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.
