000 AGXX40 KNHC 260807 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 350 AM EDT THU APR 26 2012 UPDATED CARIBBEAN SEA SECTION TO INCLUDE MENTION OF MODEL DEPICTION OF A CARIBBEAN LOW IN THE NEAR FUTURE MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... A 1020 MB HIGH CENTER OVER THE E GULF CENTERED AT 27N85W WITH A RIDGE WSW TO NE MEXICO IS MAINTAINING CONTROL OF THE WIND REGIME THROUGHOUT. BUOY AND OIL PLATFORM OBSERVATIONS ARE REPORTING S-SW WINDS OF 10-15 KT N OF THE RIDGE E OF 91W...AND HIGHER S-SW WINDS OF 15-20 KT N OF THE RIDGE W OF 91W WHERE A TIGHTER PRES GRADIENT BETWEEN THE RIDGE AND DEEPENING LOW PRES IN THE SRN PLAINS IS INDUCING THESE HIGHER WINDS. S OF THE RIDGE BUOYS REVEAL MUCH LIGHTER WINDS...E TO SE IN DIRECTION...AT 5-10 KT WITH SOME WINDS OF 10-15 KT IN THE SW PORTION OF THE GULF. THE BUOYS ARE GENERALLY REPORTING SEAS OF 1-3 FT...EXCEPT 3-5 FT IN THE NW PORTION OF THE GULF...AND 6-7 FT IN THE FAR WRN PART OF THE NW GULF UNDER THE 15-20 KT WINDS. AS FOR THE FORECAST...LATEST AND PREVIOUS MODEL RUNS IN GOOD AGREEMENT THAT THE 1020 MB HIGH CENTER SHIFTS TO INLAND W CENTRAL FLORIDA THIS AFTERNOON. AN ATLC RIDGE WILL THEN REPLACE THIS HIGH CENTER AS IT BEGINS TO RIDGE WWD ALONG 27N TO THE CENTRAL TEXAS COAST. THIS SET UP WILL MAINTAIN THE CURRENT WIND REGIME WITH INCREASING SE RETURN FLOW IN THE WRN GULF INTO SUN DUE TO THE TIGHTENING PRES GRADIENT BETWEEN THE HIGH AND DEEPENING LOW PRES IN THE SRN PLAINS. SEAS BUILD TO 6-9 FT IN THE FAR WRN GULF FROM 24N TO 28N TONIGHT AND CONTINUE INTO LATE SAT BEFORE SUBSIDING SOME INTO SUN AS THE RIDGE LIFTS NWD TO 29N FRI...TO 30N SAT AND TO JUST INLAND THE SE U.S. SUN AND MON. THE PRES GRADIENT WEAKENS IN THE FAR WRN GULF DURING THE DAY SUN AND INTO MON ALLOWING FOR THE SE RETURN FLOW WINDS TO BECOMING MORE ELY AND DIMINISH TO 15 KT. GFS MODEL GUIDANCE INDICATES THAT WINDS BACK TO THE NE IN THE FAR ERN PORTION BY SUN IN RESPONSE TO AN APPROACHING W ATLC TROUGH. THIS GUIDANCE IS STILL THE STRONGEST WITH THESE WINDS...WHERE OTHER MODELS SHOW VERY LITTLE IF ANY WIND SHIFT TO THE NE. WILL LEAN TOWARD THE MORE TAMER SOLNS OF THE OTHER NWP MODELS REGARDING WINDS IN THE E GULF FOR DAYS 3-5 PER WAVEWATCH GUIDANCES WILL FORECAST LOW SEA THROUGHOUT DURING THE PERIOD...EXCEPT IN THE FAR WRN PORTION UNDER THE INCREASING SE RETURN FLOW AS DESCRIBED ABOVE. SW NORTH ATLC S OF 31N W OF 65W... THE PRELIMINARY 6 UTC SURFACE ANALYSIS HAS A WEAKENING STATIONARY FRONT EXTENDING FROM 26N64W SW TO 23N67W WHERE IT BECOMES A TROUGH TO ACROSS THE CENTRAL PORTION OF HISPANIOLA. A 1022 MB HIGH IS CENTERED NEAR 29N70W WITH A RIDGE SW ACROSS CENTRAL FLORIDA. RECENT AND CURRENT SATELLITE IMAGERY SHOWS VERY DEEP ATMOSPHERIC MOISTURE PRODUCING SCATTERED TO NUMEROUS SHOWERS AND ISOLATED TSTMS ASSOCIATED WITH THE FRONT AND TROUGH CONFINED TO THE E AND SE SECTIONS OF THE BASIN. BOTH ASCAT DATA FROM LAST