Rare HIGH RISK of Severe Weather Issued

02 March 2012 David Reimer 0 Comments

1300Z - Friday's Severe Weather Outlook

The Storm Prediction Center has upgraded a portion of their enhanced moderate risk to an extremely significant, rare HIGH RISK. These high risks are only issued one or two times a year and mean there is a very high confidence that there is the potential for very significant, deadly, severe weather. Don’t think just because you’re not in the high risk that you’re not in danger. The significant risk of severe weather extends all the way south into Mississippi and Alabama, northward into the Ohio Valley. Surrounding that significant risk, we have the standard “slight” risk of severe weather. That extends all the way west towards Arkansas/Louisiana, northeastward into the Great Lakes. Severe weather coverage will be higher in the moderate/high risk zones, but severe weather is possible in the standard risk zones as well.

Here’s a zoomed in shot of the high risk zone, just to give a little more detail on the specific major cities at risk. As you can see, Nashville and Louisville are just some of the cities in this rare, extremely dangerous HIGH RISK.

Chance of a tornado occurring within 25 miles

Here’s a little bit more specific information. This graphic shows the probability of experiencing a tornado within 25 miles of your location today. The red line is where the high risk zone has been issued, and means there is nearly a 1 in 3 chance of a tornado occurring within 25 miles of downtown Nashville and Louisville. Obviously the 15% risk (orange line) is also very significant. Today still appears ready to be a major tornado outbreak. It’s going to be very busy and we’ll do our best to keep you informed.

Thursday’s Severe Weather Risk Trimmed for Texas

22 February 2012 David Reimer 0 Comments

Latest model guidance has come in less aggressive for Thursday’s severe weather potential. In fact, the Storm Prediction Center has removed all except extreme Southeast Texas from the standard risk of severe weather. We’ll continue monitoring this potential event and post an update a little later today, but at this point it looks like Thursday might be quieter then we thought yesterday.

February 23, 2012 Severe Weather Risk – Discussion #1

21 February 2012 David Reimer 0 Comments

Please watch our Daily Weather Video for complete details on the upcoming severe weather threat…

The Storm Prediction Center has placed much of Southeast Texas and South Texas in a standard risk of severe weather for Thursday. A standard risk is defined as a 15 percent chance of experiencing severe weather within 25 miles of any location. Just east of Texas, SPC has issued an elevated risk of severe weather for a large portion of Dixie Alley. Those folks could be dealing with a major severe weather event on Thursday, but we’re not out of the woods in Texas.

Unlike the past few systems that have moved through Texas, moisture will not be an issue. The North American Model (NAM) is showing a large warm sector across the south, with dewpoint values AOA (At Or Above) 60°F with some locations even above 65°. Those numbers are quite impressive for February and are always a warning sign that something nasty could be coming down the track. These projected dewpoint values are more then supportive of organized thunderstorms.

With the rich moisture in place and a strong storm system coming in aloft, instability values will be in excess of 1,500 joules per kilogram (J/Kg). During the winter months, we generally want to see values of at least 500 J/Kg to support the possibility of severe weather. Obviously values over 1,500 J/Kg are more then favorable to support organized severe weather, assuming other factors are in place.

This graphic shows winds at 500 millibars or 18,500 feet above sea level. When looking for the potential of organized thunderstorms, I want to see values at or above 35 to 40 knots. That’s the rough threshold I like to use when determining wind shear aloft. Values should be above 65 knots, so we definietly have enough wind shear to support thunderstorms.

We’re still three days out from this potential event, so a lot can and probably will change. Current data suggests the highest severe weather threat will be east in Louisiana and Mississippi, but there will be enough instability and wind shear in Southeast Texas to support some chance of severe weather. Current data suggests the primary severe weather threats in Texas will be large hail and damaging straight line winds. There may be some tornado threat, but the primary tornado threat will be to our east. We’ll be able to determine the specific hazards once we get a little closer to Thursday. In terms of timing, it looks like it should be a 2 PM to 10 PM deal. We’ll have continuing coverage on this possible event. I’ll try to post an update later tonight once evening model data arrives.

Flood Watches for East, Southeast, South Texas

17 February 2012 David Reimer 0 Comments

Overview of Flood Watches

Several National Weather Services across the state have issued Flood Watches due to the potential for very heavy rainfall overnight and into the first part of Saturday. Currently, Flood Watches have been issued for areas like Austin, San Antonio, east to Houston, and northeastward into Northeast Texas. There are so many counties that they’re not really worth listing, however we have included more specific graphics below with city names. Please reference them for your specific location.

Flood Watch from the Austin/San Antonio National Weather Service

Flood Watch from the Houston National Weather Service

Flood Watch from the Shreveport National Weather Service

Tornado Watch Coming for LA/AR/W. MS

22 January 2012 David Reimer 0 Comments

Mesoscale Discussion #45

MESOSCALE DISCUSSION 0045
   NWS STORM PREDICTION CENTER NORMAN OK
   0226 PM CST SUN JAN 22 2012

   AREAS AFFECTED...NERN TX...NRN LA...SRN/ERN AR...NWRN MS...WRN TN

   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   VALID 222026Z - 222230Z

   SEVERE THUNDERSTORMS SHOULD INITIATE BY EARLY EVENING NEAR THE
   ARKLATEX THEN RACE NEWD TOWARD WRN TN/NWRN MS AFTER DARK.  DAMAGING
   WINDS AND ISOLATED TORNADOES ARE EXPECTED.  A TORNADO WATCH WILL
   LIKELY BE REQUIRED BY 00Z.

   LEADING EDGE OF WELL DEFINED UPPER TROUGH IS ADVANCING ACROSS ERN
   OK/NERN TX AND WILL SOON OVERSPREAD THE LOWER MS VALLEY.  IN ADVANCE
   OF THIS FEATURE...WARM MOIST BOUNDARY LAYER HAS SPREAD INTO SRN/ERN
   AR...AS NOTED BY SFC DEW POINTS RISING THROUGH THE UPPER 50S INTO
   THE 60S...WHILE A STUBBORN WEDGE OF COOLER AIR HAS YET TO BE
   DISPLACED OVER MUCH OF CNTRL/NWRN AR.  CURRENT THINKING IS GREATEST
   AIRMASS DESTABILIZATION WILL OCCUR TO THE S-E OF THE AFOREMENTIONED
   WEDGE FRONT AND THIS WILL BE THE CORRIDOR OF GREATEST SEVERE
   THUNDERSTORM POTENTIAL.

   LATEST VIS IMAGERY DEPICTS AN INCREASING BAND OF LOW LEVEL CU ALONG
   THE DRY LINE NEAR I-35 OVER NCNTRL TX.  THIS IS ALONG THE LEADING
   EDGE OF STEEPER LAPSE RATES AND IS CERTAINLY INDICATIVE OF STRONGER
   FORCING THAT WILL SOON OVERSPREAD THE ARKLATEX.  WITH TIME
   THUNDERSTORMS COULD EVOLVE ALONG THIS LINE...OR PERHAPS EVEN DEVELOP
   WELL AHEAD OF THE WIND SHIFT WITHIN DEEPER CONFLUENT ZONE NEAR THE
   LA BORDER AS EXHIBITED BY SHOWERS BEGINNING TO DEEPEN FROM NEAR TYR
   TO JUST WEST OF SHV.  NEEDLESS TO SAY VERY STRONG SHEAR WILL SUPPORT
   SUPERCELL DEVELOPMENT AND THE POTENTIAL FOR TORNADOES.

   ..DARROW.. 01/22/2012