Chase 2009 Day 5 Discussion - Ok And Ks

[Nick F]

Well today it looks like the emphasis for severe storms shifts NEwards, so a drive NE into Oklahoma looks likely. Supercells less likely to develop tornadoes today perhaps, and the cold front slowly moving SE and outflow boundaries will be the main forcing mechanism rather than the dry line which will be over Wern TX today with no storm forecast there. Looking at CAPE values, central Oklahoma looks favourable for highest values and this is overlapped by fairly decent helicity values too. I think there will be some tornado reports over central OK and S-central KS later today, though main threat large hail and damaging winds.

I would initially target central Oklahoma near Dave Ewoldt's (our American chasing pal) house in Orkarche near OK City.

WRF 00z Fri SBCAPE:

WRF 00z Fri 0-3km and 0-1km helicity:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1252 AM CDT THU APR 30 2009

VALID 301200Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE

CNTRL/SRN PLNS NEWD INTO THE MID-MS AND OH RVR VLYS...

...SYNOPSIS...

LOW-AMPLITUDE CYCLONIC FLOW REGIME WILL CONTINUE ACROSS THE PLNS AND

INTERMOUNTAIN WEST ALONG SRN FRINGE OF AN ELONGATED UPR TROUGH OVER

THE NRN TIER OF THE COUNTRY. ERN PORTIONS OF THE TROUGH WILL

AMPLIFY TODAY...TRANSLATING FROM THE NRN PLNS INTO ONT.

MEANWHILE...A WEAKER BELT OF WLYS WILL EXIST ACROSS THE SRN PLNS

INTO THE OH VLY...CARRYING NUMEROUS MESOSCALE ENHANCED VORTICITY

CENTERS NEWD FROM TX/OK INTO THE OH VLY.

AT THE SFC...A LOW ATTENDANT TO THE NRN PLNS DISTURBANCE WILL TRAVEL

FROM NWRN MN EARLY THURSDAY INTO NWRN ONT BY THURSDAY EVE. A

FRACTURED CDFNT WILL SETTLE SEWD THROUGH THE UPR MS VLY AND

CNTRL/SRN PLNS THROUGH THE PD. MEANWHILE...A DIFFUSE WRMFNT/OUTFLOW

BOUNDARY WILL REDEVELOP/WASH-OUT ACROSS THE LWR MS VLY/ARKLATEX

REGION THROUGHOUT THE DAY WHILE A SYNOPTIC WRMFNT RAPIDLY DEVELOPS

NEWD THROUGH THE LWR GRTLKS REGION/OH VLY.

...ARKLATEX NEWD INTO THE OH VLY...

TWO MCV/S ARE EXPECTED TO PLAY PIVOTAL ROLES IN ENHANCING TSTM

THREATS ON THURSDAY. THE LEAD WAVE...NOW MOVING ACROSS THE MID-MS

VLY...WILL TRANSLATE ACROSS THE MIDWEST/UPR OH VLY THIS AFTN/EVE.

ENHANCED LOW/MID-LVL WSWLY FLOW OF 40-50 KTS ALONG SRN EDGE OF THIS

FEATURE WILL TRANSPORT A RESERVOIR OF 1.5 INCH PWATS NWD YIELDING AT

LEAST MARGINAL DESTABILIZATION. QUESTIONS REMAIN ON MAGNITUDE OF

HEATING...BUT THE UNIDIRECTIONAL NATURE AND STRENGTH OF THE FLOW

COULD RESULT IN BOWING LINE SEGMENTS GIVING DMGG WIND GUSTS AND

HAIL.

FARTHER TO THE SW...THE CURRENT RED RVR VLY MCS ACROSS SRN OK/NCNTRL

TX WILL LIKELY BE ONGOING AT 12Z THURSDAY OVER WRN AR AND NERN TX.

FORWARD FLANK OF THIS SYSTEM MAY STRENGTHEN DURING THE AFTN/EVE OVER

AR NEWD INTO SERN MO. DOWNSTREAM AIR MASS IS LIKELY TO BE

COMPARATIVELY MORE UNSTABLE ACROSS THIS REGION THAN ON WEDNESDAY AND

COUPLED WITH 40-45 KT SWLY FLOW BENEATH MODEST WLY H5 FLOW...SMALL

SCALE BOWS/BRIEF SUPERCELL STRUCTURES WILL BE POSSIBLE WITH DMGG

WINDS AND HAIL.

