SWODY2
SPC AC 250532
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1132 PM CST MON DEC 24 2007
VALID 261200Z - 271200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
MODELS INDICATE CONTINUATION OF AN AMPLIFIED SPLIT FLOW PATTERN
ACROSS THE CONUS WITH A SERIES OF STRONG PROGRESSIVE SHORT WAVE
TROUGHS IN THE SRN BRANCH OF THE WESTERLIES. PRIMARY SHORT WAVE
TROUGH THAT WILL IMPACT CONVECTIVE POTENTIAL ON WEDNESDAY IS
FORECAST TO MOVE FROM THE SRN PLAINS AT THE START OF THE PERIOD NEWD
ACROSS THE TN AND OH VALLEYS AS UPSTREAM TROUGH DIGS SEWD FROM THE
PACIFIC NW TOWARD THE FOUR-CORNERS AREA. A SURFACE LOW OVER TX IS
EXPECTED TO MOVE EWD/NEWD ACROSS LA AND LOWER MS VALLEY DURING THE
DAY BEFORE WEAKENING AFTER 00Z AS THE DYNAMIC SUPPORT LIFTS AWAY
FROM THE COAST. A COLD FRONT TRAILING SWWD FROM THE LOW WILL MOVE
SEWD ALONG THE NWRN GULF COASTAL REGION.
..SERN TX/LA/SRN MS...
VERY STRONG DYNAMIC FORCING FOR LARGE SCALE ASCENT WILL BE
ASSOCIATED WITH THE SRN PLAINS TROUGH AS IT MOVES NEWD TOWARD THE
TN/OH VALLEYS DURING THE DAY. PRIMARY FACTORS IMPACTING COVERAGE
AND INTENSITY OF THUNDERSTORM ACTIVITY ARE THE STRENGTH OF THE
MOISTURE RETURN INLAND AND THE EVOLUTION OF THE THERMODYNAMIC
PROFILES FROM SERN TX ACROSS PARTS OF LA AND SRN MS.
RECENT COLD FRONT PASSAGE HAD SPREAD VERY DRY AIR ACROSS PARTS OF
THE NRN/WRN GULF...HOWEVER AIR MASS MODIFICATION HAS BEEN OCCURRING
OVER THE CENTRAL GULF WHERE BUOY DATA INDICATE DEW POINTS IN THE
UPPER 50S. MOISTURE IS FORECAST TO SPREAD TOWARD THE TX AND LA
COAST BY WEDNESDAY AS A STRONG SSWLY LOW LEVEL JET DEVELOPS ACROSS
THIS AREA...WITH MID/UPPER 50S DEW POINTS MOVING INLAND DURING THE
DAY.
FORECAST SOUNDINGS FROM THE NAM AND ETA-KF CONTROL MEMBER FROM THE
SREF EXHIBIT A WELL-DEFINED INVERSION BASED IN THE 850-750 MB LAYER
PRIOR TO FRONTAL PASSAGE...WHICH IS EXPECTED TO CAP LIFTED PARCEL
UPWARD ACCELERATION AND LIMIT COVERAGE OF THUNDERSTORMS. THE ETA-KF
SOUNDINGS MAINTAIN THE CAP WHILE THE NAM SOUNDINGS BRIEFLY WEAKEN
THE CAP AT THE TIME OF FRONTAL PASSAGE SUGGESTING THE POSSIBILITY OF
A NARROW LINE OF LOW-TOPPED CONVECTION FORMING NEAR THE FRONT.
HOWEVER...SHALLOW CONVECTIVE PROCESSES IN THE BMJ PARAMETERIZATION
APPEAR TO BE RESPONSIBLE FOR THE WEAKENING CAP IN THE NAM
SOUNDINGS...AND PAST EXPERIENCE SUGGESTS THE KF SOUNDINGS MAY BE
MORE REALISTIC IN THESE INSTANCES.
THERE IS POTENTIAL FOR ISOLATED STRONG/SEVERE THUNDERSTORMS TO
DEVELOP ON WEDNESDAY GIVEN THE FAVORABLE SYNOPTIC PATTERN AND STRONG
VERTICAL SHEAR ACROSS THE AREA. HOWEVER...OWING TO THE CONCERNS
ABOUT THE THERMODYNAMIC PROFILES...WILL INTRODUCE A 5% SEVERE AREA
AND NOT DELINEATE A CATEGORICAL RISK AT THIS TIME. AREA WILL NEED
TO MONITORED CLOSELY FOR CHANGES IN MOISTURE RETURN/INSTABILITY AND
ASSOCIATED VERTICAL SOUNDING STRUCTURE GIVEN THE FAVORABLE VERTICAL
SHEAR FORECAST OVER THE AREA.
.WEISS.. 12/25/2007
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@PO.UIUC.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment