[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291749
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 29 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL STORM KAREN WAS DOWNGRADED TO TROPICAL DEPRESSION AT
29/1500 UTC AND IS CENTERED NEAR 16.8N 53.8W OR ABOUT 460 NM
EAST OF THE LEEWARD ISLANDS MOVING NW AT 8 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1009 MB. MAXIMUM SUSTAINED WIND SPEED IS 30
KT WITH GUSTS TO 40 KT. SEE LATEST NHC FORECAST ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY
UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. KAREN REMAINS
UNDER HEAVY UPPER LEVEL SHEAR WITH THE LOW LEVEL CENTER
COMPLETELY EXPOSED AND BECOMING ELONGATED. SCATTERED STRONG
CONVECTION IS TO THE E OF THE LOW LEVEL CENTER WITHIN 75 NM OF
LINE FROM 14N56W TO 18N50W. SCATTERED MODERATE CONVECTION IS
FROM 12N-21N BETWEEN 46W-50W.

TROPICAL STORM MELISSA IS CENTERED NEAR 15.2N 28.4W OR ABOUT 260
NM WEST OF THE CAPE VERDE ISLANDS AT 29/1500 UTC MOVING NW AT 7
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SEE LATEST
NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR
MORE DETAILS. MELISSA IS BECOMING EFFECTED BY MODERATE UPPER
LEVEL SHEAR ALTHOUGH THE CONVECTION IS BEGINNING TO REFORM.
SMALL CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
ARE WITHIN 120 NM OF THE CENTER WITH THE STRONGEST TO THE N.

...TROPICAL WAVES...

TROPICAL WAVE BETWEEN T.S. MELISSA AND T.D. KAREN IS ALONG
38W/39W S OF 18W MOVING W NEAR 15 KT. WEAK WAVE PATTERN WITH
ISOLATED SHOWERS FROM 10N-13N BETWEEN 34W-39W.

TROPICAL WAVE IN THE W CARIBBEAN IS ALONG 84W S OF 20N MOVING W
10-15 KT. WAVE IS MOSTLY OVER CENTRAL AMERICA HINDERING THE
SATELLITE SIGNATURE. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 120 NM ALONG THE COAST OF NICARAGUA AND
HONDURAS N OF 13N W OF 87W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N12W 8N24W 9N40W 10N63W. SCATTERED
MODERATE/STRONG CONVECTION IS WITHIN 120 NM N OF THE ITCZ AXIS
FROM 18W-20W. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION ARE WITHIN 120 NM OF 5N BETWEEN 7W-23W.

DISCUSSION...

GULF OF MEXICO...
DEEP LAYERED TROUGH COVERS THE FAR E US INTO THE W ATLC DIPPING
S OVER THE E GULF N OF 25N E OF 87W. THE ASSOCIATED COLD FRONT
DRAPES INTO THE W ATLC ACROSS CENTRAL FLORIDA INTO THE GULF JUST
N OF TAMPA W TO JUST OFF THE TEXAS COAST NEAR 28N94W. THE FRONT
IS DELINEATED BY A WIND INCREASE AND DRIER AIR WITH NO SHOWERS
OR CONVECTION ARE ALONG THE FRONT E OF 92W. AN UPPER HIGH IS
OVER THE BAY OF CAMPECHE WITH AN UPPER RIDGE EXTENDING TO THE N
GULF COAST NEAR THE LOUISIANA/TEXAS BORDER. UPPER LEVEL MOISTURE
AND SIGNIFICANT DIFFLUENCE IS GENERATING HEAVY RAIN WITH
EMBEDDED THUNDERSTORMS N OF 24N TO THE W END OF THE ABOVE COLD
FRONT W OF 93W TO JUST INLAND OVER TEXAS AND NE MEXICO. THE COLD
FRONT IS EXPECTED TO CONTINUE S TO OVER S FLORIDA WHILE THE
REMAINDER BECOMES NEAR STATIONARY.

