NOLA area pm rush hour severe outbreak

[Ed Mahmoud]

Pretty good low level jet off the Gulf


Decent looking upper feature, starting to go negative tilt


Thursday January 31st SPC Outlook

[Squarethecircle]

It would be pretty disturbing to get another fairly sizable outbreak, maybe even a smallish one, again this January.

[wall_cloud]

They don't "see" an outbreak. They see the potential for one (if everything comes together for a Day 7 forecast).

----------------------------------------------

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 250851
SPC AC 250851

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 AM CST FRI JAN 25 2008

VALID 281200Z - 021200Z

...CNTRL/ERN GULF CST SVR POTENTIAL THU/THU NIGHT 31 JAN-1 FEB...
SEVERAL UPR SYSTEMS WILL EJECT ACROSS THE CONUS THROUGH THE EXTENDED
PERIOD AS THE PROGRESSIVE FLOW REGIME CONTINUES. ONE SIGNIFICANT
SYSTEM WILL TRANSLATE FROM THE WRN STATES ACROSS THE PLAINS AND INTO
THE NERN STATES IN THE MON-TUE TIME FRAME. LIMITED GULF MOISTURE
RETURN AHEAD OF THIS FEATURE WILL MAINTAIN LOW RISKS FOR A
WIDESPREAD SVR TSTM EVENT...THOUGH ISOLD SVR TSTMS COULD OCCUR
ACROSS PARTS OF THE DEEP SOUTH. COLD FRONT ASSOCD WITH THIS IMPULSE
WILL LIKELY NOT TRAVERSE APPRECIABLY FAR S INTO THE GULF BASIN.

MORE SIGNIFICANT SYSTEM...WITH FAIRLY UNANIMOUS MODEL
GUIDANCE...WILL DIG INTO THE TX BIG BEND REGION BY EARLY THU 31
JAN...THEN QUICKLY EJECT ENEWD ACROSS THE TN VLY/DEEP SOUTH BY THU
NIGHT BEFORE EXITING THE ERN SEABOARD BY NEXT WEEKEND. WAVELENGTH
BETWEEN THE AFOREMENTIONED SYSTEM AND THIS STRONG FEATURE WILL
LIKELY ALLOW MORE ROBUST LOW-LEVEL MOISTURE RETURN. AS SUCH...GIVEN
THE POTENTIAL MAGNITUDE OF THIS SYSTEM AND FAVORABLE MOISTURE
TRAJECTORIES/BOUNDARY LAYER STRUCTURES...THE THREAT FOR A HIGHER END
SVR EVENT SEEMS PSBL ON THU 31 JAN OVER PORTIONS OF THE CNTRL/ERN
GULF CSTL REGION NEWD INTO THE DEEP S/LWR TN VLY.

..RACY.. 01/25/2008

[RL3AO]

"THE THREAT FOR A HIGHER END SVR EVENT SEEMS PSBL ON THU 31 JAN".

Interesting (to me but maybe it is not unusual) for them to say "higher end" on a day 7 forecast.

[Ed Mahmoud]

70 knot LLJ off the Gulf...

Pretty deep 500 mb feature


Of course, this is 12Z on Friday, best action might occur later, which suggests the Euro has slowed a tad from the 0Z run.

18Z GFS is a bit quicker, and despite Gulf flow, is pretty weak on instability, but I have a feeling that will change as event approaches.

[wall_cloud]

I think they mean higher end relative to the isolated remark in the first paragraph.

[Ed Mahmoud]

Latest SPC outlook pushes the big show back to Friday, but still stays pretty bullish

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0255 AM CST SAT JAN 26 2008

VALID 291200Z - 031200Z

...CNTRL/ERN GULF CST SVR POTENTIAL FRI/FRI NIGHT 1-2 FEB...
PROGRESSIVE AMPLIFIED PATTERN WILL PERSIST INTO NEXT WEEKEND AS A
WAVETRAIN OF SHORTWAVE TROUGHS TRAVERSE THE COUNTRY. THE NRN STREAM
IMPULSE EXPECTED TO ARRIVE IN THE CNTRL PLAINS LATE ON MONDAY WILL
CONTINUE ENEWD INTO THE INTO THE GRTLKS AND OH/UPR TN VLYS ON WED.
MODIFIED GULF MOISTURE WILL BE IN PLACE ACROSS THE DEEP S INTO THE
TN VLY AS THE LARGER SCALE HEIGHT FALLS SPREAD NE...SUPPORTING
TSTMS. ISOLD-SCT SVR TSTMS WILL BE POSSIBLE...PRIMARILY ACROSS THE
TN VLY AND PARTS OF THE DEEP S ON TUE 29 JAN...BUT COVERAGE/
INTENSITY SHOULD NOT FALL WITHIN THE MEDIUM RANGE SVR CRITERIA.

A MUCH STRONGER UPR WAVE WILL DIG SEWD FROM THE N PAC AND GRT BASIN
TO THE SRN PLAINS BY THU 31 JAN...THEN GO NEGATIVE TILT AS IT MOVES
ENEWD THROUGH THE TN VLY/DEEP S FRI-SAT 1-2 FEB. THOUGH THE LATEST
GFS IS FASTER WITH THIS WAVE...LAST 4-5 GFS MODEL RUNS HAVE BEEN
TRENDING SLOWER AND SUSPECT ECMWF/CMC MODEL/S SLOWER SOLUTIONS ARE
SUPERIOR.

THE FRONT ASSOCD WITH THE FORMER SYSTEM WILL LIKELY NOT PENETRATE
VERY FAR S INTO THE GULF BASIN. THUS...AS THE LOW/MID-LVL FLOW
BACKS IN ADVANCE OF THE LATE WEEK IMPULSE...ROBUST GULF MOISTURE
SHOULD RETURN NWD. MAGNITUDE OF FORCING ASSOCD WITH THIS SYSTEM AND
POTENTIAL FOR QUALITY MOISTURE RETURN COMBINED WITH A NEARLY 100+ KT
H5 JET WOULD SUGGEST POTENTIAL FOR A HIGHER END SVR EVENT ACROSS THE
LWR MS VLY...DEEP S...PARTS OF THE TN VLY AND EWD INTO SRN GA AND
NRN FL FROM 12Z FRI 1 FEB THROUGH 12Z SAT 2 FEB.

..RACY.. 01/26/2008

[CrazyC83]

Still quite a bold forecast for mid-winter. At least this doesn't have the penetration of the incredible January 7-10 outbreak...

[JonathanBelles]

The area marked now pretty much includes me. Seems strange for this time of year.

[RL3AO]

Here we go again. Could we finish with 150 tornadoes in JANUARY!?!?!?

[CrazyC83]

The area marked now pretty much includes me. Seems strange for this time of year.

For you, February is peak season...

[CrazyC83]

Here we go again. Could we finish with 150 tornadoes in JANUARY!?!?!?

Probably not, but February could get off to a fast start...

[JonathanBelles]

The area marked now pretty much includes me. Seems strange for this time of year.

For you, February is peak season...

Usually its later in the month, but I agree that Feb and March are peak seasons.

[Ptarmigan]

I read somewhere that La Nina years are more favorable for tornado outbreaks. Some of the biggest tornado outbreaks occurred in La Nina years.

[wall_cloud]

I read somewhere that La Nina years are more favorable for tornado outbreaks. Some of the biggest tornado outbreaks occurred in La Nina years.

depends on where you are. La Nina tends to shift the normal storm track.

[Ed Mahmoud]

Friday should be the more interesting day, but living near Houston, GFS has some promise



Looking at my handy pay-per-view AccuWx skew-T generator shows poor low level instability, almost zilch CAPE and almost 200 J/Kj of CINH, but a TT of 52, and an 850 mb LLJ near 50 knots at 3pm. Can't get too excited yet, but when there is no winter weather on the horizon down here, have to look for something.


Anyway, maybe a surprise strong storm around here for Tuesday.

