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Chase 2009 Day 18 Discussion


Nick F

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

    SPC have expanded SW the MDT risk area for today into Oklahoma, so this gives the team a reachable target in N and NE OK perhaps. Chance of this going high risk given the 45% given for hail and wind. I fancy targeting Stillwater, OK to perhaps get on the SWern tail end where cells may stay more discrete.

    WRF SBCAPE and Preciptn. for 00z Thurs (18z CDT):

    post-1052-1242198377_thumb.pngpost-1052-1242198410_thumb.png

    post-1052-1242198528_thumb.png post-1052-1242198549_thumb.png post-1052-1242198539_thumb.png

    DAY 1 CONVECTIVE OUTLOOK

    NWS STORM PREDICTION CENTER NORMAN OK

    0100 AM CDT WED MAY 13 2009

    VALID 131200Z - 141200Z

    ...THERE IS A MDT RISK OF SVR TSTMS FROM THE MIDDLE MISSISSIPPI

    VALLEY TO THE SOUTH CENTRAL PLAINS...

    ...THERE IS A SLGT RISK OF SVR TSTMS MUCH OF THE MIDWEST TO SOUTHERN

    PLAINS...

    ...SYNOPSIS...

    ON THE LARGE SCALE...PRIMARY IMPETUS FOR DEEP CONVECTIVE POTENTIAL

    ACROSS THE CENTRAL STATES TODAY WILL BE TIED TO A POTENT UPPER

    TROUGH WHICH WILL CROSS THE NORTHERN PLAINS TODAY...AND REACH THE

    UPPER MISSISSIPPI VALLEY/WESTERN GREAT LAKES LATE TONIGHT AS IT

    BEGINS TO TAKE ON MORE OF A NEGATIVE TILT. AHEAD OF THIS SYSTEM...A

    RATHER MOIST AIRMASS WILL CONTINUE TO QUICKLY SURGE NORTHEASTWARD

    INTO THE MIDWEST AHEAD OF AN EAST-SOUTHEAST MOVING COLD FRONT ACROSS

    THE MIDWEST/SOUTH CENTRAL PLAINS.

    ...MIDWEST TO SOUTH CENTRAL PLAINS...

    INITIALLY...ON THE NOSE OF A RATHER STRONG SOUTHWESTERLY LOW LEVEL

    JET AND EASTERN FRINGE OF A PLAINS ELEVATED MIXED LAYER...SCATTERED

    TO NUMEROUS TSTMS ARE LIKELY TO BE ONGOING AT THE BEGINNING OF THE

    PERIOD ACROSS THE MIDWEST...INCLUDING PORTIONS OF IA/MO/IL/INDIANA.

    AT LEAST SOME OF THESE ELEVATED TSTMS WILL BE CAPABLE OF SEVERE HAIL

    THROUGH THE MORNING.

    ALTHOUGH SOME QUESTIONS EXIST REGARDING THE TIMING/DEGREE OF DIURNAL

    DESTABILIZATION WITH NORTHEASTWARD EXTENT ACROSS THE MIDDLE/UPPER

    MISSISSIPPI VALLEY IN THE WAKE OF EARLY DAY ACTIVITY...RAPID

    DESTABILIZATION IS EXPECTED TO OCCUR FROM THE SOUTHWEST...WITHIN A

    NARROW PRE-COLD FRONTAL WARM/UNSTABLE SECTOR ACROSS MO/SOUTHEAST IA

    INTO ADJACENT IL. PROVIDED SUFFICIENT DESTABILIZATION THROUGH THE

    AFTERNOON/EARLY EVENING...STRONG/SEVERE TSTMS SHOULD QUICKLY

    DEVELOP...WITH A MIXED MODE OF SUPERCELLS/BOWS POSSIBLE BENEATH 50

    KT MID LEVEL FLOW. ASIDE FROM SEVERE HAIL...TORNADOES WILL BE

    POSSIBLE GIVEN STRONG 40-50 KT FLOW IN THE LOWEST 1 KM AND AMPLE LOW

    LEVEL SRH. THIS THREAT COULD BE HEIGHTENED IN VICINITY OF WARM FRONT

    AND/OR ANY REMNANT MODIFIED OUTFLOW ACROSS THE MIDDLE MISSISSIPI

    VALLEY INCLUDING PORTIONS OF MO/SOUTHEAST IA INTO IL.

