New Severe Weather Outlook

08 March 2012 David Reimer 0 Comments

The Storm Prediction Center has released their new severe weather outlook for Thursday. Generally, nothing has changed from the graphic I posted yesterday afternoon. The standard “slight” risk of severe weather includes much of Central and Northeast Texas, along with Arkansas, Louisiana, Mississippi, and Alabama. The severe weather threat looks to be highest (I’m using that in a relative term) as a cold front pushes southeastward this afternoon into the evening hours. A nearly solid line of thunderstorms will develop along the cold front. Large hail and damaging outflow winds are the primary severe weather threats. The tornado threat is non-zero (very low).

Here is the discussion from the Storm Prediction Center. This does contain some nerdy weather terms.

..CNTRL TEXAS EAST NORTHEAST THRU THE N CNTRL GULF STATES  
  
CONSIDERABLE THUNDERSTORM ACTIVITY MAY BE ONGOING AT 12Z THIS  
MORNING...MAINLY TO THE NORTH OF THE SOUTHEASTWARD ADVANCING  
FRONT...ACROSS PARTS OF THE SOUTH CENTRAL PLAINS THROUGH THE OZARK  
PLATEAU INTO THE LOWER OHIO VALLEY. DURING THE DAY...  
THOUGH...MODELS SUGGEST THAT UPWARD VERTICAL MOTION BENEATH BROADLY  
DIFLUENT...AND INCREASINGLY DIVERGENT...UPPER FLOW WILL WEAKEN  
INHIBITION TO THE SOUTH OF THE FRONT...WHERE INSOLATION MAY  
CONTRIBUTE TO WEAK TO MODERATE MIXED LAYER CAPE OF 500-1000 J/KG.  
COUPLED WITH MODEST...BUT FAIRLY STRONGLY SHEARED...SOUTHWESTERLY  
DEEP LAYER MEAN FLOW...THIS MAY PROVE CONDUCIVE TO THE DEVELOPMENT  
OF A FEW ORGANIZED STORM CLUSTERS...AND PERHAPS ISOLATED SUPERCELLS.  
 THE PRIMARY SEVERE THREATS APPEAR TO BE THE RISK FOR LOCALLY  
DAMAGING WIND GUSTS AND LARGE HAIL...WITH THE LARGE HAIL POTENTIAL  
GENERALLY CONFINED TO A STEEPER LAPSE RATE ENVIRONMENT EXPECTED  
ACROSS PORTIONS OF CENTRAL TEXAS INTO THE ARKLATEX.

Long Track Tornado continues in East Alabama

02 March 2012 David Reimer 0 Comments

This image shows how fast the winds are turning within this thunderstorm. Those bright colors right next to each other is called a couplet, indicative of very strong rotation. In fact, a tornado has been confirmed with this storm in Tallapoosa County. This storm has been producing a tornado for the past three hours and it’s likely this has produced multiple long-track tornadoes. Significant damage has occurred and current indications are that it will continue to produce a significant tornado for a while longer.

Here is the latest Tornado Warning.

BULLETIN – EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1100 PM CST FRI MAR 2 2012

THE NATIONAL WEATHER SERVICE IN BIRMINGHAM HAS ISSUED A

* TORNADO WARNING FOR…
NORTHERN CHAMBERS COUNTY IN EAST CENTRAL ALABAMA…

* UNTIL 1145 PM CST

* AT 1058 PM CST…EMERGENCY MANAGEMENT REPORTED A TORNADO 8 MILES
NORTHWEST OF RIDGE GROVE…OR 9 MILES NORTHEAST OF DADEVILLE.
DOPPLER RADAR SHOWED THIS TORNADO MOVING EAST AT 60 MPH.

* LOCATIONS IMPACTED INCLUDE…
STROUD…TRAMMEL CROSSROADS…PENTON…BUFFALO…WHITE PLAINS…
WELCH…FREDONIA…POST OAK FORKS…VEASEY CREEK PARK AND AMITY
PARK.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

TO REPEAT…A TORNADO IS ON THE GROUND. TAKE COVER NOW. FOR YOUR
PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY
BUILDING.

The event is just beginning in MS/AL/GA…

02 March 2012 David Reimer 0 Comments

Composite Reflectivity (6:36 PM CST)

This has already been a historic tornado outbreak with numerous significant tornadoes hitting small towns all across the Ohio Valley. However, the event is really just beginning to ramp up across Mississippi/Alabama/Georgia. The above graphic shows the radar image at 6:36 PM CST/7:36 PM EST. Notice that all the storms are by themselves and not in a squall line. This means the tornado potential remains quite elevated along with the destructive hail and damaging straight-line wind potential. Once these storms begin to congeal into a line of thunderstorms, the straight-line wind potential will increase and the tornado potential will begin to decrease, but not completely.

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.

Enhanced Severe Weather Risk Expanded

02 March 2012 David Reimer 0 Comments

The Storm Prediction Center has released the new Severe Weather Outlook for Friday. The standard “slight” risk extends from Louisiana northward into Arkansas, all the way east into North Carolina and western New York. Inside that standard risk, an enhanced risk (outlined in red) has been issued. That enhanced risk extends from Winona, MS on the west side, north to Jackson, TN, north into southern IL, much of Indiana and Ohio, and back south into southwest West Virginia, into Tennessee and Alabama. Locations within the enhanced zone have the highest risk of experiencing large, long-track tornadoes, severe straight-line winds, and very large hail. The severe weather coverage is expected to be less in the standard risk zone, but severe weather is still possible.

These three graphics further define the severe weather hazards. These graphics show the probability of experiencing severe weather within 25 miles of any given point. The orange line denotes the standard risk of severe weather, a 15% chance of experiencing severe weather within 25 miles. The dark-orange line denotes a 30% chance of experiencing severe weather within 25 miles. Finally, the red line is our Moderate Risk zone and shows a 45% chance of experiencing severe weather within 25 miles of any given point.

