SWODY2
SPC AC 201730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT TUE OCT 20 2009
VALID 211200Z - 221200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
IN MID-UPPER LEVELS...PROGRESSIVE SHORTWAVE TRAIN WILL BE EMBEDDED
WITHIN NEARLY ZONAL LARGE-SCALE PATTERN OVER CONUS. MAIN SHORTWAVE
TROUGH FOR THIS FCST IS EVIDENT IN 12Z RAOB ANALYSES AND MOISTURE
CHANNEL IMAGERY INVOF SRN TIP OF NV. THIS FEATURE IS EXPECTED TO
EVOLVE INTO CLOSED CYCLONE COVERING MUCH OF NM...SRN CO AND ERN AZ
BY 21/12Z. LOW THEN SHOULD PIVOT NEWD ACROSS SRN/CENTRAL HIGH
PLAINS DAY-2...WEAKENING SLIGHTLY BUT MAINTAINING HIGHLY AMPLIFIED
SHORTWAVE TROUGHING OVER WRN PORTIONS KS/OK/TX BY END OF PERIOD. BY
THAT TIME...THIS FEATURE WILL PHASE AT LEAST PARTIALLY WITH BOTH
REMAINS OF EAST-PACIFIC TS RICK AND WEAKER/NRN-STREAM TROUGH OVER
UPPER MIDWEST...RESULTING IN TROUGHING FROM LS ACROSS CENTRAL CONUS
TO W-CENTRAL MEX. SPECTRAL MODEL YIELDS SLOW/OUTLIER SOLUTION WITH
THIS SYSTEM COMPARED TO WRF AND MOST SREF MEMBERS...WITH SREF
CONSENSUS BEING CLOSE TO OPERATIONAL WRF AND PREFERRED FOR THIS
FCST.
AT SFC...WAVY/QUASISTATIONARY FRONTAL ZONE IS ANALYZED FROM WRN IA
SWD THROUGH WEAK LOW OVER SERN CO...THEN WWD ACROSS S-CENTRAL CO AND
NWWD TO W-CENTRAL CO. FRONT IS FCST TO INTENSIFY E OF ROCKIES
OVERNIGHT DAY-1 THEN PLUNGE SEWD ACROSS MOST OF ERN NM AND TX
PANHANDLE BY 22/00Z. BY 22/12Z...FRONTAL-WAVE LOW SHOULD FORM INVOF
NRN LOWER MI AHEAD OF NRN STREAM SHORTWAVE TROUGH...WITH COLD FRONT
TRAILING ACROSS SRN WI...SERN IA...SERN OK...TO CENTRAL TX AND SRN
EDWARDS PLATEAU REGION. WEAK FRONTAL-WAVE LOW MAY PERSIST
ALONG...AND MOVE EWD WITH...THAT SEGMENT OF BAROCLINIC ZONE OVER SRN
KS AND SWRN MO.
TWO AREAS OF MRGL/CONDITIONAL SVR POTENTIAL APPEAR ATTM...WITH LACK
OF MORE ROBUST BUOYANCY/INSTABILITY BEING LIMITING FACTOR FOR
GREATER UNCONDITIONAL SVR PROBABILITIES. SOME POTENTIAL EXISTS FOR
SPATIAL OVERLAP OR BLENDING OF THESE REGIMES...HENCE A SINGLE/LARGE
5-PERCENT SWATH.
...SRN HIGH PLAINS...OK...SRN KS...N TX...
ANALYZED 20/12Z 850 MB CHART INDICATES MOISTURE ABOVE SFC EMANATING
FROM CONFLUENCE OF BOTH GULF OF MEXICO AND PACIFIC SOURCES -- LATTER
INCLUDING TS RICK. COMBINED MOISTURE SOURCE WILL FUEL ONGOING
CONVECTION AT START OF PERIOD...WITH MODIFIED GULF FETCH BECOMING
MORE DOMINANT EWD ACROSS THIS REGION. SCATTERED TO NUMEROUS TSTMS
ARE POSSIBLE INVOF COLD FRONT MOVING EWD FROM TX PANHANDLE EARLY IN
PERIOD ACROSS OK AND SRN KS DURING DAYTIME AND EVENING. FCST
VERTICAL WIND PROFILES FEATURE STG UPPER LEVEL WINDS...MEAN WIND
VECTOR ALIGNED NEARLY PARALLEL TO FRONTAL ZONE...AND BACKING OF FLOW
WITH HEIGHT FROM ROUGHLY 850-700 MB. THIS INDICATES PREDOMINANTLY
LINEAR MODE. EARLY/MRGL HAIL AND GUST THREAT OVER SRN HIGH PLAINS
WILL TRANSITION TO EPISODIC POTENTIAL FOR STG TO ISOLATED SVR GUSTS
WITH BOW/LEWP FORMATIONS AS SYSTEM SHIFTS EWD. PARCELS SHOULD
BECOME SFC-BASED OR VERY NEARLY SO FROM VICINITY KS/OK BORDER SWD
WITH WAA AND DIFFUSE DIURNAL HEATING. HOWEVER...DESPITE INCREASING
LOW LEVEL MOISTURE...MLCAPE MAY ATTAIN ONLY 100-500 J/KG RANGE AHEAD
OF FRONT. POTENTIAL FOR APPRECIABLE DESTABILIZATION WILL BE LIMITED
BY COMBINATION OF RELATIVELY WEAK LAPSE RATES ALOFT AND PRESENCE OF
EXTENSIVE CLOUD/PRECIP COVER TO LIMIT DIABATIC SFC HEATING.
...E TX...ARKLATEX REGION...
INITIALLY SEPARATE AREA OF SCATTERED TSTMS MAY DEVELOP ACROSS
PORTIONS CENTRAL/SERN TX AND MOVE NEWD...WITHIN ZONE OF STG LOW
LEVEL WAA AND MOIST ADVECTION. THIS MAY BE FOLLOWED AFTER 22/00Z
BY BACKBUILDING OF OK LINEAR CONVECTION REGIME SWWD ALONG COLD
FRONT...AS FRONT ADVANCES INTO PROGRESSIVELY HIGHER-THETAE BOUNDARY
LAYER. BACKED SFC WINDS IN WARM SECTOR MAY ENHANCE LOW-LEVEL SHEAR
PROFILES AND SRH IN SUPPORT OF SOME SUPERCELL POTENTIAL...BUT MAIN
STORM MODES MAY BE CLUSTERED AHEAD OF FRONT AND LINEAR ALONG IT.
THERMAL PROFILES APPEAR TOO WARM TO SUPPORT MUCH HAIL THREAT WITH
THIS REGIME...BUT ISOLATED DAMAGING GUSTS ARE POSSIBLE...AND
MRGL/CONDITIONAL TORNADO POTENTIAL MAY DEVELOP.
..EDWARDS.. 10/20/2009
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment