000 AGXX40 KNHC 201910 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 310 PM EDT MON AUG 20 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 AREA CONTINUES TO BE THE WESTERN EXTENSION OF THE ATLC RIDGE THAT EXTENDS ACROSS CENTRAL FLORIDA SW TO NEAR 23N92W. THE OTHER FEATURE IS NEW WEAK 1011 MB LOW PRES THAT HAS FORMED IN THE SW GULF AT 23N97W...WHICH IS AT THE SRN END OF A NE TO SW TROUGH THAT STRETCHES FROM THE WRN FLORIDA PANHANDLE SW TO THE LOW. LATEST SATELLITE IMAGERY ALONG WITH NWS RADAR IMAGERY SHOWS NUMEROUS TSTMS WITHIN 75 NM EITHER SIDE OF THE TROUGH...AND WITHIN 150 NM SE OF THE LOW. SCATTERED STRONG TSTMS ARE WITHIN 120 NM OF THE LOW IN THE NW QUADRANT. CURRENT AND LATEST BUOY AND OIL RIG PLATFORM OBSERVATIONS SHOW S-SW WINDS OF 15-20 KT BETWEEN THE RIDGE AND THE TROUGH. AN ASCAT PASS FROM 1512 UTC THIS MORNING REVEALED SUCH WINDS BETWEEN THE TROUGH AND 85W. DURING THE MORNING AND EARLY AFTERNOON THE OBSERVATIONS HAVE REVEALED SEAS IN THE 2-4 FT RANGE. HIGHER WINDS AND SEAS ARE POSSIBLE WITH THE TSTM ACTIVITY MENTIONED ABOVE. THE REPORTED SEA HEIGHT VALUES MATCH VERY CLOSE TO THE 12 UTC NOAA III WAVEWATCH MODE RUN. WILL AGAIN FOLLOW THIS GUIDANCE CLOSELY FOR THIS FORECAST PACKAGE FOR SEAS IN THE GULF. THE WEATHER WILL REMAIN UNSETTLED OVER THE NRN GULF WATERS THROUGH AT LEAST THU AS THE SURFACE TROUGH IS REPLACED BY A WEAK FRONTAL BOUNDARY THAT DROPS S ACROSS THOSE WATERS TUE...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. THE NORTHERN PORTION OF A TROPICAL WAVE IN THE CARIBBEAN CURRENTLY ALONG 83W IS EXPECTED TO MOVE THROUGH THE FAR S CENTRAL GULF TONIGHT INTO TUE...AND ACROSS THE REMAINDER OF THE SRN GULF WATERS TUE THROUGH THU. MODEL INDICATIONS ARE THAT THIS FEATURE WILL BE RATHER WEAK...AND SHOULD HAVE LITTLE IMPACT ON WINDS AND SEAS AS IT LOSES ITS IDENTITY IN THE SW PART OF THE GULF. THERE MAY BE A FEW BRIEFLY OF E-SE WINDS OF 15 KT BEHIND THE WAVE ALONG WITH ISOLATED TO WIDELY SCATTERED SHOWERS AND TSTMS THAT MAY ACCOMPANY IT. THE LOW PRES FEATURE AT 23N97W IS FORECAST TO DRIFT NE THROUGH TUE NIGHT BEFORE IT TRACKS WESTWARD TOWARDS THE NE MEXICAN COAST WED. THIS LOW HAS A MEDIUM CHANCE OF INTENSIFYING INTO A TROPICAL CYCLONE BEFORE IT MAKES LANDFALL WED MOST LIKELY IN NE MEXICO. WILL ADJUST SEAS UPWARD SOME...HIGHER THAN WAVEWATCH GUIDANCE... IN THE WRN PORTION OF THE SW GULF THROUGH THE NEXT 36 HRS TO ACCOUNT FOR THE POSSIBILITY OF THE LOW STRENGTHENING. WILL ALSO RAISE WINDS THERE SOME...BUT KEEPING IN MID THE HIGH UNCERTAINTY WITH THE TRACK AND EXACT STRENGTH THIS FEATURE MAY ACQUIRE OVER THE NEXT 24 TO 48 HRS. CARIBBEAN SEA AND TROPICAL N ATLC W OF 55W... A TROPICAL WAVE IS ALONG 83W S OF 20N MOVING W AT 15 KT. THIS WAVE WILL WILL MOVE INLAND THE YUCATAN PENINSULA AND ENTER THE FAR SRN GULF LAT TONIGHT INTO TUE. THE COMBINATION OF ATLC RIDGING AND BROAD LOW PRES OVER THE SE CARIBBEAN SEA IS BRINGING FRESH TO STRONG EASTERLY TRADES OVER PORTIONS OF THE CENTRAL CARIBBEAN. THIS WINDS MAY SPREAD W INTO THE ERN PART OF THE WRN CARIBBEAN TUE THROUGH WED...INCLUDING THE GULF OF HONDURAS. ANOTHER TROPICAL WAVE CURRENTLY ALONG 53W MOVING W AT ABOUT 15 KT. THE WAVE IS FORECAST TO MOVE ACROSS THE REMAINDER OF THE TROPICAL N ATLC ZONES TONIGHT...AND ACROSS THE EASTERN CARIBBEAN SEA TUE AND THE REMAINDER OF THE SEA WED THROUGH FRI. NE-E WINDS OF 15-20 KT WILL ACCOMPANY THE WAVE N OF 15N AS IT MOVED ACROSS THE AFFECTED ZONES. WILL AGAIN UTILIZE THE GFS/ECMWF 10 M WIND GUIDANCE FIELD AND FOR THESE WINDS WITH THE WAVE AS FOR POSNS. AGAIN...AS STATED IN PREVIOUS FORECAST DISCUSSIONS THE MAIN FOCUS FOR UPCOMING FEATURES TO AFFECT THE FORECAST WATERS WILL BE LOW PRES IN THE TROPICAL N ATLC E OF THE FORECAST ZONES AT 16N46W MOVING W AT 22 KT WITH AN ATTENDANT TROPICAL WAVE. THIS LOW CONTINUES TO HAVE A HIGH CHANCE OF DEVELOPING INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. FOLLOWING THE GENERAL MODEL ENSEMBLE GUIDANCE WITH HIGH UNCERTAINTY AS WELL WILL TRACK THE LOW WESTWARD ACROSS THE TROPICAL N ATLC TUE AND TUE NIGHT...AND INTO THE EASTERN AND CENTRAL CARIBBEAN THU THROUGH FRI AND NW ACROSS THE NW CARIBBEAN SEA AND GREATER ANTILLES SAT AND SUN FOLLOWING MORE OF GFS MODEL TRACK AT THAT TIME. LATEST SATELLITE IMAGERY SHOWS THAT THIS SYSTEM HAS A LARGE CYCLONIC ENVELOP...BUT REMAINS LIMITED WITH DEEP CONVECTION NEAR THE CENTER. WILL BUILD SEAS TO ABOUT 9 FT N OF THE CENTER AND KEEP WINDS TO 30 KT IN THE NRN SEMICIRCLE FOR NOW UNTIL IF AND WHEN THIS SYSTEM DOES INTENSIFY. WINDS MAY GUST TO HIGHER THAN 30 KT WITHIN ABOUT 240-300 NM IN THE NRN SEMICIRCLE OVER THE NEXT FEW DAYS. WILL FOLLOW THE MEDIUM RANGE POINTS AS COORDINATED BETWEEN NHC/HPC FOR FOR THIS SYSTEM IN THE GRIDS. 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 1021 MB HIGH CENTER E OF AREA AT 27N61W WITH A RIDGE SW TO WRN CUBA AND IN ACROSS THE GULF OF MEXICO. BUOYS SHOW SE-S WINDS OF 10-15 KT 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 3-5 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 SAT AS IT SHIFTS EASTWARD. 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 TROPICAL ATLC E OF THE FORECAST ZONES AT 16N46W. WITH THIS LOW HAVING THE POTENTIAL TO BECOME A TROPICAL CYCLONE OVER THE NEXT FEW DAYS... CHANGES WITH RESPECT TO WINDS AND SEAS WILL THEN HAVE TO BE MADE TO THE FORECAST GRIDS AND MANUAL GRAPHICAL CHARTS FOR THE SRN PORTION OF THE THIS AREA DUE TO THE POSSIBILITY OF THE PRES GRADIENT SIGNIFICANTLY TIGHTENING UP THERE. WILL HAVE TO WAIT TO SEE WHAT TRANSPIRES WITH THIS FEATURE AS IT PROGRESSES WESTWARD IN THE COMING DAYS...AND ADJUST FORECAST GRIDS AND GRAPHICS ACCORDINGLY. A BLEND OF THE GFS WITH THE PREVIOUS FORECAST GRIDS WAS USED FOR THE OFFSHORE WATERS FOR THIS FORECAST PERIOD. 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