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18-20 March 2012 severe prospects


tornadotony

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Tony - what product is this? I see it on here often, and I was wondering where I go to pull it?

This is significant tornado ingredients, and it is a percent chance of a significant tornado using probabilities of reaching CAPE, mixed layer LCL, 0-1 km helicity, 0-6 km shear, and convective precip thresholds.

You can get it at the SPC Forecast Tools link http://www.spc.noaa.gov/exper/

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What a crazy night. Both Cory and I are ok...we are at work. He was on shift and I was called in for OT before it hit the fan. The tor hit a couple miles from my place.

Nothing like destruction to pad the wallet. :/ (I work in emergency services, I'm allowed to be snarky about that.)

Do you know if the tweets about the TV station getting hit were true?

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DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1231 PM CDT MON MAR 19 2012

VALID 201200Z - 211200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER SOUTHEAST TEXAS....THE

ARKLATEX REGION AND OZARKS...

...SYNOPSIS...

HIGH AMPLITUDE FLOW REGIME WILL FEATURE AN ANOMALOUSLY DEEP CYCLONE

SITUATED OVER THE SOUTHWEST AND SRN HIGH PLAINS AND AN EXTENSIVE AND

JUST AS ANOMALOUS UPPER RIDGE AXIS OVER THE ERN 1/3RD OF NORTH

AMERICA. BETWEEN THESE TWO LARGE SCALE ANOMALIES WILL EXIST ANOTHER

ANOMALY...HIGH AMOUNTS OF ATMOSPHERIC WATER VAPOR BEING TRANSPORTED

NWD FROM THE SUB-TROPICS ACROSS THE NWRN GULF COAST AND INTO THE

CNTRL CONUS. GIVEN THE LARGE SCALE BLOCKING...EVOLVING DEEP-LAYER

CLOSED LOW FORECAST TO TAKE FORM IN THE BASE OF THE LARGE SCALE

TROUGH OVER THE SOUTHWEST WILL MAKE ONLY VERY SLOW EWD PROGRESS THIS

PERIOD. AS ALLUDED IN PREVIOUS DY2 OUTLOOK...MODELS CONTINUE TO

TREND SLOWER IN THE EWD PROGRESSION OF THE LOW THROUGH EARLY WED.

...SERN TX/ARKLATEX TO OZARKS...

LIFT ALONG LEADING EDGE OF HEIGHT FALLS ASSOCIATED WITH THE SLOWLY

ADVANCING DEEP-LAYER CYCLONE WILL CONTINUE TO OCCUR COINCIDENT WITH

AN UNUSUALLY WARM AND MOIST AIRMASS. THIS SHOULD SUSTAIN PERSISTENT

DEEP CONVECTION IN ORGANIZED LINEAR BANDS..AND OCCASIONAL LARGER

CLUSTERS...ACROSS ERN TX THROUGH TONIGHT. MODEL GUIDANCE CONTINUES

TO TREND WWD WITH THE PLACEMENT OF THE STRONGEST MCS SIGNAL INTO

EARLY TUESDAY WITH LATEST INDICATIONS SUGGESTING THE CORRIDOR FOR

GREATEST TSTM POTENTIAL AT THE BEGINNING OF THIS FORECAST PERIOD

FROM SOUTHEAST TX ACROSS ERN OK TO SWRN AR. ANAFRONTAL

CHARACTERISTICS TO THIS SYSTEM WILL BE SUPPORTED BY 1) THE SLOW EWD

MOVEMENT OF THE UPPER SYSTEM...AND 2) DEEP-LAYER MERIDIONAL FLOW.

AHEAD OF THE LINEAR MCS ANTICIPATED ACROSS SERN TX AND ERN

OK...SHEAR AND INSTABILITY EAST ACROSS THE WARM/MOIST SECTOR WILL

REMAIN MORE THAN ADEQUATE FOR ORGANIZED/SEVERE STORMS.

HOWEVER...WITH LIFT ESSENTIALLY FOCUSED NEAR THE LEADING EDGE OF THE

CONVECTIVE SYSTEM...OVERALL STORM EVOLUTION AND SEVERE THREAT

THROUGH THE DAY REMAINS SOMEWHAT UNCERTAIN IN BOTH ERN AND NRN

EXTENT.

MESOSCALE GUIDANCE HINTS AS SMALLER SCALE WAVES OF LOW PRESSURE

DEVELOPING AMIDST THE CONVECTIVE SYSTEM THROUGH THE MORNING AND INTO

THE AFTERNOON. FORECAST SHEAR PROFILES NEAR THESE WEAK DISTURBANCES

REVEAL SUBSTANTIAL ENVIRONMENTAL EFFECTIVE HELICITY ON THE ORDER OF

200-300 M2/S2 AND...WHEN COMBINED WITH THE HIGH MOISTURE AND LOW LFC

LIKELY WITHIN THE SLGT RISK CORRIDOR...THIS SUGGESTS THAT A COUPLE

OF TORNADOES SEEM POSSIBLE.

AS IS USUALLY THE CASE WITH REPEAT/TRAINING CONVECTION OF THIS

NATURE...STORM SCALE INTERACTIONS AND CAPE/INSTABILITY VARIATIONS

INTRODUCE CONSIDERABLE UNCERTAINTY AT THIS FORECAST RANGE. THERE

DOES APPEAR TO BE SOME CHANCE FOR A STRONG TORNADO IN THIS

ENVIRONMENT. HOWEVER...ATTEMPTING TO HIGHLIGHT A GREATER RISK AT

THIS TIME IS NOT LIKELY TO PROVE ACCURATE. WILL AWAIT ADDITIONAL

INFORMATION AND A HIGHER PROBABILITY TORNADO AREA MAY BE INCLUDED IN

AN UPCOMING DY1 OUTLOOK.

...TX PNHDL/SWRN OK/NWRN TX...

AS THE LARGER SYSTEM BECOME OCCLUDED AND COLD CORE PIVOTS ACROSS

NRN TX AND OK COINCIDENT WITH SOME POTENTIAL FOR SURFACE

HEATING...IT SEEMS REASONABLE TO EXPECT LOW-TOPPED CONVECTION WITH

SOME HAIL AND GUSTY WIND POTENTIAL IN THESE AREAS.

..CARBIN.. 03/19/2012

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SPC's new outlook stays with the same probs, and mentions mostly linear mode? Am I missing something here? Serious question.

Shear vectors progged to be more parallel with the boundary and deep shear magnitudes are borderline for supercells over most of the area.

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I'm sure not going to question SPC after their impressive handling of yesterday, when so many (including me) doubted them. Even aside from that, I'm struggling to see how coverage of tornado reports is likely to justify a more aggressive outlook, given the convective mode issues. I can maybe see making the case for hatching parts of the 10% area given low-level shear, if anything.

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Shear vectors progged to be more parallel with the boundary and deep shear magnitudes are borderline for supercells over most of the area.

I see the 14z HRRR run breaks out a significant number of prefrontal cells. Those would be the ones with the greatest likelihood to stay discrete based on progged shear vectors.

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Shear vectors progged to be more parallel with the boundary and shear magnitudes not as favorable over most of the area either.

We had discrete tornadic supercells in shear vectors/magnitude similar to this in Nebraska yesterday night. Sure the storm coverage was less than is expected today, but I would have to think that with increasing large scale ascent and plenty of instability well out ahead of the front, that we'll see discrete supercells as the dominant mode somewhere today, over how large an area that may be, well that's the big question...

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We had discrete tornadic supercells in shear vectors/magnitude similar to this in Nebraska yesterday night. Sure the storm coverage was less than is expected today, but I would have to think that with increasing large scale ascent and plenty of instability well out ahead of the front, that we'll see discrete supercells as the dominant mode somewhere today, over how large an area that may be, well that's the big question...

Well if you have stronger/deeper forcing and/or it's closer to the boundary then linear will be more prevalent. Also if the CIN is lower than linear is more favored. I was busy yesterday and didn't really pay attention so I'm not sure if they are forecasted to form closer to the boundary today than yesterday. From what you said it sounds like today has stronger forcing involved than yesterday. And just a quick scan it appears CIN may be a little lower today also. You know how this stuff is all conditional, rarely is there a magic bullet that answers everything haha.

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