Severe Weather February 21-23

[TropicalAnalystwx13]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0338 AM CST THU FEB 14 2013

VALID 171200Z - 221200Z

...DISCUSSION...
BOTH THE GFS AND ECMWF AGREE THAT SRN STREAM MID LEVEL SPEED MAX
WILL EJECT ACROSS NRN MEXICO INTO SCNTRL TX MONDAY AS NRN STREAM
SHORT-WAVE UNIFIES WITH THIS FEATURE OVER THE MS VALLEY. THIS
STRONG SYSTEM WILL LIKELY INDUCE CONVECTION AS IT INTERACTS WITH
MOIST/WEAKLY BUOYANT AIRMASS OVER EAST TX...THEN ACROSS THE CNTRL
GULF STATES TUESDAY. HOWEVER...WEAK INSTABILITY SHOULD PRECLUDE
WIDESPREAD SIGNIFICANT SEVERE WITH THIS SYSTEM.

LATER IN THE WEEK A POTENTIALLY MORE SIGNIFICANT CONVECTIVE EVENT
MAY UNFOLD FROM EAST TX INTO THE LOWER MS VALLEY AS 100KT+ MID LEVEL
SPEED MAX APPROACHES WHAT SHOULD BE A MORE MOIST/BUOYANT
ENVIRONMENT. IF UPPER 60S SFC DEW POINTS MANAGE TO ADVANCE
SUBSTANTIALLY INLAND AN ORGANIZED SEVERE SCENARIO MAY UNFOLD DURING
THE DAY8 PERIOD. WILL NOT INTRODUCE 30 PERCENT SEVERE PROBS GIVEN
THE POSSIBILITY THIS SYSTEM MAY SLOW ENOUGH THAT THE MAIN THREAT
COULD BE BEYOND THE MEDIUM RANGE PERIOD.

[RL3AO]

If thats not a classic early March looking setup, I don't know what is.

[Ntxw]

Agree this looks like one of those high end moderate risks that are seen days in advance by the spc

[TropicalAnalystwx13]

I'd like to say that the GFS has officially went insane.

60F dewpoints, low-level wind shear OVER 70 knots, a 100 knot mid-level jet streak, and ESRH values over 1100 m2/s2.

[Cyclenall]

I'd like to say that the GFS has officially went insane.

60F dewpoints, low-level wind shear OVER 70 knots, a 100 knot mid-level jet streak, and ESRH values over 1100 m2/s2.

I'm officially excited. I'm already getting that tingling feeling.

[TropicalAnalystwx13]

I'd like to say that the GFS has officially went insane.

60F dewpoints, low-level wind shear OVER 70 knots, a 100 knot mid-level jet streak, and ESRH values over 1100 m2/s2.

I'm officially excited. I'm already getting that tingling feeling.

I refuse to get excited for an event before the day of that particular event because it typically ends up changing just to taunt me.

Still eight days out...but there is surprisingly good model consistency. ECMWF has the same general setup with a low situated farther north.

[cycloneye]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0357 AM CST FRI FEB 15 2013

VALID 181200Z - 231200Z

...DISCUSSION...
AFTER SEVERAL DAYS OF DRYING NORTHWESTERLY LOW-LEVEL FLOW...A
GRADUAL MODIFICATION OF THE BOUNDARY LAYER OVER THE GULF OF MEXICO
APPEARS LIKELY TO COMMENCE EARLY NEXT WEEK...AS A SERIES OF
SIGNIFICANT SHORT WAVE TROUGHS BEGIN TO PROGRESS ACROSS THE NATION.
AN INITIAL IMPULSE PROGRESSING EAST OF THE ROCKIES LATE THIS COMING
WEEKEND...APPEARS LIKELY TO REACH THE PLAINS/MISSISSIPPI VALLEY
REGION TOO SOON...AND TOO FAR NORTH...FOR A SUBSTANTIVE RETURN FLOW
OF MOISTURE TO DEVELOP AND CONTRIBUTE TO AN APPRECIABLE RISK FOR
SEVERE THUNDERSTORMS. HOWEVER...MEDIUM RANGE FORECAST MODELS HAVE
BEEN FAIRLY CONSISTENT FOR SEVERAL DAYS NOW...SUGGESTING THAT THE
STRONG UPSTREAM IMPULSE WILL DIG INTO THE SOUTHERN GREAT
BASIN...BEFORE LIFTING EAST NORTHEASTWARD ACROSS THE CENTRAL AND
SOUTHERN ROCKIES/PLAINS AND MIDDLE MISSISSIPPI VALLEY DURING THE
MIDDLE TO LATTER PORTION OF NEXT WEEKEND. AT THIS POINT...TIMING
INTO THE PLAINS WEDNESDAY NIGHT...AS MORE FAVORABLE INLAND MOISTURE
RETURN BEGINS TO OCCUR OFF THE WESTERN GULF OF MEXICO...DOES NOT
APPEAR OPTIMAL FOR SEVERE WEATHER POTENTIAL. BUT...BY THURSDAY...AT
LEAST ON THE SOUTHERN FRINGE OF STRONGER HIGH-LEVEL DIFLUENCE AND
MID-LEVEL HEIGHT FALLS...THERE APPEARS A GOOD LIKELIHOOD THAT
LARGE-SCALE FORCING FOR UPWARD VERTICAL MOTION AND BOUNDARY LAYER
DESTABILIZATION WILL BECOME FAVORABLY JUXTAPOSED TO SUPPORT THE RISK
FOR SEVERE STORMS...INCLUDING POTENTIAL FOR AT LEAST ISOLATED
TORNADOES.

..KERR.. 02/15/2013

[WeatherGuesser]

I'm officially excited. I'm already getting that tingling feeling.

Always bothers me when people get 'excited' over people possibly dying or having their homes or businesses destroyed.

[cycloneye]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0354 AM CST SAT FEB 16 2013

VALID 191200Z - 241200Z

...DISCUSSION...
THE LATEST MEDIUM RANGE MODELS AND MODEL ENSEMBLES REMAIN FAIRLY
CONSISTENT WITH RUNS OVER THE PAST SEVERAL DAYS...PARTICULARLY WITH
REGARD TO A STRONG SHORT WAVE IMPULSE THAT APPEARS LIKELY TO DIG
INTO THE CALIFORNIA COAST EARLY NEXT WEEK. A DEEP MID-LEVEL CLOSED
LOW MAY EVOLVE AS THE IMPULSE MIGRATES INLAND...BUT IT IS EXPECTED
TO REMAIN PROGRESSIVE...AS ANOTHER IMPULSE EMERGES FROM THE STRONG
UPSTREAM MID-LATITUDE PACIFIC JET...AND APPROACHES THE PACIFIC
NORTHWEST COAST BY MID WEEK.

IN ASSOCIATION WITH THE LEAD SYSTEM...WHICH STILL APPEARS LIKELY TO
LIFT EAST NORTHEAST OF THE SOUTHERN ROCKIES THROUGH THE CENTRAL
PLAINS/MID MISSOURI VALLEY REGION LATE WEDNESDAY NIGHT THROUGH EARLY
THURSDAY EVENING...SIGNIFICANT SURFACE CYCLOGENESIS APPEARS LIKELY
ACROSS THE CENTRAL PLAINS. THIS MAY BE ACCOMPANIED BY INCREASING
CONVECTIVE POTENTIAL...INCLUDING AT LEAST SOME RISK FOR SEVERE
STORMS...ACROSS PARTS OF THE CENTRAL AND SOUTHERN PLAINS LATE
WEDNESDAY/WEDNESDAY NIGHT. HOWEVER...IT STILL APPEARS MOST PROBABLE
THAT SEVERE WEATHER POTENTIAL WITH THIS SYSTEM WILL BECOME MAXIMIZED
ON THURSDAY...AS DAYTIME HEATING CONTRIBUTES TO
DESTABILIZATION...AND RETURN FLOW CONTINUES OFF AN INCREASINGLY
MOIST BOUNDARY LAYER OVER THE GULF OF MEXICO.

AS THIS MOISTURE OVERRUNS A RESIDUAL COOL/STABLE BOUNDARY LAYER
LINGERING OVER PARTS OF THE LOWER MISSISSIPPI VALLEY AND SOUTHEAST
...THE MOIST/UNSTABLE WARM SECTOR BOUNDARY LAYER MAY NOT BECOME
PARTICULARLY BROAD. BUT IT IS EXPECTED TO BECOME SIZABLE ENOUGH TO
SUPPORT A SIGNIFICANT RISK FOR SEVERE STORMS...AT LEAST ON THE
SOUTHERN FRINGE ON THE MORE STRONGLY DIFLUENT HIGH-LEVEL FLOW... AND
MID-LEVEL HEIGHT FALLS...ACROSS THE LOWER MISSISSIPPI VALLEY
THURSDAY AFTERNOON AND EVENING. THIS MAY INCLUDE THE RISK FOR
SUPERCELLS WITH A FEW TORNADOES.

..KERR.. 02/16/2013

[TropicalAnalystwx13]

Ouch.

[cycloneye]

Update by SPC for day 5.

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0347 AM CST SUN FEB 17 2013

VALID 201200Z - 251200Z

...DISCUSSION...
THE LATEST MEDIUM RANGE FORECAST GUIDANCE MAINTAINS GENERAL TRENDS
OF THE PAST SEVERAL DAYS CONCERNING A MAJOR UPPER TROUGH AND
ASSOCIATED STRONG JET STREAK THAT APPEAR LIKELY TO EMERGE FROM THE
SOUTHWESTERN U.S. BY THE MIDDLE OF THE COMING WORK WEEK. THE TROUGH
AXIS STILL APPEARS LIKELY TO TAKE ON A NEGATIVE TILT AS IT
PROGRESSES ACROSS THE SOUTHERN ROCKIES INTO THE CENTRAL AND SOUTHERN
PLAINS BY 12Z THURSDAY...BEFORE LIFTING NORTHEASTWARD AND
DEAMPLIFYING ACROSS THE UPPER MIDWEST ON FRIDAY. PRIMARY SURFACE
CYCLOGENESIS IS EXPECTED ACROSS EASTERN COLORADO INTO WESTERN
KANSAS...BUT MODELS INDICATE SECONDARY WAVE DEVELOPMENT FROM PARTS
OF NORTHWEST INTO EASTERN TEXAS WEDNESDAY NIGHT. THIS MAY
EVENTUALLY BECOME THE FOCUS FOR AN EVOLVING SQUALL LINE...AND
INCREASING SEVERE WEATHER POTENTIAL...AS FORCING ENCOUNTERS BETTER
MOISTURE RETURN OFF THE GULF OF MEXICO. HIGHEST SEVERE
PROBABILITIES STILL APPEAR TO EXIST ON THURSDAY...AS THE WAVE AND
ASSOCIATED SQUALL LINE DEVELOP EASTWARD ALONG A WARM FRONT ACROSS
THE LOWER MISSISSIPPI VALLEY. SURFACE DEW POINTS IN THE WARM SECTOR
OF THE WAVE MAY REACH THE MID 60S ACROSS PARTS OF SOUTHEAST TEXAS
INTO SOUTHERN LOUISIANA AND MISSISSIPPI. ASSOCIATED BOUNDARY LAYER
DESTABILIZATION ON THE SOUTHERN PERIPHERY OF THE DIFLUENT HIGH LEVEL
FLOW AND MID-LEVEL HEIGHT FALLS COULD BECOME SUPPORTIVE OF DISCRETE
SUPERCELLS NEAR/AHEAD OF THE SQUALL LINE... WITH A RISK FOR
TORNADOES...IN ADDITION TO DAMAGING WIND GUSTS.

[TropicalAnalystwx13]

Overall, Thursday's event looks less significant. The warm sector is very narrow, leading to skinny CAPE. The brunt of the mid-level energy and support will be passing to the northwest the main severe area. Tomorrow's disturbance will also take away moisture and hamper return flow later in the week.

Overall, this looks to be a general event with a few tornadoes and quite a bit of hail/wind reports.

[MississippiWx]

Models always underestimate instability this far in advance. I would expect it to increase as we get closer. This could be a significant event, and possibly affect us here in Hattiesburg again.

[TropicalAnalystwx13]

Models continue to indicate a stable atmosphere for Thursday across Louisiana and Mississippi. While isolated severe weather is still possible, saturated soundings and poor lapse rate suggest more of a heavy rainfall event than anything else.

HOWEVER, if we can get a supercell to develop, it has good potential to produce a strong tornado given phenomenal wind shear.



...DISCUSSION...
MEDIUM RANGE MODELS INDICATE THAT BROAD UPPER TROUGHING WILL PERSIST
WITHIN ONE BRANCH OF A SPLIT UPPER FLOW CURVING INLAND ACROSS THE
PACIFIC COAST INTO THE PLAINS/MISSISSIPPI VALLEY THROUGH MUCH OF
THIS FORECAST PERIOD. GUIDANCE HAS BEEN CONSISTENT CONCERNING THE
FIRST IMPULSE WITHIN THIS REGIME...A VERY STRONG SHORT WAVE TROUGH
FORECAST TO PROGRESS EAST OF THE SOUTHERN ROCKIES IN NEGATIVELY
TILTED FASHION LATE WEDNESDAY NIGHT ...BEFORE LIFTING NORTHEASTWARD
TOWARD THE UPPER MIDWEST THURSDAY AND THURSDAY NIGHT. STRONGEST
MID-LEVEL FORCING WITH THIS FEATURE PROBABLY WILL REMAIN WELL TO THE
NORTH AND WEST OF THE BETTER GULF RETURN FLOW. HOWEVER...IT STILL
APPEARS THAT AN INFLUX OF MOISTURE...CHARACTERIZED BY PRECIPITABLE
WATER UP TO 1.5 INCHES AND MID 60S SURFACE DEW POINTS...WILL
CONTRIBUTE TO SEVERE WEATHER POTENTIAL...AT LEAST IN A CORRIDOR
ACROSS PARTS OF SOUTHEAST TEXAS THROUGH THE LOWER MISSISSIPPI
VALLEY. THIS AREA IS EXPECTED TO BE OVERSPREAD BY DIFLUENT UPPER
FLOW...JUST NORTH OF THE SUBTROPICAL JET AXIS...ALONG THE TRACK OF A
SECONDARY SURFACE FRONTAL WAVE... WHERE A WINDOW OF OPPORTUNITY WILL
EXIST FOR BOUNDARY LAYER DESTABILIZATION AND VERTICAL SHEAR TO
SUPPORT SQUALL LINE AND SUPERCELL DEVELOPMENT. CONDITIONAL ON THE
DEGREE OF BOUNDARY LAYER INSTABILITY...THIS MAY INCLUDE THE RISK FOR
AN ISOLATED STRONG TORNADO OR TWO...ALONG WITH THE POTENTIAL FOR
DAMAGING THUNDERSTORM WIND GUSTS.

THEREAFTER...IT APPEARS ANOTHER VIGOROUS IMPULSE MAY PROGRESS
THROUGH THE UPPER TROUGH AND CONTRIBUTE TO STRONG SURFACE
CYCLOGENESIS EAST OF THE CENTRAL AND SOUTHERN ROCKIES LATE NEXT
WEEKEND INTO EARLY NEXT WEEK. HOWEVER...THE SPREAD AMONG THE MODELS
AND MODEL ENSEMBLES IS TOO LARGE WITH THIS SYSTEM TO ASCERTAIN THE
POTENTIAL FOR A REGIONAL SEVERE WEATHER EVENT.

..KERR.. 02/18/2013

[TropicalAnalystwx13]

After disagreeing since the Day 8 Outlook...Kerr and I have come into agreement regarding Thursday. The NAM has trended towards slightly more instability despite a very spatially challenged warm sector. Extremely favorable wind shear and a less stable atmosphere than previously thought, coupled with marginal lapse rates should allow the development of supercells across central Louisiana Thursday afternoon. With low-level shear near 60 knots from the south and mid-level shear near 60-70 knots from the southwest, conditions will be favorable for rotating storms. In addition, with large, looping hodographs and Effective Storm Relative Helicity values (both at 0-1km and 0-3km) over 450 m2/s2, there is a good chance we see a few strong to significant tornadoes. Thermodynamics are not all that indifferent to the system that eventually spawned the EF4 Hattiesburg tornado.

[WeatherGuesser]

SPC isn't exactly jumping up and down over this so far.

[BigB0882]

Is it ok to start this thread? Could be something to watch over the next couple of days:

[cycloneye]

Is it ok to start this thread? Could be something to watch over the next couple of days:

I merged your thread with this one to only have one thread about this event.

[cycloneye]

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1024 AM CST THU FEB 21 2013

VALID 211630Z - 221200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF EAST TX...MUCH OF
LA...AND SOUTHERN MS...

