Previous editions:
2006
2007
2008
2009
2010
So I guess that makes this the 6th annual!
As I've noted in the introduction the past few years, the content is not meant to represent a complete list of every significant weather event everywhere or images thereof, but there's a lot of stuff which will bring back memories.
This time, in addition to the blog entry, I've also put a selection of a dozen other images into a slide show on weather.com.
In 2011 there were photographs that were so dramatic and widely seen, such as of cars stranded on Lake Shore Drive in Chicago in the February blizzard, and the haboob in Phoenix in July, and the devastation and tragedies caused by the tornadoes and hurricanes and wildfires and drought (and tsunami/earthquakes), and that have been part of other year-in-review features, that I'm not including any photographs here, other than a couple not-so-noteworthy, low-resolution ones that I took myself with a cellphone camera. Instead, I'm going to focus mainly on meteorological imagery and charts; thus this year's title instead of "weather images."
There were plenty of them, as what a year it was. A record number of billion-dollar disasters in the United States, and a lot of meteorological extremes contributing to that. Let's hope for a much less dramatic 2012!
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Okay, so I took a photo of a snowy motel parking lot in January. What's the big deal? Well, it not only had personal significance (a harrowing drive to get there that night, and that was to be able to be within walking distance of TWC the following morning), but that relatively little bit of snow compared to what areas farther north experienced last winter was enough to essentially shut down the whole metro Atlanta area for days.
Stu Ostro
Like has been the case so many other times in recent years with precipitation and temperature extremes, the key to the colossal storm in early February which brought a severe blizzard to Chicago was a strong ridge of high pressure aloft (red/orange/yellow shades on the map below, which technically represent above average "500 millibar heights").
NOAA
At the same time of that storm, on the other side of the world was Severe Tropical Cyclone Yasi. In the slide show, I included the image of the "E" in the eye. Here I'm adding another freaky feature in a tropical cyclone eye that it was reminiscent of, a "2" in Hurricane Wilma in 2005.
Naval Research Laboratory; NOAA
Vortices over the Great Lakes in lake-effect snowbands are not rare; TWC severe weather expert Dr. Greg Forbes blogged about them a few years ago and authored a scientific paper on them nearly 30 years ago. However, this, approximately a week after the Groundhog Day blizzard, was a particularly vivid example and included a combo of two.
Gibson Ridge / GRLevel2
A very cold low pressure system aloft, represented by the bright colors on this map depicting temperatures a few miles up, brought snow to parts of the Tucson area in late February after doing so to the higher elevations of San Francisco.
wright-weather.com
This is not meteorological, but it has something in common with weather, as both earthquakes and wind produce waves which can be destructive. This image, which looks like a gigantic bloodshot eyeball, represents a computer model simulation of tsunami waves that were catastrophic in Japan and propagated to other locations all the way across the Pacific.
NOAA
On April 4, a potent weather system brought an astonishing number of severe weather reports (most of them straight-line wind damage). That was a bad omen for the rest of that month ...
NOAA
The next day that system ran out of steam, but as a squall line came through the Miami metro area, a webcam operated by Bryan Norcross, hurricane specialist at TWC, captured this:
Bryan Norcross
A few days later, atmospheric instability represented in the fiery model forecast image below surged way up into Wisconsin, fueling a record-setting tornado outbreak there.
WSI
This was a classic dryline-triggered eruption of thunderstorms that produced tornadoes, including a deadly one in Tushka, Oklahoma the evening of April 14. There were additional casualties in Arkansas as the system moved east overnight.
NASA/GSFC, MODIS Rapid Response (satellite); Gibson Ridge / GRLevel2 (radar)
Then a very energetic stream of wind aloft associated with that system sliced east a couple days later and led to the largest North Carolina tornado outbreak on record.
wright-weather.com
The following Friday, on a flight from Atlanta to Oklahoma City, I observed the atmospheric "cap" breaking. A few hours later a tornado hit Lambert-St. Louis International Airport.
Stu Ostro
The cap broke again on April 27. Dry air aloft as shown in the "water vapor" image on the left can, along with relatively warm air upstairs, put a lid on thunderstorm development. If the lid holds, that's good news. But the energy can build to the point that it explodes sky-high if it can break through the cap/lid. Not only did that happen as shown in the image on the right side, but there was a textbook and extreme set of other ingredients. The outcome: a tornado superoutbreak.
UCAR
I was so stunned to see this extraordinary number and concentration of supercells, many of which had "ground truth" of tornadoes, not just a radar indication of rotation aloft, that I suggested to Dr. Forbes that we should go with a "TOR:CON" index of 10 in northern Alabama, meaning a 100% chance of a tornado within a given spot, and he agreed.
