000 AGXX40 KNHC 191859 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 255 PM EDT SUN AUG 19 2012 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 MAIN FEATURE DOMINATING THE GULF IS THE WESTERN EXTENSION OF THE ATLC RIDGE THAT EXTENDS ROUGHLY ALONG 26N. THE OTHER FEATURE THAT JUST OVER THE PAST FEW HOURS HAS REVEALED ITSELF IS A TROUGH IN THE SW PART OF THE GULF WHERE SCATTERED STRONG CONVECTION HAS FIRED UP. A RATHER IMPRESSIVE ALMOST SOLID LINE OF SCATTERED STRONG TSTMS COVERS THE FAR NRN WATERS N OF 27N WHERE A NE-SW TROUGH IS CLEARLY VISIBLE. CURRENT AND LATEST BUOY AND OIL RIG PLATFORM OBSERVATIONS SHOW S-SW WINDS OF 15-20 KT S OF THE RIDGE AND SW-W 10-15 KT BETWEEN THE RIDGE AND THE NE-SE TROUGH. SEAS ARE IN THE 2-3 FT RANGE... EXCEPT 3-5 FT IN THE SW GULF ZONES. THESE REPORTED VALUES MATCH UPPER VERY CLOSE TO THE NOAA III WAVEWATCH MODEL. WILL FOLLOW THIS GUIDANCE CLOSELY FOR THIS FORECAST PACKAGE FOR SEAS IN THE GULF. THE WEATHER WILL REMAIN UNSETTLED OVER THE NRN GULF WATERS THROUGH THE FORECAST PERIOD AS THE SURFACE TROUGH IS REPLACED BY A WEAK FRONTAL BOUNDARY THAT DROPS S ACROSS THOSE WATERS... WITH SUPPORT OF A RATHER BROAD UPPER TROUGH OVER THE CENTRAL U.S. SHORTWAVE TROUGHS ROTATING THROUGH THE BASE OF THIS TROUGH WILL ADD FURTHER FUELS TO THE CONVECTIVE ACTIVITY. THIS ACTIVITY MAY BE ATTENDANT BY GUSTY WINDS AND FREQUENT LIGHTNING STRIKES AS WELL AS ALREADY NOTED. THE NORTHERN PORTION OF A TROPICAL WAVE CURRENTLY APPROACHING 80W IN THE CARIBBEAN SEA IS EXPECTED TO MOVE ACROSS THE FAR SOUTHERN WATERS TUE THROUGH THU...THEN LOSE ITS CHARACTERISTICS AS IT MOVED ACROSS THE FAR SRN PART OF THE SW GULF FRI. THE WAVE MAY BE FOLLOWED BY A BRIEF INSTANCE OF E-SE 15-20 KT. WINDS AND SEAS OVER THE REMAINDER OF THE GULF ARE EXPECTED TO VARY LITTLE FROM WHAT IS PRESENTLY BEING OBSERVED THROUGH THE PERIOD. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... A TROPICAL WAVE APPROACHING 80W N OF 13N IS MOVING W AT 15-20 KT. THIS WAVE WILL WILL MOVE INLAND THE YUCATAN PENINSULA AND ENTER THE FAR SRN GULF LAT MON NIGHT INTO TUE. THE COMBINATION OF ATLC RIDGING AND BROAD LOW PRES OVER THE SE CARIBBEAN SEA WILL RESULT IN FRESH TO STRONG EASTERLY TRADES ACROSS THE CENTRAL CARIBBEAN TONIGHT AND INTO MON SPREADING INTO THE W CARIBBEAN BY EARLY TUE INTO WED...INCLUDING THE GULF OF HONDURAS. ANOTHER TROPICAL WAVE CURRENTLY ALONG 48W/49W IS MOVING W AT ABOUT 15 KT. THE WAVE IS ACCOMPANIED BY LOW PRES NEAR 11N48W. THE WAVE IS FORECAST TO WILL ENTER THE EASTERN TROPICAL N ATLC MON MORNING...AND MOVE ACROSS THE REMAINDER OF THOSE ZONES THROUGH MON NIGHT AND ACROSS THE EASTERN CARIBBEAN SEA TUE INTO WED...THE CENTRAL CARIBBEAN DURING WED AND INTO THE WESTERN CARIBBEAN THU AND FRI. NE-E WINDS OF 15-20 KT WILL ACCOMPANY THE WAVE N OF 15N AS IT MOVED ACROSS THE AFFECTED ZONES. WILL FOLLOW PRIMARILY THE GFS/ECMWF 10 M