    OTHERWISE...DAMAGING WIND POTENTIAL MAY ULTIMATELY INCREASE THROUGH

    THE EVENING AS STORMS CONGEAL/RACE EASTWARD ACROSS THE MIDWEST.

    FARTHER SOUTHWEST...TSTMS SHOULD DEVELOP LATE THIS AFTERNOON/EARLY

    EVENING ALONG/JUST BEHIND THE SOUTHEASTWARD ADVANCING SURFACE COLD

    FRONT FROM MO/SOUTHEAST KS INTO OK...AND PERHAPS IN VICINITY OF THE

    DEEPLY MIXED AIRMASS IN CLOSE PROXIMITY TO THE SURFACE LOW/DRYLINE

    TRIPLE POINT NEAR THE WESTERN OK/TX PANHANDLE BORDER. EVEN WITH

    WEAKER MID LEVEL FLOW AT THIS LATITUDE...VERY STEEP MID LAPSE

    RATES/VEERING WIND PROFILES WILL BE FAVORABLE FOR LARGE/POTENTIALLY

    SOME SIGNIFICANT HAIL WITH SUPERCELLS. A FEW TORNADOES MAY BE

    POSSIBLE...ALONG WITH DAMAGING WINDS GIVEN THE STEEP LAPSE RATE

    ENVIRONMENT. AS AN UPSWING IN TSTM COVERAGE CONTINUES THROUGH THE

    EVENING ALONG THE FRONTAL ZONE...AND A SOUTH-SOUTHWESTERLY LOW LEVEL

    JET NOCTURNALLY INCREASES ACROSS TX...THERE IS SOME POTENTIAL THAT

    THESE TSTMS COULD CONSOLIDATE AND GROW UPSCALE INTO A FORWARD

    PROPAGATING MCS...WITH HEIGHTENED DAMAGING WIND POTENTIAL ACROSS

    OK/AR INTO THE ADJACENT ARKLATEX VICINITY.

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    Posted
  • Location: Gosport, Hampshire.
  • Location: Gosport, Hampshire.

    Some uncertainties regarding progress of cold front. Careful monitoring of this transition will be paramount for good positioning. My virtual chase starts from Kansas City where I am rather dubious about moving from ATM. Close monitoring of the dry line to my south and intersection to the cold front will be my target. Though it is noted that the strongest upper supporting winds will in fact likely occur much further NE (NE MO or Illinois). It is the latter region that will pose the highest risk of tornado events. Whilst the target to my south on the dryline has potential for isolated tornadoes and large hail. We will nevertheless see some rather fast moving storms today across MO with bowing line segment by late in the day.

    An important day for watching surface obs to develop your picture of unfolding events.

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    Posted
  • Location: Wickham, S Hampshire, UK
  • Location: Wickham, S Hampshire, UK

    I'm with Tony on this after a first glance of the morning. I would however like to be into MO if possible as I think the risk will be upgraded on the next update and tornados look more likely this evening than at any time this last two weeks.

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    Posted
  • Location: South Shields Tyne & Wear half mile from the coast.
  • Location: South Shields Tyne & Wear half mile from the coast.

    I'm with Nick on this one ,stay to the south of the cold front and gonna hang around for 'Tail-end Charlie',

    Illinois and Missouri looks potentially 'High risk' but as Paul, Nick and other experienced chasers have said

    many times before not the ideal chase terrain around those parts, could be a few PDS's issued tonight!!

