Virtual Chase Thread 2011

[Paul Sherman]

Yes Models have been pretty bad in the 3-5 day timeframe recently. Monday looked pretty amazing on yesterdays runs but now trending away and Tuesday/Wednesday could see the highest risk.

Things bubbling along nicely in my Target area of Ardmore (Ok) and should something ride the warm front then it could be game on, only negatives are Initiation could be at Sunset and Large Hail damaging yer Bonnets!

MESOSCALE DISCUSSION 0271

NWS STORM PREDICTION CENTER NORMAN OK

0343 PM CDT FRI MAR 25 2011

AREAS AFFECTED...NCNTRL/NERN TX...SCNTRL/SERN OK...SWRN AR AND

EXTREME NRN LA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 252043Z - 252315Z

LATEST VISIBLE SATELLITE IMAGERY DEPICTS A DEEPENING CUMULUS FIELD

ACROSS THE WARM SECTOR OVER SCNTRL/SERN OK AND NCNTRL TX.

HOWEVER...RIDGE/ANTICYCLONIC CHARACTER TO HIGH-LEVEL CLOUDS MOVING

OVER THE REGION AND LACK OF SUBSTANTIAL LOW-LEVEL CONVERGENCE WILL

PROBABLY BE DETRIMENTAL TO SURFACE-BASED CONVECTIVE INITIATION UNTIL

AFTER 23Z OR SO. THEREAFTER...WEAK HEIGHT FALLS ASSOCIATED WITH AN

UPSTREAM TROUGH AND THE PRE-EXISTING WARM BOUNDARY LAYER MAY BECOME

SLIGHTLY MORE FAVORABLE FOR INITIATION. THERE APPEARS TO BE ENOUGH

EVIDENCE TO SUPPORT LATEST RUC/GFS/NAM SOLUTIONS FOR AT LEAST

ISOLATED THUNDERSTORMS NEAR THE TRIPLE POINT AND SWD ALONG THE

DRYLINE FROM SCNTRL OK INTO NCNTRL TX NEAR SUNSET WHERE NRN-EXTENT

OF 1000-1500 J/KG MLCAPES WILL EXIST.

SHOULD A STORM FORM...ROUGHLY 45-50 KTS OF LARGELY UNIDIRECTIONAL

DEEP-LAYER SHEAR AND MID-LEVEL LAPSE RATES IN EXCESS OF 7 DEG C PER

KM WILL BE FAVORABLE FOR SPLITTING SUPERCELLS CAPABLE OF LARGE HAIL.

A SUSTAINED SURFACE-BASED STORM EVOLVING ALONG/N OF THE RED RIVER

NEAR A WARM FRONT COULD PRODUCE A TORNADO OR TWO...BUT THE HAIL RISK

WILL DOMINATE.

OTHERWISE...ADDITIONAL ACTIVITY IS EXPECTED TO EVOLVE AND/OR DEVELOP

ALONG/N OF THE WARM FRONT AS ELEVATED ENTITIES OVER ERN OK AND CNTRL

AR LATER THIS EVENING WITH POSSIBLE LARGE HAIL.

[Paul Sherman]

Wow Strong Cap Tonight looks like winning the Game!

Nearly Sunset so not much point in following any Chasers who are milling around down in S Central Oklahoma.

BUSTOLA CRAPOLA!

[vortex_liam]

Looks like a active day today

waiting up in nashvile at the moment, waiting for that storm to come to me watching the traffic cameras its grreat!

[NL]

Upgrade to moderate risk just about to be issued with increased chances for tornadoes (15%)

MESOSCALE DISCUSSION 0275

NWS STORM PREDICTION CENTER NORMAN OK

1021 AM CDT SAT MAR 26 2011

AREAS AFFECTED...NE MS...CNTRL/NRN AL

CONCERNING...OUTLOOK UPGRADE

VALID 261521Z - 261615Z

1630 UTC DAY 1 CONVECTIVE OUTLOOK WILL BE UPGRADING PARTS OF NE MS

AND CNTRL/NRN AL TO A MODERATE RISK. CATEGORICAL RISK WILL BE

DRIVEN BY 15 PERCENT TORNADO PROBABILITIES. REFER TO GRAPHIC FOR

DETAILED AREA.

DETAILS WILL BE FORTHCOMING IN SWODY1 BY 1630 UTC.

Edited March 26, 2011 by NL

[craig1uk]

So when do we predict the season will start? Just been looking at previous virtual chase threads, and the 26th March looks common, so I'll go for that

Not too shabby a guess really, Mod risk, 8 'nados, still no closer to knowing the definition of the start of the season, would have thought they'd have thought one up along the lines of the monsoon season criteria ?

[Paul Sherman]

Keeping my eye on Sunday at the moment, looks like there could be a Tornado Day in the Plains (Area Still Not Nailed Yet due to the Trough Placement) and then the Tennessee Valley for Monday.

One to Watch in future Outlooks

[Paul Sherman]

Strong Cap seems to be an Issue for greater Coverage of Storms for Sunday although a few could pop on the Dryline. Monday as I thought looks likely to see a Significant Severe Outbreak once again much further East over the Lower Mississippi Valley, Tennessee and Ohio River Valleys. If the Models stay the same could be seeing a Solid Moderate Risk on Monday next week (Day 6)

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0337 AM CDT WED MAR 30 2011

VALID 021200Z - 071200Z

...DISCUSSION...

DETERMINISTIC MODELS AND ENSEMBLE MEMBER SOLUTIONS HAVE COME INTO

BETTER AGREEMENT...AT LEAST THROUGH DAY 5...BUT REMAIN DISPERSIVE

BEYOND THIS TIME. NEVERTHELESS...IT APPEARS THE THREAT FOR SEVERE

STORMS WILL BEGIN TO INCREASE BY DAY 5 OVER PORTIONS OF CNTRL AND

SRN PLAINS INTO THE MID MS VALLEY...AND ESPECIALLY DAY 6 OVER THE

LOWER MS VALLEY...SERN STATES AND POSSIBLY A PORTION OF THE OH

VALLEY.

SUNDAY /DAY 5/...MODEL CONSENSUS IS THAT POSITIVE TILT UPPER TROUGH

WILL AMPLIFY SWD INTO GREAT BASIN AND SWRN STATES WITH POTENTIAL FOR

WEAKER IMPULSES TO EJECT INTO THE PLAINS. LEE CYCLONE WILL MAINTAIN

INFLUX OF MOISTURE EAST OF DRYLINE AND SOUTH OF PROGRESSIVE COLD

FRONT. WHILE THREAT FOR SUPERCELLS CANNOT BE RULED OUT OVER THE

CNTRL/SRN PLAINS ALONG DRYLINE...A WARM EML AND WEAK FORCING ALOFT

LOWERS CONFIDENCE IN MORE THAN VERY ISOLATED COVERAGE. OTHER STORMS

WILL BE POSSIBLE OVER THE CNTRL PLAINS OR MID-MS VALLEY WHERE THE

FRONT OVERTAKES THE DRYLINE AS WELL AS IN WARM ADVECTION REGIME

ACROSS THE MID-MS VALLEY.

MONDAY /DAY 6/...POTENTIAL WILL EXIST FOR A MORE SUBSTANTIAL SEVERE

THREAT AS MOISTURE ADVECTS NEWD THROUGH THE MS AND TN VALLEY

REGIONS...EAST OF AMPLIFYING...BUT PROGRESSIVE UPPER TROUGH. STORMS

MAY DEVELOP ALONG AND EAST OF SEWD ADVANCING FRONT ALONG ERN

PERIPHERY OF WARMER EML PLUME. STRENGTH OF LOW-LEVEL JET AND DEEP

SHEAR ALONG WITH ADEQUATE INSTABILITY COULD SUPPORT THE POTENTIAL

FOR A SIGNIFICANT SEVERE EVENT.

