[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 090558
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED SEP 09 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
0515 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL DEPRESSION GRACE AT 09/0300 UTC IS NEAR
14.6N 45.8W. GRACE IS MOVING TOWARD THE WEST...OR 275
DEGREES...16 KNOTS. THE MINIMUM CENTRAL PRESSURE IS 1007 MB. THE
MAXIMUM SUSTAINED WIND SPEEDS ARE 30 KNOTS WITH GUSTS TO 40
KNOTS. PUBLIC ADVISORIES ABOUT TROPICAL DEPRESSION GRACE ARE
BEING ISSUED UNDER THE WMO HEADER WTNT32 KNHC...AND UNDER THE
AWIPS HEADER MIATCPAT2. FORECAST/ADVISORIES ABOUT TROPICAL
DEPRESSION GRACE ARE BEING ISSUED UNDER THE WMO HEADER WTNT22
KNHC...AND UNDER THE AWIPS HEADER MIATCMAT2. CONVECTIVE
PRECIPITATION...SCATTERED TO NUMEROUS STRONG WITHIN A RADIUS OF
90 NM FROM THE CENTER IN THE SOUTHEASTERN QUADRANT. ISOLATED
MODERATE TO LOCALLY STRONG WITHIN A RADIUS OF 120 NM FROM THE
CENTER IN THE NORTHWESTERN QUADRANT.

TROPICAL DEPRESSION EIGHT DEVELOPED JUST RECENTLY. THE CENTER OF
TROPICAL DEPRESSION EIGHT AT 09/0300 UTC IS NEAR 30.8N 61.5W...
OR ABOUT 190 NM TO THE EAST-SOUTHEAST OF BERMUDA. THE TROPICAL
DEPRESSION IS STATIONARY FOR THE MOMENT. THE MINIMUM CENTRAL
PRESSURE IS 1011 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 30
KNOTS WITH GUSTS TO 40 KNOTS. PUBLIC ADVISORIES ABOUT TROPICAL
DEPRESSION EIGHT ARE BEING ISSUED UNDER THE WMO HEADER WTNT33
KNHC...AND UNDER THE AWIPS HEADER MIATCPAT3. FORECAST/ADVISORIES
ABOUT TROPICAL DEPRESSION GRACE ARE BEING ISSUED UNDER THE WMO
HEADER WTNT23 KNHC...AND UNDER THE AWIPS HEADER MIATCMAT3.
CONVECTIVE PRECIPITATION...NUMEROUS STRONG WITHIN A RADIUS OF
150 NM FROM THE CENTER IN THE NORTHEASTERN QUADRANT.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 23W/24W 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...ISOLATED MODERATE FROM
12N TO 16N BETWEEN 23W AND 28W. RAINSHOWERS ARE POSSIBLE
ELSEWHERE FROM 08N TO 26N BETWEEN AFRICA AND 30W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 55W/56W FROM 15N
SOUTHWARD...MOVING WESTWARD 15 KNOTS. CONVECTIVE
PRECIPITATION...NUMEROUS STRONG FROM 10N TO 13N BETWEEN 56W AND
59W. ISOLATED MODERATE ELSEWHERE FROM 09N TO 12N BETWEEN 50W AND
56W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 67W/68W FROM 16N
SOUTHWARD...MOVING WESTWARD 15 KNOTS. CONVECTIVE
PRECIPITATION...RAINSHOWERS ARE POSSIBLE FROM 16N SOUTHWARD TO
VENEZUELA AND COLOMBIA BETWEEN 64W AND 71W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 83W/84W FROM 20N
SOUTHWARD...THROUGH EASTERN HONDURAS AND EASTERN NICARAGUA...TO
COSTA RICA. THE WAVE IS MOVING WESTWARD 10 TO 15 KNOTS.
CONVECTIVE PRECIPITATION...NUMEROUS STRONG FROM 06N IN THE
EASTERN PACIFIC OCEAN TO 10N JUST OFF THE COAST OF PANAMA
BETWEEN 80W AND 84W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH COASTAL SECTIONS OF MAURITANIA
NEAR 20N16W TO THE 23W/24W TROPICAL WAVE ALONG 14N...TO 12N30W
AND 12N38W. NO ITCZ IS PRESENT AT THIS MOMENT. THE ITCZ IS BEING
BROKEN UP BY TROPICAL DEPRESSION GRACE AND THE 55W/56W TROPICAL
WAVE. CONVECTIVE PRECIPITATION...ISOLATED MODERATE FROM 03N TO
06N BETWEEN 11W AND 17W. ISOLATED MODERATE ELSEWHERE FROM 08N TO
10N BETWEEN 27W AND 60W.

