[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 220557
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON SEP 22 2008

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 SATELLITE IMAGERY THROUGH
0315 UTC.

...SPECIAL FEATURES...
A BROAD AREA OF LOW PRESSURE COVERS THE AREA WITH A 1008 MB LOW
ANALYZED OVER THE MONA PASSAGE AS THE TROPICAL WAVE CONTINUES TO
TRACK WESTWARD. THIS SYSTEM DOES NOT HAVE A WELL DEFINED CENTER
WITH MULTIPLE ROTATIONS OBSERVED ON PUERTO RICO RADAR EMBEDDED
WITHIN AN AREA OF HEAVY SHOWERS AND BANDS OF THUNDERSTORMS
WITHIN 90 NM OF LINE FROM 16N68W TO 20N63W INCLUDING PUERTO RICO
AND THE VIRGIN ISLANDS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE FROM 14N-21N BETWEEN 57W-64W ENHANCED BY UPPER LEVEL
DIFFLUENCE AND INCLUDES THE LEEWARD ISLANDS. UPPER-LEVEL WINDS
ARE GRADUALLY BECOMING MORE FAVORABLE FOR DEVELOPMENT AND THE
SYSTEM COULD BECOME A TROPICAL DEPRESSION AT ANY TIME AS IT
MOVES SLOWLY NORTH OR NORTH-NORTHWESTWARD DURING THE NEXT COUPLE
OF DAYS.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 26W/27W OF 18N MOVING W NEAR 10 KT. WAVE
IS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS
INDICATED BY MIMIC TPW ANIMATION BUT LACKS ANY WELL DEFINED
ROTATION IN EITHER THE LOW OR MID LEVELS. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 11N-15N BETWEEN
24W-29W.

TROPICAL WAVE IS ALONG 41W/42W FROM 10N-20N MOVING W NEAR 10 KT.
THIS WAVE REMAINS WEAK AND ILL-DEFINED. WAVE IS EMBEDDED WITHIN
DRY STABLE AIR...THUS NO ASSOCIATED SHOWERS/CONVECTION.

TROPICAL WAVE IS ALONG 61W/62W S OF 21N MOVING W 10-15 KT. THIS
WAVE IS MOVING INTO THE AREA OF THE BROAD LOW PRESSURE DESCRIBED
IN THE SPECIAL FEATURES WITH ANY SHOWERS/THUNDERSTORMS ENHANCED
BY THE UPPER LEVEL FEATURES.

TROPICAL WAVE IS ALONG 70W S OF 18N MOVING NEAR 10 KT. THIS WAVE
WAS PREVIOUSLY ASSOCIATED WITH THE LOW PRESSURE AREA DESCRIBED
IN THE SPECIAL FEATURES. WAVE SIGNATURE IS MASKED ON SATELLITE
IMAGERY DUE TO HIGH CLOUDS.

TROPICAL WAVE IS ALONG 88W S OF 21N MOVING W NEAR 10 KT. THE
TYPICAL INVERTED-V CURVATURE ASSOCIATED WITH THIS WAVE IS MAINLY
IN THE E PACIFIC REGION WITH ANY SHOWER ACTIVITY INLAND OVER
CENTRAL AMERICA AND IN THE E PACIFIC REGION.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 11N13W 11N22W 7N41W 7N53W 8N60W.
SCATTERED MODERATE WITH EMBEDDED CLUSTERS OF STRONG CONVECTION
ARE FROM 2N-5N BETWEEN 38W-41W AND FROM 5N-9N BETWEEN 43W-48W.
CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION FROM 2N-8N
BETWEEN 31W-43W AND FROM 5N-9N BETWEEN 48W-51W. SMALL CLUSTERS
OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 9N-12N
BETWEEN 35W-39W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH OVER THE E US EXTENDS INTO THE NW GULF
ALONG THE MISSISSIPPI VALLEY ACROSS LOUISIANA TO THE TEXAS COAST
BRINGING DRY STABLE AIR TO THE NW GULF ALONG THE LOUISIANA AND
TEXAS COASTLINES. AN UPPER RIDGE ANCHORED OVER S/CENTRAL MEXICO
EXTENDING ACROSS THE GULF NEAR BETWEEN TUXPAN AND VERACRUZ TO S
FLORIDA BETWEEN NAPLES AND THE FLORIDA KEYS. A SURFACE TROUGH
REMAINS OVER THE W GULF EXTENDING FROM 27N92W THROUGH THE BAY OF
CAMPECHE TO S MEXICO NEAR 17N91W. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE S OF 26N W OF 93W...S OF 22N W OF 87W...AND IN
THE NE GULF N OF 25N E OF 86W TO OVER FLORIDA...ALL ENHANCED BY
UPPER LEVEL DIFFLUENCE.

CARIBBEAN SEA...
THE MAIN CONCERN FOR THE NEXT FEW DAYS IS THE AREA OF LOW
PRESSURE DESCRIBED IN THE SPECIAL FEATURES ABOVE. AN UPPER
TROUGH EXTENDS FROM CENTRAL CUBA SW TO CENTRAL HONDURAS BOUNDED
BY THE UPPER RIDGE OVER THE GULF OF MEXICO AND AN UPPER RIDGE
ANCHORED IN THE CENTRAL CARIBBEAN NEAR 15N74W. AFTERNOON
THUNDERSTORMS THAT DEVELOPED ACROSS CUBA ARE NOW WITHIN 60 NM
ALONG THE S COAST BETWEEN 77W-84W. AN UPPER HIGH ASSOCIATED WITH
THE AREA IN THE SPECIAL FEATURES IS LOCATED OVER THE VIRGIN
ISLANDS AND IS ELONGATED FROM THE CENTRAL ATLC NEAR 24N58W SW TO
13N67W ENHANCING THE ACTIVITY IN THE SPECIAL FEATURES. OTHERWISE
THE REMAINDER OF THE CARIBBEAN REMAINS RATHER CALM TONIGHT WITH
THE EXCEPTION OF POSSIBLE ISOLATED SHOWERS FROM 12N-18N BETWEEN
80W-84W.

ATLANTIC OCEAN...
AN UPPER TROUGH EXTENDS ACROSS THE W ATLC FROM 28N74W INTO THE
CARIBBEAN ACROSS CENTRAL CUBA BOUNDED TO THE W BY THE UPPER
RIDGE THAT COVERS THE GULF OF MEXICO. A SURFACE TROUGH ENTERS
THE W ATLC THROUGH 32N76W SW TO OVER FLORIDA FROM MELBOURNE TO
TAMPA GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS NW OF
THE TROUGH TO INLAND OVER THE SE US AND WITHIN 75 NM SE OF THE
TROUGH N OF 30N. AN UPPER RIDGE IS IN THE CENTRAL ATLC ANCHORED
N OF THE REGION COVERING THE AREA N OF 27N FROM 50W-65W
PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS FROM 27N-31N BETWEEN 60W-65W. A
RATHER BENIGN UPPER LOW IS ALSO IN THE CENTRAL ATLC NEAR 24N48W
AND IS EMBEDDED IN DRY STABLE AIR. THE TYPICAL E/W UPPER RIDGE
COVERS THE E ATLC ALONG 15W/16W EXTENDING FROM AFRICA TO NEAR
37W GIVING THE E SUBTROPICAL ATLC NEAR ZONAL WESTERLY FLOW. THE
SURFACE OF THE ATLC IS DOMINATED BY A RIDGE E OF 70W ANCHORED BY
A 1026 MB HIGH NEAR 33N52W.

$$
WALLACE




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