[RL3AO]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 AM CST SUN JAN 27 2008

VALID 301200Z - 041200Z

..CNTRL/ERN GULF CST SVR POTENTIAL LATE THU INTO LATE FRI NIGHT...
THE STRONG LEAD UPR WAVE EXPECTED TO MOVE INTO THE NERN STATES/SERN
CANADA BY WED WILL BE FOLLOWED BY AN EVEN STRONGER SHORTWAVE TROUGH.
THIS FEATURE WILL REACH THE SRN PLAINS BY THU...BECOME
NEGATIVE-TILT AND MOVE TOWARD THE LWR GRTLKS/MID-OH VLY BY FRI/SAT.
ECMWF/CMC GUIDANCE HAS BEEN THE MOST CONSISTENT IN THE OVERALL
SCENARIO AND HAS BEEN FOLLOWED FOR THIS FCST PACKAGE.

THE COLD FRONT ASSOCD WITH THE FIRST SYSTEM IS EXPECTED TO STALL IN
THE GULF ROUGHLY ALONG A KTPA-KCRP LATITUDE DURING THE MID-WEEK
PERIOD. AS THE LOW/MID-LVL FLOW BACKS IN ADVANCE OF THE LATTER
SYSTEM...GULF MOISTURE WILL SURGE BACK NWD. INITIALLY...THIS
MOISTURE ADVECTION WILL GENERATE CLOUDS/SHOWERS OVER THE DEEP S/GULF
COASTAL REGION AS EARLY AS THU/THU NIGHT. CYCLOGENESIS WILL TAKE
PLACE OVER THE NWRN GULF THU AFTN...THEN DEVELOP NEWD INTO CNTRL OR
ERN MS BY EARLY FRI MORNING.

GIVEN PROSPECTS FOR RAPID AND RELATIVELY ROBUST MOISTURE
RETURN...NEARLY 110 KTS OF SWLY MID-LVL FLOW AND STRENGTH OF THIS
SYSTEM...ALL FACETS OF SVR WEATHER WILL BE PSBL...ULTIMATELY
DEVELOPING INTO A PSBL SQUALL LINE. THE SVR THREAT WILL LIKELY
INCREASE OVR THE LWR MS VLY AS EARLY AS THU NIGHT...THEN EVOLVE
ENEWD ACROSS THE CNTRL/ERN GULF CST AND PARTS OF THE DEEP S DURING
THE DAY FRIDAY. EWD EXTENT OF THE SVR THREAT WILL BE MODULATED BY
HOW QUICKLY THE UPR SYSTEM WILL EJECT NEWD AND HOW FAR NEWD THE
QUALITY BOUNDARY LAYER MSTR RETURNS. ATTM...IT APPEARS THAT AT
LEAST A MODEST SVR THREAT MAY EXTEND INTO PARTS OF SWRN/SCNTRL GA
AND THE FL PNHDL DURING FRI NIGHT.

[Ed Mahmoud]

RL3AO

It sounds like they expect sort of a repeat of the last few storms, with surface storm development in the Gulf, and HOU staying in the cool sector. I haven't seena robust t-storm in months, so this would be a mild bummer.

THE COLD FRONT ASSOCD WITH THE FIRST SYSTEM IS EXPECTED TO STALL IN
THE GULF ROUGHLY ALONG A KTPA-KCRP LATITUDE DURING THE MID-WEEK
PERIOD. AS THE LOW/MID-LVL FLOW BACKS IN ADVANCE OF THE LATTER
SYSTEM...GULF MOISTURE WILL SURGE BACK NWD. INITIALLY...THIS
MOISTURE ADVECTION WILL GENERATE CLOUDS/SHOWERS OVER THE DEEP S/GULF
COASTAL REGION AS EARLY AS THU/THU NIGHT. CYCLOGENESIS WILL TAKE
PLACE OVER THE NWRN GULF THU AFTN...THEN DEVELOP NEWD INTO CNTRL OR
ERN MS BY EARLY FRI MORNING.

[Ed Mahmoud]

Still looking close to home, even though the best action is probably East of here the following day. Snip from NWS HGX AFD

SFC HIGH SETTLES OVER THE AREA WITH CLEAR/DRY CONDITIONS TUE
NIGHT/WED MORNING. ONSHORE FLOW DEVELOPS LATE WED AS SFC HIGH
RETREATS EAST. 40-50 KT LOW LEVEL JET DEVELOPS WED NIGHT WHICH
WILL TRANSPORT HIGH PWS (1.3-1.5 INCHES) AND 60+ SFC DEWPOINTS BACK
NORTH INTO THE AREA. SE TX GOES INTO THE RIGHT REAR QUAD OF 120 KT
UPPER JET THU MORNING WHICH WILL ENHANCE UPPER DIFFLUENCE OVER THE
AREA. INSTABILITY WILL BECOME SUFFICIENT TO SUPPORT CONVECTIVE
DEVELOPMENT LATE WED NIGHT/THU MORNING FOR THE SE HALF OF THE
AREA. GIVEN THE STRONG LOW LEVEL SHEAR FORECAST...THERE APPEARS TO
BE THE POTENTIAL FOR A FEW STRONG STORMS THIS PERIOD. COLD FRONT
WILL CROSS THE AREA LATE THURSDAY FOLLOWED BY DRIER/COOLER WEATHER
THU NIGHT/FRIDAY. ONSHORE FLOW RETURNS FRI NIGHT WHICH WILL RESULT
IN WARMER TEMPS AND INCREASING CLOUDINESS FOR THE WEEKEND. KEPT
LOW POPS IN THE FCST FOR THE WEEKEND AS HIGHER PWS SPREAD BACK
NORTH INTO THE AREA.

[Ed Mahmoud]

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0318 AM CST MON JAN 28 2008

VALID 311200Z - 051200Z

..GULF CST SVR POTENTIAL LATE THU INTO LATE FRI NIGHT...
00Z ECMWF HAS TRENDED A LITTLE FARTHER N AND W WITH THE MID-WEEK UPR
LOW ACROSS THE SRN PLAINS. THIS SYSTEM WILL TAKE ON A NEGATIVE-TILT
AND MOVE QUICKLY NEWD INTO NWRN ONT BY EARLY IN THE WEEKEND.

AS THE SYSTEM APCHS THE PLAINS...A WAVE OVER THE NWRN GULF WILL
INTENSIFY INTO A LOW AND MOVE NNEWD INTO THE LWR MS VLY REGION BY
THU AFTN...THEN INTO THE GRTLKS REGION BY LATE FRI NIGHT. A STG
COLD FRONT WILL SWEEP EWD S OF THE LOW...REACHING THE ERN SEABOARD
AND CNTRL FL THIS WEEKEND.

GULF MSTR WILL BE QUICK TO RETURN TO THE CST LATE WED NIGHT...THEN
ADVECT INLAND INTO PARTS OF THE DEEP S BY THU AFTN. SOME OF THE
ASCENT/LIFT THAT DEVELOPS OWING TO THE BACKING OF THE LOW/MID-LVL
FLOW REGIME WILL GO INTO GENERATING CLOUDS/PCPN...BUT A MODEST WARM
SECTOR IS STILL EXPECTED OVER PARTS OF CNTRL/ERN LA NEWD INTO PARTS
OF MS/AL AND THE FL PNHDL. MAGNITUDE OF ASCENT WILL LIKELY
CONTRIBUTE TO THE EVOLUTION OF A SQUALL LINE THAT WILL MOVE QUICKLY
NEWD INTO THE SRN APLCNS/CAROLINAS BY LATE THU NIGHT. THE LINE
SHOULD GRADUALLY WEAKEN WITH EWD EXTENT AS THE PRIMARY FORCING LIFTS
NWD. ALL FACETS OF SVR WEATHER WILL BE POSSIBLE GIVEN THE STRENGTH
OF THE WIND FIELDS EXPECTED AND AT LEAST MODEST INSTABILITY.

..RACY.. 01/28/2008