435
FXUS02 KWBC 241733
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
133 PM EDT TUE JUN 24 2008
VALID 12Z FRI JUN 27 2008 - 12Z TUE JUL 01 2008
PRELIMINARY UPDATE...
THE DETERMINISTIC GFS REPRESENTS THE WESTERN...AMPLIFIED EXTREME
OF THE MODEL GUIDANCE FROM THE 00Z/24 CYCLE WITH THE TROUGH
CROSSING THE GREAT LAKES DURING THE MEDIUM RANGE PERIOD...WITH THE
00Z GEFS MEAN TAKING THE DISTINCTION OF THE FLAT...PROGRESSIVE
COUNTERPART. BECAUSE THE INDIVIDUAL ENSEMBLE MEMBERS THAT
COMPRISE THE GEFS MEAN ARE CONSIDERABLY LESS RESOLVED THAN THE
DETERMINISTIC GFS...IT IS NOT NECESSARILY AS MEANINGFUL...SAY...AS
WHEN THE DETERMINISTIC ECMWF DIFFERS FROM ITS ENSEMBLE
MEAN...WHICH IS MADE UP OF COMPARABLY RESOLVED MEMBERS. IF A
PATTERN IS POISED TO AMPLIFY VIA A PARTICULARLY ENERGETIC SHORT
WAVE...A MORE HIGHLY RESOLVED MODEL IS MORE LIKELY TO CAPTURE SUCH
A FINER SCALE MECHANISM. IN THIS CASE...THE 00Z DETERMINISTIC
ECMWF IS CLOSER TO ITS ENSEMBLE MEAN FROM THAT CYCLE THAN THE
PAIRING FROM 00Z/23...ADDING CREDIBILITY TO THE EUROPEAN CENTER
SOLUTION. FURTHERMORE...THE DETERMINISTIC GEM GLOBAL AND THE
UKMET MODELS SHOW AN AMPLITUDE AND PROGRESSION CLOSER TO THE ECMWF
AND ITS MEAN...SO FELT COULD RUN WITH THIS CLUSTER FOR THE UPDATED
FRONTS AND PRESSURES FOR DAYS 3 THROUGH 7. SPECIFICALLY...USED
THE 00Z DETERMINISTIC ECMWF FOR DAYS 3 AND 4...WITH A GRADUAL
BLEND TOWARD THE 00Z ECMWF ENSEMBLE THEREAFTER TO REFLECT THE
UNCERTAINTY IN DETAILS INHERENT AT THE LATER TIME RANGES.
FINAL...
THE 12Z GFS MADE AN ABOUT FACE FROM ITS 00Z RUN WITH THE KEY
TROUGH OVER THE GREAT LAKES...NOW INDICATING A MUCH
FLATTER...PROGRESSIVE SOLUTION. IN FACT...BY DAY 7...THE NEW
DETERMINISTIC GFS IS ACTUALLY FASTER THAN THE 00Z ECMWF ENSEMBLE
MEAN WITH THIS SYSTEM OVER THE SAINT LAWRENCE VALLEY. NEEDLESS TO
SAY...THIS IS A SIGNIFICANT VOTE OF CONFIDENCE TOWARD THE MANUAL
UPDATE PACKAGE...SO WILL MAKE NO CHANGES FOR THE FINAL ISSUANCE.
THE GREAT LAKES REGION WILL BE ONE AREA OF FOCUS FOR SIGNIFICANT
PRECIPITATION EARLY IN THE PERIOD...WITH THE ACTION SHIFTING TO
THE NORTHEAST BY LATE DAY 5. THE GULF COAST WILL ALSO SEE ITS
SHARE OF RAINFALL COURTESY OF MOIST SUBTROPICAL FLOW THROUGHOUT
THE FORECAST...PARTICULARLY DURING THE AFTERNOON AND EARLY EVENING
HOURS.
CISCO
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