[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211143
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 21 2013

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
1015 UTC.

...TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 20W TO THE SOUTH OF 20N
MOVING WESTWARD 10 TO 15 KNOTS. THE 21/0600 UTC POSITION WAS
HELD TO 20W BASED ON LONG-TERM SATELLITE IMAGERY. RAINSHOWERS
ARE POSSIBLE IN THE ATLANTIC OCEAN FROM 10N TO 20N BETWEEN 17W
AND 21W.

AN ATLANTIC OCEAN SURFACE TROUGH IS ALONG 20N33W 10N32W. THE
TROUGH SHOWED UP IN THE LONG-TERM SATELLITE IMAGERY...AND IN
EARLIER SCATTEROMETER DATA. CONVECTIVE PRECIPITATION... NUMEROUS
STRONG FROM 14N TO 16N BETWEEN 29W AND 33W. WIDELY SCATTERED
MODERATE TO ISOLATED STRONG ELSEWHERE FROM 10N TO 20N BETWEEN
30W AND 33W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 24N37W 17N39W 9N41W
MOVING WESTWARD 10 TO 15 KNOTS. A MIDDLE LEVEL TO UPPER LEVEL
TROUGH PASSES THROUGH 32N22W TO 26N27W TO 25N31W...TO A 20N34W
CYCLONIC CIRCULATION CENTER...TO 14N40W AND 11N42W. CONVECTIVE
PRECIPITATION... ISOLATED MODERATE FROM 22N TO 24N BETWEEN 36W
AND 38W. RAINSHOWERS ARE POSSIBLE ELSEWHERE WITHIN 120 NM TO 180
NM ON EITHER SIDE OF 26N35W 16N39W 10N40W.

A MIDDLE LEVEL TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS IN
THE ATLANTIC OCEAN NEAR 22N51W. CYCLONIC WIND FLOW COVERS THE
AREA FROM 17N TO 25N BETWEEN 47W AND 55W. AN ATLANTIC OCEAN
SURFACE TROUGH IS ALONG 20N54W...TO A 1012 MB LOW PRESSURE
CENTER THAT IS NEAR 15N55W...TO 9N55W. THE LOW CENTER IS
FORECAST TO MOVE WESTWARD AND DISSIPATE IN 24 HOURS OR SO.
CONVECTIVE PRECIPITATION...NUMEROUS STRONG WITHIN 30 NM ON
EITHER SIDE OF 13N BETWEEN 56W AND 57W. ISOLATED MODERATE
ELSEWHERE FROM 9N TO 20N BETWEEN 50W AND 60W.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH PASSES THROUGH THE COASTAL AREAS OF GAMBIA/
FROM 13N TO 14N BETWEEN 16W AND 17W...TO 11N20W 11N29W AND
8N34W. THE ITCZ CONTINUES FROM 8N34W TO 8N36W 7N40W AND 5N46W.
CONVECTIVE PRECIPITATION...WIDELY SCATTERED TO SCATTERED
MODERATE AND ISOLATED STRONG FROM 4N TO 10N TO THE EAST OF 60W.

...DISCUSSION...

FROM THE U.S.A. COASTAL WATERS OF THE ATLANTIC OCEAN...ACROSS
CUBA...EVENTUALLY INTO THE NORTHWESTERN CORNER OF THE CARIBBEAN
SEA...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH 32N70W TO
28N71W...TO 23N79W BETWEEN ANDROS ISLAND IN THE BAHAMAS AND
CUBA...TO 20N84W IN THE NORTHWESTERN CORNER OF THE CARIBBEAN
SEA...EVENTUALLY INTO THE GULF OF HONDURAS. THE 24-HOUR RAINFALL
TOTAL IN INCHES FOR THE PERIOD ENDING AT 21/0000 UTC...ACCORDING
TO THE PAN AMERICAN TEMPERATURE AND PRECIPITATION TABLES...
MIATPTPAN...IS 0.16 IN TEGUCIGALPA IN HONDURAS. CONVECTIVE
PRECIPITATION...SCATTERED STRONG IN THE CARIBBEAN SEA FROM 16N
TO 20N TO THE WEST OF 80W. SCATTERED MODERATE TO ISOLATED STRONG
IN THE ATLANTIC OCEAN TO THE NORTH OF 26N BETWEEN 80W AND 83W.
ISOLATED MODERATE FROM CUBA TO 24N BETWEEN 70W AND 80W.

GULF OF MEXICO...

A DEEP LAYER TROUGH IS MOVING EASTWARD THROUGH THE CENTRAL
U.S.A. THE TROUGH SUPPORTS A COLD FRONT THAT IS MOVING THROUGH
SOUTHWESTERN LOUISIANA...INTO THE GULF COASTAL WATERS OF
TEXAS...AND ACROSS THE DEEP SOUTH OF TEXAS...TO 26N100W IN
MEXICO...CURVING NORTHWESTWARD THROUGH 28N105W AND 32N108W.
CONVECTIVE PRECIPITATION...NUMEROUS STRONG WITHIN 90 NM ON
EITHER SIDE OF THE LINE FROM 32N89W ALONG THE MISSISSIPPI/
ALABAMA BORDER...TO 27N94W IN THE GULF OF MEXICO...TO 21N102W IN
MEXICO.

