[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 180559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI SEP 18 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS...AND GOES-12 SATELLITE
IMAGERY THROUGH 0315 UTC...AND METEOSAT-8 IMAGERY THROUGH
0530 UTC.

...TROPICAL WAVES...

AN EASTERN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 21W/22W TO THE
SOUTH OF 16N MOVING WESTWARD 10 TO 15 KT. DISORGANIZED ISOLATED
MODERATE SHOWERS WITHIN 120 NM TO THE EAST OF THE WAVE...AND
WITHIN 300 NM TO THE WEST OF THE WAVE FROM 13N TO 17N.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 85W/86W TO THE
SOUTH OF 21N MOVING WESTWARD 10 TO 15 KT. IT IS POSSIBLE THAT
THIS WAVE IS CONTRIBUTING SOME INSTABILITY TO THE PRECIPITATION
THAT IS OCCURRING FROM NORTHWESTERN COSTA RICA TO EL SALVADOR TO
WESTERN HONDURAS. LARGE-SCALE UPPER LEVEL CYCLONIC FLOW THAT IS
MOVING AROUND THE 15N76W CARIBBEAN SEA CYCLONIC CENTER REACHES
EASTERN NICARAGUA. A FEW OTHER SMALLER-SIZED AREAS OF CYCLONIC
FLOW ARE NEAR THE TROPICAL WAVE.

...THE ITCZ...

12N24W 12N35W 11N41W 9N50W INTO NORTHEASTERN VENEZUELA NEAR
8N62W. ISOLATED MODERATE SHOWERS WITHIN 240 NM ON EITHER SIDE
OF THE AXIS TO THE EAST OF 26W...AND WITHIN 120 NM ON EITHER
SIDE OF THE AXIS BETWEEN 26W AND 44W.

...DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH SOUTHEASTERN
LOUISIANA INTO THE WEST CENTRAL GULF OF MEXICO AND THE
SOUTHWESTERN CORNER OF THE AREA. A DISSIPATING COLD FRONT PASSES
THROUGH SOUTHEASTERN LOUISIANA TO 24N96W IN THE WESTERN GULF OF
MEXICO. A SECONDARY SURFACE TROUGH IS ABOUT 200 NM TO THE WEST
OF THE DISSIPATING FRONT...TO THE NORTH OF 27N. AN UPPER LEVEL
RIDGE PASSES THROUGH NORTHEASTERN FLORIDA INTO THE SOUTHEASTERN
GULF OF MEXICO TO THE YUCATAN PENINSULA.

THE CARIBBEAN SEA...
AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 15N76W...
AT LEAST 200 NM TO THE SOUTH OF EASTERN JAMAICA. CYCLONIC FLOW
COVERS NEARLY THE WHOLE AREA TO THE WEST OF 70W...EXCEPT FOR
THE NORTHWESTERN CORNER TO THE NORTH OF 16N TO THE WEST OF 84W.
THE COMPARATIVELY GREATEST AMOUNT OF SHOWERS AND THUNDERSTORMS
IS IN THE CENTRAL CARIBBEAN SEA FROM 15N TO 16N BETWEEN 72W AND
74W...AND FROM 16N TO 19N IN THE DOMINICAN REPUBLIC BETWEEN 68W
AND 72W. OTHER DISORGANIZED ISOLATED MODERATE SHOWERS COVER THE
AREA DIRECTLY UNDER THE LARGE-SCALE CYCLONIC FLOW OF THE 15N76W
CENTER. DEBRIS CLOUDS AND MOISTURE THAT HAVE SPUN AWAY FROM
THE 15N76W CENTER HAVE MOVED INTO THE CARIBBEAN SEA TO THE EAST
OF 70W. ISOLATED MODERATE SHOWERS ARE TO THE EAST OF 70W.

THE ATLANTIC OCEAN...
THE DEEP LAYER WESTERN ATLANTIC OCEAN TROUGH THAT WAS SUPPORTING
THE SURFACE TROUGH HAS BEEN ERODED AWAY. IT HAS BEEN REPLACED BY
UPPER LEVEL ANTICYCLONIC FLOW...AND SLOWLY-ENCROACHING UPPER
LEVEL CYCLONIC FLOW FROM THE CENTRAL ATLANTIC OCEAN. A SURFACE
TROUGH REMAINS ALONG 31N72W TO ELEUTHERA ISLAND IN THE BAHAMAS.
ISOLATED MODERATE SHOWERS ARE WITHIN 30 NM ON EITHER SIDE OF THE
TROUGH. AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR
22N57W. THIS FEATURE HAS BEEN MOVING WESTWARD DURING THE LAST
FEW DAYS. CYCLONIC FLOW AROUND THIS CENTER COVERS THE AREA FROM
14N TO 30N BETWEEN 46W AND 70W. THE 1015 MB LOW PRESSURE CENTER
THAT IS NEAR 25N64W IS THE REMNANT OF HURRICANE FRED. A TROUGH
GOES FROM 29N63W TO THE REMNANT LOW CENTER...AND THEN TO 19N63W.
ISOLATED MODERATE SHOWERS AROUND THE REMNANT LOW CENTER COVER
THE AREA FROM 23N TO 25N BETWEEN 63W AND 65W. THE CHANCE OF THE
REMNANT OF FRED DEVELOPING INTO A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS IS LOW. DISORGANIZED SHOWERS AND THUNDERSTORMS ARE
ABOUT 700 NM TO THE EAST-SOUTHEAST OF THE REMNANT OF FRED...
COVERING THE AREA FROM 18N TO 20N BETWEEN 50W AND 54W. OTHER
POSSIBLE SHOWERS ARE ELSEWHERE FROM 18N TO 28N BETWEEN 50W AND
70W. AN UPPER LEVEL TROUGH PASSES OVER THE MADEIRA ARCHIPELAGO
TO 26N26W TO 16N40W. A 1010 MB LOW PRESSURE CENTER IS NEAR
13N38W. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS COVER THE AREA
FROM 12N TO 14N BETWEEN 35W AND 38W. THE CHANCE OF THE 13N38W MB
LOW PRESSURE CENTER DEVELOPING INTO A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS IS LOW.

$$
MT



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