...DISCUSSION...

THE GULF OF MEXICO...

A MIDDLE LEVEL TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
NEAR 27N91W. CYCLONIC WIND FLOW COVERS THE GULF OF MEXICO.
CONVECTIVE PRECIPITATION...RAINSHOWERS ARE POSSIBLE FROM 28N
SOUTHWARD FROM 96W EASTWARD.

THE SURFACE PRESSURE GRADIENT IN THE GULF OF MEXICO IS
COMPARATIVELY WEAK. A WEAK RIDGE EXTENDS FROM A 1017 MB HIGH
PRESSURE CENTER THAT IS NEAR 28N73W...ACROSS LAKE OKEECHOBEE IN
SOUTH FLORIDA...INTO THE CENTRAL GULF OF MEXICO...TO THE MEXICO
GULF COAST NEAR 23N98W.

THE CARIBBEAN SEA...

AN INVERTED TROUGH IS ALONG 16N68W 14N69W 11N70W. THIS TROUGH IS
CLOSE TO THE AREA OF THE 67W/68W TROPICAL WAVE. CONVECTIVE
PRECIPITATION...RAINSHOWERS ARE POSSIBLE FROM 16N SOUTHWARD TO
VENEZUELA AND COLOMBIA BETWEEN 64W AND 71W.

UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS THE AREA FROM 72W
WESTWARD. BROKEN TO OVERCAST MULTILAYERED CLOUDS COVER THE
CARIBBEAN SEA FROM 77W 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 09N BETWEEN 73W IN COLOMBIA AND 84W
IN COSTA RICA. CONVECTIVE PRECIPITATION...NUMEROUS STRONG FROM
06N IN THE EASTERN PACIFIC OCEAN TO 10N JUST OFF THE COAST OF
PANAMA BETWEEN 80W AND 84W.

THE 24-HOUR RAINFALL TOTALS IN INCHES FOR THE PERIOD ENDING AT
09/0000 UTC...ACCORDING TO THE PAN AMERICAN TEMPERATURE AND
PRECIPITATION TABLES...MIATPTPAN/SXCA01 KNHC...ARE 0.12 IN
CURACAO.

...HISPANIOLA...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH THE ATLANTIC
OCEAN NEAR 26N63W...REACHING THE EASTERN SECTIONS OF THE
DOMINICAN REPUBLIC NEAR 19N70W. UPPER LEVEL NORTHWESTERLY WIND
FLOW REACHES MUCH OF HISPANIOLA. ONLY THE EASTERNMOST PART OF
THE ISLAND IS OBSERVING UPPER LEVEL WESTERLY WIND FLOW. 600 MB-
TO-800 MB LEVEL EASTERLY WIND FLOW ALSO IS MOVING ACROSS
HISPANIOLA. CONVECTIVE PRECIPITATION...EARLIER MONA PASSAGE
PRECIPITATION HAS WEAKENED AND DISSIPATED. ISOLATED MODERATE TO
LOCALLY STRONG FROM 18N TO 19N BETWEEN 72W AND 74W IN
SOUTHWESTERN HAITI.

