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Sunday April 10th severe outbreak


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I'm gonna (as usual) side the other way on this. Look at that GFS hodo. Good grief, even with SSW winds, that is an impressive hodo. And w/r/t the NAM, keep in mind it often underestimates low-level winds/shear/helicity, especially with events in this range.

That GFS hodograph you posted has good turning in the lowesr 1-1.5 km or so.... but above that... is the classic mid-level backing that more often than not (quite mother freaking often, actually... as it has bitten me numerous times back in the day) will screw up what will otherwise be a High Risk tornado day.

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Believe the SPC WRF graphics have updated (at least the sim radar)

http://www.emc.ncep....nt4km/conus/00/

Shows much of Wisconsin getting raked.

This is the model I'm going with; it fits severe weather events here right to the tee: impressive line of storms peters out right as it reaches the lake. Would still be quite exciting.

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This is the model I'm going with; it fits severe weather events here right to the tee: impressive line of storms peters out right as it reaches the lake. Would still be quite exciting.

Lake will have zero mitigating role in this case given the strong gradient winds out of the ssw.

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Lake will have zero mitigating role in this case given the strong gradient winds out of the ssw.

I was semi-kidding, but the model I was referring to had the storms weaken considerably by the time they reached Lake Michigan. I think normally the combination of the sun setting and the lake cause storms to weaken as they approach Milwaukee. Occasionally, like June 7/8, 2008, that is not the case.

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Main question here continues to be how fast instability wanes overnight. Models are showing MLCAPE of 500-1000 J/kg well into the overnight hours. Wind fields will obviously be strong throughout the night. If I were SPC I might go with a 30% wind for this area on this upcoming outlook. If not I imagine it won't be very far away.

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day1.gif

day1.tornado.gif

day1.hail.gif

day1.wind.gif

AMID A ROBUST LOW/MID TROPOSPHERIC WIND FIELD /HIGHLIGHTED BY 90-100 KT SOUTHWESTERLY FLOW IN MID LEVELS/...SUPERCELLS...SOME SPLITTING...WILL DEVELOP/LIKELY RACE NORTHEASTWARD AT UPWARDS OF 45-50 KT. EFFECTIVE BULK SHEAR IN EXCESS OF 50 KT WILL BE HIGHLY FAVORABLE WELL-ORGANIZED/SUSTAINED STORMS INCLUDING SUPERCELLS...AND PERHAPS EVENTUAL BOWS ECHOS BY MID/LATE EVENING.

THE GREATEST RISK FOR TORNADOES...INCLUDING THE POTENTIAL FOR STRONG/LONG TRACK TORNADOES...WILL EXIST ACROSS FAR SOUTHEAST MN/FAR NORTHEAST IA INTO WI...WITH LARGE HAIL A LIKELIHOOD AS WELL.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0104 AM CDT SUN APR 10 2011

VALID 101200Z - 111200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS SOUTHEAST MN/EASTERN IA

TO MUCH OF WI/WESTERN U.P. OF MI AND NORTHERN IL...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE UPPER

MIDWEST/GREAT LAKES REGION TO ARKLATEX...

...UPPER MS VALLEY/UPPER GREAT LAKES/MIDWEST TO ARKLATEX...

A POTENTIALLY SIGNIFICANT SEVERE EPISODE...INCLUDING FAST MOVING

SUPERCELLS AND THE POSSIBILITY OF STRONG TORNADOES...WILL EXIST FROM

MID AFTERNOON THROUGH EVENING ACROSS THE UPPER MS

VALLEY...ESPECIALLY INCLUDING PORTIONS OF EASTERN MN INTO WI.

