"Buresh Blog": Weekend severe storm & tornado outbreak - Jan. 24th

Jan. 24, 2017 — As expected.... the weekend was marred by spring-like thunderstorms & tornadoes.  So far there have been at least 19 deaths making this the 2nd deadliest January tornado outbreak on record in the U.S..... & more than all the U.S. tornado deaths in 2016 with 400+ severe storm reports within 48 hours.  The set-up (as I mentioned in a post last week) was very much like an El Nino winter storm system with a very strong upper level low moving across the deep south (of the U.S.) with virtually no connection to the polar jet stream.  So there was very little cold air on the north & west side of the surface cyclone/low pressure system but the upper level dynamic were very strong which more than made up for the lack of thermodynamic processes.

SATURDAY:

SUNDAY:

The upper level forecast for late Sunday from 4 days prior showing the strong upper level storm system with the lack of "connection" between the subtropical jet stream & the polar jet stream.

The Storm Prediction Center (SPC) upgraded North Fl. & much of Ga. to a "high risk" of severe storms & tornadoes early Sunday morning after there had already been about 24 hours of strong long track tornadoes.  This was the first high risk issued by SPC since 2014... & -- it's believed -- the first high risk for any of Fl. ever issued.  A "particularly dangerous situation" (PDS) tornado watch was issued about 12:30pm Sunday.  In the end, there was 1 long track tornado in our viewing area -- across far SE Ga. near dark from just northeast of Folkston to near Woodbine & Waverly crossing I-95 shortly after which the tornado lifted.... CBS47/Fox 30 Action News story -- here.

There were a number of instances of high winds & hail across the area (see video & photos on my Twitter feed + FB fan page).  But no other tornadoes were confirmed over NE Fl./SE Ga. despite a number of warnings.  So why not more tornadoes??  Well.... it's my opinion (& mine only).... that the mid & upper level winds were actually too strong(!).  I have seen such situations in Oklahoma when I was in college storm chasing.  What appeared to be a premium day for tornadoes turned into a dud because the t'storm updrafts could not sustaine themselves -- get much taller -- because the strong upper level winds "cut" them off.  It's too much of a good thing.  Supercell thunderstorms that produce long track tornadoes do need strong shear -- a combination of wind changing direction with height.... + strong wind speeds.  But in Sunday's case, the wind speeds may not have had quite enough directional shear but -- more importantly -- the wind speeds were simply too strong.  This "decatapitated" the t'storms before the cumulonimbus cloud could get any taller AND before the strong updraft could sustain itself & begin to rotate or maintain its rotation which would lead to the development of a tornado.  The image below is the Jacksonville atmospheric sounding (weather balloon measuring many weather parameters as the balloon ascends), &  the atmosphere is very unstable with supercell values & "significant" tornado parameters that are through the roof even by tornado alley standards.  Wind speed shear is super strong but notice not as much change in direction of winds with height as one would have seen to the north closer to the warm front.

As it was, the outbreak was very significant for the Southeast U.S. & for the First Coast.  I'm proud of how our First Alert Weather team handled the situation & am especially proud of our forecast & how we delivered that forecast.

No "over the top" forecasts or reaction like we saw from other outlets(!) [see tweet below that I sent out Fri. night]

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