...LOWER MS VALLEY...
A STRONG UPPER TROUGH IS ROTATING ACROSS THE SOUTHERN PLAINS THIS
MORNING...RESULTING IN WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY
FROM MO SOUTHWARD INTO PARTS OF TX/LA/MS. MOST OF THIS CONVECTION
IS OCCURRING ATOP A COLD/STABLE SURFACE ENVIRONMENT WITH LITTLE
SEVERE THREAT. HOWEVER...SUFFICIENT LOW LEVEL MOISTURE/INSTABILITY
WILL BE PRESENT OVER PARTS OF THE LOWER MS VALLEY FOR A RISK OF
SEVERE WEATHER THROUGH TONIGHT.

THE PRIMARY COLD FRONT IS SWEEPING EASTWARD ACROSS EAST TX...WITH A
WARM FRONT EXTENDING SOUTHEASTWARD AHEAD OF THE COLD FRONT FROM
SOUTH OF LFK TO SOUTH OF LCH. THE WARM FRONT IS EXPECTED TO LIFT
NORTHWARD THROUGH THE DAY...RESULTING IN RAPID MOISTENING OF THE
SURFACE LAYER OVER PARTS OF CENTRAL LA. CONSIDERABLE CLOUD COVER
WILL LIMIT HEATING...BUT FORECAST SOUNDINGS SUGGEST THE POTENTIAL
FOR SURFACE-BASED CONVECTION BY MID AFTERNOON. LARGE SCALE FORCING
FOR ASCENT IS PRIMARILY PASSING NORTH OF THIS REGION. THIS WILL
LIMIT THE COVERAGE OF INTENSE STORMS. HOWEVER...THERE WILL REMAIN A
RISK OF ISOLATED STRONG/SEVERE STORMS ACROSS THE SLIGHT RISK AREA.

LOW LEVEL SHEAR IS QUITE STRONG...PROVIDING A CONDITIONAL THREAT OF
SUPERCELLS AND ISOLATED TORNADOES TODAY. HOWEVER...THE PRIMARY
RISKS ARE LIKELY TO BE LOCALLY DAMAGING WINDS AND SOME HAIL IN THE
STRONGER CELLS.

..HART/MOSIER.. 02/21/2013

[cycloneye]

WFUS54 KLCH 211903
TORLCH
LAC003-039-211945-
/O.NEW.KLCH.TO.W.0004.130221T1903Z-130221T1945Z/

BULLETIN - EAS ACTIVATION REQUESTED
TORNADO WARNING
NATIONAL WEATHER SERVICE LAKE CHARLES LA
103 PM CST THU FEB 21 2013

THE NATIONAL WEATHER SERVICE IN LAKE CHARLES HAS ISSUED A

* TORNADO WARNING FOR...
EVANGELINE PARISH IN CENTRAL LOUISIANA...
THIS INCLUDES...TURKEY CREEK...MAMOU...
EAST CENTRAL ALLEN PARISH IN SOUTHWEST LOUISIANA...

* UNTIL 145 PM CST

* AT 1258 PM CST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO 8 MILES SOUTH OF
BOND...MOVING NORTHEAST AT 60 MPH.

* THE TORNADO WILL BE NEAR...
REDDELL BY 110 PM CST...
PINE PRAIRIE BY 115 PM CST...
BAYOU CHICOT...TURKEY CREEK...CHICOT STATE PARK AND INDIAN LAKE BY
120 PM CST...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

NATIONAL WEATHER SERVICE RADAR INDICATES A TORNADO MAY FORM AT ANY
TIME. TAKE COVER NOW! ABANDON MOBILE HOMES AND VEHICLES. MOVE TO AN
INTERIOR ROOM OR HALLWAY ON THE LOWEST FLOOR AWAY FROM WINDOWS.

&&

PLEASE REPORT SEVERE WEATHER TO THE NATIONAL WEATHER SERVICE AT
337-477-5285 EXTENSION 1.

LAT...LON 3092 9226 3088 9224 3085 9224 3084 9221
3079 9221 3077 9218 3051 9258 3060 9268
3100 9238 3099 9236
TIME...MOT...LOC 1903Z 219DEG 55KT 3064 9255

$$

LANDRENEAU