IF MODEL SOLUTIONS CONTINUE TO CONVERGE...A RISK AREA WILL LIKELY

NEED TO BE INTRODUCED IN THE NEXT 4-8 UPDATE...ESPECIALLY FROM THE

MS VALLEY THROUGH THE SERN STATES AND POSSIBLY INTO SRN PARTS OF THE

OH VALLEY.

[user700]

Do you think this could be a moderate risk for Texas on Sunday?

[Paul Sherman]

I Think the Cap is going to be too strong on Sunday but there might be some Isolated Storms along the Dryline in places where it bulges, latest GFS Shows Weakening Cinh on the latest 06z Run. Cape Values are Insane with 2,500 - 3,000jkg showing.

Monday Imho looks much more likely to see a Moderate Risk across the Lower Mississippi Valley, Tenessee Valley and further SE.

Paul S

[user700]

I Think the Cap is going to be too strong on Sunday but there might be some Isolated Storms along the Dryline in places where it bulges, latest GFS Shows Weakening Cinh on the latest 06z Run. Cape Values are Insane with 2,500 - 3,000jkg showing.

Monday Imho looks much more likely to see a Moderate Risk across the Lower Mississippi Valley, Tenessee Valley and further SE.

Paul S

With that much cape the isolated storms should be good if they break the cap. Something to watch.

Danny

Edited March 30, 2011 by danieluk

[Gorky]

Not seen a GFS run which breaks out precip yet. The cap is forecast to hold so far. However, there are a lot of subtle impulses which can't be forecast more than 36 hours out. Outflow boundaries are dependant on prevous evenings convection and that won't be evident until the day of the event. I certainly wouldn't write the day off based on the GFS as it is.

The following day into the Tennessee Valley looks like a higher end event, although not as chaseable for obvious reasons. Cap will certainly not be an issue for such a mature storm.

[Paul Sherman]

VERY Active Period Coming Up in the US - Saturday still looks like a Thermo Nuclear Cap - SPC Going with possible breaking of the Cap along where the Dryline gets Convergence for Sunday (3rd) Still looks likely the Big day will be Monday 4th April but as Nathan says not fun chasing across the Arklatex and Forests further East.

DAY 4-8 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0409 AM CDT THU MAR 31 2011

VALID 031200Z - 081200Z

...DISCUSSION...

SOME TIMING AND AMPLITUDE DIFFERENCES PERSIST AMONG GFS...ECMWF AND

ENSEMBLE MEMBERS. HOWEVER...MODELS HAVE GENERALLY CONVERGED TOWARD A

SIMILAR SOLUTION REGARDING UPPER TROUGH FORECAST TO AMPLIFY AND MOVE

INTO THE PLAINS LATE DAY 4...THEN MS/OH VALLEYS AND SERN STATES DAY

5 AND FINALLY ATLANTIC COASTAL REGION DAY 6. IT APPEARS THIS FEATURE

WILL REMAIN A PROGRESSIVE UPPER WAVE AS IT ADVANCES THROUGH THE ERN

2/3 OF THE COUNTRY.

...DAY 4...

LLJ ASSOCIATED WITH CNTRL PLAINS LEE CYCLONE WILL CONTINUE ADVECTING

RICHER GULF MOISTURE THROUGH WARM SECTOR ACROSS THE SRN-CNTRL PLAINS

AND LOWER-MID MS VALLEY. EML WILL EXPAND EWD AND EFFECTIVELY CAP

WARM SECTOR EAST OF DRYLINE OVER THE PLAINS. HOWEVER...POTENTIAL

WILL EXIST FOR IMPULSE TO EJECT EWD AHEAD OF MAIN UPPER TROUGH.

DIABATIC WARMING OF THE BOUNDARY LAYER AND DRYLINE CONVERGENCE MIGHT

BECOME SUFFICIENT FOR ISOLATED SUPERCELLS FROM KS SWD INTO OK AND

NRN TX. ADDITIONAL STORMS WILL BE MORE LIKELY AS THE COLD FRONT

ADVANCES SEWD AND INTERCEPTS THE DRYLINE FROM THE CNTRL PLAINS INTO

THE MID MS VALLEY AREA.