UPPER TROUGH OVER THE ROCKIES EARLY THIS MORNING WILL SHIFT

GENERALLY EASTWARD TOWARD THE PLAINS TODAY...WITH A LEAD/NORTHERN

PIECE OF THIS TROUGH SHIFTING EASTWARD OVER THE UPPER MIDWEST THIS

AFTERNOON/TONIGHT. AIDED BY THE LEFT EXIT REGION OF 100+ KT UPPER

JET STREAK...THE PRIMARY SURFACE LOW IS EXPECTED TO GRADUALLY

DEEPEN/ADVANCE NORTHEASTWARD ACROSS SOUTHERN MN INTO NORTHWEST

WI/U.P. OF MI AND LAKE SUPERIOR TONIGHT...ALL WHILE A WARM FRONT

RETREATS NORTHWARD ACROSS SOUTHERN/EASTERN MN AND WI AS WELL AS

LOWER MI. SOUTH OF THE SURFACE LOW...ASSOCIATED COLD FRONT WILL

SPREAD EAST-SOUTHEASTWARD FROM THE CENTRAL/SOUTHERN PLAINS AND

MIDWEST TOWARD THE MS VALLEY VICINITY.

INITIALLY...ON THE NOSE OF A STRONG/VEERING LOW LEVEL JET...EARLY

DAY ELEVATED TSTMS MAY POSE A SEVERE HAIL THREAT FROM PORTIONS OF MN

INTO WI/NORTHERN MI. SUCH A SEVERE THREAT COULD CONTINUE WELL

THROUGH THE MORNING.

OTHERWISE...TIED TO THE NORTHWARD ADVANCING WARM FRONT /PERHAPS

AUGMENTED TO A DEGREE BY EARLY DAY ONGOING CONVECTION/...SEASONALLY

HIGH MOISTURE CONTENT WILL QUICKLY DEVELOP NORTHEASTWARD DURING THE

DAY WITHIN THE WARM SECTOR...WITH LOWER 60S F SURFACE DEWPOINTS

BECOMING ESTABLISHED ACROSS THE MAJORITY OF THE UPPER MS VALLEY WARM

SECTOR. BENEATH A SOUTHERN ROCKIES/PLAINS EMANATING ELEVATED MIXED

LAYER...MLCAPE FROM 1500 J/KG TO UPWARDS OF 2000-2500 J/KG WILL

LIKELY BE IN PLACE BY AFTERNOON ESPECIALLY ACROSS THE UPPER MS

VALLEY.

IT IS PROBABLE THAT THE EML/CAP SHOULD LIMIT SURFACE BASED TSTM

DEVELOPMENT THROUGH EARLY/PERHAPS MID AFTERNOON...WHILE OTHERWISE

CREATING UNCERTAINTY IN THE COVERAGE/EXTENT OF DEEP CONVECTIVE

DEVELOPMENT DIURNALLY /SOUTH OF THE UPPER JET AXIS/ ACROSS AREAS

SUCH AS EASTERN IA/NORTHERN IL AND ADJACENT PORTIONS OF THE MIDDLE

MS VALLEY. THAT SAID...THE MOST LIKELY/HIGHEST CONFIDENCE SCENARIO

WOULD BE FOR VIGOROUS DEEP CONVECTIVE DEVELOPMENT AHEAD OF THE

ADVANCING SURFACE LOW AND NEAR THE WARM FRONT/ADJACENT WARM SECTOR.

ACCORDINGLY...CURRENT EXPECTATIONS ARE FOR SEVERE TSTMS TO ERUPT BY

MID/LATE AFTERNOON...INITIALLY ACROSS PORTIONS OF SOUTHEAST MN/FAR

WESTERN WI/NORTHEAST IA. THIS SCENARIO IS WELL SUPPORTED BY MOST 00Z

DETERMINISTIC NUMERICAL GUIDANCE...AS WELL AS THE 00Z RUNS OF THE

WRF-NMM/WRF-NSSL.

AMID A ROBUST LOW/MID TROPOSPHERIC WIND FIELD /HIGHLIGHTED BY 90-100

KT SOUTHWESTERLY FLOW IN MID LEVELS/...SUPERCELLS...SOME

SPLITTING...WILL DEVELOP/LIKELY RACE NORTHEASTWARD AT UPWARDS OF

45-50 KT. EFFECTIVE BULK SHEAR IN EXCESS OF 50 KT WILL BE HIGHLY

FAVORABLE WELL-ORGANIZED/SUSTAINED STORMS INCLUDING

SUPERCELLS...AND PERHAPS EVENTUAL BOWS ECHOS BY MID/LATE EVENING.

THE GREATEST RISK FOR TORNADOES...INCLUDING THE POTENTIAL FOR

STRONG/LONG TRACK TORNADOES...WILL EXIST ACROSS FAR SOUTHEAST MN/FAR

NORTHEAST IA INTO WI...WITH LARGE HAIL A LIKELIHOOD AS WELL.

FARTHER SOUTH/SOUTHWEST...OTHER STRONG/SEVERE TSTM DEVELOPMENT IS

PROBABLE TOWARD/AFTER DARK ALONG THE DRYLINE/OVERTAKING COLD FRONT

FROM THE MIDDLE MS VALLEY/OZARKS TO THE ARKLATEX. SEVERE

HAIL/DAMAGING WINDS AND A TORNADO OR TWO WILL BE POSSIBLE AS STORMS

INCREASE/ADVANCE EAST-SOUTHEASTWARD THROUGH THE NIGHT.

...LOWER GREAT LAKES REGION...

SURFACE WARM FRONT IS EXPECTED TO RETREAT NORTHEASTWARD TOWARD THE

REGION THROUGH THE DAY...WITH MODEST BOUNDARY LAYER

MOISTENING/INCREASING PW ATTENDANT TO THE WARM FRONT. AMID MARKEDLY

STRENGTHENING NORTHWESTERLY FLOW ALOFT...CONVECTION COULD CREST THE

UPPER RIDGE AND CROSS SOUTHERN ONTARIO/LAKE ERIE VICINITY INTO NY

AND PERHAPS ADJACENT PORTIONS OF PA/WESTERN NEW ENGLAND DURING THE

AFTERNOON...OR MORE LIKELY THIS EVENING/TONIGHT. THIS COULD RESULT

IN A MARGINAL WIND/HAIL THREAT.

..GUYER/HURLBUT.. 04/10/2011

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day1.wind.gif

AMID A ROBUST LOW/MID TROPOSPHERIC WIND FIELD /HIGHLIGHTED BY 90-100 KT SOUTHWESTERLY FLOW IN MID LEVELS/...SUPERCELLS...SOME SPLITTING...WILL DEVELOP/LIKELY RACE NORTHEASTWARD AT UPWARDS OF 45-50 KT. EFFECTIVE BULK SHEAR IN EXCESS OF 50 KT WILL BE HIGHLY FAVORABLE WELL-ORGANIZED/SUSTAINED STORMS INCLUDING SUPERCELLS...AND PERHAPS EVENTUAL BOWS ECHOS BY MID/LATE EVENING.

THE GREATEST RISK FOR TORNADOES...INCLUDING THE POTENTIAL FOR STRONG/LONG TRACK TORNADOES...WILL EXIST ACROSS FAR SOUTHEAST MN/FAR NORTHEAST IA INTO WI...WITH LARGE HAIL A LIKELIHOOD AS WELL.

There's my 30% wind haha.

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DVN AFD. Possible downgrade to a slight risk for DVN CWA.

