Chase 2009 Day 20 Discussion - Tx/ok/ks

[Tony Gilbert]

This post would be better placed in the day 20 discussion. But can't get access!

Today the 15th May looks to create three target zones ATM;- TX Panhandle dry line, Central south KS (cold front) , Illinois (cold front).

My virtual target zone allows me to stay put in Pratt Kansas. Are the V2 guys there, because I expect they are?

Todays outlook is rather complicated IMO. With the best upper support staying almost north of the cold front for much of the period. Particular interest is given to Pratt region due the models continuing to show exceptional dynamic ascent indicated within the upper humidity values. A sharp low level jet looks to dive south by late afternoon rapidly increasing low level shear. It will therefore be essential for chasers to remain just SE of the coldfront as it moves east where the vorticity will be strongest. Upper support looks to remain steady and enough to allow for storm longevity but avoiding the fast movers. It is however noted that a condition of negative directional shear will exist Kansas between 850mb and 500mb. Mid level meso development will be unlikely. But central portion of current hodograph forecast show enough shear for low level meso and tornado development

ATM I expect the tornado risk to rise from 5% to 15% by mid day EDT and the outlook to go moderate.

Edited May 15, 2009 by Tony Gilbert

[nsrobins]

But central portion of current hodograph forecast show enough shear for low level meso and tornado development

ATM I expect the tornado risk to rise from 5% to 15% by mid day EDT and the outlook to go moderate.

Looks potentially tasty agreed, Tony, but with a focii of 2.00+ low layer EHI on the border (06 NAM) I might be tempted to start a bit further South, say Medicine Lodge.

The LLJ cranks-up quite impressively with an 850mb level wind of 45kn over my target. A few south-side of front low-based sups looks possible.

[Nick F]

Quite a large area under the severe risk today, but if I were in team 2, my personal target today would be Arnett in western OK:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1256 AM CDT FRI MAY 15 2009

VALID 151200Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN AND CNTRL PLAINS

INTO THE MIDDLE MS AND OH VALLEYS...

...SYNOPSIS...

PROGRESSIVE UPPER TROUGH OVER THE NRN ROCKIES WILL REACH THE UPPER

MS VALLEY BY FRIDAY EVENING AND THE UPPER GREAT LAKES FRIDAY NIGHT.

ATTENDANT LEE CYCLONE WILL ADVANCE EWD TO MN BY LATE AFTERNOON WITH

TRAILING COLD FRONT EXTENDING SWWD THROUGH THE CNTRL PLAINS. DRYLINE

WILL EXTEND THROUGH WRN TX INTO SWRN KS WHERE IT WILL INTERSECT THE

SWD ADVANCING COLD FRONT. FRONTAL BOUNDARY CURRENTLY EXTENDING FROM

OK EWD THROUGH THE TN VALLEY WILL LIFT NWD THROUGH THE MIDDLE MS AND

OH VALLEYS DURING THE DAY. SLOW MOVING VORT MAX OVER NRN MEXICO WILL

MOVE INTO WRN TX DURING THE AFTERNOON.

...MID MS THROUGH OH VALLEYS...

STORMS WILL BE ONGOING EARLY FRIDAY FROM NERN KS THROUGH NRN MO AND

IA WITHIN ZONE OF ISENTROPIC LIFT ASSOCIATED WITH SWLY LOW LEVEL

JET. THIS FEATURE WILL SLOWLY DEVELOP ENEWD TOWARD THE GREAT LAKES

DURING THE DAY WITHIN ZONE OF LARGE SCALE FORCING FOR ASCENT

ASSOCIATED WITH EWD MIGRATING SHORTWAVE TROUGH. A MOIST WARM SECTOR

WITH MID-UPPER 60S DEWPOINTS WILL ADVECT NWD TO THE SOUTH OF ONGOING

STORMS AND CONTRIBUTE TO POTENTIAL FOR MODERATE INSTABILITY AS THE

BOUNDARY LAYER WARMS. INITIAL STORMS WILL LIKELY BE ELEVATED...BUT

THREAT FOR SURFACE BASED STORMS WILL INCREASE AS DIABATIC HEATING

COMMENCES. THIS REGION WILL REMAIN WITHIN SRN FRINGE OF STRONGER

WLYS WITH 40 KT BULK SHEAR SUPPORTIVE OF ORGANIZED STORMS INCLUDING

SUPERCELLS AND BOWING SEGMENTS. LARGE HAIL AND DAMAGING WIND WILL BE

POSSIBLE WITH THE STRONGER STORMS. THE EWD MIGRATING LOW LEVEL JET

WILL MAINTAIN SUFFICIENT 0-1 KM HODOGRAPHS FOR A THREAT OF ISOLATED

TORNADOES DURING THE AFTERNOON AND EARLY EVENING.

