000 AGXX40 KNHC 180659 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 300 AM EDT WED AUG 18 2011 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... ASIDE FROM DIURNALLY DRIVEN MODERATE TO FRESH NE BREEZE OFF THE W COAST OF THE YUCATAN...WINDS WILL REMAIN AT OR BELOW A MODERATE BREEZE ACROSS THE ENTIRE GULF THROUGH FRI. MORE UNCERTAINTY COMES INTO PLAY BY THE WEEKEND WITH THE TRACK AND STRENGTH OF THE TROPICAL WAVE THAT WAS NEAR 79W AT 00Z. THE FORECAST GUIDANCE AGREES ON KEEPING THE SYSTEM S OF THE AREA AND GIVEN ITS 20 KT WESTWARD FORWARD MOTION...DO NOT THINK IT WILL HAVE MUCH OF A CHANCE TO GAIN A LOT OF LATITUDE BEFORE REACHING THE YUCATAN. THE 00Z GFS SEEMS REASONABLE. CARIBBEAN SEA... THE 0254 UTC ASCAT PASS SHOWS A VERY SMALL AREA OF STRONG WINDS S OF JAMAICA ASSOCIATED WITH THE TROPICAL WAVE ALONG 79W AT 00Z. THE 00Z GFS SEEMS TO BE A BIT WEAK WITH THE SURFACE WINDS COMPARED TO THIS PASS AND THE 20 KT OBSERVATIONS FROM 0ZK02 NEAR 16N70W S OF HISPANIOLA. THE 00Z ECMWF IS BETTER INITIALIZED WITH THE WIND FIELD AND IS SLIGHTLY DEEPER AND MORE CLOSED OFF THAN THE 00Z GFS FROM 24-48 HOURS. THE MID LEVEL LOW IS WELL-DEFINED BUT THAT ASCAT PASS STILL SHOWS THE CIRCULATION HAS NOT TRANSLATED TO THE SURFACE. THE SYSTEM CONTINUES TO MOVE W AT 20 KT. THE FORECAST GUIDANCE ALL SEEMS TO THINK THE SYSTEM IS GOING TO COME TO A SCREECHING HALT IN THE NEXT 24 HOURS. CONFIDENCE IS LOW IN THE SLOW MODEL CONSENSUS...SO SPED THINGS UP A DEGREE. ITS GOING TO HAVE TO SLOW DOWN TO HAVE A CHANCE AT BEING A TROPICAL CYCLONE. NEVERTHELESS...THE FORECAST STILL CALLS FOR THIS POSSIBILITY. THE WAVE 37W AT 00Z HAS SIMILAR CHARACTERISTICS TO THE WAVE AT 79W WHEN IT WAS NEAR 40W - LITTLE DEEP CONVECTION AND A VERY LARGE CIRCULATION. STILL...THE GFS INSISTS ON MAKING IT A TROPICAL STORM ON SAT AS IT MOVES INTO THE TROPICAL N ATLC ZONE. THE 00Z UKMET AND ECMWF ARE SIMILARLY TIMED...PUTTING THE SYSTEM OVER PUERTO RICO BY EARLY MON MORNING...BUT GIVE THE SYSTEM LONGER TO COOK. THIS SEEMS REASONABLE. THE FORECAST WILL EDGE TOWARD THE 00Z ECMWF WHICH KEEPS THE SYSTEM AN OPEN WAVE THROUGH SUN...POSSIBLY CLOSING OFF MON. TROPICAL N ATLC W OF 55W... PROBLEM OF THE DAY IS THE TROPICAL WAVE ALONG 37W. SEE THE DISCUSSION IN THE CARIBBEAN SECTION ABOVE FOR DETAILS. SOUTHWEST N ATLC... A STRENGTHENED PRES GRADIENT BETWEEN THE TROPICAL WAVE TO THE SW OVER THE CARIBBEAN AND THE RIDGE ALONG 30N HAS EXPANDED THE FRESH TRADE WINDS OVER THE SOUTHERN PORTION OF THE ZONE...WITH MUCH OF THE AREA S OF 25N E OF 80W SEEING 20 KT E TO SE WINDS. THE LONG-WAVE TROUGH ALONG THE U.S. EAST COAST WILL RECEIVE A REINFORCING SHOT OF SHORTWAVE ENERGY TODAY THAT WILL AMPLIFY THE MID TO UPPER-LEVEL TROUGHING. WHILE THE LOW LEVEL BOUNDARY ASSOCIATED WITH THE AMPLIFIED LONG-WAVE TROUGH WILL REMAIN N OF THE AREA THU THROUGH SAT...THE IMPACT OVER THE SW N ATLC WILL BE A WEAKENED RIDGE AND GRADUALLY DIMINISHING TRADE WINDS OVER S WATERS LATE THU THROUGH AND SAT. THE FORECAST BECOMES MORE UNCERTAIN BY SUN WHEN THE TROPICAL WAVE THAT WAS ALONG 37W AT 00Z APPROACHES THE SE CORNER OF THE AREA. SEE THE CARIBBEAN SECTIONS FOR DETAILS. WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN AND TROPICAL N ATLC... .NONE. SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER