[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 230535
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE SEP 23 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 ANALYZED AS A 1008 MB LOW ALONG THE
N COAST OF THE DOMINICAN REPUBLIC NEAR 19N69W CONTINUES TO BRING
HEAVY RAINS TO PUERTO RICO...THE DOMINICAN REPUBLIC...THE VIRGIN
ISLANDS AND ADJACENT WATERS. SCATTERED STRONG CONVECTION IS FROM
16N-19N BETWEEN 68W-71W WITH CLUSTERS OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION ARE OVER THE AREA FROM 14N-21N
BETWEEN 61W-71W. HEAVY RAINFALL WITH LIFE-THREATENING FLASH
FLOODS AND MUDSLIDES ARE EXPECTED TO CONTINUE IMPACTING THE AREA
FROM THE VIRGIN ISLANDS THROUGH HISPANIOLA FOR TONIGHT INTO TUE.
THE ASSOCIATED SHOWERS AND THUNDERSTORMS REMAIN POORLY ORGANIZED
AT THIS TIME DUE TO UPPER-LEVEL WESTERLY WINDS WITH LITTLE
CHANGE IN ORGANIZATION. THIS SYSTEM HAS THE POTENTIAL TO BECOME
A TROPICAL DEPRESSION AT ANY TIME DURING THE NEXT DAY OR TWO AS
IT MOVES NORTHWESTWARD AWAY FROM HISPANIOLA.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 32W S OF 18N MOVING W 10-15 KT. WAVE
REMAINS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS
INDICATED BY MIMIC TPW ANIMATION. WAVE IS VERY BROAD COVERING
THE AREA BETWEEN 25W-37W. ANY CONVECTION IS ASSOCIATED WITH THE
ITCZ.

TROPICAL WAVE IS ALONG 48W S OF 15N MOVING W 10-15 KT. WAVE IS
LOW AMPLITUDE AND MOSTLY EMBEDDED WITHIN THE ITCZ. CLUSTERS OF
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE WITHIN 150
NM EITHER SIDE OF THE WAVE AXIS.

TROPICAL WAVE IS ALONG 70W S OF 17N MOVING W 10-15 KT. THIS WAVE
HAS BECOME DIFFICULT TO LOCATE DUE TO THE CLOSE PROXIMITY OF THE
LOW PRESSURE SYSTEM DESCRIBED IN THE SPECIAL FEATURES SECTION.
NO ASSOCIATED SHOWERS/CONVECTION.

TROPICAL WAVE IS ALONG 83W S OF 16N MOVING W 15-20 KT. WELL
DEFINED INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY.
NO ASSOCIATED SHOWERS/CONVECTION IS NOTED.

TROPICAL WAVE IS ALONG 93W S OF 17N MOVING W NEAR 10-15 KT. THIS
WAVE IS INLAND OVER S MEXICO AND INTO THE E PACIFIC REGION...NO
LONGER IMPACTING THE ATLC BASIN.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N12W 12N30W 9N39W 12N62W. SCATTERED
MODERATE/STRONG CONVECTION IS WITHIN 60/75 NM OF LINE FROM 4N38W
TO 8N39W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN A 60/75 NM RADIUS OF 3.5N29.5W WITH CLUSTERS OF SIMILAR
CONVECTION FROM 12N-16N BETWEEN 25W-38W AND FROM 5N-12N BETWEEN
33W-43W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH THAT COVERS THE E US EXTENDS S TO OVER THE NE
GULF E OF THE MISSISSIPPI VALLEY BRINGING DRY STABLE AIR TO THE
GULF WATERS N OF 29N E OF 90W TO OVER THE N FLORIDA PENINSULA. A
BROAD UPPER RIDGE COVERS THE REMAINDER OF THE GULF ANCHORED OVER
CENTRAL MEXICO WITH THE AXIS EXTENDING E TO OVER S FLORIDA. A
SURFACE TROUGH IS BENEATH THIS UPPER RIDGE EXTENDING FROM OFF
THE COAST OF BROWNSVILLE TEXAS TO THE BAY OF CAMPECHE NEAR
19N94W. UPPER DIFFLUENCE IS GENERATING SCATTERED SHOWERS/
THUNDERSTORMS OVER THE W GULF S OF 28N W OF 90W AND OVER THE E
GULF FROM 24N-28N E OF 90W ACROSS S FLORIDA.

CARIBBEAN SEA...
THE MAIN CONCERN FOR THE NEXT FEW DAYS CONTINUES TO BE THE AREA
OF LOW PRESSURE DESCRIBED IN THE SPECIAL FEATURES SECTION. THE
UPPER RIDGE FROM THE GULF OF MEXICO COVERS THE NW CARIBBEAN W OF
83W PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS S OF 20N W OF 83W TO INLAND OVER
THE YUCATAN PENINSULA AND CENTRAL AMERICA. AN UPPER TROUGH FROM
THE W ATLC EXTENDS OVER CUBA TO THE CAYMAN ISLANDS AND JAMAICA
PUSHING AFTERNOON THUNDERSTORMS THAT DEVELOPED OVER CUBA INTO
THE CARIBBEAN WATERS BUT ARE NOW BEGINNING TO DISSIPATE. THE
UPPER RIDGE ASSOCIATED WITH THE LOW PRESSURE SYSTEM IN THE
SPECIAL FEATURES COVER THE E CARIBBEAN FROM THE ABC ISLANDS AND
THE COAST OF VENEZUELA ACROSS THE DOMINICAN REPUBLIC TO THE
LEEWARD ISLANDS ENHANCING THE ACTIVITY ASSOCIATED THERE. BETWEEN
THE UPPER RIDGES...THE CENTRAL CARIBBEAN REMAINS CLEAR TONIGHT.

ATLANTIC OCEAN...
A NARROW UPPER RIDGE EXTENDS FROM THE N BAHAMA ISLANDS NEAR
26N78W TO BEYOND 32N73W PROVIDING UPPER LEVEL DIFFLUENCE TO
GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS W OF THE UPPER
RIDGE AXIS TO THE COAST OF GEORGIA AND SOUTH CAROLINA AND INLAND
OVER PORTIONS OF FLORIDA. A WEAKENING SURFACE TROUGH EXTENDS
ALONG THIS BOUNDARY. AN UPPER TROUGH IS TO THE E EXTENDING FROM
AN UPPER LOW NEAR 29N66W TO ACROSS CUBA AND INTO THE N
CARIBBEAN. DRY STABLE AIR COVERS THE SAME AREA LEAVING THE
REMAINDER OF THE W ATLC CLEAR TONIGHT. THE UPPER RIDGE
ASSOCIATED WITH THE LOW PRESSURE SYSTEM IN THE SPECIAL FEATURES
EXTENDS FROM 24N59W SW INTO THE CARIBBEAN COVERING THE AREA
BETWEEN THE THE DOMINICAN REPUBLIC TO THE LEEWARD ISLANDS
ENHANCING THE ACTIVITY ASSOCIATED THERE. A CUT-OFF UPPER LOW IS
IN THE CENTRAL ATLC NEAR 23N47W GENERATING ISOLATED SHOWERS FROM
22N-27N BETWEEN 47W-52W. A DEEP LAYERED LOW IS IN THE E ATLC N
OF 25N BETWEEN 20W-35W WITH THE UPPER LOW N OF THE REGION AND
THE SURFACE LOW NEAR 32N28W AND A SURFACE TROUGH EXTENDING SW TO
27N36W...GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS N OF 28N BETWEEN 21W-29W. THE TYPICAL E/W UPPER
RIDGE THAT EXTENDS FROM AFRICA TO 40W ALONG 15N HAS BEEN
SUPPRESSED TO THE S DUE TO THE UPPER TROUGH MENTIONED ABOVE. THE
SURFACE RIDGE THAT HAS BEEN IN CONTROL OF THE ATLC HAS FURTHER
WEAKENED WITH A 1023 MB HIGH E OF BERMUDA NEAR 33N58W AND A 1020
MB HIGH IN THE E ATLC NEAR 25N26W.

$$
WALLACE


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