Thursday, April 04, 2013

Severe Weather Knocking on our Door?


Besides those tornadoes in January, it has been a quiet severe weather season thus far.  However, I think that will change soon.  As I mentioned in the blog post below, it's very rare to go the first 7 days in April without any severe weather.  I have looked back to the year 2000 and every year shows some sort of severe weather in that time period.  This is likely the first year in 14 years and probably more without severe weather.

When it comes to the potential for severe weather, it's NEVER too early to talk about it especially when many aren't thinking about it due to the cool weather lately.  The specifics to next weeks system are yet to be sorted out, but heavy rainfall and some strong to severe thunderstorms is at least possible and the Storm Prediction Center thinks so as well.  Here's a portion of their discussion from Thursday morning.

"TUESDAY/D6 TO THURSDAY/D8 - ERN OK/ARKLATEX INTO THE MIDDLE AND LOWER MS VALLEY... AFOREMENTIONED COLD FRONT DEPICTED BY GFS IS FORECAST TO SURGE SWD AND WILL BECOME A PRIMARY FOCUS FOR CONVECTION FROM NRN IL INTO MO AND OK...LINKING WITH THE DRYLINE OVER N CNTRL TX. BY TUESDAY...SUBSTANTIAL BOUNDARY LAYER MOISTURE WILL BE IN PLACE WITH UPPER 60S F DEWPOINTS AHEAD OF THE FRONT. MEANWHILE...THE ECMWF SOLUTION KEEPS THE SYNOPTIC FRONT STATIONARY ACROSS SRN NEB INTO NRN IL/IND DURING THE DAY ON TUE...WITH THE DRYLINE FROM CNTRL KS INTO OK AND CNTRL TX. THIS MODEL ALSO INDICATES SUBSTANTIAL MOISTURE AND INSTABILITY POTENTIAL FROM KS/OK/TX INTO THE LOWER MS VALLEY. GIVEN THESE MODEL DIFFERENCES...PREDICTABILITY IS TOO LOW FOR AN AREA ON TUE/D6...ALTHOUGH THERE IS THE POTENTIAL FOR SIGNIFICANT SEVERE INCLUDING TORNADOES. THE THREAT SHOULD PERSIST INTO WED/D7 ACROSS THE LOWER MS VALLEY. AREAS ARE LIKELY TO BE INTRODUCED AS PREDICTABILITY INCREASES IN SUBSEQUENT OUTLOOKS."

A part of my job in these situations is to create awareness about the potential for severe weather.  While I hope nothing happens, let's face reality, it's April in Arkansas.  The cold spring thus far may not have some thinking about this so we need to communicate a message of awareness.   The more people know and prepare, I think the more likely the risk of injury or death is decreased.

The modeling shows differences, but both the major long range models do indicate a strong system we'll have to deal with next week. 

Remember the research Meteorologist John Lewis showed me at our local chapter meeting of the AMS/NWA a few weeks ago?  When the Arctic Oscillation (AO) shows a sudden rise, look out.  That's just one of the indicators.  Here's a graph.

See the black line?  That's the AO and you can see it's below zero right now.  When it's negative, we usually have weather which is cooler than average as it suppresses the jet and allows more cold air to drop southward.  See those red lines going above zero out into the second week of this month?  That's the different GFS ensembles forecast indicating agreement we will have sudden rise of that index into the positive.  When it goes positive, it usually means warmer air advances northward simply put.
The European late next Wednesday (April 11th) shows a surface low surrounded in that black line over eastern Kansas.  The front is trailing southward through OK.  High pressure is located off the east coast.  The flow around these two features is drawing in warm and moist air off the Gulf of Mexico.  See the faint gray arrows?  That's the surface flow and it's all a southerly component.  The blobs of red and yellow indicates precipitation amounts over the previous 6 hours.  What you see is likely convective (Thunderstorms)
Look at the warmth the Euro is forecasting next Wednesday afternoon.  Most of the state is in the 70s with a pocket of 80s across the far south.
Here's the latest GFS which shows a faster progression of the front through the state. It's in the delta by late Wednesday.

In summary, it's never too early to raise awareness about the potential for severe weather.  It's impossible to know the specifics this far in advance so this can and is likely to change.  The bottom line... there's a system next week, it's April, and it's Arkansas.  Let's watch this one!

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