Well time is starting to fly by now and we are nearly at the start of March, Xmas only seems like yesterday and Spring is just around the corner, which means 1 thing............Tornado Season!
About this time of the year we start to look forward to what we might expect in Tornado Alley and the Northern Plains for May and June 2013!
I am a firm believer in active, normal and below active seasons following the ENSO Pattern, 2011 was best characterised by this and one of the strongest La Nina events since the 1950's expecting a very active Season in Dixie Alley and the eastern part of the Plains. A near record number of EF5 Tornadoes that season occured as expected and unfortunately hitting populated parts of the USA meant the season would be remembered for all the wrong reasons, starting with Tuscaloosa (Alabama) on the 27th April and also Joplin (Missouri) on the 22nd May!
The last above active El Nino event (2007) actually saw amazing conditions in the Texas Hill country, most parts of Texas and the Central Plains, abundant wild flowers and countryside greener than most parts of the Uk, that Season again will be remembered for the first ever EF5 Tornado that struck Greensburg on the evening of Friday 4th May 2007. Storms that year were very grungy looking but numerous in nature and risk days seemed to be ongoing from 11am most days with no discernable Cap in place meaning numerous storms all hitting each other, the lack of strong heating also stopped the formation of Isolated Supercells, subsequent years have certainly either been La Nina or Nuetral years depicting the ongoing extreme drought conditions (Not too dis-similar to the Dustbowl years of the 1930's) but obviously nowhere near as extreme as that episode.
So what to expect in Spring 2013 ??
This year I am going for an above active season for places East of I-35 (Interstate35) meaning parts of Arkansas, Missouri, Iowa, Minnesota, Illinois etc will be above average for the early part of the Season (April through to Mid May) as Neutral conditions look like prevailing in the late winter and early part of Spring, I would also expect the Sub Tropical Jet to play its part in a more South and Eastern active season, this would bring Louisiana, Arkansas, Eastern Texas, Mississippi and Alabama into play even into Early May when their season should be waning. SST's in the Gulf Of Mexico currently run at 1-3c above average so a much more humid airmass will be prevalent as gulf moisture will be plentifull.
Moving through the rest of the Season is a bit more tricky due to ongoing uncertanties with regards to the ENSO Cycle either staying neutral until summer or trending towards El Nino as some models are expecting.
If we can get an early El Nino then the Central Plains could become active from the start of may and not later as has been the case for the last 5 years, if this occurs the natural progression for the season to shift Northwards could come earlier to the Dakotas in Mid to 3rd week of May onwards, if we stay neutral would expect June to be much more active than in 2012 with the Jet Stream being in its traditional position by the 3rd week of May.
Whatever happens (All speculation at present) hoping everyone stays safe and abides by the rules of the roads, safety etc at all times, and here's to a great season of Structure, Tornadoes over Open Prairies and lots of fun chasing the most amazing storms on Planet Earth.