000 AGXX40 KNHC 101323 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 930 AM EDT THU SEP 10 2009 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. SW N ATLC...THE FRONTAL TROUGH CURRENTLY STRETCHED FROM NEAR 31N72W TO S FL IS ANCHORED BY A 1012 MB LOW PRES SYSTEM NEAR 36N70W. THIS LOW IS EXPECTED TO WEAKEN AND RETROGRADE NW TOWARD THE DELMARVA PENINSULA THROUGH FRI...DRAGGING THE TROUGH NW AND CLOSER TO THE FL COAST. AT THE SAME TIME...A WAVE IS EXPECTED TO DEVELOP ALONG THE FRONTAL TROUGH OFF THE N FL COAST. THE MODELS DISAGREE ON THE TIMING OF THE WAVE AS IT MOVES NE AWAY FROM FORECAST WATERS...WITH THE GFS AMONG THE SLOWEST AND MORE WESTERLY SOLUTIONS. ADJUSTMENTS WILL BE MADE TOWARD THE MODEL CONSENSUS. AS THE FRONTAL WAVE SHIFTS NE...EXPECT THE TROUGH TO PUSH S INTO THE STRAITS OF FL AND E INTO NE FORECAST WATERS MON/TUE. GFS ENSEMBLES DO NOT ALLOW FOR WINDS TO REACH 20 KT OVER FORECAST WATERS THIS PERIOD. GULF OF MEXICO...THE LIGHT WINDS AND SEAS 3 FT OR LESS SEEN THE LAST WEEK OR TWO IN THE GULF HAVE COME TO AN END AS EVIDENCED IN THE NUMEROUS OBSERVATIONS THIS MORNING OVER THE NORTHERN GULF OF SE WINDS 15 KT OR ABOVE. THE MODELS AGREE ON CONTINUING A PATTERN WITH A STRONGER PRESSURE GRADIENT AND WINDS TO 15 KT ACROSS MUCH OF THE GULF AS THE SURFACE TROUGH CURRENTLY OVER THE SE GULF RETROGRADES NW AS A WARM FRONT TO THE NORTHERN GULF COAST. BY THE WEEKEND...THE MODELS DIVERGE AS A NEW COLD FRONT IS EXPECTED TO SWEEP THROUGH TEXAS TOWARD THE COAST BY SUN...WITH THE GFS...UKMET...AND CAN BRINGING THE FRONT OFFSHORE INTO THE FAR NW GULF EARLY NEXT WEEK WHILE THE ECMWF AND NOGAPS REMAIN ONSHORE. THE LOCATION OF THE FRONT WILL DETERMINE THE AREA OF STRONGEST WINDS AND LARGEST FETCH MON/TUE BETWEEN HIGH PRESSURE OVER THE SE GULF BUILDING W OF THE ATLC FRONTAL TROUGH AND THIS FRONT OVER THE NW GULF COAST WITH THE ECMWF AND NOGAPS MORE TO THE WEST WITH THE BELT OF STRONGEST SOUTHERLY WINDS COMPARED TO THE OTHER MODELS. A BLEND OF THE MORE WESTERLY ECMWF AND THE GFS WILL BE USED FOR THE FORECAST. CARIBBEAN AND TROPICAL N ATLC... TRADES HAVE INCREASED THIS MORNING IN THE VICINITY OF THE TROPICAL WAVE ALONG 73W...WITH THE 1038 UTC QUIKSCAT PASS SHOWING 20 TO 25 KT EASTERLY WINDS ALONG THE TROUGH AXIS S OF 15N AND SEVERAL OBSERVATIONS S OF 14N ALONG THE COAST OF COLOMBIA AND VENEZUELA ALSO AT 20 TO 25 KT. GLOBAL MODELS SHOW SURFACE HIGH PRESSURE STRENGTHENING SLIGHTLY OVER THE CENTRAL ATLC THROUGH FRI NIGHT AS TROUGHING BUILDS IN THE WESTERN GULF OF MEXICO. THIS PATTERN WILL MAINTAIN MODERATE TO FRESH TRADES ACROSS THE CENTRAL CARIBBEAN AND INCREASE SE FLOW OVER THE NW CARIBBEAN INTO SAT. OVER THE WEEKEND...THE HIGH IS EXPECTED TO WEAKEN AND DRIFT SOUTHEAST IN RESPONSE TO A COLD FRONT MOVING ACROSS THE W ATLC. THIS WILL ALLOW WINDS TO DECREASE ACROSS THE EASTERN CARIBBEAN AND TROPICAL N ATLC. HOWEVER...SE WINDS SHOULD BE MAINTAINED OVER NW CARIBBEAN DUE TO THE TROUGH OF LOW PRESSURE OVER THE WESTERN GULF OF MEXICO. ONLY IMPACT FROM HURRICANE FRED WILL BE LONG PERIOD E SWELL ELEVATING SEAS TO 6-8 FT OVER THE NE PART OF THE TROPICAL N ATLC ZONE BEGINNING SUN AND SHIFTING S THROUGH THE ZONE EARLY NEXT WEEK. WARNINGS ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE $$ FORECASTER SCHAUER CLARK