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    Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

    Best threat for tornadoes doe look to be Ern Missouri and much of Illinois looking at 0-1km and 0-3km shear looking at latest RUC output that goes out to 21z ... and as a virtual chase I'd probably choose that area. However, the team would not be able to drive that far unless they got up early in the morning and drove for hours, still think N and NE OK holds good potential for strong supercells to develop with risk of a tornado - given very large CAPE modelled by RUC later today - especially after 00z.

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    Posted
  • Location: Wickham, S Hampshire, UK
  • Location: Wickham, S Hampshire, UK

    I concede that chase geography is a key factor, so maybe if you can get there then Vinita or Big Cabin, OK would be worth aiming for.

    Could this be a day for a monster tail-end-charlie I wonder? Over 5500 mean CAPE available if it can be realised.

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    Posted
  • Location: Leigh On Sea - Essex & Tornado Alley
  • Location: Leigh On Sea - Essex & Tornado Alley

    Guys

    I dont doubt today has the best Shot at Tornadoes since we have been here, and I fully expect to see near 20 By the end of the day in Illinios and Misery but we are going to hold back for the TEC! Some of the Models break out some nice chances further South and as Nick says there is a chance of a Tornado or 2 down here but this threat should be mainly after dark as the Low Level Jet cranks up.

    Good luck to Nathan as I know he was up at 4am to drive to Illinios and Is in fact now 5 hours into his mammoth drive.

    We will be targeting North of Ok City Initially and Take it from there.

    Best

    Paul S

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    Posted
  • Location: Long Stratton Norfolk: Tornado Hot Spot.
  • Location: Long Stratton Norfolk: Tornado Hot Spot.

    Ok change of plan making WOODWARD INITIALLY due to mileages involved hope to get something before dark, take care

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    Posted
  • Location: Wickham, S Hampshire, UK
  • Location: Wickham, S Hampshire, UK

    Can't do a major technical on this but if you possibly can creep further northeast Paul then do. I get the feeling that the further you go the better the chance of catching something in good daylight by 6pm say.

    If it all kicks off after dark into C OK and the AR/MO corner you really don't want to be going in there. The film 'Wrong Turn' springs to mind LOL.

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    Posted
  • Location: Gosport, Hampshire.
  • Location: Gosport, Hampshire.

    My virtual decision to stay in Kansas City last night gives me a relatively short drive to Jefferson City, central Missouri. By late afternoon the RUC increases upper and low level shear for this region!

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    Posted
  • Location: Scarborough, North Yorkshire - 80m ASL
  • Weather Preferences: Tornadoey
  • Location: Scarborough, North Yorkshire - 80m ASL

    I'm in Springfield, Mo now after 6 hours drive. got another 3 left till I get to IL at least, :huh: Hope thigns hold off till I get to st louis.

    Will check back again in an hour for updates.

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    Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

    Think you will do well Paul to stick to a target of Nern OK, though a look at 12z WRF shows cold front will shift smartly SE in the evening - to be running roughly parrallel to the I-44 between OK City and St Louis by midnight CDT, so will need to keep moving E and SE to avoid being munched:

    post-1052-1242232165_thumb.pngpost-1052-1242232177_thumb.png

    I suppose being a cold front and with large amounts of moisture - supercells IMO could quickly turn HP and form one big squall line - especially across MO and IL - so good idea perhaps to stay on the SWern end of the line of storms likely to develop INVOF cold front where storms maybe more discrete - could be difficult further NE across MO and IL trying to avoid getting munched by HP storms with large hail and potential for rain-wrapped tornadoes - so take care Gorky!

    WRF also showing some reasonable helicity along with large CAPE across Nern OK ahead and along the frontal boundary:

    post-1052-1242232519_thumb.pngpost-1052-1242232482_thumb.png

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    Posted
  • Location: Rossland BC Canada
  • Location: Rossland BC Canada

    In the main threat zone, looks like northeast Missouri, southeast Iowa and western Illinois will produce the best results, the front seems to have slowed down slightly from yesterday's scenario, and the upper support sharpens up considerably for that region. May not be necessary to cross the Mississippi River but would head for Mexico MO and towards Hannibal with option to cross to Qunicy IL. (for Gorky at least, seems like the other crews are in OK).

    The chances seem pretty good for major action even in central OK, agree with Stillwater as a good target.

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    Posted
  • Location: South Cheshire
  • Location: South Cheshire

    Anyone else struggling to get the live feed? Not been able to get on it for a couple of hours now but it could be my internet connection.

    Typical!! As soon as I post, it's back on!! :whistling:

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    Posted
  • Location: South Shields Tyne & Wear half mile from the coast.
  • Location: South Shields Tyne & Wear half mile from the coast.

    SPC have issued MD severe potential for S/SE Kansas,N/central/W Oklahoma.

    886

    ACUS11 KWNS 132022

    SWOMCD

    SPC MCD 132021

    OKZ000-KSZ000-132145-

    MESOSCALE DISCUSSION 0814

    NWS STORM PREDICTION CENTER NORMAN OK

    0321 PM CDT WED MAY 13 2009

    AREAS AFFECTED...SRN/SERN KS AND NERN INTO CENTRAL/WRN OK

    CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

    VALID 132021Z - 132145Z

    THUNDERSTORM INITIATION IS POSSIBLE BY 21-23Z OVER PORTIONS OF

    SRN/SERN KS AND NRN INTO CENTRAL/WRN OK. AREA IS BEING MONITORED FOR

    A WW.

    WATER VAPOR IMAGERY REVEALS A S/W TROUGH PROGRESSING ENE ACROSS THE

    CENTRAL/NRN PLAINS...ACCOMPANIED BY A 70+ KT MID LEVEL JET SAMPLED

    BY NLG PROFILER. MEANWHILE AT THE SURFACE...A COLD FRONT POSITIONED

    FROM ROUGHLY STJ TO ICT TO GAG AT 19Z IS FORECAST TO CONTINUE

    SAGGING SWD ACROSS SERN KS INTO NRN AND WRN OK THROUGH THE EVENING.

    STRONG SLY SURFACE WINDS OVER MUCH OF OK VEER TO SWLY ALONG THE

    FRONT...AND THEN NLY IN ITS WAKE...RESULTING IN STRONG LOW LEVEL

    CONVERGENCE. TEMPERATURES AHEAD OF THE COLD FRONT HAVE WARMED INTO

    THE MID 80S TO AROUND 90 DURING THE AFTERNOON...AND SURFACE

    DEWPOINTS RESIDE IN THE MID TO UPPER 60S. MODIFIED 18Z OUN SOUNDING

    FOR A TEMPERATURE OF 90 AND DEWPOINT IN THE UPPER 60S YIELDS OVER

    3500 J/KG OF MLCAPE. HOWEVER...A WARM CAPPING INVERSION STILL

    RESIDES NEAR 700 MB...EVIDENT BY STABLE CUMULUS FIELD IN VISIBLE

    SATELLITE IMAGERY. SHORT TERM DETERMINISTIC AND ENSEMBLE FORECAST

    GUIDANCE INDICATES THAT COMBINATION OF LARGE SCALE ASCENT WITH UPPER

    WAVE PASSING TO THE NORTH ALONG WITH FRONTAL CONVERGENCE WILL

    ERODE/LIFT THE CAPPING INVERSION BY 23Z...RESULTING IN INCREASING

    PROBABILITY OF THUNDERSTORM INITIATION FROM SERN/SRN KS INTO NRN/WRN

    OK.

