000 AXNT20 KNHC 080550 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT TUE SEP 08 2015 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0545 UTC. ...SPECIAL FEATURES... THE CENTER OF TROPICAL STORM GRACE AT 08/0300 UTC IS NEAR 14.0N 39.2W. GRACE IS MOVING TOWARD THE WEST...OR 275 DEGREES...17 KNOTS. THE MINIMUM CENTRAL PRESSURE IS 1006 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 35 KNOTS WITH GUSTS TO 45 KNOTS. PUBLIC ADVISORIES ABOUT TROPICAL STORM GRACE ARE BEING ISSUED UNDER THE WMO HEADER WTNT32 KNHC...AND UNDER THE AWIPS HEADER MIATCPAT2. FORECAST/ADVISORIES ABOUT TROPICAL STORM GRACE ARE BEING ISSUED UNDER THE WMO HEADER WTNT22 KNHC...AND UNDER THE AWIPS HEADER MIATCMAT2. CONVECTIVE PRECIPITATION...NUMEROUS STRONG WITHIN A RADIUS OF 90 NM OF THE CENTER IN THE SOUTHWESTERN QUADRANT. ...TROPICAL WAVES... AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 22W/23W FROM 21N SOUTHWARD...MOVING WESTWARD 10 TO 15 KNOTS. CONVECTIVE PRECIPITATION...ISOLATED MODERATE FROM 07N TO 23N BETWEEN 10W AND 28W. AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 48W/49W FROM 15N SOUTHWARD...MOVING WESTWARD 15 KNOTS. CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO ISOLATED STRONG FROM 11N TO 13N BETWEEN 47W AND 51W...AND FROM 07N TO 09N BETWEEN 50W AND 54W. AN ATLANTIC OCEAN-TO-CARIBBEAN SEA TROPICAL WAVE IS ALONG 60W/61W FROM 16N SOUTHWARD...MOVING WESTWARD 15 KNOTS. CONVECTIVE PRECIPITATION...SCATTERED STRONG FROM 11N TO 13N BETWEEN 63W AND 75W. ISOLATED MODERATE ELSEWHERE FROM 10N TO 14N BETWEEN 58W AND 68W. A CARIBBEAN SEA TROPICAL WAVE EXTENDS FROM SOUTHEASTERN CUBA...TO EASTERN JAMAICA...TO 15N77W AND 10N77W. THE WAVE IS MOVING WESTWARD 10 TO 15 KNOTS. CONVECTIVE PRECIPITATION... SCATTERED MODERATE TO ISOLATED STRONG IN SOUTHEASTERN CUBA FROM 20N TO 21N BETWEEN 76W AND 78W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH PASSES THROUGH SOUTHERN COASTAL SECTIONS OF MAURITANIA NEAR 17N16W...TO 12N20W 11N24W AND 13N29W. THE REST OF THE MONSOON TROUGH...AND THE ITCZ...ARE BROKEN UP BY TROPICAL STORM GRACE AND THE 48W/49W TROPICAL WAVE. NO SIGNIFICANT DEEP CONVECTIVE PRECIPITATION. ...DISCUSSION... THE GULF OF MEXICO... A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH SOUTHEASTERN MISSISSIPPI/SOUTHWESTERN ALABAMA...INTO THE SOUTHWESTERN CORNER OF THE AREA. A SURFACE TROUGH EXTENDS FROM A 1011 MB LOW PRESSURE CENTER IS NEAR 28N84W TO 26N84W AND 25N86W. CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO STRONG IN THE COASTAL WATERS OF THE FLORIDA BIG BEND FROM 29N TO 30N BETWEEN 84W AND 85W. ISOLATED MODERATE ELSEWHERE ACROSS THE OPEN WATERS OF THE GULF OF MEXICO FROM 22N NORTHWARD FROM 94W EASTWARD. THE CARIBBEAN SEA... PLEASE REFER TO THE SECTION THAT IS ABOUT HISPANIOLA AND THE SECTION THAT IS ABOUT TROPICAL WAVES...FOR MORE DETAILS ABOUT THE CARIBBEAN SEA CUBA-TO-JAMAICA-ALONG 77W TROPICAL WAVE. UPPER LEVEL ANTICYCLONIC WIND FLOW AND BROKEN TO OVERCAST MULTILAYERED CLOUDS COVER THE CARIBBEAN SEA FROM 70W WESTWARD. A RIDGE EXTENDS FROM THE SOUTHWESTERN CORNER OF THE CARIBBEAN SEA...NORTHWESTWARD...TO THE YUCATAN CHANNEL AND WESTERN CUBA. THE MONSOON TROUGH IS ALONG 09N76W IN COLOMBIA...TO 10N80W... BEYOND NORTHERN IN COSTA RICA...INTO THE EASTERN PACIFIC OCEAN. CONVECTIVE PRECIPITATION...WIDELY SCATTERED TO SCATTERED STRONG IS IN COLOMBIA FROM 05N TO 10N BETWEEN 72W IN VENEZUELA AND 76W IN COLOMBIA. ISOLATED MODERATE TO LOCALLY STRONG FROM 05N IN COLOMBIA TO 12N IN NICARAGUA BETWEEN 76W AND 86W INCLUDING IN THE GULF OF URABA OF COLOMBIA. THE 24-HOUR RAINFALL TOTALS IN INCHES FOR THE PERIOD ENDING AT 08/0000 UTC...ACCORDING TO THE PAN AMERICAN TEMPERATURE AND PRECIPITATION TABLES...MIATPTPAN/SXCA01 KNHC...ARE 0.02 IN BERMUDA. ...HISPANIOLA... HIGH LEVEL NORTHWESTERLY WIND FLOW IS MOVING ON TOP OF 600 MB-TO- 800 MB LEVEL EAST-TO-SOUTHEAST WIND FLOW. CONVECTIVE PRECIPITATION...ISOLATED MODERATE ALONG THE SOUTHWESTERN COASTAL WATERS FROM 18N TO 19N BETWEEN 74W AND 75W IN THE WINDWARD PASSAGE. A CARIBBEAN SEA TROPICAL WAVE EXTENDS FROM SOUTHEASTERN CUBA...TO EASTERN JAMAICA...TO 15N77W AND 10N77W. THE WAVE IS MOVING WESTWARD 10 TO 15 KNOTS. CONVECTIVE PRECIPITATION... SCATTERED MODERATE TO ISOLATED STRONG IN SOUTHEASTERN CUBA FROM 20N TO 21N BETWEEN 76W AND 78W. CURRENT CONDITIONS...AT PORT-AU-PRINCE IN HAITI...THE LAST OBSERVATION FOR 08/0100 UTC SHOWED SCATTERED LOW LEVEL CLOUDS. IN THE DOMINICAN REPUBLIC...RAINSHOWERS WITH THUNDER ARE BEING OBSERVED IN SANTO DOMINGO. FEW LOW LEVEL CLOUDS ARE IN LA ROMANA. FEW LOW LEVEL CLOUDS AND SCATTERED HIGH LEVEL CLOUDS ARE IN PUNTA CANA. SCATTERED LOW LEVEL CLOUDS ARE IN SANTIAGO. FEW LOW LEVEL CLOUDS ARE IN PUERTO PLATA. THE GFS MODEL FORECAST FOR 250 MB SHOWS THAT HISPANIOLA FINDS ITSELF IN THE MIDDLE OF THE FOLLOWING WEATHER FEATURES...A RIDGE FROM THE SOUTHWESTERN CORNER OF THE CARIBBEAN SEA TO HISPANIOLA...AN INVERTED TROUGH AFFECTING THE SOUTHEASTERN CORNER OF HISPANIOLA...AN EAST-TO-WEST ORIENTED ATLANTIC OCEAN- TO-HISPANIOLA RIDGE...AND A TROUGH THAT IS CLOSE TO THE NORTHEASTERN CORNER OF THE ISLAND. THE RIDGE THAT STRETCHES FROM THE SOUTHWESTERN CORNER OF THE CARIBBEAN SEA TO HISPANIOLA EVENTUALLY DOMINATES AFTER THE FIRST 12 HOURS OF THE 48-HOUR FORECAST PERIOD...INTO THE END OF THE FIRST DAY. NORTHERLY WIND FLOW LASTS DURING ALL OF DAY TWO...AS HISPANIOLA REMAINS ON THE EASTERN SIDE OF THE SAME SOUTHWESTERN CARIBBEAN SEA RIDGE. A TROUGH ALSO AFFECTS THE NORTHEASTERN CORNER AND EASTERN SECTIONS DURING DAY TWO. THE GFS MODEL FORECAST FOR 500 MB SHOWS THAT AN ANTICYCLONIC CIRCULATION CENTER WILL BE IN THE ATLANTIC OCEAN ABOUT 120 NM TO THE NORTHEAST OF HISPANIOLA AT THE START OF THE 48-HOUR FORECAST PERIOD. EAST-TO-SOUTHEAST WIND FLOW WILL CROSS THE ISLAND AT THE START. THE ANTICYCLONIC CENTER WILL MOVE TOWARD THE TURKS AND CAICOS AND GREAT INAGUA BY THE END OF THE FIRST 24 HOURS...WITH MORE EAST-TO-SOUTHEAST WIND FLOW. THE ANTICYCLONIC CENTER EVENTUALLY WILL MOVE TOWARD AND MERGE WITH A SECOND ANTICYCLONIC CIRCULATION CENTER...AND BE NEAR THE NORTHERN BAHAMAS BY THE END OF THE 48-HOUR FORECAST PERIOD. NORTHEASTERLY WIND FLOW WILL CROSS HISPANIOLA DURING DAY TWO. THE GFS MODEL FOR 700 MB SHOWS THAT EAST-TO-SOUTHEAST WIND FLOW WILL MOVE ACROSS HISPANIOLA DURING THE NEXT 48 HOURS. A RIDGE WILL BE ALONG 25N/26N DURING THAT TIME PERIOD. THE ATLANTIC OCEAN... PLEASE REFER TO THE SPECIAL FEATURES SECTION FOR MORE DETAILS ABOUT TROPICAL STORM GRACE. A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH 32N43W TO 26N48W. A STATIONARY FRONT PASSES THROUGH 32N37W TO 29N47W...TO A 1014 MB LOW PRESSURE CENTER THAT IS NEAR 31N61W...TO 32N68W. THE LOW PRESSURE CENTER IS FORECAST TO REMAIN STATIONARY FOR THE NEXT DAY OR SO...AND THEN IT IS FORECAST TO MOVE NORTHWARD 5 TO 10 KNOTS BY WEDNESDAY. THE CHANCE OF FORMATION INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS IS LOW. CONVECTIVE PRECIPITATION...WIDELY SCATTERED TO SCATTERED STRONG FROM 29N TO 31N BETWEEN 57W AND 62W. ISOLATED MODERATE ELSEWHERE TO THE NORTH OF THE LINE THAT PASSES THROUGH 32N29W 26N38W 22N55W 20N70W. A SURFACE RIDGE EXTENDS FROM A 1022 MB HIGH PRESSURE CENTER THAT IS NEAR 35N17W...THROUGH 32N23W...TO 28N30W...TO 24N38W...TO A 1014 MB HIGH PRESSURE CENTER THAT IS NEAR 25N59W...TO THE CENTRAL BAHAMAS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ MT