CURRENT CONDITIONS...AT PORT-AU-PRINCE IN HAITI...THE LAST
OBSERVATION FROM 09/0200 UTC SHOWS SCATTERED LOW LEVEL CLOUDS
ARE IN PORT-AU-PRINCE. IN THE DOMINICAN REPUBLIC...THE LAST
OBSERVATION FROM BARAHONA AT 09/0000 UTC SHOWS FEW CUMULONIMBUS
CLOUDS. SCATTERED LOW LEVEL CLOUDS ARE IN SANTO DOMINGO. FEW LOW
LEVEL CLOUDS ARE IN LA ROMANA. SCATTERED LOW LEVEL CLOUDS ARE IN
PUNTA CANA. FEW LOW LEVEL CLOUDS ARE BEING OBSERVED IN SANTIAGO.
FEW LOW LEVEL CLOUDS AND A HIGH LEVEL CLOUD CEILING ARE IN
PUERTO PLATA.

THE GFS MODEL FORECAST FOR 250 MB SHOWS THAT THE CURRENT TROUGH
THAT IS IN THE EASTERN SECTIONS OF HISPANIOLA REMAINS ACROSS THE
EASTERN SECTIONS OF THE ISLAND FOR THE WHOLE 48 HOUR FORECAST
PERIOD. THAT MEANS MOSTLY NORTHERLY WIND FLOW ON THE WESTERN
SIDE OF THE TROUGH...AND SOUTHWESTERLY WIND FLOW ON THE EASTERN
SIDE OF THE TROUGH. THE GFS MODEL FORECAST FOR 500 MB SHOWS THAT
AN ANTICYCLONIC CIRCULATION CENTER WILL BE BETWEEN ANDROS ISLAND
IN THE BAHAMAS AND SOUTH FLORIDA. A RIDGE WILL EXTEND FROM THE
ANTICYCLONIC CIRCULATION CENTER TO HISPANIOLA FOR THE FIRST 24
HOURS OF THE 48-HOUR FORECAST PERIOD. THE RIDGE WILL MOVE
WESTWARD...BRINGING NORTHEASTERLY WIND FLOW ACROSS THE AREA FOR
THE REST OF THE FORECAST TIME. THE GFS MODEL FOR 700 MB SHOWS
THAT NORTHEAST-TO-EAST WIND FLOW WILL PASS ACROSS THE AREA FOR
THE FIRST 12 TO 18 HOURS...FOLLOWED BY TIME PERIODS OF EAST-TO-
SOUTHEAST WIND FLOW.

THE ATLANTIC OCEAN...

PLEASE REFER TO THE SPECIAL FEATURES SECTION FOR MORE DETAILS
ABOUT TROPICAL DEPRESSION GRACE AND TROPICAL DEPRESSION EIGHT.

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH 33N43W TO A
25N52W CYCLONIC CIRCULATION CENTER...TO 20N52W. A STATIONARY
FRONT PASSES THROUGH 32N29W TO 31N36W...TO 31N42W 27N48W... AND
TO 29N55W. CONVECTIVE PRECIPITATION...ISOLATED MODERATE TO
LOCALLY STRONG WITHIN 180 NM ON EITHER SIDE OF THE LINE THAT
PASSES THROUGH 32N30W TO 29N41W 25N53W 24N67W.

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH 32N24W TO
25N29W TO 20N35W. COMPARATIVELY DRIER AIR IN SUBSIDENCE IS
WITHIN 150 NM ON EITHER SIDE OF THE TROUGH.

A SURFACE RIDGE EXTENDS FROM A 1020 MB HIGH PRESSURE CENTER THAT
IS NEAR 33N18W...TO A 1020 MB HIGH PRESSURE CENTER THAT IS NEAR
27N32W...TO 25N46W...TO THE 1017 MB HIGH PRESSURE CENTER THAT IS
NEAR 28N73W...TO LAKE OKEECHOBEE IN SOUTH FLORIDA.

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

$$
MT
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