000 AGXX40 KNHC 180630 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 230 AM EDT WED MAY 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. SW N ATLC... THE DEEP LAYERED LOW CENTERED OVER THE CENTRAL APPALACHIANS WILL WEAKEN AND PULL NORTHWESTWARD...CARRYING THE SURFACE TROUGHING OVER THE NW PORTION OF THE AREA AWAY WITH IT TODAY THROUGH THU. BOTH THE 00Z GFS AND ECMWF CONTINUE TO AGREE ON BRINGING WINDS BELOW 20 KT BY WED EVENING AND GENERALLY ALLOW THE SUBTROPICAL RIDGE TO ESTABLISH ITSELF BETWEEN 28N-30N THU THROUGH SUN. HOWEVER...BOTH OF THESE MODELS ALSO CARRY SOME OF THE ENERGY ALOFT FROM THE NE CARIBBEAN NORTHWARD THROUGH FAR EASTERN WATERS THU-FRI. THE 00Z GFS HAS TRENDED EASTWARD COMPARED TO ITS 00Z RUN LAST NIGHT. THIS IS A TREND TOWARD THE MORE CONSISTENT ECMWF FORECAST. THE ECMWF ALSO REMAINS WEAKER THAN THE GFS. THE GFS APPEARS TO ENHANCE THIS ENERGY ON SAT MORE THAN THE SYNOPTIC SET UP WOULD SEEM LIKELY TO ALLOW. THE TOTAL PRECIPITATION FORECAST WITH THE SYSTEM NEAR 30N60W IS AS HIGH AS 2.8 INCHES DURING THE OVERNIGHT HOURS FRI NIGHT WHILE THE CONVECTIVE COMPONENT IS LESS THAN AN INCH. THIS IS AN INDICATION OF CONVECTIVE FEEDBACK. THEREFORE...WILL LEAN TOWARD THE WEAKER ECMWF FORECAST WHICH SHOWS THE RIDGING AS THE DOMINANT FEATURE OVER THE SW N ATLC ZONE THU THROUGH SUN. CARIBBEAN SEA AND THE TROPICAL N ATLANTIC ... PERSISTENT TROUGHING ALOFT OVER THE U.S. EAST COAST EXTENDS INTO THE CENTRAL CARIBBEAN. AT THE SURFACE...A TROUGH CONTINUES TO LIE OVER THE CENTRAL CARIBBEAN. MOISTURE WILL CONTINUE TO POOL ON THE EASTERN SIDE OF THE DEEP LAYER TROUGHING THAT EXTENDS INTO THE CENTRAL CARIBBEAN TODAY...MAKING RAINFALL OVER THE EASTERN CARIBBEAN THE PRIMARY SENSIBLE WEATHER CONCERN. THE TROUGHING BOTH ALOFT AND AT THE SURFACE IS EXPECTED TO WEAKEN AND SHIFT NORTHWARD...ALLOWING THE SUBTROPICAL RIDGE THAT CURRENTLY EXTENDS FROM THE CENTRAL ATLC TOWARD THE NE CARIBBEAN TO LIFT NW OVER THE SW N ATLC TO ALONG 28N-30N ON THU THROUGH SAT. MODERATE EASTERLY TRADE WINDS WILL DOMINATE THE EASTERN AND CENTRAL CARIBBEAN FRI THROUGH SUN AS A RESULT. MEANWHILE...A LOW AMPLITUDE TROPICAL WAVE MOVING THROUGH THE TROPICAL N ATLC ZONE TODAY AND TONIGHT WILL PASS INTO THE EASTERN CARIBBEAN BY THU WHERE IT WILL ENCOUNTER THE PREVALENT EASTERLY TRADE WIND FLOW. WHILE THE TROPICAL WAVE WILL BRING MORE MOISTURE TO SUPPLY SHOWERS AND TSTMS OVER THE EASTERN CARIBBEAN...ITS IMPACT ON THE WIND FIELD IS EXPECTED TO BE MINIMAL THU AND FRI AS THE SUBTROPICAL RIDGE BECOMES MORE ZONAL...DECREASING THE PRES GRADIENT HERE. THE LARGEST DIFFERENCES IN THE MODELS COME BY THE WEEKEND WHEN THE GFS DEVELOPS A SURFACE LOW ALONG THE TROPICAL WAVE AS IT PASSES THROUGH THE WESTERN CARIBBEAN. THE 00Z GFS SOLUTION IS THE DEEPEST OF THE MODELS AND IS THE ONLY ONE TO CARRY 20 KT WINDS ON THE NE SIDE OF THE LOW OVER THE WEEKEND AS IT MOVES W-NW THROUGH THE SW CARIBBEAN. THE 00Z NOGAPS AND UKMET BRIEFLY CARRY A CLOSED LOW ALONG THE WAVE...BUT DO NOT BUILD 20 KT WINDS. MEANWHILE...THE 00Z ECMWF IS EVEN WEAKER STILL AND MAKES THE WAVE INDISTINGUISHABLE BY SUN. CONFIDENCE IS LOW IN THE STRONG GFS...BUT THERE SEEMS TO BE ENOUGH MODEL AGREEMENT TO AT LEAST CARRY THE WAVE THROUGH THE SW CARIBBEAN. THEREFORE...USED THE NOGAPS/UKMET SOLUTIONS AS A GUIDE. GULF OF MEXICO... TROUGHING OVER THE EASTERN GULF WILL DISSIPATE LATER TODAY. HIGH PRES OVER THE NW TO N CENTRAL GULF WILL GRADUALLY MOVE EASTWARD. THE GRADIENT BUILDS BETWEEN THIS RIDGING AND TROUGHING OVER THE SOUTHERN HIGH PLAINS WILL ALLOW SE RETURN FLOW TO INCREASE TO 20 KT IN MUCH OF THE WESTERN GULF BY TONIGHT. THE 0302 UTC ASCAT PASS AND MULTIPLE OBSERVATIONS SHOW WINDS HAVE ALREADY REACHED 20 KT ALONG THE TX AND NE MEXICAN COAST W OF 96W. FRESH RETURN FLOW IS EXPECTED TO INCREASE TO FRESH TO STRONG IN THE EARLY MORNING HOURS OF FRI AND SAT AS A COLD FRONT SLOWLY MOVES THROUGH CENTRAL TX...INCREASING THE PRES GRADIENT. THE 00Z ECMWF HAS COME AROUND TO THE STRONG FLOW SEEN IN THE GFS HERE THE LAST FEW DAYS. BY SUN...THE STRONGEST TROUGHING IN THE PLAINS LIFTS NORTHWARD AND THE PRES GRADIENT OVER THE GULF RELAXES A BIT ALLOWING WINDS TO DIMINISH A NOTCH. THE MODELS ARE IN REASONABLY GOOD AGREEMENT ON THIS SOLUTION. WARNINGS.. ATLC... .NONE. CARIBBEAN... .NONE. GULF OF MEXICO... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER SCHAUER