723
FXUS02 KWBC 151827
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
226 PM EDT TUE JUL 15 2008
VALID 12Z FRI JUL 18 2008 - 12Z TUE JUL 22 2008
PRELIMINARY UPDATE...
THE 00Z DETERMINISTIC GFS WAS NOT USED FOR THE UPDATED FRONTS AND
PRESSURES FOR THE UNITED STATES FOR DAYS 3 THROUGH 7...MOSTLY DUE
TO ITS SPECIOUSLY DEEP VORTEX ROLLING EASTWARD ALONG THE CANADIAN
BORDER...AS WELL AS SEVERAL SPURIOUS FEEDBACK VORTICITY MAXIMA
CIRCULATING THROUGH THE SUBTROPICAL RIDGE OVER THE SOUTHERN
STATES. INSTEAD...RELIED ON AN EVEN BLEND OF THE 00Z
DETERMINISTIC ECMWF AND THE ECMWF ENSEMBLE MEAN FROM THAT MODEL
CYCLE...WHICH ARE IN HARMONY WITH THE 00Z GEFS MEAN FOR THE LONG
WAVE PATTERN. CHOSE TO NOT INCORPORATE THE GEFS MASS FIELDS DUE
TO THEIR LOWER RESOLUTION...WHICH WOULD HAVE UNDULY SLACKENED THE
SURFACE PRESSURE GRADIENTS...ALREADY AT A SEASONABLE MINIMUM AS IT
IS.
FINAL...
THE 12Z GFS STILL STANDS OUT AMONGST THE CROWD OF OTHER MODELS
WITH THE VIGOR OF THE SHORT WAVE TROUGH CROSSING THE NORTH CENTRAL
STATES DURING THE PERIOD...WITH THE LATEST UKMET AND GEFS MEAN A
MODICUM WEAKER...AND THE GEM GLOBAL ABOUT AS SHEARED AND
PROGRESSIVE AS THE BLEND USED FOR THE UPDATED PROGS. THE GEM
GLOBAL WAS THE BIGGEST REASON THAT NO CHANGES WERE MADE FOR THE
FINAL ISSUANCE...WITH THAT MODEL SUPPORTING THE MANUAL SURFACE
FRONTS RIGHT THROUGH DAY 6.
MOST OF THE RAINFALL DURING THIS PERIOD WILL EXTEND FROM THE
MONSOON AREAS OF THE SOUTHWEST TO THE UPPER MIDWEST...WHERE
FRONTAL FORCING WILL WRING THE MOISTURE PLUME. A SECOND AREA OF
FOCUS WILL BE NEAR THE OTHER WEAKNESS IN THE SUBTROPICAL RIDGE
ALONG THE SOUTHEAST COAST.
CISCO
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