February 5-6: Super Tuesday Outbreak... 57 dead

[HarlequinBoy]

Memphis Afternoon Disco Snippet
BY MONDAY THE FRONT WILL BE NORTH OF THE REGION WITH THE MID SOUTH
SOLIDLY IN THE WARM SECTOR. EXPECT VERY WARM...PERHAPS NEAR RECORD
TEMPERATURES...MONDAY AFTERNOON. SURFACE DEWPOINTS WILL CLIMB
ABOVE 60 DEGREES UNDER PERSISTENT SOUTHERLY FLOW.

A STRONG UPPER LEVEL TROF AND ASSOCIATED COLD FRONT WILL MOVE INTO
THE REGION ON TUESDAY. THE AIRMASS ACROSS THE MID SOUTH WILL
BECOME UNSTABLE WITH CAPES NEAR 1000 J/KG AND LIFTED INDICES OF
-2C TO -4C. WIND FIELDS ALOFT LOOK IMPRESSIVE AS WELL WITH
SIGNIFICANT DIRECTIONAL AND SPEED SHEAR. 0-3KM HELICITY VALUES ARE
FORECAST TO CLIMB ABOVE 300 M2/S2 WITH 850 MB WINDS OF 60 KTS AND
500 MB WINDS ABOVE 80 KTS. OF COURSE TUESDAY IS STILL 4 DAYS AWAY
AND THE TIMING AND STRENGTH OF THE SYSTEM CAN CHANGE BUT AT THIS
TIME THE INGREDIENTS LOOK TO BE LINING UP FOR A SIGNIFICANT SEVERE
WEATHER OUTBREAK.

Jackson HWO
.DAYS TWO THROUGH SEVEN...SATURDAY NIGHT THROUGH THURSDAY

A VERY ACTIVE WEATHER PATTERN WILL BEGIN SUNDAY AND PERSIST THROUGH
TUESDAY AS A SERIES OF UPPER LEVEL DISTURBANCES INTERACT WITH
INCREASING LOW-LEVEL WARMTH AND MOISTURE.

STRONG THUNDERSTORMS AND HEAVY RAIN ARE EXPECTED TO DEVELOP SUNDAY
AND CONTINUE THROUGH SUNDAY NIGHT...ESPECIALLY ALONG AND NORTHWEST
OF THE NATCHEZ TRACE. LOCAL AREAS COULD RECEIVE UP TO THREE INCHES OF
RAINFALL...THUS RAISING CONCERNS FOR LOCALIZED FLOODING. THE RISK FOR
SEVERE WEATHER...INCLUDING DAMAGING WINDS...MAY INCREASE SUNDAY
AFTERNOON AND SUNDAY NIGHT OVER SOUTHWEST PORTIONS OF THE AREA...
ESPECIALLY IN THE AREA SOUTH OF INTERSTATE 20 AND WEST OF INTERSTATE
55.

A GREATER RISK FOR SEVERE THUNDERSTORMS EXISTS TUESDAY WHEN A STRONG
COLD FRONT IS FORECAST TO SWEEP ACROSS THE AREA. THE HIGH DEGREE OF
INSTABILITY AND WIND SHEAR EXPECTED AHEAD OF THE COLD FRONT SUGGESTS
THAT AN OUTBREAK OF SEVERE WEATHER IS POSSIBLE OVER THE ENTIRE
OUTLOOK AREA TUESDAY.

PERSONS IN THE OUTLOOK AREA SHOULD MONITOR LATER FORECASTS AND
OUTLOOKS CONCERNING THE SEVERE WEATHER AND HEAVY RAIN POTENTIAL FOR
EARLY NEXT WEEK.

[Ed Mahmoud]

Snip from HGX, sounds like they expect a repeat of yesterday here, with had some borderline severe hail just North of HOU, but the line came through at the coolest/most stable time of day, and wasn't all that bad.