CARIBBEAN SEA...
THE UPPER RIDGE OVER THE W GULF OF MEXICO IS GIVING THE FAR NW
CARIBBEAN UPPER NW FLOW AND DRIER AIR WHILE AN UPPER HIGH IN THE
CENTRAL CARIBBEAN IS ANCHORED NEAR 14N76W ADVECTING TROPICAL
MOISTURE OVER THE REMAINDER OF THE W CARIBBEAN AND CENTRAL
AMERICA. AN INDUCED INVERTED TROUGH EXTENDS BETWEEN FROM NE
HONDURAS TO E CUBA AND PRODUCING ENOUGH DIFFLUENCE TO ENHANCE
CONVECTION ASSOCIATED WITH THE TROPICAL WAVE AND GENERATE
CLUSTERS OF SCATTERED SHOWERS/THUNDERSTORMS WITHIN 75 NM OF LINE
FROM COLOMBIA NEAR 9N76W TO NICARAGUA NEAR 12N83W. BROAD UPPER
LOW CENTERED IN THE W/CENTRAL ATLC COVERS THE THE E CARIBBEAN
WITH UPPER WESTERLY FLOW PRODUCING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 90/120 NM OF LINE FROM OVER HISPANIOLA SE
ACROSS THE LESSER ANTILLES NEAR 13N61W TO NEAR 12N55W.

ATLANTIC OCEAN...
THE DEEP LAYERED TROUGH OVER THE FAR E US EXTENDS OVER THE W
ATLC N OF 25N W OF 76W ACROSS FLORIDA INTO THE GULF OF MEXICO.
THE ASSOCIATED COLD FRONT ENTERS THE REGION NEAR 32N72W
EXTENDING W ACROSS CENTRAL FLORIDA NEAR DAYTONA BEACH CONTINUING
INTO THE GULF OF MEXICO WITH NO SHOWERS OR CONVECTION ASSOCIATED
WITH THE FRONT W OF 75W. A SURFACE TROUGH EXTENDS FROM 30N75W
ACROSS THE N BAHAMAS TO NEAR 23N79W. THIS SURFACE TROUGH IS
ALONG THE BOUNDARY OF AN UPPER RIDGE THAT EXTENDS FROM THE
GREATER ANTILLES NEAR THE WINDWARD PASSAGE N TO BEYOND 32N68W
PRODUCING ENOUGH DIFFLUENCE TO GENERATE CLUSTERS OF SCATTERED
SHOWERS/THUNDERSTORMS E OF THE SURFACE TROUGH AND W OF A LINE
FROM THE WINDWARD PASSAGE ACROSS THE TURKS AND CAICOS TO BEYOND
BERMUDA. LARGE UPPER LOW IS IN THE W/CENTRAL ATLC NEAR 26N62W
PROVIDING STRONG WESTERLY UPPER LEVEL WINDS THAT IS SHEARING
T.D. KAREN AND GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 90 NM OF LINE FROM 21N66W TO 26N58W AND A
SMALL CLUSTER WITHIN 75 NM RADIUS OF 28N54.5W. A SURFACE RIDGE
EXTENDS FROM A 1028 MB HIGH JUST N OF THE REGION NEAR 35N50W TO
NW OF KAREN NEAR 26N60W. A SECOND LARGE UPPER LOW IS OVER THE
FAR NE ATLC WELL N OF THE REGION DIPPING OVER THE E ATLC N OF
27N E OF 40W WITH THE ASSOCIATED FRONTAL BOUNDARY N OF THE
REGION AS WELL. THE TYPICAL E/W UPPER RIDGE EXTENDS FROM OFF
AFRICA ACROSS THE TROPICAL ATLC WITH THE AXIS ALONG 12N
PROVIDING WESTERLY UPPER WINDS THAT IS SHEARING T.S. MELISSA. A
WEAK 1020 MB HIGH IS WSW OF THE CANARY ISLANDS NEAR 26N23W.

$$
WALLACE




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