...CNTRL/SRN PLNS...

CONSIDERABLE UNCERTAINTY EXISTS ON THURSDAYS CONVECTIVE SCENARIO

OVER KS...OK AND WRN MO. OVERALL LARGE SCALE WOULD SUGGEST THAT

PRIMARY SVR THREATS WILL ACCOMPANY THE STRONGER LLJ SEGMENTS FARTHER

E OVER THE OH/MS VLYS. HOWEVER...LLVL MOISTURE WILL BE MAINTAINED

ALONG/AHEAD OF THE SEWD MOVING FRACTURED CDFNT/OUTFLOW BOUNDARIES

AND COUPLED WITH VERY STEEP MID-LVL LAPSE RATES...THERE WILL BE A

CONCERN FOR AT LEAST ISOLD SVR TSTMS. STRENGTH OF THE EML...WEAK

FEATURES ALOFT AND RELATIVELY WEAK LLVL FLOW SUGGEST THAT STRONG

HEATING WILL BE NEEDED TO ERODE THE CAP AND CONTRIBUTE TO POSSIBLE

AFTN TSTM INITIATION...PRIMARILY FROM WRN MO SWWD INTO SRN KS.

ISOLD STORMS MAY ALSO FORM ALONG A DIFFUSE OUTFLOW BOUNDARY ACROSS

CNTRL/NRN OK. THOUGH THE OVERALL BULK SHEAR WILL BE

MEAGER...INSTABILITY /UPWARDS OF 3000 J PER KG MLCAPES/ WILL BE

QUITE STRONG AND ANY STORM THAT FORMS COULD BRIEFLY BECOME

SUPERCELLULAR WITH WILL VERY LARGE HAIL AND DMGG WINDS.

ON THE HIGHER PLNS...ISOLD TSTMS WILL LIKELY FORM ACROSS SERN

WY...FAR WRN NEB PNHDL AND NERN CO WHERE MODESTLY MOIST UPSLOPE FLOW

MEETS THE HIGHER TERRAIN. REGION WILL RESIDE ALONG SRN PERIPHERY OF

50 KT WLY MID-LVL WLY FLOW AND SUFFICIENT SHEAR WILL EXIST FOR

ROTATING STORMS WITH ISOLD LARGE HAIL. A LOOSELY ORGANIZED MCS MAY

EVOLVE THURSDAY NIGHT AND MOVE INTO PORTIONS OF KS/SWRN NEB WITH

PERHAPS ISOLD HIGH WINDS/HAIL.

[stevestorms]

Looks good Nick, but Dave has promised us some beers so pin pointing Dave's house for a target area has be slightly worried :-) well its tonight myself and Martin leave catching a flight first thing tomorrow, should be driving from DFW to Norman by around 1500hrs CDT would welcome some lightning just south of OKC for tomorrow night although I think most of the show should be east of here unless things have changed. :-)

Edited April 30, 2009 by stevestorms

[Paul Sherman]

Central Oklahoma and into South Central Kansas today for me, Not going to venture too far East and into the Jungles and hope a Cell can fire in the Better Chase Country further West!

Nice Cape Today B)

:o

[Stuart]

that a lot of caps we dont get as much here B)

[NL]

Spc have also upgraded tornado chances too, still only 5% but at least its move in the right direction.

Latest visible sat image

Latest NWS hazadous weather forecast,Oklahoma.

HAZARDOUS WEATHER OUTLOOK

NATIONAL WEATHER SERVICE NORMAN OK

1014 AM CDT THU APR 30 2009

OKZ004>048-050>052-TXZ083>090-011000-

HARPER-WOODS-ALFALFA-GRANT-KAY-ELLIS-WOODWARD-MAJOR-GARFIELD-NOBLE-

ROGER MILLS-DEWEY-CUSTER-BLAINE-KINGFISHER-LOGAN-PAYNE-BECKHAM-

WAonionsA-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-MCCLAIN-CLEVELAND-

POTTAWATOMIE-SEMINOLE-HUGHES-HARMON-GREER-KIOWA-JACKSON-TILLMAN-

COMANCHE-STEPHENS-GARVIN-MURRAY-PONTOTOC-COAL-COTTON-JEFFERSON-

CARTER-JOHNSTON-ATOKA-LOVE-MARSHALL-BRYAN-HARDEMAN-FOARD-WILBARGER-

WICHITA-KNOX-BAYLOR-ARCHER-CLAY-

1014 AM CDT THU APR 30 2009

THIS HAZARDOUS WEATHER OUTLOOK COVERS NORTHERN...WESTERN...