...DAY 5...

WIDESPREAD SEVERE STORMS ARE BECOMING INCREASINGLY PROBABLE DAY 5.

GULF MOISTURE WILL ADVECT NWD THROUGH LOWER-MID MS VALLEY...SERN

STATES AND OH VALLEY IN ASSOCIATION WITH VERY STRONG EWD MIGRATING

LLJ. MORE WIDESPREAD THUNDERSTORM DEVELOPMENT WILL BECOME PROBABLE

AS FORCING FOR DEEP ASCENT ATTENDING THE UPPER TROUGH SHIFTS EAST OF

STRONGER EML. THREAT WILL EXIST FOR SUPERCELLS AND LINE SEGMENTS

WITH TORNADOES...LARGE HAIL AND DAMAGING WIND.

...DAY 6...

SEVERE THREAT SHOULD CONTINUE THROUGH THE REMAINDER OF THE SERN

STATES AND THE MID ATLANTIC SEABOARD.

[nsrobins]

Big loaded gun set-up Sunday Paul with a really stiff LLJ.

'Once it pops watch those funnels drop'

[Paul Sherman]

Hi Neil

Had a look at the 18z Models and Still looking like an Unbreakable Cap for Kansas, Oklahoma and Texas. Until one of the Main Models shows "Something" Then we have to presume that Suntans are the order of the day, but as you say all that energy and Forecast Skew-T's point to the Loaded Gun Scenario, If one Pops in daylight hours it could be quite the Supercell off the Dryline.

Interestingly on viewing the GFS18z and Twisterdata they now both break out a Lone Supercell at 00z Monday (6pm Usa Time) in the Sand Hills Region of Nebraska, Weakening Cinh with Middle to Upper 50's Dewpoints and Temperatures of 73f (73/59) Maybe the Elevation like the panhandles does not need such rich moisture (We Shall See)

Very nice Dewpoints Further South in the Mid to High 60's but what the hell is going to trigger it

The Low currently is progged to move across the Kansas and Nebraska Border.

If we were Chasing at the moment would be sitting around the Hays (Kansas) Area and awaiting further Model runs esp the NAM & RUC Models.

Paul S

Edit: Lol Twisterdata uses GFS Data as well - Doh!

[Paul Sherman]

As we are getting nearer to the Sunday Timeframe finer scale Mesoscale Features are now coming into play and showing what could be the trigger for Storms To Fire. It now looks like where a SE Moving Cold Front intercepts the Dryline will be the focus for Supercells to kick off, favoured areas at the moment seem to be Eastern Half of Oklahoma into Arkansas and Missouri around the 22z Timeframe.

Paul S

[user700]

Apr 1, 2011 0730 UTC Day 3 Severe Thunderstorm Outlook

DAY 3 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0255 AM CDT FRI APR 01 2011

VALID 031200Z - 041200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE MID MS VALLEY TO SRN

PLAINS...

...SYNOPSIS...

00Z GFS/ECMWF ARE IN FAIR AGREEMENT WITH THE MID-UPPER LEVEL TROUGH

MOVING INTO THE WRN U.S. ON DAY 2 WHICH WILL UNDERGO FURTHER

AMPLIFICATION AS IT PROGRESSES EWD AND EXTENDS NEWD FROM THE SRN

ROCKIES TO THE NRN PLAINS AS A POSITIVELY-TILTED TROUGH. TWO

PRIMARY SHORTWAVE TROUGHS COMPRISING THIS SYSTEM WILL REMAIN IN

PHASE...WITH ONE TRACKING EWD FROM THE NRN ROCKIES TO THE UPPER

MIDWEST...AND THE SECOND DIGGING SEWD TOWARD NM BY 12Z MONDAY.