...CNTRL AND SRN PLAINS...

MID-UPPER 60S BOUNDARY LAYER DEWPOINTS HAVE ADVECTED NWWD BENEATH 8+

C/KM 700-500 MB LAPSE RATES...RESULTING IN A RESERVOIR OF STRONG

INSTABILITY OVER THE SRN PLAINS. THE ATMOSPHERE WILL DESTABILIZE

THROUGH MUCH OF KS AS MOISTURE ADVECTS FARTHER NWD IN WAKE OF

RETREATING WARM FRONT. MLCAPE FROM 2500-3000 J/KG WILL BE LIKELY

FROM PORTIONS OF KS THROUGH THE SRN PLAINS AS THE BOUNDARY LAYER

WARMS FRIDAY AFTERNOON. STORMS SHOULD INITIATE BY MID-LATE AFTERNOON

ALONG PROGRESSIVE COLD FRONT ACROSS KS AND DEVELOP SEWD. MUCH OF

THIS REGION WILL REMAIN ON SRN FRINGE OF STRONGER WLYS WITH BULK

SHEAR GENERALLY AOB 35 KT. GIVEN POTENTIAL FOR STRONG UPDRAFT

ACCELERATIONS DUE TO STEEP LAPSE RATES AND LARGE CAPE WITHIN THE

MODESTLY SHEARED ENVIRONMENT...SOME STORMS WILL LIKELY DEVELOP

SUPERCELL STRUCTURES AND BECOME CAPABLE OF PRODUCING VERY LARGE

HAIL. AS THE LOW LEVEL JET SHIFTS AWAY FROM THE REGION...0-1 KM

HODOGRAPHS WILL NOT BE PARTICULARLY LARGE. HOWEVER...STRONG UPDRAFT

ACCELERATIONS ASSOCIATED WITH SUPERCELLS DEVELOPING IN VICINITY OF

THE BOUNDARY SUGGEST ISOLATED TORNADOES WILL ALSO BE POSSIBLE

THROUGH EARLY-MID EVENING. STORMS MAY EVOLVE INTO MORE LINEAR MODES

OVERNIGHT.

OTHER MORE HIGH BASED STORMS ARE EXPECTED ALONG THE DRYLINE WHERE

VERTICAL SHEAR WILL BE SOMEWHAT WEAKER. LARGE HAIL AND ISOLATED

DAMAGING WIND WILL BE THE MAIN THREATS WITH THIS ACTIVITY.

[nsrobins]

Nick - could you move the thoughts for Day 20 over from the other thread please?

Thanks

[NL]

SPC have updated the slight risk today increasing Tornado chances to 10% over E/Kansas C/N Missouri

into W/Cen Illinois.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0748 AM CDT FRI MAY 15 2009

VALID 151300Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM W TX AND WRN/NRN OK NE

INTO THE MID MS/LWR OH VLYS...

...SYNOPSIS...

PATTERN WILL REMAIN PROGRESSIVE BUT MORE AMPLIFIED OVER THE NRN HALF

OF THE U.S. THIS PERIOD AS TROUGH NOW OVER THE NRN RCKYS CONTINUES

TO THE UPR MS VLY AND PHASES WITH NRN STREAM IMPULSE NOW OVER SK.

FARTHER S...A SERIES OF WEAKER DISTURBANCES WILL TRACK E/ENE FROM

THE SRN RCKYS TO THE MID MS VLY...AND A VORT OVER NRN MEXICO WILL

DRIFT E INTO SW TX.

AT THE SFC...LOW NOW CONSOLIDATING OVER THE DAKOTAS SHOULD MOVE NE

TO THE MN ARROWHEAD BY THIS EVE AS TRAILING COLD FRONT AND

PRE-FRONTAL TROUGH ACCELERATE SSE ACROSS THE CNTRL PLNS. DIFFUSE

WARM FRONT NOW OVER SRN KS/MO WILL CONTINUE NNE INTO THE MID MS AND

LWR OH VLYS LATER TODAY...WHILE DRY LINE REMAINS MORE OR LESS STNRY

FROM SW KS INTO W TX.

...MID MS/LWR OH VLYS...

ONGOING WAA STORMS OVER SRN NEB/NE KS/SRN IA/NRN MO SHOULD PERSIST

THROUGH MIDDAY...WITH ADDITIONAL DEVELOPMENT LIKELY EWD INTO IL AND

PERHAPS NRN IND/SRN MI AS LLJ VEERS AHEAD OF AMPLIFYING UPR TROUGH.

SLIGHTLY ELEVATED MOISTURE TRANSPORT WITH THE JET SHOULD SUPPORT

SUFFICIENT DESTABILIZATION FOR SCTD SVR HAIL WITH ANY SUSTAINED/MORE

ISOLD STORMS.

ALONG SRN EDGE OF THE ELEVATED STORMS...MODERATE TO STRONG

INSTABILITY /SBCAPE AOA 2500 J PER KG/ SHOULD DEVELOP THIS AFTN FROM

FAR ERN KS INTO NRN/CNTRL MO AND CNTRL/SRN IL AS BOUNDARY LAYER

WARMS AND MOISTENS. THIS REGION WILL REMAIN ALONG SRN FRINGE OF

40-50 KT WSWLY MID LVL FLOW. THUS...POTENTIAL WILL EXIST FOR

SUPERCELLS AND LEWPS/SMALL SCALE BOWS WITH SVR HAIL AND DMGG WIND.

IN ADDITION...ENEWD MOVEMENT OF LLJ AND WEAK SFC WAVE IN TANDEM WITH

WARM FRONT AND/OR OUTFLOW BOUNDARY LEFT BY THE ELEVATED CONVECTION

MAY YIELD ENLARGED LOW LVL HODOGRAPHS. THIS COULD CONTRIBUTE TO AN

ENHANCED THREAT FOR TORNADOES THIS AFTN AND EARLY EVE...ESPECIALLY

FROM NRN MO INTO CNTRL/NRN IL.

...CNTRL/SRN PLNS...

VERY STRONG INSTABILITY /SBCAPE AROUND 4000 J PER KG/ WILL DEVELOP

WITH HEATING TODAY FROM ERN KS WSW INTO NRN/WRN OK AS MID/UPR 60S F

SFC DEWPOINTS SPREAD NWD BENEATH DEEP EML. STORMS SHOULD FORM BY

MID-LATE AFTN ALONG PROGRESSIVE PRE-FRONTAL TROUGH OVER KS...WITH

MORE ISOLD ACTIVITY EXPECTED A BIT LATER SWD ALONG DRY LINE INTO NW

OK/W TX.

MODERATE /40+ KT/ 500 MB WLY FLOW WILL EXIST ACROSS KS...BUT SPEEDS

SHOULD REMAIN AOB 25 KTS IN OK AND TX. COMBINATION OF INSTABILITY

AND SHEAR SHOULD SUPPORT AT LEAST A FEW SUPERCELLS IN KS...BEFORE

PROGRESSIVE NATURE OF FRONT AND STORM MERGERS THAT RESULT AS IT

OVERTAKES PRE-FRONTAL TROUGH FAVOR EVOLUTION INTO BROKEN LINE

SEGMENTS. INTENSE UPDRAFTS IN THE STORMS COULD YIELD VERY LARGE

HAIL AND POSSIBLY ONE OR TWO TORNADOES. FARTHER S...SIZABLE DEGREE

OF DIRECTIONAL SHEAR...SOMEWHAT WEAKER CONVERGENCE...AND POTENTIAL

FOR STRONG UPDRAFT ACCELERATIONS ALSO SHOULD SUPPORT SUPERCELL

STRUCTURES ...DESPITE WEAKER BULK SHEAR. THESE STORMS WILL ALSO

HAVE THE POTENTIAL FOR VERY LARGE HAIL AND A BRIEF TORNADO OR TWO

THROUGH MID EVE...GIVEN DEGREE OF INSTABILITY AND FACT THAT TREND

TOWARD LINEAR DEVELOPMENT WILL BE LESS MARKED THAN FARTHER N. SOME

OF THE OK/TX SE STORM CLUSTERS COULD PERSIST INTO EARLY SAT...MOVING

SLOWLY S OR SSE WITH TIME.

...UPR MS VLY...

SUBSTANTIAL HEIGHT FALLS AND COLDER TEMPERATURES ALOFT AHEAD OF

AMPLIFYING TROUGH WILL COMPENSATE FOR LIMITED LOW LVL MOISTURE TO

SUPPORT STORM DEVELOPMENT ALONG COLD FRONT IN MN...NW IA...AND

PERHAPS NE NEB LATER TODAY...WHERE MODEST INSTABILITY IS EXPECTED.

50+ KT DEEP SWLY SHEAR WILL BE AMPLE FOR ORGANIZED STORMS AND

POSSIBLY SHORT-LIVED SUPERCELLS. ATTM...HOWEVER...IT APPEARS THAT

AXIS OF SFC-BASED INSTABILITY WILL REMAIN TOO WEAK AND NARROW TO

SUPPORT MORE THAN AN ISOLD SVR HAIL/WIND THREAT. THIS AREA

WILL...NEVERTHELESS...CONTINUE TO BE MONITORED FOR POSSIBLE UPGRADE

IN LATER OUTLOOKS SHOULD GREATER INSTABILITY DEVELOP THAN NOW

EXPECTED.

..CORFIDI/JEWELL.. 05/15/2009

[Paul Sherman]

We are in Witchita this morning and will assess the situation as the morning goes on for now.

Hopefully we get some decent Storms as this could be the last day for quite some time

Paul S

[nsrobins]

Paul

I'm still thinking Medicine Lodge area, so a casual trundle west towards Pratt could be in order.

The overall shear magnitudes are lower here than further north but I like the directional vectors and I'm still looking at an LLJ streak of 40kn after 00Z. Cape, juice etc no problem. So, the choice - stay south (KS/OK border) for slow moving hailers and maybe a weak tube. Go northeast (MO/IL) for slippery low-based clumps but higher tube chances.

Umm.

[Gorky]

I stayed in Cameron, Mo overnight, leaving me with 2 options available. Either back east to the same area as WEdnesday's Chase, or drop down to North East KS. I'm probably going to do NE KS for a couple of reasons. Road options and terrain are better and I think both areas will get tornadoes today, although NE MO and W IL may again be the hotspot. Early morning convection on the NE, KS border should hopefully set up an outflow boundary, and anything forming on this and the cold front should have a small window to produce. I won't me moving out for an other hour or so, so I may flip flop before then... we'll see : )

[stevestorms]

We are heading initially NE to Woodward then poss Alva Ok readjusting on route, good luck everyone.

[Paul]

Pauls briefing is now online:

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

As he says, the storms should develop early afternoon (US time) today, so there's an opportunity to watch the action on the stream before it reaches silly o'clock in the UK..

[Paul Sherman]

Paul

I'm still thinking Medicine Lodge area, so a casual trundle west towards Pratt could be in order.

The overall shear magnitudes are lower here than further north but I like the directional vectors and I'm still looking at an LLJ streak of 40kn after 00Z. Cape, juice etc no problem. So, the choice - stay south (KS/OK border) for slow moving hailers and maybe a weak tube. Go northeast (MO/IL) for slippery low-based clumps but higher tube chances.

Umm.

Certainly a Tough One Neil! No Straightforward Chases this year it seems.

Best Chase Terrain may not Yield Tornadoes and the Crap Terrain should produce More Nados.

Positioned myself last night in the Middle to see how this mornings Models panned out - Short answer is nothing is resolved <_<

Could be the last Chase day for a Week so better nail this one

Paul S

[nsrobins]

Could be the last Chase day for a Week so better nail this one

Paul S

Good luck! I'm out at an Abba themed quiz this evening ( <_< ) but should be back online by 23Z to see how things are going.

[Thermohaline Conveyor]

I've had a look and I'd target Pratt W of Wichita KS.

