[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON SEP 21 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 STORM IDA AT 21/0300 UTC IS NEAR 18.9N
47.0W. IDA IS MOVING TOWARD THE NORTHWEST...OR 310 DEGREES...12
KNOTS. THE MINIMUM CENTRAL PRESSURE IS 1005 MB. THE MAXIMUM
SUSTAINED WIND SPEEDS ARE 40 KNOTS WITH GUSTS TO 55 KNOTS.
PUBLIC ADVISORIES ABOUT TROPICAL STORM IDA ARE BEING ISSUED
UNDER THE WMO HEADER WTNT35 KNHC...AND UNDER THE AWIPS HEADER
MIATCPAT5. FORECAST/ADVISORIES ABOUT TROPICAL STORM IDA ARE
BEING ISSUED UNDER THE WMO HEADER WTNT25 KNHC...AND UNDER THE
AWIPS HEADER MIATCMAT5. CONVECTIVE PRECIPITATION...NUMEROUS
STRONG WITHIN A RADIUS OF 180 NM FROM THE CENTER IN THE EASTERN
SEMICIRCLE. ISOLATED MODERATE TO LOCALLY STRONG ELSEWHERE FROM
12N TO 22N BETWEEN 39W AND 45W.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 17W/18W FROM 16N
SOUTHWARD...JUST EMERGING FROM THE COAST OF AFRICA. CONVECTIVE
PRECIPITATION...SCATTERED STRONG FROM 12N TO 13N BETWEEN 18W AND
20W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH IS ALONG 10N20W 07N26W 06N30W 07N39W. NO ITCZ
IS PRESENT AT THIS MOMENT. CONVECTIVE PRECIPITATION...ISOLATED
MODERATE FROM 04N TO 07N BETWEEN 10W AND 15W. ISOLATED MODERATE
TO LOCALLY STRONG FROM 05N TO 08N BETWEEN 26W AND 43W. WIDELY
SCATTERED MODERATE TO ISOLATED STRONG FROM 07N TO 11N BETWEEN
46W AND 52W.

...DISCUSSION...

THE GULF OF MEXICO...

BROAD UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS THE GULF OF
MEXICO TO THE NORTH AND NORTHWEST OF THE ATLANTIC OCEAN-TO-
STRAITS OF FLORIDA TROUGH...AND TO THE NORTH OF THE AREA OF
CYCLONIC WIND FLOW THAT IS ASSOCIATED WITH THE EASTERN PACIFIC
OCEAN 14N104W CYCLONIC CIRCULATION CENTER. COMPARATIVELY DRIER
AIR IN SUBSIDENCE IS APPARENT IN WATER VAPOR IMAGERY IN THE AREA
OF ANTICYCLONIC WIND FLOW.

A STATIONARY FRONT IS INLAND...BETWEEN GEORGIA AND EAST TEXAS.
A SURFACE TROUGH IS ALONG THE FLORIDA WEST COAST.

AN EASTERN PACIFIC OCEAN MIDDLE LEVEL TO UPPER LEVEL CYCLONIC
CIRCULATION CENTER IS NEAR 14N104W. CYCLONIC WIND FLOW THAT IS
MOVING AROUND THE CENTER COVERS MEXICO AND THE SOUTHWESTERN
CORNER OF THE GULF OF MEXICO FROM 23N SOUTHWARD...FROM 92W
WESTWARD.

A DIURNAL SURFACE TROUGH EXTENDS FROM THE WESTERN PART OF THE
YUCATAN PENINSULA TO THE EASTERN PART OF THE ISTHMUS OF
TEHUANTEPEC OF SOUTHERN MEXICO. CONVECTIVE PRECIPITATION...
WIDELY SCATTERED MODERATE TO ISOLATED STRONG IS INLAND BETWEEN
87W IN HONDURAS AND 97W IN THE ISTHMUS OF TEHUANTEPEC OF
SOUTHERN MEXICO.

THE CARIBBEAN SEA...

AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 14N78W.
CYCLONIC WIND FLOW THAT IS MOVING AROUND THE 14N78W CENTER
COVERS THE CARIBBEAN SEA BETWEEN 70W AND 84W. CONVECTIVE
PRECIPITATION...ISOLATED MODERATE TO LOCALLY STRONG FROM 16N
SOUTHWARD BETWEEN 74W AND CENTRAL AMERICA.

CONVECTIVE PRECIPITATION...WIDELY SCATTERED MODERATE TO ISOLATED
STRONG COVERS THE NORTHWESTERN CORNER OF THE AREA...TO THE WEST
AND NORTHWEST OF THE LINE THAT RUNS FROM 21N80W TO THE EASTERN
COAST OF HONDURAS. UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS THE
NORTHWESTERN CORNER OF THE AREA.

AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 21N58W.
CYCLONIC WIND FLOW THAT IS MOVING AROUND THE CENTER COVERS THE
ATLANTIC OCEAN FROM 10N TO 32N BETWEEN 50W AND 70W...IN THE
CARIBBEAN SEA.

THE 24-HOUR RAINFALL TOTALS IN INCHES FOR THE PERIOD ENDING AT
06/0000 UTC...ACCORDING TO THE PAN AMERICAN TEMPERATURE AND
PRECIPITATION TABLES...MIATPTPAN/SXCA01 KNHC...ARE 0.11 IN
TEGUCIGALPA IN HONDURAS...0.05 IN BERMUDA...AND 0.02 IN HAVANA
CUBA.

...HISPANIOLA...

UPPER LEVEL NORTHERLY WIND FLOW IS REACHING THE ISLAND...PARTLY
WITH THE CYCLONIC FLOW THAT IS MOVING AROUND THE 21N58W ATLANTIC
OCEAN CYCLONIC CIRCULATION CENTER. UPPER LEVEL SOUTHEASTERLY
WIND FLOW ALSO IS REACHING THE ISLAND...WITH THE FLOW THAT IS
MOVING AROUND THE 14N78W CYCLONIC CIRCULATION CENTER. CONVECTIVE
PRECIPITATION...ISOLATED MODERATE FROM 18N TO 19N BETWEEN 73W
AND 74W IN THE LAND AND WATER AREAS THAT ARE AROUND SOUTHERN
HAITI. WARMING CLOUD TOP TEMPERATURES HAVE CAUSE INLAND
PRECIPITATION TO APPEAR TO BE WEAKENING WITH TIME.

CURRENT CONDITIONS...IN PORT-AU-PRINCE IN HAITI...THE LAST
OBSERVATION AT 21/0100 UTC SHOWED RAINSHOWERS WITH THUNDER. IN
THE DOMINICAN REPUBLIC...FEW LOW LEVEL CLOUDS WITH EARLIER
CUMULONIMBUS CLOUDS IN SANTO DOMINGO. SCATTERED LOW LEVEL CLOUDS
ARE IN LA ROMANA. FEW LOW LEVEL CLOUDS ARE IN PUNTA CANA.
SCATTERED LOW LEVEL CLOUDS ARE IN SANTIAGO AND PUERTO PLATA.

THE GFS MODEL FORECAST FOR 250 MB SHOWS THAT THE EASTERN HALF OF
THE ISLAND WILL RECEIVE NORTHERLY WIND FLOW AND THE WESTERN HALF
WILL RECEIVE SOUTHERLY WIND FLOW...BECAUSE OF THE 21N58W
CYCLONIC CENTER AND THE 14N78W CYCLONIC CENTER. ANTICYCLONIC
WIND FLOW IS FORECAST TO BUILD FROM THE SOUTH AND A RIDGE WILL
COVER HISPANIOLA FOR THE REST OF DAY ONE OF THE 48-HOUR FORECAST
PERIOD. THE SAME RIDGE WILL CONTINUE ACROSS THE AREA FOR THE
REST OF THE TIME. THE GFS MODEL FORECAST FOR 500 MB SHOWS THAT
ANTICYCLONIC WIND FLOW WILL COVER THE AREA FOR FIRST 24 HOURS.
NORTHERLY WIND FLOW WILL COVER HISPANIOLA FOR DAY TWO OF THE 48-
HOUR FORECAST PERIOD. THE ATLANTIC OCEAN CYCLONIC CENTER IS
FORECAST TO BE NEAR 23N65W. AN ANTICYCLONIC CIRCULATION CENTER
IS FORECAST TO BE NEAR 22N75W. THE GFS MODEL FOR 700 MB STARTS
WITH HISPANIOLA RECEIVING NORTHEAST-TO-EAST WIND FLOW...BEING ON
THE WESTERN SIDE OF AN INVERTED TROUGH. THE WIND FLOW VARIES
FROM EAST-SOUTHEAST...FROM THE NORTHEAST...AND FROM THE
SOUTHEAST AGAIN...DURING DAY TWO...AS AN INVERTED TROUGH SPANS
PUERTO RICO.

THE ATLANTIC OCEAN...

PLEASE REFER TO THE SPECIAL FEATURES SECTION FOR MORE DETAILS
ABOUT TROPICAL STORM IDA.

AN UPPER LEVEL TROUGH PASSES THROUGH 32N72W TO 29N76W...INTO THE
STRAITS OF FLORIDA...TO WESTERN CUBA...TOWARD THE NORTHEASTERN
COAST OF THE YUCATAN PENINSULA OF MEXICO. A SURFACE TROUGH
EXTENDS FROM A 1007 MB LOW PRESSURE CENTER THAT IS NEAR
33N71W...TO 29N74W...TO THE NORTHERN BAHAMAS NEAR 26N78W.
CONVECTIVE PRECIPITATION...ISOLATED MODERATE FROM 20N NORTHWARD
BETWEEN 64W AND 80W...AND FROM 20N TO 26N BETWEEN 76W AND THE
STRAITS OF FLORIDA...AND FROM 20N NORTHWARD BETWEEN 80W AND THE
YUCATAN PENINSULA IN THE NORTHWESTERN CORNER OF THE CARIBBEAN
SEA.

AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 21N58W.
CYCLONIC WIND FLOW THAT IS MOVING AROUND THE CENTER COVERS THE
ATLANTIC OCEAN FROM 10N TO 32N BETWEEN 50W AND 70W...IN THE
CARIBBEAN SEA. A SURFACE TROUGH IS ALONG 23N56W...TO A 1010 MB
LOW PRESSURE CENTER THAT IS NEAR 19N54W...TO 17N52W. CONVECTIVE
PRECIPITATION...SCATTERED TO NUMEROUS STRONG FROM 20N TO 23N
BETWEEN 53W AND 55W. SCATTERED STRONG FROM 25N TO 28N BETWEEN
49W AND 53W. ISOLATED TO WIDELY SCATTERED MODERATE ELSEWHERE
FROM 23N NORTHWARD BETWEEN 43W AND 57W...AND FROM 18N TO 23N
BETWEEN 57W AND 62W. RAINSHOWERS ARE POSSIBLE ALSO FROM 14N TO
20N BETWEEN 57W AND 70W IN THE CARIBBEAN SEA.

AN UPPER LEVEL TROUGH EXTENDS FROM A 32N18W CYCLONIC CIRCULATION
CENTER...TOWARD THE CAPE VERDE ISLANDS. CONVECTIVE
PRECIPITATION...ISOLATED MODERATE TO LOCALLY STRONG FROM 30N
NORTHWARD BETWEEN 26W AND 35W. RAINSHOWERS ARE POSSIBLE IN
SCATTERED TO BROKEN STRATIFORM CLOUDS THAT COVER THE AREA FROM
23N NORTHWARD BETWEEN 18W AND 40W.

SURFACE ANTICYCLONIC WIND FLOW COVERS THE ATLANTIC OCEAN TO THE
NORTH OF THE LINE THAT PASSES THROUGH 32N17W TO 25N39W AND
BEYOND 32N54W.

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

$$
MT
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