Virtual storm chase

[Gorky]

Tomorrow looks like it is shaping up to be a pretty big event. I'm wondering if they'll upgrade to a moderate risk with the next outlook. Things could get pretty hairy down towards Arkansas given progged instability and shear... should the cap not be too strong.

Edit:

SPC beat me to the post with their update and chose not to upgrade yet.. They have hatched a large area for significant weather chances however including parts of Texas/Oklahoma and Arkansas however.

Edited April 2, 2007 by Gorky

[Paul Sherman]

As Nathan says quite a massive Slight Risk for tomorrow and good Tor Progs as well, to put into perspective you could probably fit 4 of the UK into that Slight Risk area. Unfortunately areas in that risk are not favoured by Chasers and as such I would probably locate myself down near to just below the Red River, so I am going for Sherman (Texas) as that area has some nice chase area up to the forests and swaps of Eastern Oklahoma, Arkansas has some plains but again some pretty awful chase country. Tough one this but I am going for the far south-western end of the Slight Risk. Today also sees a Slight risk for parts of eastern Nebraska and eastwards from there.

Paul Sherman

[NL]

Think i'll start from Cherokee Okalahoma and travel east through to Springfield Missouri, capping will be evident but should be broken hopefully early afternoon due to surface heating do i go south to Arkansas

and risk difficult chasing conditions or continue North east to South West Illinois..???

[NL]

Tornado warning out for south west Nebraska....

Statement as of 5:42 PM MDT on April 02, 2007

The National Weather Service in North Platte has issued a

* Tornado Warning for...

Keith County in southwest Nebraska...

this includes the city of Ogallala...

* until 615 PM MDT

* at 541 PM MDT... National Weather Service Doppler radar indicated a

severe thunderstorm capable of producing a tornado near Lemoyne...

or about 11 miles northwest of Ogallala... moving east at 40 mph.

* The tornado will be near...

9 miles north of Ogallala by 550 PM MDT...

Keystone and 7 miles north of Roscoe by 555 PM MDT...

Sarben and Paxton by 610 PM MDT...

[Nick F]

SPC have slapped a MDT risk of severe storms over Illinois, Indianna, W Kentucky and SE Missouri for this evening/overnight.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1259 AM CDT TUE APR 03 2007

VALID 031200Z - 041200Z

...THERE IS A MDT RISK OF SVR TSTMS ACROSS CNTRL/SRN

IL...IND...EXTREME WRN OH...EXTREME SERN MO...WRN KY AND WRN TN THIS

AFTN AND TONIGHT...

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPR/MID MS RVR VLY

REGION EWD INTO THE OH VLY AND SWWD INTO THE SRN PLAINS...

...SYNOPSIS...

STRONG UPPER SHORTWAVE TROUGH ACCOMPANIED BY 150+ METER H5 HEIGHT

FALLS AND A 100 KT MID-LEVEL JET WILL TRANSLATE QUICKLY EWD ACROSS

THE MIDWEST AND GRTLKS REGION TODAY AND TONIGHT. AT THE SFC...LOW

WILL INTENSIFY AS IT MOVES FROM IA INTO LWR MI BY EVENING. AN

INTENSE COLD FRONT S OF THE LOW WILL SWEEP EWD INTO THE OH VLY.

TAIL END OF THE FRONT WILL SETTLE SWD INTO THE TN/LWR MS VLY AND SRN

PLAINS OVERNIGHT. THE FRONT WILL BE THE FOCUS FOR ACTIVE SEVERE

WEATHER TODAY AND TONIGHT.

...UPR/MID MS RVR VLY EWD INTO THE OH VLY...

ELEVATED TSTMS WITH LARGE HAIL MAY BE ONGOING AT THE START OF THE

PERIOD ACROSS PARTS OF SRN WI INTO LWR MI. THIS ACTIVITY WILL

LIKELY PERSIST INTO THE AFTN...ESPECIALLY ACROSS LWR MI.

