[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081111
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM GRACE AT 08/0900 UTC IS NEAR 14.1N
41.0W. 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 30 NM TO 60 NM FROM THE CENTER.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 22W/23W FROM 21N
SOUTHWARD...MOVING WESTWARD 10 TO 15 KNOTS. THIS POSITION IS A
MEAN POSITION THAT IS BASED ON SATELLITE IMAGERY AND THE 700 MB
WIND FIELD. CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO
ISOLATED STRONG FROM 14N TO 16N BETWEEN 18W AND 22W. RAINSHOWERS
ARE POSSIBLE ELSEWHERE FROM 07N TO 24N BETWEEN AFRICA AND 26W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 49W FROM 16N
SOUTHWARD...MOVING WESTWARD 15 KNOTS. CONVECTIVE
PRECIPITATION...SCATTERED MODERATE TO ISOLATED STRONG FROM 11N
TO 13N BETWEEN 48W AND 53W...AND FROM 06N TO 09N BETWEEN 51W AND
54W.

AN ATLANTIC OCEAN-TO-CARIBBEAN SEA TROPICAL WAVE IS ALONG
61W/62W FROM 16N SOUTHWARD...MOVING WESTWARD 15 KNOTS.
CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO ISOLATED STRONG
FROM 11N TO 14N BETWEEN 63W AND 66W. ISOLATED MODERATE ELSEWHERE
FROM 08N TO 15N BETWEEN 58W AND 70W.

A CARIBBEAN SEA TROPICAL WAVE EXTENDS FROM SOUTHEASTERN
CUBA...TO WESTERN JAMAICA...AND ALONG 77W/78W...INTO THE
SOUTHWESTERN CORNER OF THE CARIBBEAN SEA. THE WAVE IS MOVING
WESTWARD 10 TO 15 KNOTS. CONVECTIVE PRECIPITATION...THE
PRECIPITATION FROM SIX HOURS EARLIER HAS BEEN WEAKENING AND/OR
ALREADY HAS DISSIPATED. CONVECTIVE DEBRIS CLOUDS ARE FROM 17N
NORTHWARD BETWEEN HAITI AND THE CAYMAN ISLANDS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH COASTAL SECTIONS OF SENEGAL
NEAR 14N17W...TO 10N20W AND 10N30W. THE REST OF THE MONSOON
TROUGH...AND THE ITCZ...ARE BROKEN UP BY TROPICAL STORM GRACE
AND THE 49W TROPICAL WAVE. NO ITCZ IS PRESENT AT THIS MOMENT.
CONVECTIVE PRECIPITATION...WIDELY SCATTERED MODERATE TO ISOLATED
STRONG FROM 10N TO 12N BETWEEN 24W AND 28W. RAINSHOWERS ARE
POSSIBLE ELSEWHERE FROM 10N SOUTHWARD BETWEEN AFRICA AND SOUTH
AMERICA.

...DISCUSSION...

THE GULF OF MEXICO...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH A CYCLONIC
CIRCULATION CENTER THAT IS ON TOP OF SOUTHEASTERN LOUISIANA...
INTO THE SOUTHWESTERN CORNER OF THE AREA. A SURFACE TROUGH
EXTENDS FROM SOUTHEASTERN GEORGIA...TO A 1011 MB LOW PRESSURE
CENTER IS NEAR 29N85W...AND THEN IT CONTINUES TO 25N86W.
CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO ISOLATED STRONG
IS IN THE FLORIDA BIG BEND FROM 30N TO 31N BETWEEN 84W AND 85W.
ISOLATED MODERATE ELSEWHERE ACROSS THE OPEN WATERS OF THE GULF
OF MEXICO...AND IN THE ISTHMUS OF TEHUANTEPEC OF SOUTHERN
MEXICO.

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 COVERS THE AREA FROM 70W
WESTWARD. BROKEN TO OVERCAST MULTILAYERED CLOUDS COVER THE
CARIBBEAN SEA FROM 80W WESTWARD. A RIDGE EXTENDS FROM THE
SOUTHWESTERN CORNER OF THE CARIBBEAN SEA...NORTHWESTWARD...TO
THE YUCATAN CHANNEL AND WESTERN CUBA. MIDDLE LEVEL TO UPPER
LEVEL SOUTHEASTERLY WIND FLOW COVERS THE CARIBBEAN SEA FROM 80W
EASTWARD...WITH COMPARATIVELY DRIER AIR IN SUBSIDENCE.

THE MONSOON TROUGH IS ALONG 10N/11N BETWEEN 74W IN COLOMBIA...
BEYOND NORTHERN COSTA RICA...INTO THE EASTERN PACIFIC OCEAN.
CONVECTIVE PRECIPITATION...SCATTERED TO NUMEROUS STRONG IN
COLOMBIA FROM 05N TO 08N BETWEEN 73W AND 76W. SCATTERED MODERATE
TO ISOLATED STRONG IN THE SOUTHWESTERN CORNER OF THE CARIBBEAN
SEA FROM 11N SOUTHWARD FROM 80W WESTWARD...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 WESTERN JAMAICA...AND ALONG 77W/78W...INTO THE
SOUTHWESTERN CORNER OF THE CARIBBEAN SEA. THE WAVE IS MOVING
WESTWARD 10 TO 15 KNOTS. CONVECTIVE PRECIPITATION...THE
PRECIPITATION FROM SIX HOURS EARLIER HAS BEEN WEAKENING AND/OR
ALREADY HAS DISSIPATED. CONVECTIVE DEBRIS CLOUDS ARE FROM 17N
NORTHWARD BETWEEN HAITI AND THE CAYMAN ISLANDS.

CURRENT CONDITIONS...AT PORT-AU-PRINCE IN HAITI...FEW LOW LEVEL
CLOUDS ARE IN PORT-AU-PRINCE. IN THE DOMINICAN REPUBLIC...FEW
CUMULONIMBUS CLOUDS...OTHER SCATTERED LOW LEVEL CLOUDS AND
SCATTERED HIGH LEVEL CLOUDS ARE BEING OBSERVED IN SANTO DOMINGO.
FEW LOW LEVEL CLOUDS ARE IN PUNTA CANA. SCATTERED LOW LEVEL
CLOUDS AND A HIGH LEVEL CLOUD CEILING ARE IN SANTIAGO. FEW LOW
LEVEL CLOUDS AND SCATTERED HIGH 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 32N46W TO
24N54W AND 21N55W. A STATIONARY FRONT PASSES THROUGH 32N38W TO
29N46W...TO A 1016 MB LOW PRESSURE CENTER THAT IS NEAR
31N61W...TO 32N69W. 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 1020 MB HIGH PRESSURE CENTER THAT
IS NEAR 34N18W...TO A 1021 MB HIGH PRESSURE CENTER THAT IS NEAR
30N28W...TO 26N44W...TO A 1018 MB HIGH PRESSURE CENTER THAT IS
NEAR 25N62W...TO THE CENTRAL BAHAMAS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
MT
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