000 AGXX40 KNHC 060728 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 330 AM EDT TUE OCT 06 2009 GULF OF MEXICO... HIGH PRES IS CURRENTLY BUILDING W ACROSS THE GULF OF MEXICO. MEANWHILE...A DEEP LAYER LOW IS MOVING INTO THE CENTRAL PLAINS WITH THE ASSOCIATED COLD FRONT PUSHING INTO TX. THIS PATTERN WILL INCREASE THE PRES GRADIENT OVER THE NW GULF AND SOUTHERLY RETURN FLOW WILL INCREASE TO 20 KT LATER TODAY. THE FRONT IS EXPECTED TO REMAIN N OF THE GULF OF MEXICO...PASSING THROUGH THE SOUTHEAST U.S. AND INTO THE WESTERN N ATLC WED. STRONG HIGH PRES BEHIND THIS COLD FRONT WILL BE SLOW TO MOVE OFF THE CAROLINA COAST...ALLOWING FOR MEAN HIGH PRES TO REMAIN OVER EASTERN GULF THU AND FRI. A NEW TROUGH WILL MOVE INTO THE PLAINS STATES THU AND INITIATE SOUTHERLY RETURN FLOW OVER THE GULF WHERE THE PRES GRADIENT WILL BE ENHANCED BETWEEN THIS TROUGHING AND THE RIDGING OVER THE E GULF. GFS SHOWS WINDS REACHING THE 25-30 KT RANGE FRI...BUT DOES NOT GENERATE THESE STRONG WINDS OVER AS LARGE AN AREA AS THE 00Z/05 GFS HAD YESTERDAY. MEANWHILE...THE ECMWF AND UKMET HAVE TRENDED STRONGER AND NOW ALLOW WINDS TO REACH 25 KT. THE MODELS HAVE GENERALLY BEEN TOO STRONG WITH THE RETURN FLOW OVER THE NW GULF IN THE FORECAST PERIOD UNDER THIS PATTERN...BACKING OFF AS THE EVENT DRAWS CLOSER. THE FORECAST KEEPS WINDS TO 20 KT IN THE RETURN FLOW FRI...BUT THERE IS INCREASING UNCERTAINTY BASED ON THE MODEL TREND. THE MODELS VARY WITH THE TIMING OF THE COLD FRONT AS IT MOVES INTO THE NW GULF FRI-SAT WITH THE GFS/CMC FASTER THAN THE ECMWF/UKMET/NOGAPS. THE GFS SOLUTION WAS SLOWED TO ACCOUNT FOR THE MODEL CONSENSUS. CARIBBEAN AND TROPICAL N ATLC... THE QUIKSCAT PASS FROM 2358 UTC SHOWS WINDS INTO THE 20 TO 25 KT RANGE WITHIN 150 NM OF THE COAST OF HONDURAS AS THE TROPICAL WAVE ALONG 85W PASSES W. WINDS ARE EXPECTED TO REMAIN AT 20 KT TODAY IN THE GULF OF HONDURAS AS THE TROPICAL WAVE MAKES ITS WAY THROUGH CENTRAL AMERICA. A SLOW MOVING TROUGH PASSING INTO HISPANIOLA ALONG 70W N OF 15N IS EXPECTED TO WEAKEN AS IT MOVES SLOWLY NW INTO THE GREATER ANTILLES AND BAHAMAS OVER THE NEXT FEW DAYS. THERE ARE A FEW SHIP REPORTS NEAR THE WAVE AXIS THAT SHOW WINDS ARE AROUND 20 KT AND CONVECTION HAS INCREASED ALONG THE TROUGH FOR THE MOMENT. THE BUILDING RIDGE TO THE NORTH HAS INCREASED THE PRES GRADIENT OVER THE CENTRAL CARIBBEAN. THE 0246 UTC ASCAT PASS SHOWS 20 TO 25 KT WINDS WITHIN 120 NM OF THE COAST OF COLOMBIA AND SHIP ZCDF4 CONFIRMS THIS. THE TROPICAL WAVE CURRENTLY ALONG 61W S OF 14N WILL TRACK INTO THE CARIBBEAN TODAY AND WILL EXIT THE CARIBBEAN FRI. ANOTHER TROPICAL WAVE ALONG 48W FROM 10N TO 18N WILL MOVE INTO THE TROPICAL N ATLC ZONE LATER TODAY. THERE IS A 1010 MB LOW PRES AREA EMBEDDED ON THE TROPICAL WAVE AT 14N AND THE LOW IS EXPECTED TO SPLINTER AWAY FROM THE WAVE WED...WITH THE WAVE MOVING W TO THE CENTRAL CARIBBEAN THU AND FRI. THE MODELS SHOW SOME DEVELOPMENT OF THE LOW AS IT TRACKS WITH A WEAKNESS IN THE SUBTROPICAL RIDGE E OF THE LESSER ANTILLES AND CONTINUES TO LIFT NORTHWESTWARD REACHING 21N65W BY FRI MORNING. THE ASCAT PASS FROM 0104 UTC SHOWED WINDS TO 30 KT WITHIN 120 NM N QUADRANT. HOWEVER...THE FORECAST CALLS FOR THE SYSTEM TO BEGIN WEAKENING BY THU AS IT ENCOUNTERS AN INCREASINGLY HOSTILE ENVIRONMENT. ANOTHER TROPICAL WAVE WILL MOVE INTO THE TROPICAL N ATLC ZONE THU AND ALSO BE DRAWN NORTHWESTWARD BY THE WEAKNESS IN THE SUBTROPICAL RIDGE TO THE N. SW N ATLC... A 1012 MB LOW PRES SYSTEM OFF THE SC COAST WILL CONTINUE TO PUSH NE AND DRAG A WEAK COLD FRONT INTO FAR NW WATERS LATER TODAY. THIS SYSTEM WILL BECOME MORE AMPLIFIED AS IT MOVES INTO THE LEADING EDGE OF THE BROAD DEEP LAYER TROUGH PASSING E OF THE MISSISSIPPI RIVER TODAY. WHILE THE 2354 UTC QUIKSCAT PASS HAD A WIDESPREAD REGION OF RAIN-FLAGGED VECTORS HERE...THERE WERE ENOUGH RELIABLE RETRIEVALS TO ACCOUNT FOR 20 KT SOUTHERLY FLOW OVER FAR N WATERS AND THE MORE RECENT 0250 UTC ASCAT PASS CONFIRMS THIS. THESE WINDS SHOULD SHIFT NE WITH THE LOW TODAY. THE COLD FRONT ASSOCIATED WITH THE DEEP LAYER TROUGH WILL MOVE INTO N WATERS OVERNIGHT WED NIGHT AND SW WINDS AHEAD OF THE FRONT WILL INCREASE TO 20 KT OVER FAR NW WATERS AND WILL SHIFT E ACROSS FAR N FORECAST WATERS AS THE FRONT MOVES OFFSHORE THROUGH THU. THE FRONT WILL DIP INTO N WATERS THU AND FRI...SHIFTING WINDS NORTHEASTERLY. THE FRONT WILL MOVE E OF THE AREA AND HIGH PRES WILL BUILD FROM THE N ON FRI WHILE A NEW TROUGH WITH A SURFACE LOW TRACKS W-NW INTO THE SE PORTION OF THE ZONE AT THE END OF THE PERIOD. SEE DISCUSSION ABOVE FOR DETAILS. FINALLY...ANOTHER COLD FRONT WILL APPROACH NW WATERS AT THE END OF THE FORECAST PERIOD. WARNINGS... ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE $$ FORECASTER SCHAUER CLARK