A 1005 MB LOW PRESSURE CENTER IS NEAR 25N97W ALONG THE EXTREME
NORTHEASTERN CORNER OF THE MEXICO COAST. THE LOW CENTER IS
MOVING NORTHWARD 10 TO 15 KNOTS. THE LOW CENTER HAS BEEN LOSING
DEFINITION WITH TIME. NO SIGNIFICANT DEEP CONVECTIVE
PRECIPITATION THAT MAY NOT BE ASSOCIATED ALREADY WITH THE COLD
FRONT IS APPARENT.

FOR THE OFFSHORE OIL PLATFORM SITES THAT ARE TO THE NORTH OF 27N
TO THE WEST OF 88W...

MULTILAYERED CLOUD CEILINGS COVER THE WESTERN TWO-THIRDS OF THE
ICAO STATIONS. FAIR SKIES/CLEAR SKIES AT OR LOWER THAN 12000
FEET ARE BEING REPORTED ELSEWHERE ACROSS THE REST OF THE AREA.

MULTILAYERED CLOUD CEILINGS AND STRONG PRECIPITATION COVER THE
COASTAL PLAINS AND COASTAL WATERS FROM THE FLORIDA PANHANDLE
NEAR DESTIN WESTWARD TO THE DEEP SOUTH OF TEXAS. VISIBILITIES OF
2 MILES OR LESS WITH FOG ARE REPORTED IN BROOKSVILLE FLORIDA.

HISPANIOLA...

UPPER LEVEL SOUTHWESTERLY WIND FLOW SPANS THE AREA. THIS WIND
FLOW IS RELATED TO THE ATLANTIC OCEAN-TO-NORTHWESTERN CARIBBEAN
SEA MIDDLE LEVEL TO UPPER LEVEL TROUGH.

THE GFS FORECAST FOR 700 MB AND FOR 500 MB SHOWS THAT
ANTICYCLONIC WIND FLOW WILL COVER THE AREA. AN ANTICYCLONIC
CIRCULATION CENTER WILL BE IN THE EAST CENTRAL-TO-CENTRAL
CARIBBEAN SEA FOR THE ENTIRE TIME OF THE FORECAST PERIOD. THE
GFS FORECAST FOR 250 MB SHOWS THAT A TROUGH WILL START ON A LINE
THAT PASSES FROM THE BAHAMAS TO CENTRAL AND LATER EASTERN CUBA.
THE TROUGH EVENTUALLY WILL PASS ON TOP OF HISPANIOLA.

THE REST OF THE CARIBBEAN SEA...

UPPER LEVEL WESTERLY AND SOUTHWESTERLY WIND FLOW COVER THE
CARIBBEAN SEA TO THE WEST AND NORTHWEST OF THE LINE THAT RUNS
FROM EASTERN HISPANIOLA TO 16N80W AND THE NORTHEASTERN CORNER OF
NICARAGUA. THIS WIND FLOW IS RELATED TO THE ATLANTIC OCEAN-TO-
NORTHWESTERN CARIBBEAN SEA MIDDLE LEVEL TO UPPER LEVEL TROUGH.

NORTHERLY WIND FLOW COVERS THE CARIBBEAN SEA THAT IS TO THE
SOUTH OF 15N TO THE WEST OF 74W. UPPER LEVEL SOUTHERLY WIND FLOW
COVERS THE AREA THAT IS TO THE EAST OF 70W.

THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 8N73W...ACROSS
INTO PANAMA NEAR 8N81W...THROUGH NORTHWESTERN PANAMA...THROUGH
NORTHWESTERN COSTA RICA...THROUGH NORTHWESTERN NICARAGUA...INTO
NORTHWESTERN HONDURAS. CONVECTIVE PRECIPITATION...WARMING CLOUD
TOP TEMPERATURES AND POSSIBLE REMNANT PRECIPITATION WITHIN A 30
NM RADIUS OF 8N76W IN COLOMBIA. SCATTERED MODERATE TO STRONG
FROM NORTHEASTERN NICARAGUA INTO EASTERN HONDURAS.

THE REST OF THE ATLANTIC OCEAN...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH 32N40W TO
30N43W. THE TROUGH SUPPORTS A COLD FRONT THAT PASSES THROUGH
32N40W TO 28N50W...TO A 1006 MB LOW PRESSURE CENTER THAT IS NEAR
27N63W. A SURFACE TROUGH CONTINUES FROM 27N63W TO 23N68W...
ACROSS THE TURKS AND CAICOS...TO 21N74W TO THE WEST OF GREAT
INAGUA ISLAND. CONVECTIVE PRECIPITATION...SCATTERED STRONG FROM
22N TO 30N BETWEEN 56W AND 61W...AND FROM 20N TO 21N BETWEEN 64W
AND 65W. SCATTERED MODERATE TO ISOLATED STRONG FROM 28N TO 32N
BETWEEN 38W AND 46W. ISOLATED TO WIDELY SCATTERED MODERATE IS
ELSEWHERE WITHIN 250 NM ON EITHER SIDE OF THE LINE THAT PASSES
THROUGH 32N56W 26N58W 23N63W 21N76W.

A SURFACE RIDGE PASSES THROUGH 32N25W TO 25N33W. BROAD SURFACE
ANTICYCLONIC WIND FLOW COVERS THE AREA THAT IS TO THE NORTH OF
25N TO THE EAST OF 33W.

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

$$
MT


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