Gibson Ridge / GRLevel2
The Weather Channel
A particularly vivid "debris ball" signature on radar, between Tuscaloosa and Birmingham. Yes, that's not precipitation, it's debris blown by the tornado.
Gibson Ridge / GRLevel2
A swirl of a tropical cyclone wannabe makes landfall on the Mexico coast. What's remarkable about this is that the spin originated from a thunderstorm complex in the Great Lakes during Memorial Day weekend, swung out over the Atlantic Ocean, and then ended up here on the west coast of the Gulf of Mexico a week later!
NASA/GSFC, MODIS Rapid Response
A few days after that, a smoke plume from an Arizona wildfire inferno gets blown by strong winds at sunset. 
WeatherTAP (all WeatherTap images used with permission)
Quite a bow echo on radar, and this one was interesting in the way it was moving due north (in southeastern South Dakota).
Gibson Ridge / GRLevel2
During the peak of the summer heat, a meteorological milestone was reached: the big six-oh-oh. 600 decameters is a benchmark value for "500 millibar heights," representative of an extremely strong ridge of high pressure aloft, and the measurement above Omaha the evening of July 17 was close to being a record for that part of the country. The colorful image shows a model forecast for the ridge a few days in advance, and the verification of 600 decameters (6000 meters) was even a bit higher than what was predicted.
wright-weather.com (color map); NOAA via Colorado State University archive (B&W inset)
A few days later, on the northern periphery of the heat ridge, a particularly interesting thunderstorm outflow boundary signature on radar in Minnesota, extending like a long tail well away from the storm cell.
Gibson Ridge / GRLevel2
Tropical Storm Don and its convection croak remarkably rapidly between mid-afternoon and midnight upon arrival in extreme south Texas. Our luck would run out later in the 2011 Atlantic hurricane season ...
Naval Research Laboratory
Although Irene's inner core weakened, sparing places such as the Jersey Shore and New York City from the kind of wind and surge that otherwise would have been experienced, strong upper-level outflow to the northeast helped maintain Irene's low central pressure and overall strength, and that and the cyclone's massive size resulted in widespread wind damage and power outages from North Carolina to New England and contributed to the amount of rainfall which fell.
NOAA
Lee soon followed, and took on an odd appearance on water vapor satellite imagery along the Gulf Coast as dry air wrapped all the way in around the center but then moisture swirled in too.
NOAA
At one point Lee very closely resembled Cindy when it was in a similar position, and both went on to be prolific tornado producers.
Naval Research Laboratory
Lee's remnants and tropical moisture flowed north, and unleashed torrents of rain in the northeastern U.S., much of it occurring in association with long north-south bands of "training," in which individual showers and thunderstorms keep going over the same spot like railroad cars on train tracks. This band persisted all night.
Gibson Ridge / GRLevel2
A map of two-week rainfall which includes what fell from Irene and Lee.
NOAA
In the slide show, I featured a striking satellite image of a swirling "cutoff low," so named because they are completely cut off from the main jet stream. This one persisted in nearly the same place for many days.
NOAA via CSU
And here's another wild-looking water vapor satellite image of it along with another large swirl over the Atlantic Ocean.
WeatherTap
Within an overall large "pressure gradient" and wind field south of a high pressure system in early October, a low pressure system spun up rapidly just offshore of the east coast of central Florida and took on characteristics of a tropical storm.
Gibson Ridge / GRLevel2
That system was part of a repetitive pattern in October that featured low pressure and moisture from the western Caribbean to the subtropical Atlantic, during which, on October 18, there was this cluster of thunderstorms near the Keys, and three days later an exceptionally sharp contrast between dry and moist air aloft.
Both images above: Cooperative Institute for Meteorological Satellite Studies (CIMSS)
A critical factor in causing "Snowtober" to have the impact it did in the Northeast was so much heavy wet snow falling so early in the season, onto trees which still had leaves. Meteorologically the ingredients which came together were just enough cold air from the north meeting up with lots of tropical moisture surging up from the south, all the way from the Caribbean ...
NOAA
... and the interaction of those along with jet stream energy led to a meteorological "bomb," in which there's a drop of at least 24 millibars in 24 hours of central pressure of a cyclone. As this one passed over a buoy east of New England and south of Nova Scotia, the barometer measurement plummeted.
NOAA
Satellite imagery showing the transformation of a disorganized mass of clouds into the cyclonic bomb.
NASA Earth Science Office
This is a common sight in western Oklahoma in spring, not so common in November. This supercell on November 7 produced an EF4 tornado near Tipton, the first tornado on record to get such a high rating in Oklahoma in November.