Here is the complete text of the severe weather outlook. Just ignore the meteorological term.

DAY 1 CONVECTIVE OUTLOOK   
NWS STORM PREDICTION CENTER NORMAN OK  
1142 PM CST THU MAR 01 2012  
  
VALID 021200Z - 031200Z  
  
...THERE IS A MDT RISK OF SVR TSTMS FROM THE OH VALLEY TO THE CNTRL  
GULF STATES...  
  
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM  
THE UPPER OH VALLEY TO THE CNTRL GULF COAST...  
  
...A SIGNIFICANT SEVERE WEATHER EPISODE IS EXPECTED FRIDAY ACROSS  
MUCH OF THE OH VALLEY...SWD INTO THE CNTRL GULF STATES...  
  
A VERY STRONG JET CORE AT MID-HIGH LEVELS WILL INTENSIFY IN EXCESS  
OF 110KT AS IT OVERSPREADS SRN MO INTO THE OH VALLEY LATER TODAY.  
IN RESPONSE TO THIS FEATURE A SFC LOW OVER NCNTRL OK EARLY THIS  
MORNING WILL TRACK NEWD AND DEEPEN OVER MO INTO CNTRL IL BY MID DAY.  
 BOUNDARY LAYER MOISTURE IS RECOVERING RAPIDLY ACROSS ERN OK ATTM  
WITH 60F DEW POINTS NOW SPREADING NORTH OF I-40. THIS MOISTURE  
SURGE WILL ADVECT INTO MO BY SUNRISE AND STRONG WARM ADVECTION IS  
EXPECTED TO INDUCE MULTIPLE CLUSTERS OF ELEVATED SEVERE  
THUNDERSTORMS...CAPABLE OF PRODUCING LARGE HAIL...AHEAD OF SFC LOW  
ALONG/NORTH OF RETREATING WARM FRONT. SUBSEQUENT EXPANSION NEWD  
WITH RECOVERING AIRMASS WILL ALLOW SEVERE WARM ADVECTION STORMS TO  
SPREAD ACROSS MUCH OF THE OH VALLEY BY 18Z. WHILE LARGE HAIL WILL  
LIKELY BE THE PREDOMINANT THREAT EARLY...A FEW TORNADOES ARE  
POSSIBLE AS AIRMASS MOISTENS. IN THE WAKE OF THIS ACTIVITY BOUNDARY  
LAYER DEW POINTS WILL RISE INTO THE LOWER 60S AHEAD OF SFC COLD  
FRONT AND LOW LEVEL LAPSE RATES SHOULD STEEPEN SUCH THAT PRE-FRONTAL  
SUPERCELL DEVELOPMENT WILL LIKELY EVOLVE NEAR OR SHORTLY AFTER 18Z  
ACROSS IL. FORECAST SOUNDINGS ACROSS THE WARM SECTOR OVER SRN IL  
SUGGEST MUCAPE SHOULD BE ON THE ORDER OF 2000 J/KG WITHIN AN  
OTHERWISE VERY STRONGLY SHEARED ENVIRONMENT. THIS PRE-FRONTAL  
CONVECTION SHOULD THEN EXPAND IN AREAL COVERAGE DOWNSTREAM ACROSS  
IND/KY BEFORE DEVELOPING SWWD ALONG THE WIND SHIFT ACROSS TN INTO  
NRN AL/MS.  
  
AFTER THE INITIAL WARM ADVECTION CONVECTION ACROSS THE MID MS/OH  
VALLEY REGION...THE PRIMARY FOCUS WILL BE WITH ACTIVITY THAT EVOLVES  
AFTER 18Z AHEAD OF COLD FRONT. WITH QUITE STEEP LAPSE RATES IN  
PLACE...ENVIRONMENTAL CONDITIONS FAVOR LARGE HAIL IN ADDITION TO  
POSSIBLY STRONG TORNADOES WITH ANY DISCRETE SUPERCELLS THAT FORM  
ACROSS THE MOIST WARM SECTOR. WITH TIME A DAMAGING SQUALL LINE  
COULD EMERGE WITH VERY STRONG WINDS.  
   
..GULF STATES  
  
DURING THE OVERNIGHT HOURS IT APPEARS THE TRAILING COLD FRONT WILL  
BECOME VERY ACTIVE CONVECTIVE-WISE AS WIND SHIFT ENCOUNTERS MORE  
SIGNIFICANT MOISTURE/INSTABILITY ACROSS THE TN VALLEY/GULF STATES.  
SHEAR PROFILES ACROSS THIS REGION ALSO FAVOR SUPERCELLS...THOUGH  
FRONTAL CONVERGENCE COULD CERTAINLY ENHANCE THE PROSPECT FOR  
MULTIPLE LINE SEGMENTS.  
   
..LOWER MI  
  
WITH THE SFC LOW EXPECTED TO DEEPEN SIGNIFICANTLY OVER LOWER MI  
AFTER 00Z THERE IS SOME CONCERN THAT A STRONGLY FORCED BAND OF LOW  
TOPPED SEVERE THUNDERSTORMS COULD PRODUCE DAMAGING WINDS. MODELS  
SUGGEST ONLY MEAGER MOISTURE WILL ADVECT INTO THIS REGION AHEAD OF  
COLD FRONT BUT WITH INTENSE FORCING IT/S ENTIRELY POSSIBLE THAT A  
SEVERE SQUALL LINE COULD EXTEND INTO SERN LOWER MI DURING THE  
EVENING HOURS.  
  
..DARROW/SMITH.. 03/02/2012