615
FXUS02 KWBC 141715
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
115 PM EDT THU AUG 14 2008
VALID 12Z SUN AUG 17 2008 - 12Z THU AUG 21 2008
PRELIMINARY UPDATE...
WITH THE ADVENT OF THE COMPLETE 00Z AND 06Z NUMERICAL MODEL
SUITE...DECIDED TO RELY PRIMARILY ON THE DETERMINISTIC ECMWF FOR
THE FIRST PART OF THE MEDIUM RANGE PERIOD...WITH A PROGRESSIVE
BLEND TOWARD THE EUROPEAN CENTRE ENSEMBLE MEAN FROM DAY 5 ONWARD.
THE GFS LOOKS UNCLIMATOLOGICALLY INTENSE WITH THE TROUGH IT BRINGS
INTO THE PACIFIC NORTHWEST LATE IN THE PERIOD...WITH THE EUROPEAN
CENTRE ENSEMBLE MEAN AFFORDING A MORE REASONABLE STAND IN FOR A
POSSIBLE DEEPER SOLUTION...EVENED OUT BY THE FLATTER DETERMINISTIC
ECMWF IN THE CHOSEN BLEND.
USED YESTERDAYS COORDINATED TRACK FOR THE POSSIBLE TROPICAL SYSTEM
OVER THE BAHAMAS AND FLORIDA...WITH A SIMPLE EXTRAPOLATION FOR THE
DAY 7 POINT IN LIGHT OF THE WIDE SPREAD IN THE GUIDANCE. THE 00Z
GEM GLOBAL SENDS THE SYSTEM SOUTH OF CUBA...REPRESENTING THE LEFT
SIDE OF THE DYNAMICAL MODEL ENVELOPE...WITH THE 00Z AND 06Z GFS
SHEARING THE SYSTEM NORTHEASTWARD ACROSS BERMUDA DEFINING THIS
GUIDANCE TO THE RIGHT. WILL HAVE ANOTHER COORDINATION WITH TPC
TODAY AND TAKE A FRESH LOOK AT THIS SYSTEM.
FINAL...
THE 12Z GFS BACKED OFF ON THE DEPTH OF THE TROUGH COMING INTO THE
PACIFIC NORTHWEST LATE IN THE PERIOD...IN LINE WITH THE BLEND
CHOSEN FOR THE UPDATE PACKAGE...SO MADE NO CHANGES FOR THE FINAL
ISSUANCE OF THE FRONTS AND PRESSURES OVER MOST OF THE NATION FOR
DAYS 3 THROUGH 7. COORDINATION WITH TPC RESULTED IN DIRECTING THE
POSSIBLE TROPICAL SYSTEM NORTHWARD EAST OF FLORIDA...BUT AGREED
WITH THE SPECIALIST THERE THAT CONFIDENCE IN EITHER THE STRENGTH
OR TRACK OF THIS LOW IS QUITE LOW. THE 12Z GEM GLOBAL TAKES THE
SYSTEM SOUTH OF CUBA...THEN LIFTS IT INTO THE EASTERN GULF OF
MEXICO...WHILE THE GFS TRACKS IT NORTHWARD WELL SHORT OF THE
FLORIDA COAST IN A HEAVILY SHEARED ENVIRONMENT.
CISCO
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