WIND GUIDANCE FIELD AND FOR THESE WINDS WITH THE WAVE AS FOR PSNS. AGAIN...AS STATED IN PREVIOUS FORECAST DISCUSSIONS THE MAIN FOCUS FOR UPCOMING FEATURES TO AFFECT THE FORECAST WATERS WILL BE LOW PRES IN THE FAR EASTERN ATLC AREA NEAR 15N38W MOVING W AT 18 KT WITH AN ATTENDANT TROPICAL WAVE. THIS LOW CONTINUES TO HAVE A CHANCE OF DEVELOPING INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AND THE LATEST RUNS OF GFS AND ECMWF STILL TAKE THE LOW ACROSS THE TROPICAL N ATLC AND E CARIBBEAN THE THROUGH FRI...WHILE THE OTHER GLOBAL MODELS TURN TO CURVE IT MORE TO THE NW AS IT APPROACHES THE ERN TROPICAL N ATLC MID TUE AND WED. THE 12 UTC GFS RUN FROM THIS MORNING APPEARS FASTER THAN THE PREVIOUS RUNS. THIS MIGHT SEEM PLAUSIBLE IF THE SYSTEM REMAINS SHALLOW WILL LIMITED DEEP CONVECTION...HOWEVER LATEST SATELLITE IMAGERY SHOWS THAT THIS SYSTEM HAS BECOME SOMEWHAT MORE CONSOLIDATED WITH RESPECT TO ITS CLOUD PATTERN STRUCTURE. THE GFS STILL LIKES TO DEEPEN THIS SYSTEM THIS LOW A LITTLE MORE THAN THE ECMWF. SO WILL MAINTAIN CONTINUITY WITH PREVIOUS FORECAST THINKING AND FOLLOW THE MEDIUM RANGE POINTS AS COORDINATED BETWEEN NHC/HPC FOR FOR DAYS 3-5. INTERESTS IN THE E CARIBBEAN SHOULD CONTINUE TO MONITOR ANY DEVELOPMENTS OF THIS LOW THROUGH THE WEEK. SOUTHWEST NORTH ATLC S OF 31N W OF 55W... THE 18 UTC PRELIMINARY SURFACE ANALYSIS SHOWS A 1023 MB HIGH CENTER AT 27N59W WITH A RIDGE SW TO WRN CUBA AND THE STRAITS OF FLORIDA. SE-S WINDS OF 10-15 KT ARE S OF THE RIDGE...WITH NE-E WINDS OF 10-15 KT S OF 22N E OF THE BAHAMAS AND SW WINDS OF 10-15 KT ARE N OF THE RIDGE. SEAS ARE IN THE 2-3 FT RANGE ...EXCEPT 3-4 FT S OF 22N E OF THE BAHAMAS AND 1-2 FT SW OF THE BAHAMAS. THE RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY THROUGH TUE...THEN WEAKEN WED THROUGH FRI AS IT SHIFTS EASTWARD. A TROPICAL WAVE S OF 21N OVER CENTRAL CUBA IS EXPECTED TO HAVE JUST ABOUT NO EFFECTS ON WINDS AND SEAS OVER THE SRN WATERS AS IT MOVES FURTHER W THROUGH MON NIGHT. LITTLE OVERALL CHANGES WILL BE EXPECTED WITH REGARDS TO WINDS AND SEAS THROUGH WED...BUT UNCERTAINTY COMES INTO PLAY LATE IN THE FORECAST PERIOD WITH THE LOW PRES IN THE FAR ERN AS IT MOVES ACROSS THE CARIBBEAN SEA. IF THE LOW INTENSIFIES INTO A TROPICAL CYCLONE AS SHOWN BY THE MODELS...THEN PRES GRADIENT IN THE FAR SRN WATERS WILL SIGNIFICANTLY INCREASE ALONG WITH BUILDING SEAS. WILL HAVE TO WAIT TO SEE WHAT TRANSPIRES WITH THIS FEATURE AS IT PROGRESSES WESTWARD IN THE COMING DAYS...AND ADJUST FORECAST ACCORDINGLY. A BLEND OF THE ECMWF/GFS AND PREVIOUS FORECAST GRIDS WAS USED FOR THE OFFSHORE WATERS FOR THIS FORECAST PACKAGE ALONG WITH NOTE...GRIDDED MARINE FORECAST IS AVAILABLE AT WWW.NHC.NOAA.GOV/TAFB/GRIDDED_MARINE GULF OF MEXICO... .NONE. CARIBBEAN SEA... .NONE. SW N ATLANTIC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT WWW.HURRICANES.GOV/MARINE $$ FORECASTER AGUIRRE