    CONVECTIVE MODE ALONG FRONTAL BOUNDARY FROM MO INTO SERN/SRN KS AND

    NRN OK IS EXPECTED TO TRANSITION TOWARD LINEAR RATHER QUICKLY

    THROUGH THE EVENING...WHILE THE POTENTIAL FOR SLIGHTLY MORE DISCRETE

    ACTIVITY MAY EXIST OVER WRN OK. THE COMBINATION OF VERY STEEP MID

    LEVEL LAPSE RATES/LARGE CAPE AND EFFECTIVE BULK SHEAR AROUND 30-40

    KT INVOF THE FRONT MAY FAVOR SUPERCELL STORM STRUCTURES

    INITIALLY...POSING A THREAT OF LARGE-VERY LARGE HAIL ALONG WITH

    ISOLATED TORNADOES. HOWEVER...STRONG FRONTAL FORCING WILL FAVOR

    STORM TYPE TRANSITION TOWARD BOWS AND LEWPS WITHIN A FEW HRS AFTER

    INITIATION...RESULTING IN AN INCREASING THREAT FOR DAMAGING WIND

    GUSTS.

    ..GARNER.. 05/13/2009

    Latest Satellite images looking from east and west.

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    Posted
  • Location: Scarborough, North Yorkshire - 80m ASL
  • Weather Preferences: Tornadoey
  • Location: Scarborough, North Yorkshire - 80m ASL

    I'm in Illinois now, sat the other side of the river from Louisiana. next plan is to get somewhere with decent terrain. A little north of here probably.

    Also, I''ve just been stung by the biggest bee I've ever seen :whistling: Ouch.....

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    Posted
  • Location: Midleton, Cork, Ireland
  • Location: Midleton, Cork, Ireland

    With respect to the streaming at the moment. The guys are in worst possible are for mobile data at the moment so even though the stream is back its going to struggle for a while. It will get better as they head East, or North, or even south.... south wouldn't be great as its GPRS only but anything is better than now. Basically as long as they don't go back west of their current location things will get better. Hang tight!

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    Posted
  • Location: South Shields Tyne & Wear half mile from the coast.
  • Location: South Shields Tyne & Wear half mile from the coast.
    I'm in Illinois now, sat the other side of the river from Louisiana. next plan is to get somewhere with decent terrain. A little north of here probably.

    Also, I''ve just been stung by the biggest bee I've ever seen :whistling: Ouch.....

    Watch yasell Nath, North American Bee flu is rife at the mo..!! They reckon its one

    'ell of a buzz..!!

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    Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

    Latest satellite showing cu streets ahead of the cold front across OK and KS, some insane SBCAPE values shown on the hourly meso analysis, also shows CINH is almost diappeared in a wedge from Wern OK to S-central KS- intiation could occur in next hour or so in this area - best to get on a storm quickly before they line-out and merge into a squall after 00z:

    post-1052-1242248651_thumb.png post-1052-1242248672_thumb.png

    I see the team in a good position near Enid now in n-central OK ...

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    Posted
  • Location: Long Stratton Norfolk: Tornado Hot Spot.
  • Location: Long Stratton Norfolk: Tornado Hot Spot.

    Hi Nick we had a change of target, we went to Tulsa but ated the trees so headed back central now in spring water interesting satillite with line of Q to our nw mmmmmmmmm

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    Posted
  • Location: Omaha, Nebraska USA
  • Location: Omaha, Nebraska USA

    Storms are starting to form on the cold front, from central IA into northwest MO, and into eastern KS. That storm near Emporia,KS just exploded in the last 30 mins. SPC better get the tornado watch out for eastern Kansas soon.

    Just as I posted they put out a Severe Thunderstorm Watch. They don't think there is enough sheer in this area, and the upper level winds are not very strong for widespread tornadoes.

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    Posted
  • Location: South Shields Tyne & Wear half mile from the coast.
  • Location: South Shields Tyne & Wear half mile from the coast.

    I was just about to say the same Old Style. Visible satellite image showing the size

    that cell has grown.

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