CENTRAL...AND SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT...

THUNDERSTORM OUTLOOK...

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THIS AFTERNOON

INTO TONIGHT ACROSS ALL OF OKLAHOMA AND WESTERN NORTH TEXAS.

TIMING...

THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE FROM 4 PM

THROUGH THE NIGHT.

IMPACTS...

SOME DAMAGE TO VEGETATION...AUTOMOBILES...AND HOMES...FROM HAIL TO

THE SIZE OF TENNIS BALLS.

LOCALLY SIGNIFICANT WIND DAMAGE FROM 75 MPH WINDS.

A LOW CHANCE OF TORNADOES.

RECOMMENDED ACTIONS...

STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE

RISK AREA SHOULD PLAN FOR SEVERE WEATHER OPERATIONS FROM LATE THIS

AFTERNOON UNTIL LATE TONIGHT.

DISCUSSION...

RICH GULF MOISTURE WAS IN PLACE. DEWPOINTS WILL RISE INTO THE MIDDLE

AND LOCALLY UPPER 60S...WHILE A COLD FRONT APPROACHES FROM THE

NORTHWEST. FROM MIDDAY INTO THE AFTERNOON...A SMALL COMPLEX OF

THUNDERSTORMS WILL MOVE JUST EAST OF STILLWATER...DOWN TO INTERSTATE

40. THIS WILL PRODUCE AN OUTFLOW BOUNDARY ORIENTED NORTHWEST TO

SOUTHEAST ACROSS CENTRAL AND NORTH CENTRAL OKLAHOMA. ELSEWHERE...THE

ENTIRE REGION WILL RECEIVE PLENTY OF HEATING...RESULTING IN STRONG

INSTABILITY...WITH CAPE VALUES GREATER THAN 2500...AND POSSIBLY

APPROACHING 3500 LATE THIS AFTERNOON. CAP STRENGTH WILL BE GREATEST

TO THE WEST...AND WEAKEST NEAR THE OUTFLOW BOUNDARY. THE FRONT WILL

MOVE INTO NORTHWEST OKLAHOMA...AND A WIND SHIFT...OR TROUGH AHEAD OF

THE FRONT IS EXPECTED TO BECOME THE FOCUS FOR THUNDERSTORM

DEVELOPMENT LATE THIS AFTERNOON. THE TROUGH WILL EXTEND FROM NEAR

PONCA CITY TO WATONGA AND MANGUM. THE MOST NUMEROUS STORMS ARE

EXPECTED WHERE THE TROUGH OVERTAKES THE OUTFLOW BOUNDARY IN NORTH

CENTRAL AND CENTRAL OKLAHOMA. INITIALLY...MODERATE WIND SHEAR AND

STRONG INSTABILITY MAY RESULT IN SUPERCELLS...WITH A RISK OF VERY

LARGE HAIL...AND AT LEAST A LOW CHANCE OF TORNADOES. THE STORMS MAY

QUICKLY GROW INTO A COMPLEX...HOWEVER...AND BEGIN TO MOVE SOUTH AND

SOUTHEAST...WITH AN INCREASING THREAT OF DAMAGING WINDS...IN

ADDITION TO LARGE HAIL.

FARTHER TOWARD WESTERN OKLAHOMA AND WESTERN NORTH TEXAS...A STRONG

CAP WILL LIMIT THE NUMBER OF STORMS...BUT ANY STORMS THAT DO FORM

MAY BRIEFLY EXHIBIT SUPERCELL STRUCTURE. VERY LARGE HAIL AND

DAMAGING WINDS WILL BE POSSIBLE.

