Daweathablog

Charles E. Roop giving his own forecasts, weather discussions, photos and adventures for the Starkville, MS area, Florida, and beyond.

Tuesday, April 26, 2011

High Risk of Severe Weather for Parts of TX/AK/TN/MS

It was a wild weather day on Monday as tornadoes smashed across Arkansas, including Vilonia where the death count now stands at 4 (story from CNN). The same system may bring more storms to roughly the same area as Monday evening.

Currently at the surface, a 994-mb low sits over southern Wisconsin and northeastern Iowa with cold front stretching through Missouri, Arkansas and Texas. Dewpoints in the 60s can be found along the lower Mississippi River delta with a good southerly surface winds of roughly 15 knots at best. At 850 mb, the winds veer a bit to more out of the southwest at 40 to 50 knots. SPC mesoanalysis at 700 mb show winds remaining mostly southwest but become more west in northern Mississippi. The 700 mb layer also gives a hint of little shortwaves embedded in the trough near the Texas and Oklahoma panhandles. The 500-mb mesoanalysis show a trough with over the central plains with what looks like embedded shortwaves - one over Illinois and the other near Colorado. The 300-mb map appears somewhat similar to the 500 mb map with respect to patterns.

Both the GFS and NAM indicate a strengthening 850 mb southerly jet bewtween 0Z and 9Z Wednesday over the southern states with the GFS firing up the jet at 0Z. This could aid in pumping more moisture and warm air during the overnight hours. The 500-mb NAM gives a hint of divergence over the delta, but notably over Arkansas while the GFS indicates the same thing. Since the NAM is a mesoscale model, it indicates more vort maxes due to the embedded shortwaves in the trough. The NAM is showing some pretty good helicity numbers late tonight and early morning over the delta region. The RUC is indicating a dryline boundary over eastern Texas. Storms could initiate from this line in the evening hours.

Based on the model runs, it appears as if the best chance of severe weather will be overnight starting in Texas near this dryline and would move further east and enter more of a favorable environment. In the SPC's discussion, some things aren't clear...

THERE IS CONSIDERABLE UNCERTAINTY REGARDING THE EVOLUTION OF STORMS AS THEY PROGRESS INTO THIS ENVIRONMENT. THE STORMS MAY REMAIN DISCRETE ACROSS AR WITH A RISK OF STRONG/VIOLENT TORNADOES...OR THEY MAY GROW UPSCALE INTO A FAST-MOVING BOW ECHO WITH THE RISK OF WIDESPREAD SIGNIFICANT WIND DAMAGE AND ISOLATED TORNADOES. IN EITHER CASE...CONDITIONS ARE CLEARLY FAVORABLE A HIGH-END SEVERE WEATHER EVENT WELL INTO THE NIGHT.

How they know/don't know the evolution of the storms is out of my league of knowledge at this point. If any mets out there can explain that to me, I'm all ears.

The SPC has moved the high risk to include extreme northwestern Mississippi. Starkville is only under a slight risk category through 12Z Wednesday. The SPC highlights our area with a moderate risk for day two (12Z Wednesday to 12Z Thursday).

For now, a high risk for a tornado outbreak looks probable for parts of Arkansas, Mississippi, Tennessee, and Texas. People living in those areas need to take this event very seriously. Make sure you have a NOAA Weather Radio on standby tonight and keep tabs on the weather before you go to bed. Starkville looks to be in the red on Wednesday. I'll have a better handle on things as Wednesday approaches. Stay tuned to this blog and my Twitter feed for the latest.

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