After another La Nina season with again a lot of snow and precipitation in the north central, another active tornado season was expected and so far it has delivered on that promise. However given the La Nina was not as strong and the rebound in the Pacific towards El Nino is a month earlier than last year, the number of storms so far, have been less. Unless major outbreaks occur in late May, it looks like May will fall well short of last May’s 461 tornadoes.
TORNADO TOTALS AND RELATED DEATHS...THROUGH 05/13/2009
NWS STORM PREDICTION CENTER NORMAN OK
1048 AM CDT THU MAY 14 2009
...NUMBER OF TORNADOES... NUMBER OF KILLER
TORNADO DEATHS TORNADOES
..2009.. 2008 2007 2006 3YR 3YR 3YR
PREL ACT ACT ACT ACT AV 09 08 07 06 AV 09 08 07 06 AV
JAN 10 6 84 21 47 51 0 7 2 1 3 0 4 1 1 2
FEB 44 37 147 52 12 70 9 59 22 0 27 2 12 3 0 5
MAR 123 - 129 170 147 149 0 4 27 11 14 0 3 10 7 7
APR 269 - 189 167 244 200 6 0 9 38 16 3 0 3 9 4
MAY 165 - 461 252 139 284 6 44 14 3 20 3 10 4 1 5
JUN - - 294 128 120 181 - 7 0 0 2 - 4 0 0 1
JUL - - 93 69 70 77 - 1 0 0 0 - 1 0 0 0
AUG - - 101 75 80 85 - 0 1 1 1 - 0 1 1 1
SEP - - 111 52 84 82 - 2 0 1 1 - 1 0 1 1
OCT - - 21 86 76 61 - 0 5 0 2 - 0 3 0 1
NOV - - 15 7 42 21 - 2 0 10 4 - 2 0 3 2
DEC - - 46 19 42 36 - 0 1 2 1 - 0 1 2 1
---- ---- ---- ---- ---- ---- -- -- -- -- -- -- -- -- -- --
SUM 611 43 1691 1098 1103 1297 21 126 81 67 91 8 37 26 25 29
PREL = 2009 PRELIMINARY COUNT FROM NWS LOCAL STORM REPORTS.
ACT = ACTUAL TORNADO COUNT BASED ON NWS STORM DATA SUBMISSIONS.
TORNADO-RELATED FATALITY NUMBERS ARE ENTERED WHEN CONFIRMED BY NWS
FORECAST OFFICES.
..CARBIN/PETERS..05/14/2009
The annual summary to date can be found here.The tornadoes so far in 2009 have been in the southeast quadrant of the nation. Climatologically, that is where the season normally begins.
In 2008, the tornadoes when all was said and done, were found in all but 4 of the lower 48 states.
As we move into summer, expect the activity to shift north with the jet stream. The march of the season – climatology of tornadoes normally follows this depiction (source here)
We are above the average for tornadoes for the season to date.
But the number of severe storms to date though is lower than any recent year except 2005.
You can see in 2008 that the daily events peaked in May with the biggest day on the 23rd of May before falling off in summer as El Nino like conditions developed in the eastern Pacific. That is occurring a month earlier this year as noted and perhaps, conditions will quiet down after this week.
The activity was as usual concentrated in what is called tornado alley in the plains, Midwest to the Gulf.
The reason that this region is most vulnerable is that this is where the combination of moisture from the Gulf of Mexico, dry air in mid levels from Mexico, a strong jet with cold air aloft coming out of the Rockies and a boundary between still cool air to the north and the warm humid summer like air in the south all come together.
For more information on tornadoes a couple of good resources are
Storm Prediction Center with daily storm summaries and forecasts and many interesting graphs and charts for recent years like some of those above.
The Online Tornado FAQ at SPC
TornadoChaser.net with maps and photos and other information.
Tornado Project Online with very detailed historical information, tornado myths and oddities.
Some amazing photos of the April 29, 2009 tornadoes near power lines and wind turbines. The same storm from TTU website here – one of images shown above .
SPC page all about Derechoes
Derecho of May 5, 2009 near Lufkin Texas
Derecho of May 8, 2009 in Missouri with damage photos and radar animation
SPC Tornado Safety page
Enhanced Fujita Tornado Scale
Fujita Tornado Scale with photo examples from the Tornado FAQ
SPC lists of deadliest U.S. tornadoes, F5 tornadoes since 1950, tornadoes hitting major downtowns, and websites devoted to historical tornadoes
Tornado Oddities and Tornado Myths discussed by Tom Grazulis
A page dedicated to the 50th Anniversary of Tornado Forecasting
Questions and Answers about Thunderstorms by NSSL
