nearly total alignment for the climate deck to be stacked towards cold conditions for an entire season.

It will be interesting to see if the overall warmer than average trend continues into boreal winter 2011/2012 in light of the fact that the last two winters have been cold for most of the United States. The biggest factor for the boreal winter of 2010/2011 being cold was a persistent negative North Atlantic Oscillation. The NAO remains positive in December 2011 as of this post, but will it remain positive all winter long? I'll ask everyone to come up with their picks for boreal winter along with a "power ball" number for the overall ranking of the season. This time around the highest possible rankings would be 117/118/118 for DEC/JAN/FEB with an overall seasonal ranking of 118 since there will be another year added to NCDC's statistics starting with January 2012. The coldest possible rankings would be 1/1/1/ for DEC/JAN/FEB with an overall seasonal ranking of 1. Just for kicks and grins, also try to guess the overall ranking for 2011. That number should be from 1 to 117; but here's a hint...It will be on the warm side. I'll judge who the winner is for the second contests from those who reply before midnight on 1/1/12. Again, you will need to hit the reply button at the end of the blog to make any picks. I'm not going to make any educated guesses this time in order not to prejudice picks.

You may ask why I am writing in this motif? The short answer is that as long as carbon is being pumped into the atmosphere, humanity is "gambling" with its future. I'm not the only person writing in the "gambling" motif when referring to the overall warming trend of the planet. Someone with far better credentials than little ole' me, Dr. Jim Hanson, has also put out an article recently, which is linked here:
http://www.columbia.edu/~jeh1/mailings/2011/20111110_NewClimateDice.pdf
In the article Dr. Hanson links global warming to the Texas heat wave of 2011.

Some of you asked why I didn't show rankings in the blog Climate Dice Two before 1980. Well, I was trying to be brief by just introducing the National Climatic Data Center's ranking concept. Also, people were wondering about my take on different variables in association with global warming. The following is the full Monty with all of the data since 1900 and a brief history of the ups and downs of climate changes and trends of the 20th century. To make the charts easier to follow trends, I've continued to color code the warm months and years in red (those that have rankings above 69) and color coded the cold months and years in blue (those that have rankings below 48). The near average months are shaded in black (+ 10 or -- 10 from the average value of 58.5).

The link for the National Climatic Data Center's Climate at a Glance Site where the rankings are archived is: http://www.ncdc.noaa.gov/oa/climate/research/cag3/cag3.html

The following are the rankings so far for the 2010's:

So far, the rankings for this decade are very similar to those of the 2000's.

The 2000's was the warmest decade since 1900. The rankings for individual months and years have verified the warming trend predicted by climate models; however, there continues to by enough individual cooler than average months into this decade to fuel the criticism of skeptics.

Notice that rankings did become more blue or black in 2008 and 2009. The planet and United States did cool off some due to a strong solar minimum that took place after 2007. Warming did occur after 2009 once the next solar cycle ramped up, which was correctly forecast by NASA. Solar irradiance is a minor factor, which will slightly affect the overall warming trend of the planet. (For more information see Dr. James Hansen's book Storms of My Grandchildren pages 103 through 107.)

The warming trend continued from the 1980's with one notable exception. In June 1991 Mount Pinatubo erupted. Roughly a year later, after Pinatubo's particulates mixed into the atmosphere worldwide, temperatures got noticeable colder. Note that rankings for the United States were, for the most part, below average from June 1992 to February 1994. The eruption was strong enough to temporarily cool the planet for a couple of years once associated aerosols mixed into the atmosphere. Volcanoes are the only natural variable which will temporarily cool the planet down significantly for a few years depending upon the size and location of the eruption. (Source: The Weather of the Future by Dr. Heidi Cullen pages 41 and 42.)

Another natural factor is the El Nino/La Nina Southern Oscillation (ENSO), which can either warm or cool global averages. For example, the strongest El Nino in recorded history began in the spring of 1997 and lasted well into 1998. Worldwide averages spiked in 1997. The subsequent leveling off of global averages until 2005 became a point for contrarians to argue that the planet was not warming due to carbon pollution, but the cooling was due to the end of the strong El Nino. Note that rankings in the U.S. were very red in 1998.

After several relatively cold decades a warming trend commenced during the 1980's. The summers of 1980 and 1988 were particularly hot. Dr. James Hanson gave his testimony before Congress warning of the dangers of carbon emissions in the hot summer of 1988.

The 1960's and 1970s's were two of the colder decades of the 20th century for the U.S. It was during the 1970's that some climate scientists were thinking that the world was headed towards a new ice age. After doing more research climate scientists changed their minds and correctly forecast a warming trend for the late 2oth century.

Climate scientist suspect that aerosols from industrial pollution were a major contributing factor to a slow decline in temperature averages from the 1940's through the 1970's, which offset warming by carbon pollution. (See Dr. James Hanson's book Storms of My Grandchildren pages 99-101.) After most industrial countries began to utilize cleaner factories after the 1960's and 1970's the effects of carbon became the dominant factor for controlling the planet's temperature trends towards more warmth. Also, carbon was steadily increasing in the atmosphere during the middle of the 20th century. The reason for the temperature trend from the 1940's through the 1970's is further complicated by the Pacific Decadal Oscillation and Atlantic Decadal Oscillation. There is a debate in climate science as to how much of a role both factors played into the cooling trend of the middle part of the 20th century.

The 1930's was arguable the warmest decade of the 20th Century for the United States, but the warmth of that decade was similar to that of the 1990's. The famous Dust Bowl occurred during the hot summers between 1933 and 1936.

There is also a debate among climate scientists that a warming trend had already commenced due to carbon release by the Industrial Revolution well before the start of the 20th century. The planet could have come out of what is described as the Little Ice Age due to increased carbon in the atmosphere. There was a warming trend from the dawn of the 20th century through the 1930's.

Well, that's about it this go-round. You can check any picks for each individual month of winter around the 8th of the following month. I will post the verification in "Climate Lottery - Ranking Numbers for Boreal Winter 2011/2012" around March 10th, 2012. Have a great winter and stay warm. Yes, there will be cold periods even if we have an overall mild winter across the United States.

Guy Walton, Lead Forecaster, The Weather Channel

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