000 AGXX40 KNHC 131652 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1252 PM EDT THU AUG 13 2015 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: GFS BLENDED/ECMWF BLEND. TAFB NWPS USED FOR SEAS HEIGHTS AND PRIMARY WAVE PERIOD WITH MANUAL ADJUSTMENTS TO MATCH OBSERVATIONS. MEDIUM-HIGH CONFIDENCE. AN INVERTED THERMAL TROUGH WILL DEVELOP EACH AFTERNOON OVER THE YUCATAN PENINSULA...AND THEN MOVE W-NW ACROSS THE SW GULF WATERS GENERALLY TO THE S OF 22N BETWEEN 90-93W DURING THE EVENING THROUGH LATE NIGHT HOURS...REACHING ALONG 94-95W DURING THE EARLY DAYLIGHT HOURS...AND THEN DISSIPATING BY EARLY AFTERNOON. EXPECT THIS TROUGH TO BE ACCOMPANIED BY A NE-E 10-15 KT WIND SHIFT THROUGH SAT EVENING...THEN GUIDANCE HINTS AT 15-20 KT EVENTS ON SUN...MON AND TUE EVENING-NIGHTS. AN E TO W RIDGE EXTENDS ELSEWHERE ACROSS THE S GULF ALONG ABOUT 24N WITH A SURFACE HIGH DEVELOPING INTERMITTENTLY ALONG THE RIDGE AXIS OVER THE FAR S-CENTRAL PORTION MAINLY DURING THE LATE AFTERNOON AND EARLY EVENING HOURS. GENERALLY EXPECT 5-10 KT ANTICYCLONIC FLOW WITHIN ABOUT 150 NM OF THE RIDGE AXIS. A WEAK PRE-FRONTAL TROUGH EXTENDS FROM THE FL BIG BEND TO NEAR 27N88W AND IS ACCOMPANIED BY SCT RW/ISOL TS WHICH IS DEPICTED IN THE WEATHER GRIDS THROUGH TONIGHT. A NEARLY STATIONARY FRONT EXTENDING E-W ACROSS THE NORTHERN COASTAL PLAINS WILL MOVE SE AS A WEAK COLD FRONT THIS AFTERNOON AND TONIGHT MERGING WITH THE PRE-FRONTAL TROUGH. THE MERGED BOUNDARY WILL STALL FROM THE FL BIG BEND TO THE N-CENTRAL WATERS ON FRI. BY THEN A WEAK LOW PRES SHOULD FORM ALONG THE FRONTAL TROUGH NEAR 27N93W THEN DRIFT SLOWLY NW ON FRI NIGHT-SUN...BUT ONLY ACCOMPANIED BY 5-10 KT CYCLONIC FLOW. THE RIDGE WILL SHIFT N ACROSS THE NORTHERN GULF WATERS SUN NIGHT THROUGH TUE NIGHT. ...CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... MODEL PREFERENCE: GFS BLENDED/ECMWF BLEND. TAFB NWPS USED FOR SEAS HEIGHTS AND PRIMARY WAVE PERIOD WITH MANUAL ADJUSTMENTS TO MATCH OBSERVATIONS. MEDIUM-HIGH CONFIDENCE. ATLC RIDGE N OF THE AREA COMBINED WITH LOW PRESSURE OVER NW COLOMBIA WILL CONTINUE TO ENHANCE FRESH TO LOCALLY STRONG NOCTURNAL TRADES WITHIN ABOUT 240 NM OF THE COLOMBIAN COAST AND ALONG THE FAR NW COAST OF VENEZUELA...INCLUDING THE GULF OF VENEZUELA AS WELL. PATCHES OF ENE 20-25 KT WINDS AND NE-E SWELLS WILL GENERATE COMBINED SEAS TO 8 FT AS FAR W AS 13N81W ON SAT- TUE. A TROPICAL WAVE BETWEEN 80-82W TODAY WILL CONTINUE W AT ABOUT 18 KT PASSING THROUGH THE GULF OF HONDURAS ON FRI. ONLY A SLIGHT ENHANCEMENT TO CONVECTION IS CURRENTLY NOTED...AND WILL LIKELY CONTINUE AS THIS LOW LEVEL TROPICAL WAVE IS MOVING W ROUGHLY IN PHASE WITH THE DIFFLUENT E SEMICIRCLE OF AN ELONGATED UPPER CYCLONE CURRENTLY OVER THE CAYMAN ISLANDS. THIS CONVECTION WILL BE DENOTED IN THE WEATHER GRIDS THROUGH