Chase Discussion Day 17

[nsrobins]

The discussion for Chase Day 17 (Tues 12th) will be interesting and the choice of target as important as ever as it looks like things may well be quiet in the Plains for a few days once the cold front steams through on Wednesday.

My target of choice at the moment (and based largely on a cap that is breakable combined with some decent shear parameters) is the far NW KS, and assuming the team will be in Amarillo (see above post <_< ) on Tuesday morning I think the trek up the 83 may be achievable with an early start. Could be a good place then to head east towards the KS/MS border for the what looks like lively cold front action on Wednesday.

Big distances yes but when you've got people who need to see storms it has to be done.

An alternative would be to stay local in the OK Panhandle on Tues but it's too early to be sure what the pros and cons of this are.

[Gorky]

I was actually looking at North Platte, NE yesterday as there were some nice soundings with moderate cape juxtaposed agaisnt insane helicity values. It was only a thin sliver of instability up that way however, and I'd be driving 9 hours to get there on Tuesday morning from here.I might be gettign an early night tonight :o

It appears that the SPC have a split severe area with North Platte being right between the two, heh. Maybe I need to reevaluate after lookign at new data

Edited May 11, 2009 by Gorky

[nsrobins]

I was actually looking at North Platte, NE yesterday as there were some nice soundings with moderate cape juxtaposed agaisnt insane helicity values. It was only a thin sliver of instability up that way however, and I'd be driving 9 hours to get there on Tuesday morning from here.I might be gettign an early night tonight :o

It appears that the SPC have a split severe area with North Platte being right between the two, heh. Maybe I need to reevaluate after lookign at new data

I know what i'd be thinking if I were making decisions for tomorrow - where best for the next day? SPC have upped the ante for the cold front caberet on Weds evening, and I suspect the really sharp bow that pounded MO the other day may be keeping the SPC on it's toes for what looks like a really sheared frontal axis. The Moderate upgrade is understandable, but you need to be into central MO to pick-up on this - a good 6hr drive from far W OK yes but much further if you go chasing the northern target tomorrow which with each run is becoming a tad out of reach.

So you stay 'local', have a lazy morning and move NW of Amarillo (lunch perhaps at the Cattle Exchange in Canadian - the best peppered steak I've ever had LOL) and into W OK. The big question is will the cap bust? If it does, it could be insane with enough deep SRH to turn water into wine (in excess of 900 towards C OK on the 12Z NAM). A sharpish drline sets-up around Guymon - no real bulge but a 20-60C dp range across about 60 miles is impressive. Everything looks good TBH except the cap. Will it or won't it?

[MAF]

well this is the outlook for Tuesday from the SPC. looks like its a "slight" category but you never know

DAY 2 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1211 PM CDT MON MAY 11 2009

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CENTRAL

AND NRN HIGH PLAINS...

...NRN/CENTRAL HIGH PLAINS...

STRONG MID/UPPER LEVEL LOW NOW OFF THE B.C./WA COAST WILL MOVE

QUICKLY EWD ACROSS THE NRN ROCKIES TUESDAY AND INTO THE NRN PLAINS

TUESDAY NIGHT. ASSOCIATED 70-90 KT H5 JET MAX WILL ALSO DEVELOP

FROM THE NRN INTERMOUNTAIN REGION ACROSS THE NRN PLAINS BY THE LATE

AFTERNOON. THIS WILL INDUCE PRESSURE FALLS/LEE TROUGHING OVER THE

HIGH PLAINS DURING THE AFTERNOON...WITH PRIMARY LOW CENTER

DEVELOPING OVER CENTRAL HIGH PLAINS SHIFTING ACROSS THE CENTRAL

PLAINS OVERNIGHT ALONG LEADING COLD FRONT. DESPITE THE VERY STRONG

SHEAR DEVELOPING INTO THE CENTRAL AND NRN HIGH PLAINS...LIMITED

MOISTURE/INSTABILITY WILL EXIST WITH SURFACE DEW POINTS IN THE 40S.

REGARDLESS...VERY STRONG MIXING ALONG/WEST OF THE LEE TROUGH AND

INCREASING ASCENT/LOW LEVEL CONVERGENCE SHOULD OVERCOME CAP FROM

PORTIONS OF WRN NEB INTO WRN SD DURING THE AFTERNOON. A FEW SURFACE

BASED STORMS MAY OCCUR OVER THIS REGION INTO THE EARLY EVENING WITH

THREATS OF LARGE HAIL AND DAMAGING WINDS FROM HIGH BASED

DEVELOPMENT. ADDITIONAL CLUSTER OF STRONG/MARGINALLY SEVERE STORMS

MAY DEVELOP EWD INVOF COLD FRONT LATE IN THE DAY...NEAR VERY COLD

MID LEVEL TROUGH ACROSS PARTS OF THE NRN HIGH PLAINS. MUCH OF THIS

ACTIVITY WILL WANE AFTER DARK GIVEN NOCTURNAL STABILIZATION OF THE

BOUNDARY LAYER.