MODERATE CONFIDENCE THAT...WITH 250 JET PARALLELING THE COAST...A
SERIES OF DISTURBANCES RIDING IN ON PREDOMINANTLY W-SW MID TO
UPPER LEVEL WINDS...SHOWERS WILL BEGIN UNDER 800-750MB CAP IN THE
EARLY SUNDAY HOURS. BANKING ON THE SYNOPTIC FLOW PATTERN OF WEAK
H5 TROF ON SUNDAY TRANSITIONING TO A DEEPENING SOUTHWESTERN TROF
MONDAY...NOT ONLY FOR INCREASING POPS...BUT FOR TEMPERATURES AS
FORECAST IS FOR UNSEASONABLE WARMTH OVER THE NEXT FEW DAYS. A
A QUICK LOOK AT THE UPSTREAM W/V IMAGERY DEFINITELY SUPPORTS THIS
PATTERN. THERE IS AN AMPLE AMOUNT OF COOLER GULF OF ALASKA AIR
AGGRESSIVELY DIVING DOWN TOWARDS THE LEFT COAST. OR...HAVE NO
REASON TO DOUBT THE AGREEMENT BETWEEN THE GFS/NMA/EURO SOLUTIONS
OF CARVING OUT A NICE WESTERN US TROF TO CLOSE OUT THE WEEKEND.

MONDAY`S RAIN CHANCES WILL BE HIGHLY DEPENDENT UPON VORT MAX
TIMING SO HAVE BLANKETED CHANCE POPS DURING DAY 3. PROGRESSIVE
NATURE OF EJECTING H5 TROF OVER TEXAS ON TUESDAY...DRAGGING THE
ASSOCIATED COLD FRONT ON THROUGH DURING TUESDAY AFTERNOON...WILL
MOST LIKELY SET UP A DAY AS WE EXPERIENCED YESTERDAY. DRIZZLE
WITH INTERMITTENT SHOWERS WITHIN THE WAA AHEAD OF TUESDAY`S
BOUNDARY...WITH AREAS OF WIDESPREAD FOG DUE TO MIDDLE 60 DEW POINT
AIR OVER RELATIVELY COOLER SHELF WATERS IN THE LOWER 50S...WILL
PRECEDE EVENTUAL EARLY TUESDAY THUNDER. GFS SOUNDING INDICES SUPPORT
EARLY TUESDAY STORMINESS AS THE MAIN CF PASSES ACROSS THE CWA. A
MORE PACIFIC-BASED AIR MASS SPREADING OVER REGION EARLY WEDNESDAY
WILL MODERATE TEMPERATURES AND WINDS AS HIGH BUILDS DOWN MID
WEDNESDAY.

[Ed Mahmoud]

Impressive looking trough per 0Z WRF, but affecting SE Texas at the most stable time of day. Should be interesting towards Mississippi, especially with greater time for return flow to bring back warmth and humidity.



MU CAPE over a 1000 J/Kg, and plenty of shear, per WRF, for Houston area, even that early. Might be an interesting Fat Tuesday towards NOLA if the trend continues.

[HarlequinBoy]

This year has certainly started with a bang already severe weather wise, and next week looks likely to continue the streak.

[CrazyC83]

I wonder if the weather Gods want their own Mardi Gras event - that being of severe weather and tornadoes?

This year is definitely off to a fast start - it took until March 23 to get as many tornado reports as we have had so far this year...and some years have taken much longer than that...

[RL3AO]

...DISCUSSION...
GFS AND ECMWF NOW IN REMARKABLE AGREEMENT WITH THEIR DEPICTIONS OF
MAJOR FEATURES DAY 4 /TUESDAY FEB. 5/ -- BOTH AT THE SURFACE AND
ALOFT. BOTH MODELS FORECAST A STRONG COLD FRONT TO MOVE ACROSS THE
MS/LOWER OH/TN VALLEYS BY LATE AFTERNOON/EARLY EVENING...AND THEN ON
EWD ACROSS THE APPALACHIANS BY THE END OF DAY 4 AS SURFACE LOW
DEEPENS NEWD INTO THE LOWER GREAT LAKES REGION.

WITH A SURFACE "BERMUDA"-TYPE HIGH FORECAST TO PERSIST...NWD RETURN
OF GULF MOISTURE IS EXPECTED AHEAD OF THE FRONT...AS FAR N AS THE OH
VALLEY BY TUESDAY AFTERNOON. THIS SUGGESTS AMPLE INSTABILITY FOR
STORM DEVELOPMENT...AND ATTM IT APPEARS THAT STORMS SHOULD EVOLVE
INTO AN ORGANIZED LINE DURING THE SECOND HALF OF THE DAY 4 PERIOD.

ALONG WITH WHAT SHOULD BE AMPLE INSTABILITY...VERY STRONG DEEP-LAYER
WIND FIELD WILL ACCOMPANY THIS SYSTEM...WITH 80 KT SWLY MID-LEVEL
FLOW CURRENTLY FORECAST TO SPREAD ACROSS THE SURFACE FRONTAL ZONE.
THUS...IT APPEARS THAT THE POTENTIAL EXISTS FOR ANOTHER WIDESPREAD
DAMAGING WIND EVENT CENTERED OVER THE TN/OH VALLEYS.

Also have a day 3 slgt, mainly over Arkansas.

[MiamiensisWx]

This one looks like another potentially big event...

The new 12Z GFS looks absolutely perfect for discrete supercellular formation... a strong 582 dm ridge (500 mb) builds further west over the Bahamas and FL, while the secondary low develops over OK. The slow trend toward a consolidated trough is perfect - this means that there will be less lift over the northern Gulf, especially with the dry slot moving through the area. The moisture return would be uncontaminated by NGOM convection. The Euro shows an impressively large area of +30 m/s winds at 850 mb.

Very large warm sector...

[Squarethecircle]

Anyone want to hazard that this might approach or surpass the early January event?

[RL3AO]

MODELS CONTINUE TO INDICATE THE POTENTIAL FOR A SIGNIFICANT
SEVERE WEATHER OUTBREAK TUESDAY...POSSIBLY BEGINNING LATE MONDAY
NIGHT WEST OF THE MS RIVER. THE STRONG UPPER LEVEL TROUGH WILL
APPROACH THE MID-SOUTH TUESDAY WITH A STRONG COLD FRONT MOVING
INTO THE AREA. STRONG SOUTH WINDS...INCREASING MOISTURE AND
INSTABILITY...AND STRONG UPPER LEVEL DYNAMICS ARE ALL INDICATED.
SURFACE DEWPOINTS ARE EXPECTED TO CLIMB INTO THE LOWER AND MID 60S
AHEAD OF THE FRONT. 850 MB SOUTHERLY WINDS ARE FORECAST TO NEAR 60
KTS WITH 500 MB WINDS OF 75 KTS. SPEED AND DIRECTIONAL WIND SHEAR
ARE VERY GOOD WITH LOW LEVEL HELICITY VALUES IN EXCESS OF 300 M2/S2.
LIFTED INDICES ARE FORECAST BETWEEN MINUS 2 AND MINUS 4. A SQUALL
LINE IS EXPECTED TO DEVELOP JUST AHEAD OF THE FRONT WITH DAMAGING
WINDS. - Memphis AFD

They also mentioned CAPEs of 1000+.

[CrazyC83]

It does suggest though that this may be more of a squall line-derecho event, but that depends on shear patterns...

[CrazyC83]

This one looks like another potentially big event...

The new 12Z GFS looks absolutely perfect for discrete supercellular formation... a strong 582 dm ridge (500 mb) builds further west over the Bahamas and FL, while the secondary low develops over OK. The slow trend toward a consolidated trough is perfect - this means that there will be less lift over the northern Gulf, especially with the dry slot moving through the area. The moisture return would be uncontaminated by NGOM convection. The Euro shows an impressively large area of +30 m/s winds at 850 mb.

Very large warm sector...

That is a change from the SPC forecast...and all the way to the Great Lakes too, this could be huge! Super Tuesday in more ways than one?

Also, if there is a major tornado outbreak, it could be super-historical as it could very well impact the Presidential election by changing turnout patterns!

[brunota2003]

What about us peoples further east? Eastern NC was in it yesterday, now we dont have squat.

[Ed Mahmoud]

As a fan of watching big storms out the window at work (as compared to sleeping through them, or driving in them) I hope the 18Z WRF trend of slowing the system just a tad is right, both because line doesn't pass at coolest time of day, and I'm awake and not driving.






I hope a pro-met visits and offers a scientific opinion on whether this is a squall line event with straight line winds as the main mode of severe, or whether discrete supercells will form ahead of the front.

[Squarethecircle]

I'd suppose both will at least happen, but I would like to discern which is more likely to be the dominant effect as well.

Pro-mets? Care to inform us?

[MiamiensisWx]

Cells will likely be discrete because of 1) the low's motion and 2) the lack of linear forcing. If shear is too strong while surface winds are backed ("backed" implies westerly winds), the discrete supercells would eventually evolve into a broken or continuous squall line. Squall lines would also reduce instability ahead of the surface boundary, thus reducing the tornado threat. In this case, there is a large warm sector with decent THETA-E ahead of the boundary. The progged 500 mb ridge juxtaposition and consolidated trough also ensures adequate low-level moisture return. A large dry slot would also cap convection (in addition to less lift) over the northern Gulf, which allows an uncontaminated "return flow" and higher 12-hour maximum temps well into the Mississippi Valley. Winds will likely be veered (S or SSE) in this case, which also heightens the threat. Even closer to the low, the lack of linear forcing would likely support strong discrete cells with backed (WSW) winds.

THETA-E link:

http://www.theweatherprediction.com/habyhints/324/

Linear forcing:

http://meetings.aps.org/Meeting/DFD05/Event/36922

[CrazyC83]

Is it possible that the SPC could go wild and go MDT for Day 3 tomorrow?

[RL3AO]

Is it possible that the SPC could go wild and go MDT for Day 3 tomorrow?

I very highly doubt it. Day 2 MDT wouldn't shock me though.

[wbug1]

Uh-oh. I don't know much about atmospheric dynamics, but with temperatures that high Feb 5th (what is it, april?) followed by a cold front dropping temps 25-35 F looks like a great setup for severe weather.

[icicle]

from memphis.

A FEW
SEVERE THUNDERSTORMS ARE POSSIBLE MAINLY ALONG AND WEST OF THE MS
RIVER...MONDAY AFTERNOON INTO MONDAY NIGHT. DAMAGING WINDS AND
LARGE HAIL WILL BE THE GREATEST THREAT WITH THESE
STORMS...ALTHOUGH AN ISOLATED TORNADO CAN NOT BE RULED OUT WITH
STRONG DEEP-LAYER SPEED AND DIRECTIONAL SHEAR.