Gibson Ridge / GRLevel2
At the same time, what was described by the National Weather Service in Alaska as the strongest storm to reach the Bering Sea so far north since 1974 was developing, and during the night of November 8 it resembled a giant ? on satellite imagery.
NOAA
A high-resolution shot of the cyclone's core.
NASA/GSFC, MODIS Rapid Response
Look at the whirlpool that formed in the storm surge in Nome!
KNOM Radio Mission, photographer Matthew Smith; embedded with permission; full-sized image is here
A long nose of cold air dips down at the end of November ...
wright-weather.com
.. as another cutoff low develops, the result being up to 8" of snow reported in Arkansas to the northwest of Memphis, unusually so far south for so early in the season. That November event and Snowtober are quite ironic given the lack of snow in the central and eastern U.S. since then.
UCAR
Yet another cutoff develops, this one with quite a wind flow aloft ...
wright-weather.com
... as well as an exceptionally large (both in magnitude and geographical extent) pressure gradient at the surface, the upshot being a western windstorm which is not only no ordinary Santa Ana, with its effects so widespread in SoCal, but extreme wind gusts occur in spots all the way from there to Steamboat Springs, Colorado.
NOAA
A storm headed for Europe taps moisture from the tropics, resembling a Pacific "Pineapple Express," in this case over the Atlantic ...
NOAA
... but precipitation is not the main impact of this quickly-moving storm, it's wind. A "low-level jet" upwards of 100 mph a few thousand feet up sweeps into France and thereabouts on December 16, with powerful wind gusts blasting down to the Earth's surface.
Plymouth State University Weather Center
Much of the rest of the country was wondering in December, "Where's winter?" Well, it was certainly present in New Mexico. Surreal desolation on a closed I-40 at night was captured by this traffic webcam.
advanced.nmroads.com
What a difference a year makes for what percentage of the country experienced a white Christmas, and where.
NOAA
The turnaround from the past two winters to this one so far was primarily due to the opposite extremity of phenomena known as the AO (Artic Oscillation, shown in this set of graphs) and NAO (North Atlantic Oscillation).
NOAA
That manifested itself in a flip from anomalously strong and persistent ridges of high pressure over and near Greenland during late November and December 2010 (top map) with low pressure aloft to the south, to the reverse in late 2011. The former, an extreme "blocking pattern," led to major snowstorms and persistent cold weather in the central and eastern U.S. and in Europe.
NOAA
Something which is likely a factor contributing to the atmospheric extremity in/near the Arctic in recent years is the precipitous drop in the amount of sea ice there. The black line on this graph plots the volume, which takes into account both the area and thickness of the ice, at the time of the annual minimum each September.
The colored lines represent different mathematical slopes, and what each would do in the future if it were to follow the respective rates of decrease. Although representing different methods and phenomena compared to computer model forecasts of hurricane tracks, this range of projected potential outcomes could be thought of as analogous to the "spaghetti model" plots that have become commonly used.
Hopefully over the coming years and decades the rate of decline showed by the black line will slow down and follow a path toward zero (no ice left in late summer) more like the purple line than the green one. But the recent and current rate is troubling, given the important role that the Arctic and its ice play in the Earth's climate system, and given that this is happening faster than the climate models predicted.
Source and full-sized image: https://sites.google.com/site/arctischepinguin/home/piomas/
On the final day of 2011, Tropical Cyclone Benilde looked scary, but was safely out at sea in the southern Indian Ocean.
Naval Research Laboratory
IMAGES OF THE YEAR
These are my choices for images that were most memorable (other than the indelible photographic ones noted in the introduction) -- not the images themselves, which are simply screen captures of The Weather Channel broadcast and are small in size and not of particularly high resolution, but what they represent in terms of what happened meteorologically and the effects upon those in the storms' paths. In each case it was hard to believe what I was seeing.
Thundersnow experienced live on television by Jim Cantore in Pennsylvania in October?? Yep.
Is that whole seething black mass of cloud extending to the ground a gigantic rotating tornado, live on TV?? Yes, the power flash (bright spot) indicated that it was.
And did a supercell thunderstorm actually spew out debris -- which Jeff Morrow is holding (pieces of shingles and plexiglass) after it fell from the sky -- many miles away from the tornado??
Yes, it did.
Mike Bettes was overcome with emotion upon arriving on the scene in Joplin moments after the EF5 tornado hit.
This high a death toll from a single tornado (and from the April 2011 superoutbreak and other events last year), in the 21st century?? Yes, just as Katrina and the 2004-05 hurricane seasons could be thought of as a wake-up call for our vulnerability to weather even with today's modern forecasting and communication technology, so can 2011 with its tornadoes.