AT THE SURFACE...AN AREA OF LOW PRESSURE INITIALLY LOCATED OVER THE

CENTRAL PLAINS SHOULD MOVE ENEWD INTO IA BY SUNDAY EVENING AND THEN

TRACK TOWARD THE WRN GREAT LAKES SUNDAY NIGHT. A TRAILING COLD

FRONT WILL ADVANCE SSEWD THROUGH THE CENTRAL AND SRN PLAINS AND

INTERSECT THE NRN EXTENT OF THE DRY LINE IN ERN KS SUNDAY AFTERNOON.

THE DRY LINE WILL EXTEND SWD THROUGH CENTRAL OK TO CENTRAL TX SUNDAY

AFTERNOON. MEANWHILE...A WARM FRONT WILL LIFT NEWD FROM THE LOWER

MO VALLEY INTO THE OH VALLEY ON DAY 2.

...OH VALLEY/SRN GREAT LAKES SWWD TO CENTRAL/SRN PLAINS...

ELEVATED TSTMS ARE EXPECTED TO BE ONGOING...ALONG AND E OF THE WARM

FRONT...FROM ERN MO N/NWWD INTO IA WITHIN THE NOSE OF A STRONG SWLY

LLJ /50-60 KT/. LOW LEVEL MOISTENING/WAA WITHIN THIS REGIME BENEATH

STEEP MIDLEVEL LAPSE RATES WILL BE PROMOTING AT LEAST AN ISOLATED

SEVERE HAIL THREAT AT 12Z SUNDAY. THIS ISOLATED SEVERE THREAT

SHOULD PERSIST THROUGH SUNDAY MORNING AS ACTIVITY ADVANCES INTO IL

ALONG NOSE OF LLJ. THIS JET WILL SHIFT EWD INTO THE LOWER OH VALLEY

SUNDAY BENEATH PLUME OF STEEP MIDLEVEL LAPSE RATES ALSO SPREADING

EWD...RESULTING IN WIDESPREAD CLOUDS/SHOWERS N OF THE WARM FRONT.

MODELS SUGGEST CONVECTION SHOULD DIMINISH IN COVERAGE/INTENSITY BY

SUNDAY AFTERNOON...GIVEN HEIGHT RISES AND LACK OF STRONGER FORCING

ALOFT NEGATING ADDITIONAL TSTM INITIATION. RE-STRENGTHENING OF THE

OH VALLEY LLJ EXPECTED SUNDAY NIGHT WILL SUPPORT AN INCREASE IN

ELEVATED TSTMS ACROSS THIS REGION INTO THE SRN GREAT LAKES.

MARGINAL INSTABILITY WITH EWD EXTENT AND INCREASING EFFECTIVE BULK

SHEAR N OF THE WARM FRONT MAY SUPPORT A FEW STRONGER STORMS...SOME

SEVERE.

MEANWHILE...THE STRONG EML OVER THE WARM SECTOR SHOULD LIMIT

DIURNAL TSTM DEVELOPMENT ALONG AND E OF THE DRY LINE THROUGH MUCH OF

THE AFTERNOON. STRONG SLY LOW LEVEL FLOW THIS PERIOD FROM THE SRN

PLAINS TO LOWER MO VALLEY WILL TRANSPORT MOISTURE NWD BENEATH A

PLUME OF STEEP MIDLEVEL LAPSE RATES RESULTING IN A CORRIDOR OF

MODERATE INSTABILITY EXTENDING EWD FROM THE DRY LINE INTO WRN AR AND

THE MID MS VALLEY. THIS COMBINED WITH EFFECTIVE BULK SHEAR /35-50

KT/ WILL SUPPORT ORGANIZED STRONG TO SEVERE /SUPERCELLULAR/ STORMS.

LARGE HAIL...DAMAGING WINDS AND INCREASING LOW LEVEL SHEAR ALONG A

SECONDARY LLJ FROM OK TO MO WILL SUPPORT A TORNADO THREAT. 00Z

ECMWF AND 21Z SREF SUGGEST ISOLATED STRONG TO SEVERE STORMS

/SUPERCELLS/ WILL BE POSSIBLE LATE SUNDAY AFTERNOON...AS THE COLD

FRONT ENCOUNTERS THE DRY LINE AND SWD ALONG THE DRY LINE WHERE

SURFACE HEATING WILL BE MAXIMIZED. TSTM COVERAGE IS EXPECTED TO

INCREASE SUNDAY NIGHT AND SPREAD E AND SE ALONG AND AHEAD OF THE

COLD FRONT. MODERATE INSTABILITY INTO THE OVERNIGHT PERIOD COMBINED

WITH BACKING SHEAR VECTORS SUGGESTS STORMS SHOULD EVOLVE INTO A

LINEAR MODE.

[nsrobins]

12Z NAM and I'm thinking this could develop into a big event Sunday evening - and I'm targetting SC KS.

Really impressive gulf moisture streaming up (68F) under a cooler 700mb layer moving in with the cold front will provide ample instability (circa 2000 CAPE) in a really turbulant environment. It seems the stout LLJ is turning up to 8 EHI (wow) in a bullseye NC OK - but (big but) the lid doesn't dissipate until 00Z if at all here - but does seem to dissolve enough a bit further north in my target area.

We've seen these set-ups before and should the juxtaposition of de-inhibition and DL/cold front intersection - providing the nudge - fall together it could be a big event for massive supercells with plenty of vertical rotation.

All might change, though one to watch.

The action then transfers east with equally big prospects for a widespread severe event Monday.

SPC may well go moderate on Sun quite early on this.

[Paul Sherman]

Okay going to go with a Prelimary Chase Target here and firm up for definate tomorrow evening (Have to make this as real as if we are out there) Last night I said we would be in Hays (Kansas) So we would have re-positioned this evening to be staying at Topeka (Kansas) as 3 of the last 4 Model runs have consistantly broken out a Lone Supercell in NE Kansas moving into SW Iowa. Not only that but I still do not think the Cap will go further South until the Cold Front triggers it off. But I can see where Neil is coming from as if something can get that Dryline Firing Further South an Amazing Supercell could rampage across Southern Kansas. So would be favouring the Warm Front play atm over the Dryline (This is rare for me as I am a Massive Lover of Dryline Set-Ups)

Some 18z Charts From Netweather will post NAM Tomorrow and RUC Sunday!

- 2,000 - 3,000jkg of CAPE To Work With

- Can see the Cap eroding in NE Kansas at the 00z Timeframe

- Lone Storm Firing at 00z (Has been on the last 3 runs in same area)

- NE Of the Surface Low

- Temps up to 74f in Target Zone

- Dp's around the 59f Mark

So my Chase Target at the Moment is the NE Kansas and SW Iowa Border.

Paul S

[user700]

My chase target for tomorrow is east Kansas also but I am not seeing any precipitation totals. The cap maybe to strong.

Edited April 2, 2011 by danieluk

[Rob]

No storm warnings out for today, at least not yet anyway

[Paul Sherman]

Latest GFS Now showing the Risk area pushed even further South East and the Dryline firing further down into SE Kansas, before it all evolves into a Huge MCS The size of the UK

Saturday 9th April at the moment looks incredible on the GFS :wacko:

[Rob]

Latest GFS Now showing the Risk area pushed even further South East and the Dryline firing further down into SE Kansas, before it all evolves into a Huge MCS The size of the UK

Saturday 9th April at the moment looks incredible on the GFS :wacko:

Can you post these charts, would be good to take a look at this!

[Paul Sherman]

Can you post these charts, would be good to take a look at this!

- 6pm Usa Time - Convection Fires Much further SE Than earlier Model Runs

- Midnight Usa Time and That MCS covers a massive area

Meant to Say Friday 8th Looks amazing and Not Saturday 9th (00z Saturday)

[Rob]

Wow CAPE values over 3,000! I don't think i've ever seen that over the UK. I've got to go on one of these chases to experience some real storms!

[Paul Sherman]

Tomorrow's Risk is upto 3,000jkg as well. Last year's biggest Cape Totals we chased were 7,000jkg but with that comes Giant Hail upto Softball Sized or Larger - Lol