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Slight Risk 17th April - Tx, Ok


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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)

    post-1052-1239987800_thumb.png post-1052-1239987827_thumb.png post-1052-1239987816_thumb.png

    DAY 1 CONVECTIVE OUTLOOK

    NWS STORM PREDICTION CENTER NORMAN OK

    1128 AM CDT FRI APR 17 2009

    VALID 171630Z - 181200Z

    ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF TEXAS...WRN

    OK...SW KS AND SE CO...

    ...EAST TEXAS...

    THE LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL LOW OVER THE SRN

    ROCKIES WITH A BROAD DRY SLOT EXTENDING EWD TO AN MCS LOCATED IN

    ECNTRL TX. THE MCS WILL MOVE ENEWD ACROSS EAST TX THIS AFTERNOON.

    THE SRN PART OF THE MCS SHOULD STRENGTHEN MOVING EWD ALONG A WARM

    FRONT AND GRADIENT OF MODERATE INSTABILITY INTO THE

    HOUSTON/GALVESTON AREAS. ALTHOUGH MUCH OF THE MCS MAY BE SLIGHTLY

    ELEVATED ATTM...FORECAST SOUNDINGS QUICKLY WEAKEN THE CAP OVER SE TX

    OVER THE 1-2 HOURS WHICH WILL ALLOW THE STORMS TO BECOME SFC-BASED.

    STRONG VERTICAL SHEAR PROFILES ALREADY IN PLACE WILL SUPPORT

    ISOLATED SUPERCELLS. IN ADDITION...THE RUC ANALYZES A 45 TO 55 KT

    LOW-LEVEL JET OVER SOUTHEAST TEXAS AND THE HOUSTON WSR-88D VWP

    CONFIRMS THIS WITH A 55 KT SLY WIND AT 1 KM. THIS IS PRODUCING A

    LOW-LEVEL SHEAR ENVIRONMENT FAVORABLE FOR AT LEAST AN ISOLATED

    TORNADO THREAT. THIS THREAT SHOULD EXPAND EWD WITH TIME AND MAY

    AFFECT AREAS OF FAR SE TX LATER THIS AFTERNOON.

    NORTH OF THE WARM FRONT IN THE LUFKIN AND TYLER AREAS...INSTABILITY

    DROPS OFF DRAMATICALLY AND VERTICAL SHEAR IS WEAKER. THESE TWO

    FACTORS SHOULD KEEP THE SEVERE THREAT MORE ISOLATED AS THE

    SQUALL-LINE OVER ECNTRL TX AFFECTS NERN TX THIS AFTERNOON.

    ...WCNTRL TX/TX PANHANDLE/WRN OK/SE CO/SW KS...

    A 65 TO 75 KT MID-LEVEL JET IS CURRENTLY ROUNDING THE BASE OF AN

    WELL-DEVELOPED UPPER-LEVEL LOW OVER THE SRN ROCKIES. AT THE SFC...A

    WELL-DEFINED DRYLINE IS PRESENT EXTENDING SEWD ACROSS THE TX

    PANHANDLE INTO WCNTRL TX. THUNDERSTORMS WITH HAIL POTENTIAL ARE

    ONGOING ON THE NERN SIDE OF THE UPPER-LEVEL LOW OVER SE CO AND THE

    OK PANHANDLE. MID-LEVEL LAPSE RATES ARE STEEP AND TEMPS ALOFT ARE

    COLD ASSOCIATED WITH THE UPPER-LEVEL LOW. THIS SHOULD CONTINUE TO BE

    FAVORABLE FOR HAIL ESPECIALLY AS SFC TEMPS WARM THIS AFTERNOON. THE

    HAIL THREAT SHOULD EXPAND SEWD WITH TIME ACROSS THE ERN TX PANHANDLE

    WHICH IS SUPPORTED BY THE SHORT-RANGE MODELS.

    FURTHER SOUTH ALONG THE DRYLINE IN WCNTRL TX...SFC DEWPOINTS ARE

    CURRENTLY IN THE UPPER 50S F. THE AIRMASS IS NOT YET UNSTABLE DUE TO

    LOW CLOUD COVER IN THE WAKE OF AN MCS WHICH WILL CONTINUE TO HAMPER

    DESTABILIZATION THIS AFTERNOON...DELAYING CONVECTIVE INITIATION

    UNTIL THIS EVENING ALONG THE DRYLINE. BY THAT TIME...03Z MODEL

    FORECASTS DEVELOP SUFFICIENT INSTABILITY IN A STRONGLY SHEARED

    ENVIRONMENT FOR SUPERCELLS. FORECAST SOUNDINGS THIS EVENING ACROSS

    WCNTRL TX SHOW 55 TO 65 KT OF VERTICAL SHEAR WITH 500 MB TEMPS IN

    THE -17 TO -19 C RANGE. THIS SHOULD SUPPORT A THREAT OF LARGE HAIL

    AND AN ISOLATED THREAT FOR VERY LARGE HAIL SHOULD EXIST WITH ANY

    SUPERCELLS THAT BECOME DOMINANT DURING THE MID TO LATE EVENING.

    ALTHOUGH MORE CONDITIONAL...A TORNADO WILL BE POSSIBLE AS WELL.

    ..BROYLES/GARNER.. 04/17/2009

    First tornado watch of the morning there:

    post-1052-1239987974_thumb.png

    http://www.spc.noaa.gov/products/watch/ww0159.html

    Once this MCS stuff moves on we should see storms firing further to the west and NW as the dry line moves in from the west later, think I'll target somewhere like Throckmorton, TX - Abilene, TX area in west-central Texas.

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

    Hi Nick. Yep I'm going to try and get back on this one later this evening. Though a quick look seems to be rather restrictive on tornado development ATM. Though given the likely development of surface boundaries some weak CZ tornadoes could get reported.

    PS. Last nights risk for tornadoes was definitely underestimated by the SPC IMO

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    Posted
  • Location: SE London
  • Location: SE London

    cheers nick, thats my evening and night sorted if its quiet here in work :drunk:

    Current watch status

    Probability of 2 or more tornadoes Mod (30%)

    Probability of 1 or more strong (F2-F5) tornadoes Low (10%)

    courtesy NOAA

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    Posted
  • Location: SE London
  • Location: SE London

    Watch 162 issued

    SEL2

    URGENT - IMMEDIATE BROADCAST REQUESTED

    TORNADO WATCH NUMBER 162

    NWS STORM PREDICTION CENTER NORMAN OK

    345 PM CDT FRI APR 17 2009

    THE NWS STORM PREDICTION CENTER HAS ISSUED A

    TORNADO WATCH FOR PORTIONS OF

    TEXAS COASTAL PLAINS

    COASTAL WATERS

    EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING FROM 345 PM UNTIL

    1000 PM CDT.

    TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

    GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

    AREAS.

    courtesy NOAA

    full text here > http://www.spc.noaa.gov/products/watch/ww0162.html

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