NIGHT ALONG WITH RECENT AND CURRENT BUOY OBSERVATIONS REVEAL SW WINDS OF 15-20 KT IN THE FAR NW PORTION...NE 20 KT S OF 24N W OF TROUGH TO 76W...AND LIGHTER NE TO E WINDS 10-15 KT ELSEWHERE BEHIND THE FRONT/TROUGH AND THE RIDGE. NW-N WIND OF 5-10 KT ARE IN THE FAR NE PORTION. LATEST BUOY OBSERVATIONS AND SEA STATE ANALYSIS FROM OPC SHOW SEAS NOW HAVING SUBSIDED TO 3-5 FT OVER MUCH OF THE AREA... WITH SLIGHTER HIGHER SEAS BETWEEN THE SE BAHAMAS...CUBA AND HISPANIOLA. GLOBAL MODELS SUGGEST THAT THE REMAINDER OF THE STATIONARY FRONT WILL GRADUALLY WEAKEN TO A TROUGH ALONG A PSN FROM 26N67W TO NW HAITI BY 48 HRS. THE TROUGH IS DEPICTED IN THE GUIDANCE ...MOST NOTICEABLY BY THE GFS...AS FEATURE THAT TRACKS WWD OVER OVER THE NEXT FEW DAYS. FOR THIS SCENARIO WILL LEAN TOWARDS THE MORE WEAKER ECMWF SOLN WITH SPEED OF THE TROUGH SINCE IT TOO FAST WITH THE WWD MOTION...BUT WILL RELY ON GFS GUIDANCE FOR WINDS (NE TO E 20 KT) IN THE SRN PORTION DUE TO A TIGHTER PRES GRADIENT THERE EXPECTED INTO SUN. BY LATE SUN...GFS MERGES THIS AREA OF STRONGER NE TO E WINDS WITH AN AREA OF NE 20-25 KT WINDS THAT SPREADS SWD ACROSS THE WRN PART OF THE BASIN INTO MON. THE GFS IS SIMILAR TO THE UKMET WITH THIS SCENARIO...BUT FOR THIS FORECAST WILL USE MORE OF A SUBTLE ECMWF/UKMET BLEND FOR WINDS IN THE WRN PORTION FOR DAYS 4 AND 5. AFTER 48 HRS THE TROUGH IS EXPECTED TO REACH FROM NEAR THE CENTRAL BAHAMAS TO CENTRAL BY LATE SAT WHERE IT SLOWS DOWN AS IT APPROACHES THE NW BAHAMAS SUN AND MON. THE GFS IS AGGRESSIVE IN DEVELOPING A LOW LATE SUN INTO MON OVER THE WRN BAHAMAS...THEN TAKES IT BACK E MON IN RESPONSE TO THE LARGE AREA OF NE 20-25 KT WINDS THAT SPREADS SWD ACROSS WRN PART OF THE BASIN AT THAT TIME. THE ECMWF CONTINUES TO BE MORE SUBTLE WITH THIS FEATURE AS THE 00 UTC RUN KEEPS IT AS TROUGH THAT MOVES ACROSS S FLORIDA MON. THE 18 UTC RUN DEPICTED A LOW SIMILAR TO THE GFS...BUT NOT AS STRONG WITH THE ASSOCIATED WINDS. I DO PREFER THE 00 UTC RUN OF THE ECMWF IN THE LONG TERM PORTION OF THE FORECAST SHOWING THE TROUGH MOVING WWD AND NOT DEVELOPING INTO A LOW. FOR NOW WILL FORECAST ELY WINDS OF 20 KT OVER THE SRN PORTION FOR THE SHORT AND MEDIUM TERM OF THE FORECAST...AND OVER THE WRN PORTION TOWARDS THE END OF THE FORECAST PERIOD. WILL CLOSELY MONITOR FUTURE MODEL TRENDS AS TO HOW THEY CARRY THIS FEATURE OVER THE NEXT SEVERAL DAYS BEFORE IT IS DESCRIBED MORE SPECIFICALLY IN FORECASTS. THE 1020 MB HIGH WILL SHIFT NE TO NEAR BERMUDA LATER TODAY WITH A RIDGE EXTENDING SW TO CENTRAL FLORIDA. BY FRI EVENING...THE RIDGE WILL EXTEND FROM NEAR 30N65W TO CENTRAL FLORIDA THEN SHIFT N TO NEAR 29N SAT AND TO 30N BY SUN. THE SW 15-20 KT OVER THE FAR NW WATERS WILL SPREAD E TO NEAR 70W BY TONIGHT BEFORE DIMINISHING TO 10-15 KT AND REMAINING LIKE THAT ITO SUN. A BACK DOOR FRONT THEN DROPS S INTO THE NRN SECTION OF THE WRN PART OF THE AREA LATE SUN INTO MON USHERING IN THE NE 20-25 KT WINDS MENTIONED ABOVE. WINDS ELSEWHERE BECOME NE TO E 15 KT S OF THE RIDGE INTO THE MID AND LONG TERM PERIODS AS MENTIONED ABOVE. CARIBBEAN SEA... THE PRELIMINARY 06 UTC ANALYSIS HAS A TROUGH EXTENDING FROM 18N78W TO 11N 77W. BUOY OBSERVATIONS ACROSS THE BASIN ARE REPORTING NE TO E WINDS 20 KT E OF THE TROUGH TO 71W AND N TO NE 20 KT WINDS W OF THE TROUGH S OF 15N. NE 20-25 KT ARE THROUGH AND NEAR THE WINDWARD PASSAGE. SEAS ARE IN THE RANGES OF 3-5 FT BETWEEN 65W AND 74W...AND 2-4 FT ELSEWHERE E OF 78W. SEAS ARE 4-6 FT W OF 78W...EXCEPT 6-7 FT S OF 15N BETWEEN 74W-82W. THE TROUGH WILL CONTINUE TO TRACK WWD REACHING FROM NEAR 20N81W TO 15N80W IN 24 HRS WHILE SLOWLY BECOMING DIFFUSE AS IT REACHES FROM JUST S OF WRN CUBA TO TO 11N78W BY FRI EVENING. THE PRES GRADIENT BETWEEN THE TROUGH AND CENTRAL ATLC HIGH PRES WILL INDUCE A LARGE FETCH OF E 20 KT WINDS IN THE WAKE OF THE TROUGH THROUGH THE PERIOD. N TO NE 20 KT WINDS AHEAD OF THE TROUGH WILL BE CONFINED TO MAINLY S OF 16N...AND TO ALONG THE COASTS OF NICARAGUA AND NE HONDURAS. NE 20-25 KT WINDS CAN BE EXPECTED THROUGH THE WINDWARD PASSAGE INTO FRI...BEFORE DIMINISHING TO NE TO E 10-15 KT FOR DAYS 4 AND 5. BY SAT AFTERNOON...WINDS BECOME E 15-20 KT OVER JUST ABOUT THE ENTIRE SEA...EXCEPT IN THE NW PORTION WHERE LIGHTER E WINDS OF 10-15 KT SHOULD BE IN PLACE THROUGH SUN WITH THE TROUGH WEAKENING. THE GLOBAL MODELS DEPICT LOW PRES MOVING OFF NW COLOMBIA AND INTO THE FAR SW CARIBBEAN TONIGHT...AND TRACKS IN A GENERAL WNW DIRECTION THROUGH LATE SAT AS IT SLOWLY BECOMES DIFFUSE IN THE FAR W AND NW PORTION OF THE SW CARIBBEAN ALONG THE COAST OF NE HONDURAS AND NICARAGUA SAT. THIS APPEARS TO BE ON THE FAR SOUTHERN PART OF THE SURFACE TROUGH DESCRIBED ABOVE SO FOR THIS FORECAST PACKAGE WILL FOCUS ON THE TROUGH AND ASSOCIATED WINDS ON EITHER SIDE OF IT SINCE THE CORRESPONDING TIGHT PRES WILL BE MORE ATTRIBUTED TO THE TROUGH THEN THE LOW. TROPICAL N ATLC S OF 19N W OF 55W... LIGHT NE TO E WINDS PREVAIL THROUGHOUT...EXCEPT S OF ABOUT 14N WHERE SLIGHTER STRONGER NE WINDS OF 15-20 KT CONTINUE. SEAS IN THIS PART OF THE ATLC ARE IN THE RANGE OF 3-5 FT EXCEPT 5-6 FT S OF 14N. BY TONIGHT NE TO E WINDS OF 15-20 KT MATERIALIZE ACROSS MOST OF THE TROPICAL N ATLC...AND ARE EXPECTED TO LAST THROUGH MON. SEAS ARE FORECAST TO BUILD TO 6-8 FT LATE SAT AND CONTINUE INTO MON. NOTE... EFFECTIVE APR 3, 2012 AT 1800 UTC THE OFFSHORE WATERS FORECAST ZONES CHANGED FOR THE CARIBBEAN AND SW N ATLANTIC AND THE GULF OF MEXICO. ISSUANCE TIME FOR THE GULF OF MEXICO OFFSHORE WATERS FORECASTS IS REFERENCED TO THE EASTERN TIME ZONE. FOR DETAILS SEE WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF GRIDDED MARINE OUTPUT IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE (LOWER CASE). GULF OF MEXICO... .NONE. .CARIBBEAN SEA... .NONE. .TROPICAL N ATLC... .NONE. .SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER AGUIRRE