[ian cameron]

An Moderate risk has been issued for our area T minus three hours to the action

[Old Style]

Tornado Watch issued for most of northern MO and far northeast Kansas.

[John Hanrahan]

I stayed in Cameron.

I did that one night too, but Ian didn't appreciate it and was walking funny for a few days after

[pottyprof]

I heard a few people were going through Sherman too...

[NL]

I heard a few people were going through Sherman too...

Perhaps we best not start to think how many went through Noble......!!

[pottyprof]

Perhaps we best not start to think how many went through Noble......!!

shhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh!!

[Paul]

Clouds starting to bubble up on the stream..

[Paul]

Couple of storm watches up close to kansas city now.

[pottyprof]

Now that's what ya call a caravan!!!

[Paul]

They're on the move now, some menacing skies ahead of them too.

[NL]

Tornado watch LIKELY E/SCentral Kansas NW/Oklahoma into TX panhandle.

807

ACUS11 KWNS 151945

SWOMCD

SPC MCD 151944

MOZ000-KSZ000-OKZ000-TXZ000-152015-

MESOSCALE DISCUSSION 0835

NWS STORM PREDICTION CENTER NORMAN OK

0244 PM CDT FRI MAY 15 2009

AREAS AFFECTED...MUCH OF ERN TO SOUTH CENTRAL KS INTO NWRN OK AND

NERN TX PANHANDLE

CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY

VALID 151944Z - 152015Z

MUCH OF ERN TO SOUTH CENTRAL KS INTO NWRN OK...AND POSSIBLY THE NERN

TX PANHANDLE...WILL REQUIRE A TORNADO WATCH SOON.

EARLY AFTERNOON SURFACE ANALYSIS SHOWED A COLD FRONT EXTENDING SSWWD

THROUGH ERN NEB TO NORTH CENTRAL KS...EAST OF CNK...TO THE ERN OK

PANHANDLE...THEN EXTENDING WSWWD THROUGH THE NRN TX PANHANDLE...AND

NWWD THROUGH NERN NM TO SERN CO. DRY LINE HAS MIXED EWD ACROSS THE

TX PANHANDLE AND INTERSECTS THE COLD FRONT IN ROBERTS COUNTY TX

WHERE VISIBLE IMAGERY INDICATED AN INCREASE IN CU. REGIONAL RADARS

INDICATED RECENT TSTM DEVELOPMENT OVER NERN KS /W/NW OF TOP/ ALONG

SWRN PERIPHERY OF NRN MO/IA MCS...WHILE STORMS WERE DEVELOPING ALONG

THE COLD FRONT FROM GAGE COUNTY NEB TO JUST EAST OF SALINE COUNTY

KS.

AIR MASS FROM ERN TX PANHANDLE/WRN OK INTO CENTRAL/NERN KS HAS

BECOME VERY UNSTABLE THIS AFTERNOON WITH MLCAPE RANGING FROM

3000-4000 J/KG. SWLY MID LEVEL FLOW ACROSS THE CENTRAL PLAINS WILL

CONTINUE TO STRENGTHEN AS UPPER TROUGH PROGRESSES EWD THROUGH THE

NRN PLAINS. THIS WILL SUPPORT INCREASING EFFECTIVE BULK SHEAR

/35-50 KT/...MAINLY ACROSS KS. ALTHOUGH DEEP LAYER SHEAR WILL TEND

TO BE WEAKER INTO NWRN OK...STRONGER INSTABILITY SHOULD COMPENSATE

FOR THE WEAKNESS IN THE SHEAR AND ALSO SUPPORT SUPERCELLS INTO NWRN

OK. DESPITE WEAK UPPER FORCING THIS AFTERNOON ACROSS KS/OK...THE

STRONGER CAP SHOULD RESULT IN LIKELIHOOD FOR DISCRETE STORMS

BECOMING SEVERE RAPIDLY ONCE THEY FORM GIVEN THE VERY STRONG

INSTABILITY.

..PETERS.. 05/15/2009

Edited May 15, 2009 by NL

[plymouthflye]

They're on the move now, some menacing skies ahead of them too.

Have they lost the grey car? Or has the view switched to the lead car, or just swapped places?

We NEED to know these things. :lol:

AHA! There it is. Panic over lol.

Edited May 15, 2009 by plymouthflye