000 AGXX40 KNHC 170648 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 250 AM EDT WED AUG 17 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... THE STATIONARY BOUNDARY IN THE NE GULF WILL WEAKEN AS IT MIGRATES N TODAY. 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 70W AT 00Z. THE CURRENT FORECAST THINKING LEANS TOWARD THE 16/12Z ECMWF WHICH WAS STRONGER WITH THE SYSTEM THAN THE 00Z GFS OVER THE CARIBBEAN...SHOWING A CLOSED LOW LEVEL CIRCULATION OVER THE WESTERN CARIBBEAN BY THU EVENING. THIS LOW HAS THE POTENTIAL TO BECOME A TROPICAL CYCLONE OVER THE CARIBBEAN WITHIN THE NEXT 48 HOURS. THE PREFERRED ECMWF FORECAST WEAKENS THE SYSTEM BACK TO AN OPEN WAVE OVER THE YUCATAN SAT AND MOVES THE NORTHERN PORTION OF THE WAVE INTO THE SW GULF ON SUN. CONFIDENCE IS LOW IN THIS FORECAST. CARIBBEAN SEA... THE PRES GRADIENT WILL CONTINUE TO STRENGTHEN TODAY N OF THE TROPICAL WAVE ALONG 70W AT 00Z AS THE RIDGE BUILDS OVER THE SW N ATLC. THE 0134 UTC ASCAT PASS SHOWS STRONG NE WINDS N OF 15N TO HISPANIOLA AHEAD OF THE WAVE. THE MODELS HAVE TRENDED TOWARD A SLOWER TRACK TO THIS SYSTEM AS IT PASSES THROUGH THE CENTRAL AND WESTERN CARIBBEAN AND IT HAS INCREASED POTENTIAL TO BECOME A TROPICAL CYCLONE IN THE NEXT 48 HOURS. THE CURRENT FORECAST THINKING LEANS TOWARD THE 12Z/16 ECMWF WHICH WAS STRONGER WITH THE SYSTEM THAN THE 00Z GFS...SHOWING A CLOSED LOW LEVEL CIRCULATION OVER THE WESTERN CARIBBEAN BY THU EVENING. FURTHER ADJUSTMENTS MAY BE MADE TO THE FORECAST PACKAGE BASED ON THE 00Z ECMWF COMING IN NOW. THE NEXT TROPICAL WAVE IS EXPECTED TO MOVE INTO THE EASTERN CARIBBEAN BY SUN. GIVEN THE LACK OF CONVECTION NEAR THIS WAVE...WHICH WAS NEAR 30W AT 00Z...WILL WILL STICK WITH THE A WEAKER FORECAST THAN THE 00Z GFS WHICH DEVELOPS A 1005 MB TROPICAL STORM OUT OF THE SYSTEM OVER THE EASTERN GULF BY SUN NIGHT. IT IS A LITTLE WORRISOME THAT THE 00Z UKMET IS NEARLY AS STRONG AT THAT TIME AND CLOSES THE LOW OFF FASTER THAN THE GFS OVER THE TROPICAL N ATLC. CONFIDENCE IS LOW IN THIS FORECAST. TROPICAL N ATLC W OF 55W... BUOY 41043 IN THE NW PORTION OF THE ZONE REPORTED 19 KT E WINDS AND 8 FT SEAS AT 03Z WITH BUOY 41044 NEAR 22N59W SHOWING 17 KT AND 8 FT SEAS AND SHIP A8IN9 ALSO REPORTING 8 FT SEAS AND 15 KT WINDS AT THE SAME TIME. THESE FRESH E WINDS BEHIND THE TROPICAL WAVE IN THE CARIBBEAN ALONG 70W AT 00Z SHOULD DISSIPATE TODAY AS THE WAVE MOVES E. THE NEXT TROPICAL WAVE TO MOVE INTO THE AREA WAS ALONG 30W AT 00Z. THE 00Z GFS HAS TRENDED TOWARD WAITING TO MAKE THIS SYSTEM A TROPICAL STORM UNTIL IT IS ALREADY OUT OF THE TROPICAL N ATLC ZONE. THE GRADUAL BACKING OFF ON THIS FORECAST BY THE GFS IS SIMILAR TO THE FORECAST HISTORY FOR THE TROPICAL WAVE CURRENTLY NEAR 70W WHICH HAS YET TO DEVELOP. THIS WAVE NEAR 30W HAS SIMILAR CHARACTERISTICS TO THE PREVIOUS WAVE WHEN IT WAS NEAR 30W - LITTLE DEEP CONVECTION AND A VERY LARGE CIRCULATION. CONFIDENCE IS LOW...BUT THE FORECAST FOLLOWS THE MORE OPEN WAVE SOLUTION SEEN IN THE ECMWF. SOUTHWEST N ATLC... HIGH PRES BUILDING WESTWARD ALONG 28N IS BEGINNING TO SHOVE THE WEAKENING STATIONARY FRONT OVER NW WATERS NORTHWARD. AN INVERTED TROUGH FROM THE CENTRAL BAHAMAS TO CENTRAL CUBA AT 00Z IS JOINING FORCES WITH THE TROPICAL WAVE TO ITS S OVER THE CARIBBEAN TO INCREASE THE PRES GRADIENT AND TRADE WINDS OVER THE SOUTHERN PORTION OF THE ZONE BETWEEN THIS TROUGHING AND THE BUILDING RIDGE TO THE N. MEANWHILE...THE LONG-WAVE TROUGH ASSOCIATED WITH THE FRONT CURRENTLY OFF THE NE FL COAST WILL RECEIVE A REINFORCING SHOT OF SHORTWAVE ENERGY THU 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 30W AT 00Z COULD APPROACH THE SE CORNER OF THE AREA. SEE THE TROPICAL N ATLC AND CARIBBEAN SECTIONS FOR DETAILS. THE CURRENT THINKING IS TO KEEP THE SYSTEM ON A MORE SOUTHERLY TRACK AS AN OPEN WAVE. 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