STRONG LARGE SCALE ASCENT ASSOCD WITH THE UPPER LEVEL TROUGH WILL

SPREAD ACROSS THE MID/UPR MS RVR AREA LATE THIS MORNING...THEN EWD

INTO THE MIDWEST BY THIS EVENING. STRONG SSWLY LOW-LEVEL FLOW IN

ADVANCE OF THIS SYSTEM WILL TRANSPORT MODEST BOUNDARY LAYER MOISTURE

NWD AHEAD OF THE COLD FRONT. BY MID-AFTN...SFC DEW POINTS WILL

RANGE FROM THE MID 50S TO MID 60S. LATE EVENING OBSERVED SOUNDINGS

SAMPLED A PLUME OF VERY STEEP LAPSE RATES /7+ DEG C PER KM/

STREAMING NEWD ATOP THIS MOISTURE TRANSPORT. GIVEN THE ANTICIPATED

SUNSHINE IN THE WARM SECTOR...MLCAPES WILL LIKELY RANGE FROM

1500-2500 J/KG THIS AFTERNOON.

GIVEN STRENGTH OF THE SYSTEM...TSTMS WILL PROBABLY DEVELOP BOTH

ALONG THE COLD FRONT AND IN THE DOWNSTREAM WARM SECTOR AS THE

LOW-LEVEL FLOW BEGINS TO RESPOND /I.E. PRE-FRONTAL CONFLUENCE/.

PRIND THAT INITIATION WILL BE ACROSS NCNTRL/NERN MO AND WRN IL BY

MID-AFTN...THEN DEVELOP/MOVE E AND SEWD INTO IL...SERN MO AND NERN

AR DURING THE EVENING. THE MEAN WIND VECTORS WILL LARGELY BE NORMAL

TO THE INITIATING BOUNDARIES...SUGGESTING THAT INITIAL STORMS MAY

REMAIN DISCRETE FOR A FEW HOURS. VERTICAL SHEAR IN EXCESS OF 40 KTS

WILL FAVOR SUPERCELLS WITH VERY LARGE HAIL AND DAMAGING WINDS. A

FEW TORNADOES WILL BE POSSIBLE WITH ANY DEVIANT RIGHT-MOVING

MEMBERS...THOUGH THE LFC/S WILL BE SOMEWHAT HIGH.

AIR MASS DOWNSTREAM ACROSS THE OH VLY WILL MOISTEN AND DESTABILIZE

QUICKLY DURING THE LATE AFTN/EVE. AS THE STRONGER DPVA SWEEPS EWD

LATE IN THE AFTN...EVOLUTION INTO A FAST MOVING BOW ECHO TYPE OF

SYSTEM WILL PROBABLY TAKE PLACE ACROSS IL...IND AND OH. AS A

RESULT... DAMAGING WINDS WILL BECOME THE PRIMARY SEVERE

THREAT...THOUGH HAIL/ISOLD SPIN-UPS WILL ACCOMPANY EMBEDDED

SUPERCELL STRUCTURES. ERN EDGE OF THE SVR THREAT WILL LIKELY BE

ACROSS THE MID/UPPER OH VLY REGION OVERNIGHT AS THE STORMS BEGIN TO

MOVE BEYOND THE INSTABILITY AXIS.

FARTHER S...SUPERCELL STORMS MAY LAST LONGER AS THEY BACKBUILD INTO

THE STRONGER INSTABILITY POOL ACROSS THE MID-SOUTH. THIS REGION

WILL RESIDE ALONG THE SRN PERIPHERY OF 40 KT H5 FLOW. AS A

RESULT...VERY LARGE HAIL WILL BE LIKELY ALONG WITH AN ISOLD TORNADO

THREAT WELL INTO THE EVENING ACROSS THESE AREAS.

...AR SWWD INTO TX...

WHILE THE PRIMARY SVR EPISODE WILL OCCUR ALONG NRN REACHES OF THE

COLD FRONT...TSTMS WILL BACKBUILD SWWD THROUGH AR AND INTO PARTS OF

TX DURING THE EVENING AS CINH BEGINS TO ERODE ALONG THE FRONT.

VERTICAL SHEAR WILL BE COMPARATIVELY WEAKER THAN AT POINTS TO THE

NORTHEAST...BUT VERY STEEP LAPSE RATES AND QUALITY BOUNDARY LAYER

MOISTURE WILL RESULT IN MLCAPES IN EXCESS OF 2500-3000 J/KG. AS A

RESULT...VIGOROUS UPDRAFTS CAN BE EXPECTED WITH RISKS FOR VERY LARGE

HAIL AND PERHAPS A TORNADO OR TWO. WWD EXTENT OF THE SVR RISKS ARE

UNCERTAIN...BUT LOW PROBABILITIES WILL EXIST AS FAR W AS THE DRYLINE

IN PARTS OF CNTRL TX...SHOULD THE CAP BECOME BREACHED.

...DEEP S...

LEADING EDGE OF RICH BOUNDARY LAYER MOISTURE WILL ADVECT NEWD INTO

PARTS OF THE DEEP S TODAY AND TONIGHT. WEAK PERTURBATIONS EMANATING

FROM A BAJA UPPER LOW WILL ADVANCE NEWD AND ENHANCE TSTMS THAT FORM

ALONG THE MOISTURE RETURN. AT THE SAME TIME...NRN STREAM

LOW-AMPLITUDE CYCLONIC CURVATURE WILL SKIRT ACROSS AT LEAST NRN

PARTS OF THE SRN STATES DURING THE EVE. LAPSE RATES ALOFT ARE QUITE

STEEP AND ANY STORM WILL BE CAPABLE OF LARGE HAIL.

..RACY/JEWELL.. 04/03/2007

[Nick F]

00z GFS progs suggest max CAPE in the SWern part of the MDT area at 00zUTC tonight, around SE MO, W KY and S IL. Also strongest capping here aswell. though slight capping often allows the strongest storms to develop, due to keeping the heat at the surface until the cap finally erodes due to forcing from the strong cold front predicted to move in from the NW. So this SW part of the MDT area IMO most likely to see supercells spawn a tornado, though main risk atm seems to be large hail and v. strong straight line gusts.

[Gorky]

I'm sticking with North Eastern Arkansas into the Missouri Bootheel. There is some reasonable chase terrain in the area, although you would want to plan any potential river crossings in advance by not positioning too far from a bridge over the Mississippi River. Hopefully things will have less of a tendency to turn linear further south and the storms can tap into some of the best instability in the area.

[Nick F]

SPC have enlarged the MDT risk area this afternoon, now including a larger portion of Arkansas, SW Missouri and W Tennesse. Not great chase country over E Arkansas/SW Missouri I gather - with this area quite hilly and wooded. However this looks likely the area for severe potential to produce tornadoes, there's now a tornado watch out aswell for this area along with parts of Sern IL, SW Indiana and W KY. This SW part of the MDT risk area is weakly capped ahead of the surface cold front which is NW of St. Louis, and as a result the highest amount of CAPE is likely to be released in this area resulting in greater chance of tornadoes as low-level wind shear increases as the surface cold front moves through SEwards.

URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 111

NWS STORM PREDICTION CENTER NORMAN OK

1150 AM CDT TUE APR 3 2007

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

SOUTHERN ILLINOIS

FAR SOUTHWESTERN INDIANA

WESTERN AND PARTS OF CENTRAL KENTUCKY

MUCH OF THE SOUTHERN MISSOURI

EFFECTIVE THIS TUESDAY MORNING AND EVENING FROM 1150 AM UNTIL 800

PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 75 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 15 MILES NORTH OF JOPLIN

MISSOURI TO 20 MILES EAST OF EVANSVILLE INDIANA. FOR A COMPLETE

DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE

(WOUS64 KWNS WOU1).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS.

OTHER WATCH INFORMATION...CONTINUE...WW 109...WW 110...

DISCUSSION...RAPID INTENSIFICATION OF THUNDERSTORMS EXPECTED ACROSS

THE WATCH AREA THROUGH THE AFTERNOON AS THE AIRMASS HAS BECOME VERY

UNSTABLE AND WEAKLY CAPPED. SHEAR SUFFICIENT TO SUPPORT ORGANIZED

LINES/BOWS AND SUPERCELLS. TORNADOS MOST LIKELY ASSOCIATED WITH ANY

SUPERCELL WITH POTENTIAL FOR WIDESPREAD DAMAGING WINDS DEVELOPING

SEWD FROM SRN MO INTO LOWER OH VALLEY BY MID AFTERNOON.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 27035.

...HALES

[kold weather]

Plenty of strength to the jet streak that runs over the to pof the area that is highlighted as mod.

As you say Nick the area is presently weakly capped however looing at the models they are progging that the cap to weaken a lot as the front comes down from the NW. I'd suppose that as the cap decays a little more and tmeps start to max out over the next 3-5hrs ahea dof the frontal system around between 22-26C by the looks of things. This should be enough IMO to break the weak cap thats present though as the cap completely decays there could be quite a few cells breaking out so it may become a little messy, though no doubt any cells that do beocme supercells will obviously become quite potent. Cape probably somewhere between 1500-2000kj's of cape so while its not going to be one of those blockbuster days with utter monsters there is certainly enough energy present for some potent storms which could be nasty and given some decent shear that is present thanks to a jet streak which extends well upto in the atmopshere.

Until the cap finally compeltely decays as the front comes through could be some quite neat looking cells breaking out and some good phot chances I dare say.

Edited April 3, 2007 by kold weather

[Nick F]

Yes Kold, some decent Low-level shear and SR Helicity from current progs over Sern Missouri, NE Arkansas, Sern Illinois, W Kentucky and W TN - any tornadoes most likely under supercells which form in this area of strong LL shear and SR Helicity over next 2-6hrs:

sfc-1km shear vector:

Storm relative (SR) Helicity:

When the weak cap is eroded SE of St. Louis (where storms are currently activating along/ahead the CF) lots of CAPE (2500-3000 j/kg) is suggested to be released over the SW portion of the MDT risk area aswell which will help tornado formation through enhanced instability, here's the 18z CAPE/wind chart, you can clearly see where the SW-NE cold front is where winds veer sharply from S/SW to NW:

IMO these cold front storms look high preciptn. and could be rather messy with low cloud and rain/hailcores - classic dry line storms tend to be less messy to chase and photograph.

[Paul Sherman]

Ukww Chase Team 1 have been sitting in North Eastern Arkansas since yesterday so could have some joy from the first Uk Chase team for 2007. Will update you later on their progress. Eastern Arkansas and the MO Bootheel actually dont have that bad a Chase Territory compared with the Central and Western Parts of Arkansas which is like Eastern and South-Eastern Oklahoma (Think Swamps and Forests) , so if its to be had then the only problems to encounter are River crossings across the Mississippi.

Paul Sherman

[Nick F]

Yes Paul, Chase team 1 should be well positioned to go in the Mississipi Valley where it's flat and fairly tree free to move North.

Tornado warning for a few counties in Sern Illinois atm:

... A Tornado Warning remains in effect until 115 PM CDT for western

Clark and northeastern Cumberland counties...

At 1255 PM CDT... National Weather Service Doppler radar continued to

indicate a tornado. This tornado was located near Union Center... or

about 10 miles northeast of Toledo... moving east at 30 mph.

People near these locations are still threatened...

Union Center...

Martinsville...

When a Tornado Warning is issued based on Doppler radar... it means

that strong rotation has been detected in the storm. A tornado may

already be on the ground... or is expected to develop shortly. If you

are in the path of this dangerous storm... move indoors and to the

lowest level of the building. Stay away from windows. If driving... do

not seek shelter under a Highway overpass.

[NL]

[Nick F]

Some extreme echoes along the CF storm line passing SE through SEern MO, Sern Illinois and now coming into extreme NE tip of Arkansas, suspect there some rather big hail in there - golf ball size going by the warnings:

Further East, and not in the Tornado Watch area, isolated area of supercells over Sern Tennessee has spawned a Tornado Warning, not great chase territory there with hills and trees looking at the maps - so don't expect many chasing there:

... A Tornado Warning remains in effect until 415 PM CDT for Grundy

County...

At 353 PM CDT... National Weather Service Doppler radar continued to

indicate a tornado. This tornado was located near Coalmont... or

about 18 miles west of Dunlap... moving northeast at 40 mph.

The tornado will be in...

rural northeastern Grundy County at 410 PM CDT

In addition to the tornado... this storm is capable of producing

golfball size hail.

Anyway ... keep an eye on the SW tail end of the CF storm line coming across SErn Missouri into NE Arkansas ... favour a tornado report there soon, Chase Team 1 maybe in that general area too.

[WhiteFox]

It's a big-assed system alright!

A very potent cold front too. Some wide temperature variations between the Upper Midwest in Minnesota and Northern Illinois. Got to love this time of year!

