000 AGXX40 KNHC 140459 MIMATS MARINE WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1259 AM EDT TUE JUL 14 2009 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... EAST TO NORTHEASTERLY UPPER LEVEL FLOW AT THE SE PERIPHERY OF A BROAD UPPER LEVEL RIDGE EXTENDING FROM THE SOUTH CENTRAL PLAINS OF THE UNITED STATES INTO THE CENTRAL GULF IS PROVIDING DEEP LAYER SUBSIDENCE ACROSS THE GULF...SUSTAINING A SURFACE RIDGE ACROSS THE N GULF ALONG 26N WITH A SURFACE HIGH NEAR 26N91W. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE SURFACE RIDGE. ANTICYCLONIC FLOW AROUND THE RIDGE IS ASSOCIATED WITH A BROAD SWATH OF E WINDS OF 10 KT ACROSS THE SOUTHERN HALF OF THE GULF. A TROPICAL WAVE OVER THE BAY OF CAMPECHE IS MOVING W AT 15-20 KT FOLLOWED BY SE WINDS AT 10-15 KT...AND IS ALSO ACCOMPANIED BY SCATTERED SHOWERS AND THUNDERSTORMS. ACROSS THE REMAINDER OF THE GULF...THE RELATIVELY LIGHT WINDS ARE GENERATING WIND WAVE HEIGHTS OF 1 TO 3 FT...WITH HEIGHTS OF 2 TO 4 FT ACROSS THE BAY OF CAMPECHE. THE SURFACE RIDGE WILL REMAIN IN PLACE ACROSS THE GULF FOR MUCH OF THIS WEEK...THOUGH IT WILL SLIDE EASTWARD AS SUBSIDENCE OVER THE GULF WEAKENS IN RESPONSE TO THE SUPPORTING UPPER RIDGE TRANSLATING WESTWARD. AS A RESULT...SE WINDS OF 10-15 KT WILL AFFECT MUCH OF THE GULF FOR THE LATTER HALF OF THIS WEEK INTO THE WEEKEND. HOWEVER...NE WINDS TO 20 KT WILL BE A COMMON OCCURRENCE DURING THE EVENINGS NEAR THE W COAST OF THE YUCATAN PENINSULA...ENHANCED BY NEARBY TERRAIN VARIATIONS. FOR TODAY...A WEAK NEAR-SURFACE WAVE COULD RIDE EASTWARD ACROSS THE N PERIPHERY OF THE SURFACE RIDGE... LOCALLY INCREASING WINDS TO NEAR 15 KT AND ACCENTUATING A WIND SHIFT ACROSS THE NORTH CENTRAL AND NORTHEAST GULF NEAR THE WAVE TODAY. BOTH THE GFS AND ECMWF DEPICT THIS SCENARIO...THOUGH THE GFS APPEARS TO OVER-AGGRESSIVELY AMPLIFY THIS FEATURE GIVEN THE LACK OF DEEP-LAYER SUPPORT. CARIBBEAN... FRESH TO STRONG TRADE WINDS WILL AFFECT THE CARIBBEAN DURING THE NEXT SEVERAL DAYS BETWEEN THE SURFACE RIDGE OVER THE GULF OF MEXICO AND CENTRAL NORTH ATLC...AND BROAD LOW PRESSURE OVER NORTHERN SOUTH AMERICA. THROUGH THIS EVENING...THE PRIMARY FOCUS OF THESE STRONGER WINDS WILL BE FROM 11N TO 18N W OF 67W. THE STRONGEST WINDS WILL BE FOUND NEAR THE COAST OF COLOMBIA...WHERE WINDS WILL PERIODICALLY REACH 30 KT TODAY. ADDITIONALLY...SEAS OF 8 TO 11 FT WILL ALSO BE COMMON FROM 11N-18N W OF 70W THROUGH TODAY. ALSO...NE WINDS TO 20 KT WILL OCCASIONALLY OCCUR IN THE WINDWARD PASSAGE DURING THE NEXT SEVERAL DAYS. A WESTWARD-MOVING TROPICAL WAVE...CURRENTLY TILTED NW-SE AND EXTENDING FROM 19N57W TO 5N52W...WILL MOVE ACROSS THE TROPICAL N ATLC THIS MORNING AND ENTER THE E CARIBBEAN LATER TODAY. THE EASTERLY LOW LEVEL JET UPSTREAM OF THE WAVE AXIS IS RATHER STRONG...AND IS FORECAST TO INTENSIFY AS THE LOW LEVEL HEIGHT GRADIENT STEEPENS S OF A WEST-SOUTHWESTWARD-DRIFTING HIGH. IN FACT...WINDS AT 700 MB ARE FORECAST TO INCREASE TO 45 KT BEHIND THE WAVE AS IT TRACKS ACROSS THE CARIBBEAN. THE STRONG MEAN LOW LEVEL FLOW WILL LIKELY ACCELERATE THE WAVE TO A FORWARD SPEED OF 20-25 KT AFTER IT ENTERS THE CARIBBEAN. ALSO...THE EASTERLY LOW LEVEL JET FOLLOWING THE WAVE WILL CAUSE THE AREA OF 20-25 KT 10-METER WINDS TO EXPAND ACROSS A LARGE PART OF THE E CARIBBEAN BY WED. GIVEN THE ORIENTATION OF THE TOPOGRAPHY NEAR THE COAST OF COLOMBIA...WINDS WILL LIKELY REACH GALE FORCE WED-FRI NEAR THE COAST OF COLOMBIA. THUS...A GALE WARNING IS IN EFFECT FROM 11.5N-14N BETWEEN 72W-77W...INCLUDING THAT PORTION OF THE SW AND E CARIBBEAN NEAR THE COAST OF COLOMBIA WED-FRI. MAXIMUM SEAS WILL BUILD TO 14-15 FT NEAR THE COAST OF COLOMBIA BY LATE THIS WEEK. THE WAVE WILL ALSO BE ACCOMPANIED BY...AND FOLLOWED BY...A STRONG SURGE OF SAHARAN AIR...WHICH WILL LIMIT THE AREAL COVERAGE OF DEEP CONVECTION NEAR THE WAVE...BUT WILL ALSO INCREASE THE THREAT FOR STRONGER DOWNDRAFTS AND GUSTY OUTFLOW WINDS WITH ANY CONVECTION THAT DEVELOPS. ATLC... THE SURFACE PATTERN ACROSS THE AREA WILL BE CHARACTERIZED BY A SURFACE RIDGE ALONG 28N ACROSS THE CENTRAL AND SW NORTH ATLC. THIS WILL MAINTAIN NE TO E TRADE WINDS OF 15 TO 20 KT ACROSS THE TROPICAL N ATLC AND FAR SOUTHERN PORTIONS OF THE SW NORTH ATLC FOR THE NEXT FEW DAYS...WITH SW WINDS OF 15 KT ACROSS THE FAR NW PORTIONS OF THE SW NORTH ATLC. WEAK PERTURBATIONS ROTATING AROUND THE RIDGE WILL LOCALLY ENHANCE THESE WINDS TO AROUND 20 KT...WITH SEAS IN THE 6 TO 8 FT RANGE. A TROPICAL WAVE EXTENDING FROM 19N57W TO 5N52W IS MOVING W 15-20 KT. A STRONG LOW TO MIDDLE LEVEL WIND SURGE FOLLOWS THE WAVE...AND WILL MOVE ACROSS THE TROPICAL ATLC OVER THE NEXT FEW DAYS. THE POST-WAVE E WINDS OF 20 TO 25 KT WILL GENERATE BUILDING SEAS ACROSS THE TROPICAL N ATLC N OF 13N/14N THROUGHOUT THE WEEK. THE FRESH TO STRONG TRADE WINDS...AND SIGNIFICANT HAZE IN SAHARAN AIR...WILL DOMINATE THE TROPICAL ATLC BY THE MIDDLE OF THE UPCOMING WEEK WITH THIS WIND SURGE. THE STRONGER WINDS WILL BUILD SEAS TO 8 TO 9 FT. ANOTHER TROPICAL WAVE...CURRENTLY ALONG 31W...WILL TRACK WESTWARD AT 15-20 KT DURING THE NEXT FEW DAYS...PRECEDED BY A LEADING...ALBEIT WEAK...VORTICITY MAXIMUM. THE WAVE WILL LIKELY ENTER THE TROPICAL N ATLC BY THE END OF THE WEEK. WHILE THE GFS SHOWS THE POTENTIAL FOR TROPICAL CYCLOGENESIS ALONG THIS WAVE...THIS APPEARS TO BE A GRIDSCALE FEEDBACK ISSUE...AS LITTLE GLOBAL MODEL GUIDANCE OR CLIMATOLOGY BACK UP THIS SOLUTION. WINDS OF 20 KT...HOWEVER...WILL LIKELY ACCOMPANY THE WAVE. WARNINGS ATLC... .NONE. CARIBBEAN... .GALE WARNING IN EFFECT FOR PORTIONS OF AMZ084 AND AMZ086 WED THROUGH FRI. GULF OF MEXICO... .NONE. FORECASTER COHEN. TROPICAL PREDICTION CENTER.