PROBABILITY TABLE...

VALID THROUGH 500 AM CDT FRIDAY MAY 1.

PROBABILITY OF THUNDERSTORMS OCCURRING IN THE

NWS NORMAN COUNTY WARNING AREA...70 PERCENT.

PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...90 PERCENT.

[Paul]

The team are about to set off and Paul has recorded his briefing for today, which you can view here:

http://www.netweather.tv/index.cgi?action=...ase-video;sess=

[Ross B]

Live stream is up now as well.

http://www.netweather.tv/index.cgi?action=chaselive;sess=

[Paul]

Talking of the live streaming page, we've now added the weather warning boxes to the google map, so when tornado or severe storm warnings are issued, you can see where the team are in relation to them.

[anvilhead]

yeah looks like storms in the better chase country will be more isolated - I wouldnt really know where to start, but setting up just north of OK city would be my option - incase the front stalls atall, then following them SE if necessary in the bounds of the 62 & 69 - any move south would be good for the coming days by the looks of the outlook ..

[Ross B]

Talking of the live streaming page, we've now added the weather warning boxes to the google map, so when tornado or severe storm warnings are issued, you can see where the team are in relation to them.

Nice one. A radar overlay would be good as well if that's possible

[Sno' problem]

There is a cell building to the NE of Oklahoma City right now, looks like the NW team are heading there now.

No tornado activity as yet, but there are flash flood warnings out from the NOAA at the moment to the East of Ponca City.

Edited April 30, 2009 by Sno' problem

[Roger J Smith]

Would suggest a watch on the region from Woodward to Clinton in western OK ... not a certainty for this region, but if it did fire, the storms would be isolated and better for chasing and viewing, perhaps.

Tomorrow's risk looks more like being fairly close to DFW.

[Nick F]

There is a cell building to the NE of Oklahoma City right now, looks like the NW team are heading there now.

No tornado activity as yet, but there are flash flood warnings out from the NOAA at the moment to the East of Ponca City.

Not really worth going that far to see that stuff NE of OK City, as it's mostly elevated convection and non-severe. They are in western OK atm, so rather a long way to go to those storms too.

Main play will be later when surface based storms start to develop as temperatures rise. Nice cumulus field developing over Wern and central OK now:

[anvilhead]

not sure what to make of that outflow boundary http://www.hpc.ncep.noaa.gov/sfc/lrgnamsfcwbg.gif - the meso low on that cold front may stop the cf overtaking the boundary - would put play further south I'd imagine - what say ye all ?

[anvilhead]

starting to think they should hold back west ...

[chionomaniac]

starting to think they should hold back west ...

The cumulus is building nicely looking at the live streaming. From my (very) amateur point of view I was thinking earlier that a line from Lawton to Enid would be likely where any initiation might occur. It will be interesting to see where any storms do form and how right or wrong I am.

[Nick F]

Looking at the hourly mesoscale charts, best CAPE appears to be across SW and southern Oklahoma;

... though here looking at the obs the sfc winds are veered to the SW which is nor so great for tornado prospects

- over N-central OK 0-1km wind shear vectors/helicity values are more favorable and also we have the an outflow boundary running W to E just north of the I-35 corridor as picked up by the current meso discussion where winds are alot more backed at the surface:

Perhaps the team, if they are still headed to north-central OK will find some supercells firing along this boundary with better potential for mesocyclones and tornadoes to form here.

[Gorky]

I'm thinking the Dryline/Cold Front Intersection myself. There is a weak outflow boundary which cells forming off this might also latch on running east west a little north of OKC though this is by no means as strong a feature as any of yesterdays. There is a tongue of 3000j kg Cape up to Elk City and with pretty poor SRH all over, it'll be the storms on the boundaries which again should be the plays of the day.

My target - Elk City, OK but southern options right down to Wichita Falls seem fine on such a marginal day as this.

[anvilhead]

I'm thinking the Dryline/Cold Front Intersection myself. There is a weak outflow boundary which cells forming off this might also latch on running east west a little north of OKC though this is by no means as strong a feature as any of yesterdays. There is a tongue of 3000j kg Cape up to Elk City and with pretty poor SRH all over, it'll be the storms on the boundaries which again should be the plays of the day.

My target - Elk City, OK but southern options right down to Wichita Falls seem fine on such a marginal day as this.

yeah its a difficult one as always on marginal days - to me the dryline/low interaction looks a good place for storms, but as the forecast stands I dont think windfields would sustain tornadic supercells there. The 0-1km windfields that look good at the moment in the area of the north, will be almost matched by a line running through south OK at the 00z period, with higher cape maximums and an arguably better windfield - althoug i'd still be heading for north of OK city right now. If that low deepens any more than forecast though, i'd imagine the gameplan will change rapidly..

[Paul Sherman]

Hi Guys

Holding Tight here in Weatherford (Ok) with a great N/S & Obviously I40 West to East. Liking what I see at the moment with the Cumulus Field around here, and if it kicks just West of Me at least we are East of the Developments. Wish us luck!

Paul S & Team

[anvilhead]

Hi Guys

Holding Tight here in Weatherford (Ok) with a great N/S & Obviously I40 West to East. Liking what I see at the moment with the Cumulus Field around here, and if it kicks just West of Me at least we are East of the Developments. Wish us luck!

Paul S & Team

Good shout Paul. What are your thoughts on the dryline and that meso low to your meso NW ?

Good luck!

[John Hanrahan]

Good shout Paul. What are your thoughts on the dryline and that meso low to your meso NW ?

Good luck!

Hi Sam

It is certainly something I am keeping an eye on at the moment, and if you look on Spotter Network quite a few of the Chasers are around the Woodward area including the TIV

Certainly need to jump on a Storm Quickly once it pops today, so when we see something we will be off straight away.

Paul S

[Nick F]

The emphasis does seem to be on Wern Oklahoma now for strongest instability towards the sfc low over OK Panhandle and S along dry line over TX Panhandle as per recent SPC outlook update

...SOUTHERN PLAINS...

AN OLD OUTFLOW BOUNDARY APPEARS TO BE WEAKENING/LIFTING NORTH OF THE

RED RIVER...BUT STRONGEST DESTABILIZATION APPEARS TO BE FOCUSED NEAR

A WEAK SURFACE LOW OVER THE EASTERN TEXAS PANHANDLE/WESTERN

OKLAHOMA...AND SOUTHWARD ALONG THE DRY LINE INTO NORTHWEST TEXAS.

BENEATH STEEP LAPSE RATES...MIXED LAYER CAPE IS ON THE ORDER OF 3000

J/KG...IN THE PRESENCE OF WEAK TO MODEST...BUT PROBABLY SUFFICIENT

SHEAR...FOR SUPERCELLS...IF STORMS CAN INITIATE. THIS STILL APPEARS

POSSIBLE AS CONVECTIVE TEMPERATURES ARE APPROACHED LATE THIS

AFTERNOON...PARTICULARLY ACROSS PARTS OF WESTERN OKLAHOMA...WHERE

LOW-LEVEL CONVERGENCE APPEARS STRONGEST. OTHERWISE...THE BEST

CHANCE FOR STORMS APPEARS TO EXIST LATER THIS

EVENING/OVERNIGHT...WITHIN AN ELEVATED WARM ADVECTION REGIME ON THE

NOSE OF A NOCTURNALLY STRENGTHENING LOW-LEVEL JET NEAR THE

KANSAS/OKLAHOMA BORDER AREA.

... winds are certianly more backed up towards Woodward (NW OK) near the low looking at Obs compared to winds from SW over SW OK:

Maybe worth sitting tight at Weatherford or heading north a bit.

[anvilhead]

good news - your nicely in position there.

Latest sat showing some nice roll clouds in the low level shear for that area http://www.rap.ucar.edu/weather/satellite/...&duration=5

I'm off to the pub for a bit - hopefully you'll be on the business end of a supercell by the time i get back . Good luck and stay safe!

Sam

[Gorky]

I like the look of the SW moving boundary showing on the Vance Radar animation it's oriented in a way in which any storm riding it would have deviant motion to the ESE. Of course, we havn't even had any development yet so whether that plays out is a big IF. I'm thinking jogging north a bit towards the OFB.. perhaps to Woodward, or maybe Taloga in Dewey County to get a bit ahead of the dryline