[Paul Sherman]

http://www.nws.noaa.gov/nwr/streamaudio.html#livestream

Get on the Fort Smith Weather radio, some interesting storms developing at present

Anyone find a better one, dont know where Morrilton or Springthingy is in Arkansas?? Need them to be near to the North East of the State

Actually Morrilton is better

[pottyprof]

somebody's using all their bandwidth.....

[Paul Sherman]

Interesting couple of Md's issued for Central and North Central Texas areas near to Fort Worth for the next few hours. I would rather be on the Tail enders in Central Arkansas than the Junkvection eastward moving Cold Front further North East, would be spectacular to see the approaching gust front but after that you would be in precip for about 10 hours

Paul S

**Just had another Warning come through on the Weather radio, seems Storms are initiating in Central Arkansas.

[Nick F]

Tornado Warning for Clay County Arkansas, will Chase Team 1 be in the area?

The National Weather Service in Memphis has issued a

* Tornado Warning for...

Clay County in eastern Arkansas...

* until 615 PM CDT

* at 522 PM CDT... National Weather Service Doppler radar indicated a

severe thunderstorm capable of producing a tornado near Corning...

moving east at 35 mph.

* Other locations in the warning include but are not limited to

Hickoria... McDougal... Pollard... Greenway... Piggott and St. Francis

.If no basement is available... Seek shelter on the lowest floor of

the building in an interior hallway or room such as a closet. Use

blankets or pillows to cover your body and always stay away from

windows.

.If in Mobile homes or vehicles... Evacuate them and get inside a

substantial shelter. If no shelter is available... lie flat in the

nearest ditch or other low spot and cover your head with your hands

More tail-end cells firing up further SW over Arkansas as the cap erodes on approach of the cold front and the pre-frontal convergence.

[pottyprof]

Is that just a quirk of the radar over SE Marshall County??

[Nick F]

Here's the storm line over NE Arkansas and SE Missouri, purple diamond on far left shows poss. tornado over clay county - very high preciptn ... would have to keep moving SE to get ahead of the line of storms as there's no other way round em - but to to go under them with risk of large hail!

[Paul Sherman]

By the looks of that radar Nick, it looks like if not already will certainly be close to producing a Tornado, nice hook echo, also another interesting storm breaking ahead of the front way up to the North East. Would expect the Tornado count to pick up in the next 2-3 hours.

Paul S

[Paul Sherman]

Nicks Hook echo cell

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 615 PM CDT FOR CLAY

COUNTY...

AT 543 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO

INDICATE A TORNADO. THIS TORNADO WAS LOCATED 6 MILES NORTHWEST OF

RECTOR...MOVING EAST AT 40 MPH.

OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO

GREENWAY AND PIGGOTT.

AT 532 PM CDT...A TRAINED SPOTTER REPORTED QUARTER SIZE HAIL IN

NORTH CORNING.

Paul S

[pottyprof]

Damn... Beat me to it Paul..

2 tornado reports from NOAA

2118 2 N AUSTIN SCOTT IN 3877 8581 TORNADO ON THE GROUND (LMK)

2250 RECTOR CLAY AR 3626 9029 (MEG)

Times are GMT

[AudMun]

Just been looking at the Models and looks like quite a lull possibly setting up with the Omega Block scenario and North West Flow over the Alley, dont mind if the "Death Ridge" sets up for a few weeks in April, just as long as it clears off in 4 weeks time

Paul S

Sorry for being a little behind with this post but could someone tell me if I am on the right track here.

Omega is basically a way of describing the movement of air. Low level hot air with driven cooler air above will create a 'shear' effect and if this warmer air has moisture in it as well then it will allow hail and rain to be created once the moist air gains sufficient height and therefore enters a cooler region. This process will cause extra heat to be released again aiding the further heating of the surrounding air, that had begun to lose any upward movement due to the cooling process, meaning that the cloud will continue to grow. In this case the high pressure area is causing the 'Omega Block'.

Having the high pressure system running diagonally through the center of the country at the moment will mean that this cool air is not allowed in so any air movement will only therefore be vertical. This is what is being referred to as the 'Death Ridge'.

One thing I can't find an answer to and that is what causes the revolving storm air to head for and ultimately reach the ground thereby creating a tornado?

I do hope that I am somewhere in the region of right here but please can someone be kind enough to point me in the right direction if not.

Many thanks

Stewart