FRI NIGHT. A LOW LEVEL TROUGH HAS BEEN INTRODUCED TO THE SURFACE ANALYSIS ACROSS THE N- CENTRAL CARIBBEAN TO THE S OF HISPANIOLA. THIS LOW LEVEL TROUGH IS A REFLECTION OF THE ELONGATED UPPER CYCLONE AND CONSIDERABLE CONVECTION IS ALSO ENHANCED NEAR 17N71W...AND WILL BE FORECAST VIA THE WEATHER GRIDS FOR A DAY OR SO. A SECOND TROPICAL WAVE...CURRENTLY ALONG 52W...WILL CONTINUE W AT 12 KT PASSING 55W THIS EVENING AND PASS THROUGH THE E CARIBBEAN ON FRI-SAT...REACHING THE CENTRAL CARIBBEAN LATE IN THE WEEKEND AND PASS THROUGH THE W CARIBBEAN EARLY NEXT WEEK. EXPECT A SLIGHT INCREASE IN THE TRADES WITHIN ABOUT 240 NM OF THE WAVE. UPPER SUBSIDENCE IS CURRENTLY SUPPRESSING CONVECTION TO ONLY INTERMITTENT CLUSTERS...AND LITTLE CHANGE EXPECTED AS THE UPPER DRY AIR/SUBSIDENCE IS SPREADING W ACROSS THE WINDWARDS AND FAR SE CARIBBEAN ATTM. ...SW N ATLANTIC INCLUDING THE BAHAMAS... MODEL PREFERENCE: GFS/ECMWF BLEND. TAFB NWPS USED FOR SEAS HEIGHTS AND PRIMARY WAVE PERIOD WITH MANUAL ADJUSTMENTS TO MATCH OBSERVATIONS MEDIUM-HIGH CONFIDENCE. AN UPPER LEVEL LONGWAVE TROUGH HAS MEAN AXIS N OF 28N ALONG 80W AND WILL EFFECTIVELY RETROGRESS WESTWARD TONIGHT AND FRI AS A STRONG REINFORCING DRY SHORTWAVE IS PUSHING SE INTO THE LONGWAVE PATTERN. STRONG UPPER DIFFLUENCE E OF THE LONGWAVE CONTINUES TO ENHANCE CONVECTION ACROSS THE ATLC WATERS FROM THE NORTHERN BAHAMAS TO NEAR 31N71W. THIS WILL BE DENOTED IN THE WEATHER GRIDS FOR THE INITIAL 36 HOURS. AN ATLC SURFACE RIDGE EXTENDING NE-SW FROM BERMUDA TO EXTREME SE FL WILL CONTINUE TO SHIFT N TONIGHT REACHING FROM 31N66W TO FORT PIERCE FL ON FRI...AND FROM BERMUDA TO PORT CANAVERAL FL ON SAT. A WEAK COLD FRONT IS STALLING ACROSS THE FAR NW WATERS WHERE IT WILL MEANDER THROUGH EARLY SAT...THEN BE PUSHED NW BEGINNING LATE SAT AS THE RIDGE SHIFTS FURTHER N REACHING PORT OF JACKSONVILLE BY EARLY MON. THE RIDGE WILL RETRACT E ON MON NIGHT INTO TUE ALLOWING REMNANTS OF THE FRONT TO DRIFT E OVER THE FAR NW WATERS AGAIN. MODERATE E-SE TRADES ARE OBSERVED S OF THE RIDGE...EXCEPT INCREASING TO FRESH ALONG THE N COAST OF HISPANIOLA ON SAT AND SUN EVENINGS WHEN THE RIDGE HAS MOVED N OF 28N. $$ .WARNINGS...ANY CHANGES IMPACTING COASTAL NWS OFFICES WILL BE COORDINATED THROUGH AWIPS 12 PLANET CHAT OR BY TELEPHONE: .GULF OF MEXICO... NONE. .CARIBBEAN SEA AND TROPICAL N ATLANTIC FROM 07N TO 19N BETWEEN 55W AND 64W... NONE. .SW N ATLANTIC INCLUDING THE BAHAMAS... NONE. $$ *FOR DETAILED ZONE DESCRIPTIONS PLEASE VISIT: HTTP://WWW.NHC.NOAA.GOV/ABOUTTAFBPROD.SHTML#OWF NOTE: GRIDDED MARINE FORECASTS ARE AVAILABLE IN THE NATIONAL DIGITAL FORECAST DATABASE (NDFD) AT: HTTP://WWW.NHC.NOAA.GOV/MARINE/GRIDS.PHP FOR ADDITIONAL INFORMATION PLEASE VISIT: HTTP://WWW.HURRICANE WARNINGS.GOV/MARINE $$ .FORECASTER NELSON. NATIONAL HURRICANE CENTER.