THE MORE SIGNIFICANT EMPHASIS FOR SEVERE WEATHER COMES TUESDAY.
MODELS CONTINUE TO INDICATE A WIDESPREAD SEVERE THUNDERSTORM
OUTBREAK IS POSSIBLE TUESDAY...IF ANYTHING...THE LATEST MODELS ARE
EVEN MORE IMPRESSIVE. DAMAGING WINDS AND LARGE HAIL ARE POSSIBLE
TUESDAY ALONG WITH THE THREAT OF TORNADOES. THE STRONG UPPER LEVEL
TROUGH WILL APPROACH THE MID-SOUTH TUESDAY WITH INCREASING SOUTH
TO SOUTHWEST WINDS AT THE SURFACE AND ALOFT. A DEEPENING SURFACE
LOW OF 998 MB IS FORECAST BY THE GFS OVER NORTH-CENTRAL AR AT NOON
TUESDAY WITH A SOUTHWARD TRAILING COLD FRONT. GRADIENT WINDS WILL
BE FROM THE SOUTH AROUND 25 MPH WITH GUSTS TO NEAR 40 MPH
TUESDAY...AND A WIND ADVISORY WILL PROBABLY BE NEEDED. THIS WILL
ALLOW SURFACE DEWPOINTS TO SURGE INTO THE LOWER AND MID 60S AHEAD
OF THE FRONT WITH TEMPERATURES CLIMBING INTO THE LOWER AND MID
70S. THE RIGHT ENTRANCE REGION OF A STRONG UPPER LEVEL JET OF 120
KTS WILL MOVE INTO THE MID-SOUTH DURING THE DAY WITH 850 MB SOUTH-
SOUTHWESTERLY FLOW OF 60 KTS. MIXED LAYER MOST UNSTABLE CAPES ARE
FORECAST TO REACH BETWEEN 1000 AND 1500 J/KG ACROSS PARTS OF THE
AREA...AND THIS COULD ACTUALLY BE HIGHER AS THE GFS OFTEN SEEM TO
UNDERESTIMATE THE CAPE. 0-1 KM HELICITY IS FORECAST NEAR 325 M2/S2
WITH GOOD LOW LEVEL DIRECTIONAL SHEAR. IN ADDITION...A MID-LEVEL
DRY SURGE IS FORECAST TO ADVECT INTO THE AREA BEHIND THE COLD
FRONT. AS A RESULT OF ALL THESE INGREDIENTS...DISCRETE SUPERCELLS
ARE POSSIBLE DURING THE DAY TUESDAY AHEAD OF THE COLD FRONT WITH
A TORNADO THREAT...IF ENOUGH INSTABILITY IS REALIZED. AN INTENSE
SQUALL LINE IS FORECAST TO EVENTUALLY DEVELOP JUST AHEAD OF THE
COLD FRONT TUESDAY WITH DAMAGING WINDS...LARGE HAIL...AND ISOLATED
TORNADOES A THREAT ALONG THIS LINE.

[Ed Mahmoud]

Moderate for Tuesday issued tomorrow?




Relevant snip of SWODY3

...LA/AR/SERN MO/OH VALLEY EWD TO THE APPALACHIANS...
WIDESPREAD SEVERE WEATHER EVENT -- INCLUDING DAMAGING WINDS AND THE
POTENTIAL FOR TORNADOES -- IS ANTICIPATED ACROSS A LARGE PART OF
THIS REGION.

STORMS SHOULD BE ONGOING ACROSS WRN PORTIONS OF THIS AREA AT THE
START OF THE PERIOD...WHILE SLY FLOW ACROSS THE WARM SECTOR
MAINTAINS A MOIST BOUNDARY LAYER /SURFACE DEWPOINTS APPROACHING 60
AS FAR N AS THE LOWER AND MIDDLE OH RIVER VALLEY/. WHILE STORMS ARE
FORECAST WITHIN BROAD ZONE OF WARM ADVECTION WELL AHEAD OF THE
FRONT...GREATEST SEVERE POTENTIAL IS FORECAST CLOSER TO THE
IMMEDIATE COLD FRONT AS IT ADVANCES EWD. WITH TIME...EXPECT A
SQUALL LINE TO DEVELOP ALONG THIS FRONT...AND THEN CONTINUE EWD
THROUGH THE AFTERNOON AND INTO THE EVENING.

WHILE STRONG/DAMAGING WINDS ARE EXPECTED TO BE THE MAIN SEVERE
THREAT...LOW-LEVEL WINDS VEERING/INCREASING WITH HEIGHT WILL LIKELY
RESULT IN LOW-LEVEL ROTATION -- BOTH WITHIN SMALL-SCALE BOWS ALONG
THE LARGER CONVECTIVE LINE AS WELL AS WITH ANY STRONGER CELLS AHEAD
OF THE MAIN LINE. THEREFORE...TORNADOES ARE ALSO ANTICIPATED --
WITH THE POTENTIAL SPREAD ACROSS A BROAD ZONE FROM THE GULF COAST
NWD ACROSS THE TN VALLEY AND PERHAPS INTO THE OH VALLEY.

WHILE SEVERE THREAT SHOULD DIMINISH SOMEWHAT INTO THE UPPER OH
VALLEY AS FRONT APPROACHES AFTER DARK...GREATER INSTABILITY ACROSS
THE MID SOUTH AND GULF COAST REGIONS MAY SUPPORT A PERSISTENT SEVERE
THREAT THROUGH THE END OF THE PERIOD.