000 AGXX40 KNHC 201835 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 235 PM EDT THU SEP 20 2012 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... FRONTAL ZONE MEANDERING ACROSS GULF THIS AFTERNOON...FROM CENTRAL BAY OF CAMPECHE TO N CENTRAL FLORIDA. CYCLONIC TURNING NOTED IN VIS STLT IMAGERY ACROSS THE SW GULF AND CAMPECHE REGION...WITH RECENT 1612 ASCAT PASS SHOWING SHARP TROUGH IN BAY OF CAMPECHE. FRONTAL ZONE GRADUALLY MORPHING INTO INVERTED TROUGH ACROSS THE SW GULF...AND MODELS FORECAST THIS FEATURE TO FRACTURE AWAY FROM REST OF DYING BOUNDARY AND REMAIN N TO S ACROSS SW GULF THROUGH WEEKEND. SEAS LIKELY 3-5 FT W OF TROUGH AND WRN BAY OF CAMPECHE ATTM. OTHERWISE...LIGHT TO MODERATE E TO NE FLOW PREVAILS N AND NW OF FRONTAL ZONE...AND E TO SE WINDS SE OF FRONTAL ZONE. BROAD AND STATIONARY UPPER TROUGH ACROSS THE U.S. CONTINUES TO SLOWLY DIG INTO THE GULF AND ACTING TO ENHANCE CNVTN ALONG FRONTAL ZONE THIS AFTERNOON. RESPONSIBLE S/W WILL LIFT OUT OF REGION TONIGHT AND LEAVE LESS UNSTABLE CONDITIONS...WITH BEST LIFT EXPECTED ACROSS E AND NE GULF ON FRI. ELY FLOW FORECAST TO BUILD THROUGH THE STRAITS AND INTO SE GULF ON FRI AND COULD YIELD 15-20 KT THROUGH STRAITS. OTHERWISE...SEASONABLE WINDS AND SEAS EXPECTED THROUGH EARLY SUN WITH WEAK FRONTAL BOUNDARY SINKING S INTO N GULF SUN MORNING. TROPICAL WAVE ACROSS THE W CARIBBEAN ATTM TO MOVE SLOWLY ACROSS YUCATAN OVER THE WEEKEND AND WILL GRADUALLY BECOME ABSORBED IN MONSOONAL TROUGHING ACROSS MEXICO AND CENTRAL AMERICA...AND MEAN TROUGHING ACROSS SW GULF. THIS WAVE WILL ENHANCE EVENING CONVECTION ACROSS THE YUCATAN SAT AND SUN. SOUTHWEST NORTH ATLC S OF 31N W OF 55W... STALLED FRONTAL ACROSS NW PORTIONS WAS ILL DEFINED THIS MORNING BUT NNE FLOW OFF THE CAROLINA COASTS FORCING NEW ZONE OF CONVERGENCE AND MODERATE CONVECTION. HIGH PRES ACROSS NW ATLC CONTINUES TO RIDGE SSW INTO THE REGION...TO THE W OF DEVELOPING SUB TROPICAL LOW ACROSS CENTRAL ATLC. THIS FEATURE GAINING CONVECTION NEAR CENTER AND COULD BECOME CLASSIFIED AS SUB TROPICAL CYCLONE NEXT 24-36 HOURS. HOWEVER...GALES OCCURRING ATTM N OF LOCAL AREA WILL SHIFT AWAY...AND GALE FORCE OR STORM FORCE WINDS NOT EXPECTED INTO LOCAL WATERS. MILD WINDS AND SEAS TO PREVAIL THROUGH SAT WITH E TO SE FLOW AT LOW LATS ATTEMPTING TO BUILD WWD INTO BAHAMAS THROUGH THE WEEKEND. CONVERGENCE LINES WITH MODERATE TO ISOLATED DEEP CNVTN TO CONTINUE ACROSS OPEN ATLC WATERS NEXT 24-36 HOURS AND GRADUALLY SHIFT N AND NW. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... GENTLE TO MODERATE TRADE WINDS PREVAIL ACROSS THE CARIBBEAN WATERS AND THE TROPICAL N ATLC WATERS...EXCEPT FOR MODERATE TRADEWINDS ACROSS THE SOUTHERN CENTRAL CARIBBEAN WATERS...AND MODERATE ENE WINDS AHEAD OF TROPICAL WAVE IN CENTRAL CARIB. WINDS IN SRN CARIB WILL BEGIN TO SLOWLY FRESHEN TONIGHT AS HIGH PRES ACROSS ERN U.S. SHIFTS SLOWLY SE NEXT FEW DAYS...WITH 20-25 KT TYPICAL TRADES ACROSS MUCH OF SRN CORRIDOR BY SAT EVENING. SEAS THERE WILL GRADUALLY BUILD FROM 5-6 FT ATTM TO 6-9 BY SUN. TROPICAL WAVE WILL CONTINUE MOVING W ACROSS THE NW CARIB NEXT 48 HOURS AND INTO YUCATAN AND THEN GRADUALLY BECOME ABSORBED IN MONSOONAL TROUGHING ACROSS SRN MEXICO AND CENTRAL AMERICA...AND PERSISTENT TROUGHING ACROSS SW GULF. TROPICAL WAVE ENTERING SW N ATLC WATERS ATTM TO ENCOUNTER SELY STEERING FLOW AND MOVE MORE WNW NEXT COUPLE OF DAYS...AND ALMOST IMPOSSIBLE TO FOLLOW IN MODEL GUIDANCE BY 72 HOURS AS MID LEVEL DEFORMATION ZONE SETS UP N OF PR/USVI REGION. OTHER THAN CONVECTION OCCURRING WITH INTERACTION OF THIS WAVE AND MID ATLC TROUGH...NO SIGNIFICANT EFFECTS IN WINDS AND SEAS EXPECTED WITH THIS WAVE. A NEXT TROPICAL WAVE WILL REACH THE TROPICAL N ATLC WATERS MON....ACCOMPANIED BY A BROAD LOW LEVEL WIND SURGE AND SEAS 8-9 FT. NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .NONE. CARIBBEAN SEA AND TROPICAL N ATLC... .NONE. SW N ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER STRIPLING