MESO: Mesoscale Discussion 0022

ACUS11 KWNS 201758
SWOMCD
SPC MCD 201758
CAZ000-201930-

MESOSCALE DISCUSSION 0022
NWS STORM PREDICTION CENTER NORMAN OK
1158 AM CST WED JAN 20 2010

AREAS AFFECTED...COASTAL AREAS OF CENTRAL AND SRN CA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 201758Z - 201930Z

THE THREAT FOR AN ISOLATED DAMAGING WIND GUST AND TORNADO WILL EXIST
OVER CENTRAL PORTIONS OF THE CA COAST DURING THE LATE MORNING/EARLY
AFTERNOON...BEFORE TRANSITIONING TO A MARGINAL HAIL/WIND THREAT
AFTER 20Z. FARTHER S OVER SRN PORTIONS OF THE CA COAST...LOW LEVEL
WIND PROFILES WILL REMAIN FAVORABLE FOR ROTATING THUNDERSTORMS
THROUGH MUCH OF THE AFTERNOON WITH AN ATTENDANT THREAT FOR AN
ISOLATED DAMAGING WIND GUST AND TORNADO.

HI-RES AND COMPOSITE RADAR IMAGERY INDICATE AN INTENSIFICATION OF
THUNDERSTORM ACTIVITY DURING THE LATE MORNING IMMEDIATELY OFFSHORE
OF THE CENTRAL AND SRN CA COASTLINE. THIS STRENGTHENING TREND
APPEARS TO BE ASSOCIATED WITH INCREASING LARGE SCALE ASCENT AND LOW
LEVEL CONVERGENCE ATTENDANT TO THE APPROACH OF A S/W TROUGH. SURFACE
OBSERVATIONS ALSO SHOW A COOL BUT RATHER MOIST AIRMASS RESIDES ALONG
THE COASTLINE...WITH TEMPERATURES IN THE LOW TO MID 50S AND
DEWPOINTS IN THE UPPER 40S TO LOW 50S. GIVEN THE RELATIVELY WARM MID
LEVEL TEMPERATURES AHEAD OF THE UPPER TROUGH AND COOL SURFACE
TEMPERATURES...LAPSE RATES AND CONVECTIVE INSTABILITY ARE PRESENTLY
RATHER MODEST. HOWEVER...MID LEVEL TEMPERATURES ARE FORECAST TO
STEADILY DECREASE THROUGH THE AFTERNOON AS THE UPPER TROUGH MOVES
ACROSS THE REGION...WHICH WILL AID IN STEEPENING LAPSE RATES AND
LEAD TO THE DEVELOPMENT OF SEVERAL HUNDRED J/KG OF MLCAPE...FIRST
OVER THE CENTRAL CA COAST...AND THEN FARTHER S AS EVENING
APPROACHES. THIS INCREASING INSTABILITY MAY AID IN ADDITIONAL STORM
INTENSIFICATION...WITH A GRADUAL THREAT OF MARGINALLY SEVERE HAIL
DEVELOPING AS A RESULT.

IN ADDITION...LOW LEVEL HODOGRAPH STRUCTURE WILL REMAIN ENLARGED
OVER THE CENTRAL CA COAST THROUGH 20Z...SUGGESTING A NON-ZERO THREAT
FOR AN ISOLATED TORNADO EXISTS. AFTER 20Z...LOW LEVEL FLOW IS
FORECAST TO BECOME PROGRESSIVELY VEERED...WHICH MAY LEAD TO A
PRIMARY THREAT OF BOWING LINE SEGMENTS POSING A THREAT OF ISOLATED
DAMAGING WIND GUSTS AND HAIL. FARTHER S...LOW LEVEL WIND PROFILES
WILL REMAINED BACKED FOR A LONGER PERIOD OF TIME...THOUGH MID LEVEL
INSTABILITY WILL BE SOMEWHAT MARGINAL. THUS...AN ISOLATED
TORNADO/DAMAGING WIND GUST WILL LIKELY REMAIN THE PRIMARY SEVERE
THREAT INVOF OF THE LOS ANGELES METRO AREA THROUGH 00Z.

..GARNER.. 01/20/2010

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LOX...MTR...

LAT...LON 34651934 34181837 33651805 33571839 34121962 34362063
35132090 36222200 37482265 37792240 37112179 36022119
35242036 34772018 34651934

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