...SRN HIGH PLAINS...

RISK OF SEVERE THUNDERSTORMS SOUTH OF NERN CO/NWRN KS/NEB PANHANDLE

ALONG THE DRY LINE IS VERY CONDITIONAL AS MODELS MAINTAIN STRONG CAP

AND A LACK OF LARGE SCALE LIFT/FOCUS. NAMKF SUGGESTS STRONG HEATING

INTO THE 90S WILL BREAK CAP OVER NWRN TX LATE IN THE DAY...WHILE

NAM/GFS ONLY INITIATES STORMS OVER FAR W/SW TX. GIVEN THE VERY

UNSTABLE AIR MASS...AND MARGINAL DEEP LAYER SHEAR FOR SUPERCELLS...

AT LEAST LOW SEVERE PROBABILITIES ARE WARRANTED ATTM ALONG THE

LENGTH OF THE DRY LINE. HOWEVER...CONFIDENCE IN ANY ONE AREA

REMAINS LOW FOR ISOLATED SEVERE LATE IN THE DAY.

...MID MO RIVER VALLEY TOWARDS THE MID/UPPER MS RIVER VALLEY...

PLUME OF STEEP LAPSE RATES AND DEEP ASCENT WILL INCREASE EWD LATE IN

THE PERIOD ACROSS THIS REGION ALONG NOSE OF 70+ KT LLJ. APPEARS

SUFFICIENT MOISTENING ALONG BOTTOM OF EML...WITH H85 DEW POINTS FROM

12C-14C...FOR MODERATE MUCAPE WITH WEAK ELEVATED CINH. GIVEN THE

STRONG SHEAR AND MODERATE MUCAPE...ELEVATED THUNDERSTORMS SHOULD

SUPPORT AT LEAST A LOW PROBABILITY RISK OF LARGE HAIL...AFTER

06-09Z.

...PORTIONS OF ERN OK/MID SOUTH INTO FL...

VERY WEAK FLOW REGIME WILL PERSIST OVER FL...WITH ONLY MODEST

LOW/MID LEVEL WINDS FROM THE SRN PLAINS INTO THE LOWER MS RIVER

VALLEY/CENTRAL GULF COAST. HOWEVER...VERY MOIST/UNSTABLE AIR MASS

IS EXPECTED BY THE MID AFTERNOON...WITH VERY LITTLE CAPPING. THIS

SUGGESTS WIDESPREAD THUNDERSTORMS...ESPECIALLY NEAR RESIDUAL OUTFLOW

BOUNDARIES AND OCEAN BREEZE CIRCULATIONS THROUGH THE DAY. SHEAR

WILL LIKELY BE INSUFFICIENT FOR MUCH STORM-SCALE

ORGANIZATION...HOWEVER STRONG INSTABILITY WARRANTS AT LEAST A THREAT

OF ISOLATED SEVERE HAIL/WIND FROM THE STRONGER CORES. OVERALL

THREAT SHOULD DIMINISH THROUGH THE EVENING WITH LOSS OF DIURNAL

INSTABILITY.

...NEW ENGLAND...

VERY COLD MID LEVEL TEMPERATURES WILL SUPPORT WEAK SBCAPE ACROSS

PORTIONS OF SRN NEW ENGLAND TUESDAY AFTERNOON. APPEARS SUFFICIENT

INSTABILITY WILL EXIST FOR SCATTERED LOW TOPPED THUNDERSTORMS...WITH

A RISK OF HAIL WITH THE STRONGER CORES. ACTIVITY WILL WANE QUICKLY

AFTER DARK.

[John Hanrahan]

Looks like the video feed from the main table at the big texan is down at the moment. Atleast from my location anyway.

Ian should be having his go some time after 1:00 our time.

Hopefully it will be up soon

http://www.bigtexan.com/free72.html

[plymouthflye]

well this is the outlook for Tuesday from the SPC. looks like its a "slight" category but you never know

Yes it's down for me as well at the mo. I was looking forward to tonight as well!

Oops, used the wrong quote. It's for the message above, but i'm sure you get the gist.

Edited May 11, 2009 by plymouthflye

[Roger J Smith]

I am seeing disturbing similarities to the Greensburg tornado set-up of late May 4th, 2007 in the situation late Tuesday.

Forcing is rapid after 00z and a strong thickness ridge develops by that time over eastern Colorado. By Wed morning, a squall line is likely to have reached western IA and the KS-MO border regions. This would imply explosive tornadic development somewhere near the CO-KS border region around sunset Tuesday (02-03z).

Although the track of most severe storms may be a little further north than it was on that fateful occasion, the general scenario may be similar. Of course, the Greensburg tornado developed around sunset on that occasion and hit the town around an hour after darkness had fallen. If something similar develops tomorrow, extreme caution will be required for safety and the actual chase (video) potential may be limited before darkness falls. I would suggest a location not far from Oakley KS although the idea of south to west central Nebraska may prove to be ideal for the daylight hours.

Good luck ... this is looking like perhaps the most active day yet (eventually).

[nsrobins]

I agree with Roger in that there are similarities with that fateful day, but having had a quick flick through NAM this morning I'm actually not moving too far now. Potential is there right along the dryline but the thinnish inversion is a cap too far IMO for the mid-Plains target. However, NAM does release some impressive potential just south and west of their current position from 00Z, with tornadic indices favourable.

Target: Turkey, TX

Additional: For forward planning, think Central Missouri for Weds. It's simmering!

Edited May 12, 2009 by nsrobins

[Nick F]

I agree that the CO/KS border and SW Nebraska looks good for discrete supercells later where the dry line interacts with a narrow tongue of high CAPE extending N from TX Panhandle up into Wern NE. But can't really see any similarities with May 4th 2007 - as upper winds are less strong (the jet core is way up over Sern Montana and the Dakotas) and SPCs 2% risk of tornadoes suggests turning of winds/shear doesn't look strong enough for a tornado outbreak or strong tornadoes.

Think anywhere from Wern TX north upto NW Nebraska looks good for discrete supercells to fire along the dryline that sets up across the high Plains later.

[nsrobins]

06Z NAM update: At 21Z the dryline looks sharper to me, especially on the OK panhandle. About 2500 CAPE is released just ahead of the DL in this location by 00Z but is better (>3000) further south towards Plainview. Shear parameters give a crazy 550+ blob of 0-3 Helicity just over the River in far SW OK and ppn composite pops a discrete cell just west of the I27 at the same time. The Cap situation has improved IMO, with NAM dropping it out over the target area but keeping a lid further North.

Conclusion? I'll stick with my original target and recommend a Turkey shoot!

Edit: Oh, and it's gonna be hot :lol:

Edited May 12, 2009 by nsrobins

[nsrobins]

10Z RUC: Just a sneak preview of conditions early afternoon and the RUC also starts to erode the cap in a tongue from NM across LBK, which by my untrained eye may place initiation further down the I27 towards Plainview. I think I need to have a break and look again later this afternoon, but target stays Turkey, TX.

[Gorky]

Argh, this is a difficult choice for me. I'd really wanted to head over to IL for tomorrow as the possibility is there for a big tor outbreak, but being a structure lover, the chance of a lone supercell or two coming off the caprock is almost too much to resist. I'll probably stay around the panhandle for much of the day and see what soundings are like later, but if the cap looks unbreakable, I'll have to scoot off east. I'd like to be East of OKC at the end of the day if IL is going to be a viable target tomorrow.

[nsrobins]

Argh, this is a difficult choice for me. I'd really wanted to head over to IL for tomorrow as the possibility is there for a big tor outbreak, but being a structure lover, the chance of a lone supercell or two coming off the caprock is almost too much to resist. I'll probably stay around the panhandle for much of the day and see what soundings are like later, but if the cap looks unbreakable, I'll have to scoot off east. I'd like to be East of OKC at the end of the day if IL is going to be a viable target tomorrow.

Perhaps someone could open a thread for tommorow to keep this clear for this evening?

I'm not convinced at the moment that you need to head so far east for Wednesday's potential action. The CF will do enough right into OK IMO if the GFS is anything to go by, but yes it appears maximum Tor parameters seem focussed on Central/West IL and into MO. Actually there's growing opinion that a two-three hour period of major severe weather is likely.

Back to the here and now and although I understand your concerns about travelling, the risk of missing a lovely high-based supercell sliding across the caprocks and starting to tighten-up as it encouters higher SRH and lower LCLs towards the river is too much for you surely?

[nsrobins]

The complex currently down the spine of OK is clearing slowly east (with a kick in the tail - TVS near Wichita KS I see) and the high cirro-stratus shield on the outflow stretches into the TX panhandle.

What's promising is the sharpish clearence now into the I27 corridor. Clear skies and hot, hot 2ms will develop in the next four hours - but can we bust the cap? Yes, I reckon we can and Turkey is still my target (or maybe a bit South of here). If instability can be realized - it going to explode!

[Tony Gilbert]

Signals from what I can see ATM is that the CAP may in fact not be breached on the TX Panhandle. But even if it does the upper shear will barely separate the updraft /downdraft and thus could all become very messy even with phenomenal instability in place! The SPC must be basing the 5% tornado risk on sharp initiation of early cell development with brief spin ups possible.

Conditions are favoured further north central west KS with a very strong upper jet nosing in by nightfall. Though once again some doubt as to what time the cap will break in this location. Quite possible these storms could initiate just after dark making chasing a very anti social affair indeed!

Serious considerations needs to be made today by chasers that are on the plains as to whether to get into position for tomorrows moderate risk. Chasing either of these targets today could easily make the journey to central east Missouri or Illinois just too far to get to in time!

Based on what I can see on the models ATM I would certainly consider using today to get in position ready for tomorrows outlook. At this point I would consider getting to Kansas City for the night and finely tune my plans for Weds Outlook.

I cannot entirely rule out an increase in risk for west KS today but by 2pm CDT it will probably be too late to get in position in any case!

Edited May 12, 2009 by Tony Gilbert

[NL]

NWS/SPC have updated for today and have given a 5% chance of tornadoes for NW Texas

fringing west Oklahoma.

...SRN HIGH PLAINS...

DRY LINE WILL MIX EWD INTO SWRN KS SWD THRU CENTRAL TX PANHANDLE TO

E OF DAVIS MTS BY MID AFTERNOON. DEWPOINTS AOA 60F WILL CONTINUE

SPREADING NWD E OF DRY LINE THRU THE AFTERNOON ALONG THE WRN OK/TX

BORDER. WITH ADIABATIC LAPSE RATES IN PLACE BY MAX HEATING ALONG/W

OF DRY LINE...AIR MASS BECOMES STRONGLY UNSTABLE AT LEAST AS FAR N

AS ERN TX PANHANDLE E OF DRY LINE. A WEAK BUT WELL DEFINED MID

LEVEL VORT NOTED ON W/V IMAGERY NOW ENTERING FAR SWRN TX COULD BE A

FACTOR IN PROVIDING SOME ENHANCED LIFT AND SHEAR ACROSS DRY LINE

ABOUT TIME OF MAX HEATING. AT LEAST ISOLATED SEVERE THUNDERSTORMS

COULD DEVELOP ALONG AND JUST E OF DRY LINE BY LATE AFTERNOON SWD TO

BIG BEND. PRIMARY RISK WILL BE VERY LARGE HAIL AND DOWNBURST WINDS

WITH ANY STORM THAT DEVELOPS...AS GIVEN THE 3000 J/KG OR GREATER OF

MLCAPE...SUPERCELLS ARE EXPECTED. ISOLATED TORNADOES ALSO

POSSIBLE...PARTICULARLY IN THE AREA OF ENHANCED LOW LEVEL SHEAR

WHERE THE INTERSECTION OF RETURNING WARM FRONT AND DRY LINE ERN TX

PANHANDLE.

http://www.spc.noaa.gov/products/outlook/day1otlk.html

[Nick F]

Ern TX Panhandle looks good for something to form along and move east off the Cap Rock Escarpment, though as any storms that fire are likely to be isolated given the strong cap, I wouldn't target any particular place.

Tds are now recovering into the low 60s over the Sern TX Panhandle as the warm front lifts north over the Red River ... the warm front and dry line triple point may develop sufficient low level shear + 12z WRF is indicating a strong low-level jet developing over NW Texas NNE through Wern OK and Kansas after 00z - this will likely increase overall shear and perhaps increase the tornado threat - helped by large amounts of CAPE (3000j/kg+). I wouldn't be suprised if we had a small moderate risk if storms do look likely to intiate across TX Panhandle and NW OK later especially 00z-03z.

[Roger J Smith]

Jet core appears likely to drop rapidly southeast after 21z and may set off late supercells in eastern CO heading for w KS and sw NE. Activity in the TX panhandle is likely to occur in phase with this but quite possibly after sunset. Still concerned for major tornadic outbreak 03-06z in the region near the I-70 across northern KS.

Nathan, I think you could do well in central IL tomorrow although other opportunities may develop closer to OK-TX border.

Tonight's severe outbreak is likely to hold together as a squall line into e KS-NE and even w MO-IA until after 09z. Anyone chasing in this region would need to be on the alert for fast-developing F3-4 potential storms in the time frame 03-09z.

[MAF]

just issued

Meo Discussion # 0801

MESOSCALE DISCUSSION 0801

NWS STORM PREDICTION CENTER NORMAN OK

0122 PM CDT TUE MAY 12 2009

AREAS AFFECTED...ERN KS...WRN MO...ERN NEB AND WRN IA

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 121822Z - 121915Z

WW MAY BE NEEDED FOR PARTS OF ERN KS/WRN MO INTO SERN NEB AND SWRN

IA THIS AFTERNOON DUE TO INCREASING THREAT FOR ELEVATED STORMS

PRODUCING SEVERE HAIL.

WATER VAPOR IMAGERY INDICATED A SHORT WAVE TROUGH LOCATED OVER

CENTRAL NEB...WITH A WEAKER IMPULSE PROGRESSING ENEWD INTO ERN KS.

SO FAR TODAY...THE STRONGEST TSTM ACTIVITY /ACROSS OK AND SERN KS/

HAS BEEN ASSOCIATED WITH ASCENT ATTENDANT TO KS IMPULSE AND

MOISTURE/WARM AIR ADVECTION ALONG NRN EXTENT OF SRN PLAINS SSWLY

LLJ. EARLY AFTERNOON LOW LEVEL STREAMLINE ANALYSIS SHOWED AN AREA

OF CONFLUENCE EXTENDING FROM ERN OK INTO ERN KS...AS MOISTURE

CONTINUES TO STREAM NNEWD WITH 1 INCH PW TO THE SERN NEB/KS BORDER.

REGIONAL RADARS INDICATED MORE RECENT TSTM DEVELOPMENT FROM THE SERN

NEB/KS BORDER REGION AND SWD THROUGH ERN KS ALONG THE ZONE OF LOW

LEVEL MASS CONVERGENCE. ERN EXTENT OF STEEP MID LEVEL LAPSE RATE

PLUME /7-8 C/KM/ EXTENDS INTO THE ERN PLAINS WITH THESE LAPSE RATES

EXPECTED TO SPREAD FARTHER E INTO WRN IA/WRN MO THIS EVENING. 40-50

KT SSWLY LLJ WILL CONTINUE TO DEVELOP ACROSS THE ERN PLAINS INTO

LOWER MO VALLEY/IA. WAA ALONG THE LLJ AND FORCING FOR ASCENT WITH

AFOREMENTIONED MID LEVEL IMPULSES SHOULD MAINTAIN LIKELIHOOD FOR NEW

TSTM DEVELOPMENT EWD TOWARD SWRN IA AND WRN MO.

NOAA/SPC

[stevestorms]

Ok Tom Paul and gang we are sorted YEYYYY! UPS arrived about 1230 in went the disc and shes booted up fine ---we now have eyes can see you have made Plainview will prob head off soon , see yer on the road.

Steve and Martin

[Old Style]

The storms over me (I'm in Nebraska) are elevated and should not produce tornadoes. I do agree with Tony Gilbert regarding tomorrow, the 13th. The best tornado threat of the week appears to be coming tomorrow in MO and IL. I would give up on today's low chances, and heard towards Kansas City for the night. Tomorrow if you needed to drive towards St.Louis or even Chicago, you would be in a much better position. Just my opinion.

On a personal note: I am a meteorologist here in the US, and I have absolutely LOVED following this group as they chase across the Plains. I love the real time streaming, along with the posting of the pics and the video. This site is great! I wish more groups of weather enthusiasts would do something like this! If the group is ever in Omaha,NE for a stop, I'd like to meet you guys. Hopefully you are not here to see a tornado (I love tornadoes, but I love my house even more! )

[MAF]

welcome to Netweather Old Style. glad you are here to add your input.

[stevestorms]

Thanks Old Style, myself and Martin are a 2 man team we ahve been waiting for Baron software to arrive at the Big T in Amarilo which it now has, so we are waiting and watching in Amarillo to see what pops, very nice post you have put up for us Brits :-)

[Gorky]

Glad the software has arrived.

I'm still in the panhandle down in Silverton, and will make a decision on today by 5pm local time, there are still a few question tomorrow regarding warm sector activity which is keeping me from ditching today right now to position. I've stocked up on energy drinks if I need to drive until late tonight

Some Vortex2 team members have just shown up here OK make that a convoy now...

Edited May 12, 2009 by Gorky

[Roger J Smith]

Convection firing in eastern CO, despite the lack of official guidance or statements I am expecting a PDS to develop now in western KS after 23z. Would suggest Scott City to Gove for intercept.