UPDATE 11/4: The number of confirmed tornadoes investigated by NWS-Shreveport is up to 22 with another 7 confirmed by NWS-Little Rock! Some of the pictures from the Arkansas tornadoes (EF-0 through EF-2 in strength) are just incredible:
I am pretty impressed by the 16 (so far) confirmed tornadoes in the Shreveport area from last Thursday's tornado outbreak. There were 34 tornado reports submitted to the SPC that day, which was the highest number since May 13th.*
That means that the October 29th outbreak ranks as #5* in Tornado Days this year, pretty impressive for a Fall outbreak. Here is a SPC graph of the number of tornadoes per day so far in 2009:
However, this has been an unusually slow year for tornadoes in general. How slow has it been? According to the graph below, which attempts to adjust the number of reports for duplicates, we are barely at the 10% level, meaning that 90% of the years surveyed (1950-2009?) were more active than this one at this point in the year - or another way of puttin that is that only 6 years have had lower tornado counts than 2009. I'm not sure the graph below includes the 10/29 outbreak but if not for the increased activity in October, we'd be under 10%!).
But compared to the last 5 years, it's actually not that crazy; 2005, 2006 and 2007 had similar low counts, though only 2006 was lower than 2009; 2005 proved that you can significantly up your count late in the year. Certainly compared to 2008 or 2004, this year is coming in way under. The interesting thing is that when you start talking about all severe weather reports (instead of just tornadoes) this year ranks near all of them except 2008:
SPC does not have a graph of percentage trends over all years but I suspect that (like the graph above) it would not show as much of a record low as the tornado-only graph does. This means that, while the cool Summer may have robbed the United States of some of the energy or temperature differential required to generate tornadic storms, we still had a closer-to-normal severe weather year in general (something that was hinted at when we checked lightning stats in June and they weren't less than the previous year). This may mean that you can rob the atmosphere of tornadic potential but (at least with the cool air centered in the East) you can't stop the thunderstorms. I'm guessing here; a more in-depth study is needed.
*The data quoted on the SPC site for 2009 is a little out of date, it mentions 8/19/09 at 35 reports but that has fallen to 30 (the numbers change slightly as reports are adjusted after the fact.
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there should be 2 tornado dots in that graph- one of them by pine bluff,ar and another one in scott,ar where our nws storm surveys determined that 2 more tornadoes touched down- they were pretty short tracked http://www.srh.noaa.gov/lzk/?n=pns110209txt.htm also wanted to say that what impresses me was the long tracked tornado that started southwest of east camden and finnally dissipated west of princeton for a total path lenghth of 25 and 3/4 miles
Posted by Donny | November 3, 2009 5:43 PM