000 AGXX40 KNHC 181024 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 624 AM EDT SUN SEP 18 2016 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W...AND THE SW N ATLANTIC INCLUDING THE BAHAMAS. ...GULF OF MEXICO... MODEL PREFERENCE: GLOBAL MODEL CONSENSUS. MID LEVEL TROUGH PERSISTS FROM NE MEXICO TO LOUISIANA COASTAL WATERS AND CONTINUES TO MAINTAIN UNSTABLE CONDITIONS ACROSS MUCH OF N CENTRAL PORTIONS WITH PULSING CONVECTION OVERNIGHT THAT HAS SINCE DIMINISHED. MODELS FORECAST TROUGH TO SINK VERY SLOWLY S AND WEAKEN NEXT 36 HR. ASSOCIATED LOW LEVEL TROUGH LOOKS TO BE ALONG THE LA COAST AND SHOULD DRIFT INLAND NEXT 24 HOURS. OTHERWISE...MILD MARINE CONDITIONS PREVAIL WITH SEAS 3 FT OR LESS. WEAK RIDGE EXTENDING INTO NE PORTIONS WILL SHIFT SLOWLY WWD NEXT FEW DAYS BEFORE COLLAPSING WED AND LEAVING LIGHT TO MODERATE FLOW ACROSS THE BASIN. A WEAK THERMAL TROUGH WILL DEVELOP OVER THE YUCATAN PENINSULA DURING THE LATE AFTERNOONS AND CONTINUE INTO THE EARLY EVENINGS. EXPECT GENTLE TO MODERATE NE-E WINDS TO DEVELOP EACH DAY ALONG THE N AND NW COASTS OF THE WESTERN YUCATAN PENINSULA BEGINNING IN THE LATE AFTERNOONS...AND ENDING BEFORE MIDNIGHT EACH NIGHT AS THE INVERTED TROUGH MOVES W-NW ACROSS THE SW GULF ACCOMPANIED BY 2-3 FT SEAS. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... MODEL PREFERENCE: GLOBAL MODEL CONSENSUS. BROKEN ATLC RIDGE PRODUCING WEAK PRES GRADIENT ACROSS THE BASIN TODAY AND YIELDING LIGHT TO MODERATE TRADES. TRADES HAVE INCREASED TO STRONG ALONG THE NW COAST OF COLOMBIA AGAIN OVERNIGHT AND WILL PERSIST THROUGH TONIGHT. A NNE TO SSW ORIENTATED UPPER LOW ACROSS ERN CARIB ALONG 66-67W IS INTERACTING WITH A WEAK LLVL REFLECTION AND A TROPICAL WAVE ACROSS THE LESSER ANTILLES TO PRODUCE SCATTERED CONVECTION THAT HAS RECENTLY FOCUSED ACROSS THE NE CARIB. UPPER LEVEL FORECAST TO WEAKEN SLOWLY AND SHIFT W NEXT 48 HOURS. TROPICAL WAVE EXPECTED TO MOVE SLOWLY W NEXT 36 HOURS BEFORE ACCELERATING SLIGHTLY TUE AND WED AS IT CROSSES CENTRAL CARIB. OTHERWISE...GENERALLY MILD MARINE CONDITIONS TO PREVAIL. NE TO E SWELL FROM TROPICAL STORM KARL WILL REACH THE TROPICAL N ATLC WATERS LATE MON...WITH KARL'S ASSOCIATED WINDS SWEEPING NW ACROSS THE WATERS N OF 17N E OF 57W TUE AND WED. TROPICAL STORM CONDITIONS ARE POSSIBLE ACROSS THESE TROPICAL N ATLC WATERS DURING THAT TIME. GFS AND ECMWF DO NOT DEPICT A SIGNIFICANT TC DURING THIS TIME AND HAVE USED UKMET WINDS TO ATTEMPT TO MANUALLY CREATE WIND AND WAVE GRIDS THROUGH TUE. ...SW N ATLANTIC INCLUDING THE BAHAMAS... MODEL PREFERENCE: GLOBAL MODEL CONSENSUS. SURPRISE SURPRISE...DEEP CONVECTION WITH JULIA HAS MADE A SIGNIFICANT COMEBACK OVERNIGHT...AS UPPER SHEAR HAS WEAKENED AND CHANGED DIRECTIONS. CONVECTION IS WRAPPING AROUND CENTER OF JULIA IN PAST HOUR OR SO AND INTENSIFICATION...HOWEVER BRIEF...MAY BE OCCURRING. THUS FORECAST FOR THIS SYSTEM HAS LOW CONFIDENCE AS MODELS HAVE NOT HANDLED IT WELL THROUGH WHOLE LIFE TIME. EXPECT SMALL TO MODERATE NE SWELL TO CONTINUE TO AFFECT NW WATERS THROUGH TONIGHT...AT LEAST. ELY SWELL FROM TS KARL WILL REACH THE SE WATERS LATE MON...WITH ASSOCIATED CONDITIONS PASSING THROUGH THE TROPICAL WATERS E OF 62W LATE MON NIGHT THROUGH TUE NIGHT...THEN KARL WILL MOVE NW THROUGH THE DISCUSSION WATERS BETWEEN 55W AND 65W ON TUE NIGHT THROUGH THU...AND PASSING THROUGH THE WATERS S OF BERMUDA ON FRI. AGAIN...GFS AND ECMWF NOT DEPICTING A SIGNIFICANT TC DURING THIS TIME AND HAVE USED A UKMET BLEND FOR WINDS THROUGH WED THEN AN EC BLEND BEYOND. WITH GFS AND ECMWF NOT ACCURATELY DEPICTED A STORM THEIR ASSOCIATED WAVE OUTPUT NOT EXTREMELY USEFUL AND HAVE BLENDED A POTIONS OF NWPS TO DEPICT CORE OF KARL AS IT MOVES ACROSS SE AND THEN E WATERS MON-WED.