CAP WEAKENS SOMEWHAT AS COLD FRONT APPROACHES BUT FORCING ANDCONVERGENCE NOT IMPRESSIVE ALONG THE FRONT. BETTER DYNAMICSASSOCIATED WITH SURFACE LOW WELL TO OUR NORTH. ISOLATED TO SCATTEREDCONVECTION THAT CAN DEVELOP WILL TAP A STRONG WIND FIELD BUTUNIDIRECTIONAL FLOW SUGGESTING DAMAGING WINDS THE MAIN ISSUE. THETORNADO THREAT APPEARS TO BE WELL NORTH ACROSS EASTERN MN AND MUCHOF WI CLOSER TO THE SURFACE LOW/WARM FRONT. MODERATE RISK OF SEVEREIN THE DVN CWA BUT SPC MAY DOWNGRADE TO A SLIGHT WITH THE 12ZOUTLOOK. AFTER DARK THE CONVECTION SHOULD FORM INTO A BKN-SOLID LINEALONG THE COLD FRONT EAST OF THE DVN CWA. HAVE LOWERED POPS TO ONLY30-50 PERCENT BUT WILL MAINTAIN A MENTION OF SEVERE LATE THISAFTERNOON INTO THE EVENING...AGAIN THE MAIN THREAT DAMAGING WINDS.WILL BE GOING DRY AFTER MIDNIGHT AS THE FRONT WILL HAVE CLEARED THECWA. MIN TEMPS TONIGHT FALLING INTO THE 40S WEST TO LOWER 50S EASTWITH CONTINUED BRISK WINDS.

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I really don't know what to say after reading all the AFDs from local offices, things looked so great for so many runs/days, then the 00z collectively crapped the bed, and everyone is backing off all at once. I really hope that this doesn't come back to bite them.

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I really don't know what to say after reading all the AFDs from local offices, things looked so great for so many runs/days, then the 00z collectively crapped the bed, and everyone is backing off all at once. I really hope that this doesn't come back to bite them.

Some of the NWS offices have been waffling back and forth, so nothing new. To be honest I never knew what was so impressive about this setup in the first place.

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from Gino....was texting me earlier tonight about the 0z runs

REALLY PULLING OUR HAIR OUT THIS MORNING AS MODEL GUIDANCE HAS

MADE SOME SIZABLE ADJUSTMENTS FROM PREVIOUS RUNS. MOST

NOTABLY...THE WEAK PRE-FRONTAL TROUGH/CONVERGENCE ZONE ADVERTISED

IN THE 12Z GUIDANCE IS GONE THIS FAR NORTH. IN ADDITION...UPPER

LOW IS PROGGED TO BE MUCH WEAKER/MORE POSITIVELY TILTED RESULTING

IN LESSER HEIGHT FALLS AND LARGE SCALE ASCENT OVER THE WARM

SECTOR THIS AFTERNOON/EVENING. GIVEN THE PRESENCE OF VERY

IMPRESSIVE EML AS SAMPLED BY UPSTREAM 00Z RAOBS

(SGF/TOP/OAX)...WEAKER LARGE SCALE ASCENT TO LIFT THROUGH

CAP...AND ABSENCE OF PRE-FRONTAL TROUGH IN LATEST GUIDANCE...THE

CONFIDENCE IN PRE-FRONTAL CONVECTION DEVELOPING HAS DECREASED

SUBSTANTIALLY. IN FACT...HARD TO FIND A MODEL THATS STILL SHOWING

ANY PRE-FRONTAL DEVELOPMENT AND MANY ARENT DEVELOPING ALL THAT MUCH

CONVECTION EVEN ALONG THE FRONT OVER THE CWA.

AS ALLUDED TO YESTERDAY...AFTERNOON ENVIRONMENT WILL BE PRETTY

UNFAVORABLE FOR TORNADOES WITH VERY HIGH LCL HEIGHTS. REGARDING

TORNADO POTENTIAL THIS EVENING...BIG QUESTIONS HAVE NOW ARISEN

REGARDING EXTENT OF CONVECTIVE DEVELOPMENT. IN ADDITION...ANY

STORMS THAT DO DEVELOP ARE LOOKING TO BE TIED MORE TO THE COLD

FRONT...WHERE CLOUD BEARING LAYER SHEAR VECTORS ARE PROGGED TO BE

ORIENTED PARALLEL TO THE INITIATING BOUNDARY...SO THE POTENTIAL

FOR DISCRETE STORMS IS LOOKING DRAMATICALLY LOWER THAN PREVIOUSLY

FEARED. WHILE CONDITIONS WILL BECOME MORE FAVORABLE FOR TORNADOES

THIS EVENING WITH LOWERING LCL HEIGHTS AND VERY STRONG LOW LEVEL

SHEAR AS LLJ INTENSIFIES...TORNADO THREAT WILL BE LARGELY

CONDITIONAL ON STORM MODE...WHICH NOW APPEARS TO BE MORE LINEAR

AND THUS A FAR LESSER (THOUGH NOT QUITE ZERO) TORNADO THREAT.

GIVEN THE PRESENCE OF STRONG SHEAR AND STEEP LAPSE RATES/MODERATE

INSTABILITY...ANY STORMS THAT DO DEVELOP WOULD CERTAINLY CARRY A

RISK FOR LARGE HAIL AND DAMAGING WINDS...THOUGH THIS IS NO LONGER

LOOKING LIKE A HIGHER END THREAT.

MOST LIKELY CONVECTIVE SCENARIO NOW APPEARS TO BE SUPERCELLULAR

STORM DEVELOPMENT WELL TO OUR NORTHWEST OVER MN/WI...CLOSER TO THE

STRONGER/DEEPER ASCENT AND WEAKER CAP. ADDITIONALLY...CONVECTION

WILL LIKELY DEVELOP OVER MISSOURI AS COLD FRONT OVER TAKES PRE-

FRONTAL TROUGH/DRYLINE TOWARD EVENING...WITH THOSE STORMS PROGGED

TO DEVELOP NORTHWARD AS THEY MOVE EAST. SEEMS QUITE LIKELY STORM

MODE WITH THIS CONVECTION WILL BE LARGELY LINEAR...SO MAINLY A

WIND AND MODEST HAIL THREAT WITH A MUCH MORE LIMITED TORNADO

POTENTIAL.

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Some of the NWS offices have been waffling back and forth, so nothing new. To be honest I never knew what was so impressive about this setup in the first place.

Good shear, unseasonably strong system/warmth ahead of it, good moisture flow from the gulf, and impeding EML/dryline. Just to name a few things that would/could make this impressive.....

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Good shear, unseasonably strong system/warmth ahead of it, good moisture flow from the gulf, and impeding EML/dryline. Just to name a few things that would/could make this impressive.....

I mean like, for the really strong wording we've seen, and the Day 3 MDT, etc.

Certainly a setup enough to warrant a MDT day 1 at least, but iono, I just feel like this event's been played up a lot more than others have. Not saying it won't perform, but just thought that was interesting, because this is about just on par with the other setups we've seen this year imo.

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I mean like, for the really strong wording we've seen, and the Day 3 MDT, etc.

Certainly a setup enough to warrant a MDT day 1 at least, but iono, I just feel like this event's been played up a lot more than others have. Not saying it won't perform, but just thought that was interesting, because this is about just on par with the other setups we've seen this year imo.

Yeah I think we will just agree to disagree here on this one.

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I mean like, for the really strong wording we've seen, and the Day 3 MDT, etc.

Certainly a setup enough to warrant a MDT day 1 at least, but iono, I just feel like this event's been played up a lot more than others have. Not saying it won't perform, but just thought that was interesting, because this is about just on par with the other setups we've seen this year imo.

The SPC still has the moderate risk for day 1. So you're saying that's a bad forecast?

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Yeah I think we will just agree to disagree here on this one.

Key will be how much fires farther ahead of the cold front. Directional shear is a little marginal but deep layer shear is way more than enough for supercells. Situation has dangerous potential as is but if the surface flow ends up 10 or 20 degrees more backed, it will take this to another level.

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