[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 30 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LAURA IS CENTERED NEAR 41.2N 48.8W AT 30/1500 UTC
OR ABOUT 375 NM SSE OF CAPE RACE NEWFOUNDLAND MOVING N AT 11 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 996 MB. MAXIMUM SUSTAINED
WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. PLEASE SEE THE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32
KNHC FOR MORE DETAILS. LAURA CONTINUES TO ACCELERATE AND A TURN
TO THE N-NE IS EXPECTED TONIGHT INTO WEDNESDAY. LAURA IS QUICKLY
BECOMING EMBEDDED WITHIN WEAK UPPER TROUGHING OVER THE NORTH
ATLANTIC AND IS EXPECTED TO SLOWLY WEAKEN AS IT MOVES INTO THE
WESTERLIES...AND BEGIN EXTRATROPICAL TRANSITION. CLUSTERS OF
SCATTERED MODERATE CONVECTION ARE FROM 42N-46N BETWEEN 42W-49W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 33W S OF 19N MOVING W NEAR 15 KT. WAVE IS
WELL DEFINED WITH INVERTED-V CURVATURE OBSERVED IN THE LOW LEVEL
CLOUD FIELD. SAHARAN DUST FOLLOWS TO THE EAST OF THE WAVE AXIS N
OF 15N. SCATTERED MODERATE CONVECTION IS FROM 12N-16N BETWEEN
32W-35W.

TROPICAL WAVE IS ALONG 45W/46W FROM 11N-20N MOVING W 5-10 KT.
LOW LEVEL CLOUDINESS EXHIBITS INVERTED-V SIGNATURE ON SATELLITE
IMAGERY WITH MID-LEVEL ENHANCEMENT DUE TO AN UPPER TROUGH
LOCATED WEST OF THE WAVE PROVIDING SWLY UPPER FLOW ALOFT.
POSSIBLE SCATTERED SHOWERS ARE NORTH OF 16N BETWEEN 42W-48W.

TROPICAL WAVE IS ALONG 60W S OF 16N MOVING W 10-15 KT. WAVE HAS
BECOME ILL-DEFINED AS IT NEARS THE LESSER ANTILLES AND POSITION
IS BASED ON EXTRAPOLATION. NO ASSOCIATED SHOWERS OR CONVECTION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 10N13W 7N20W 10N31W 9N35W 8N42W
8N57W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
9N-14N BETWEEN 18W-22W. SIMILAR CONVECTION IS FROM 6N-9N BETWEEN
31W-38W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH DOMINATES THE EASTERN US AND MOST OF THE GULF W
OF 84W WITH A PAIR OF SURFACE LOWS OVER THE SERN GULF. A SURFACE
TROUGH EXTENDING FROM THE W ATLC CROSSES SRN FLORIDA NEAR 26N81W
TO A 1012 MB LOW IN THE SE GULF WATERS NEAR 25N84W. THE SURFACE
TROUGH CONTINUES SW TO A 1012 MB LOW NORTH OF THE YUCATAN
PENINSULA NEAR 22N90W AND THEN S OVER THE WRN YUCATAN AND INTO
SRN MEXICO. A BROAD UPPER RIDGE ANCHORED IN THE W ATLC COVERS
THE REMAINDER OF THE GULF DRAWING MOIST UPPER FLOW N OVER THE
SE GULF PROVIDING UPPER LEVEL SUPPORT FOR SCATTERED SHOWERS AND
TSTMS FROM 22N-27N BETWEEN 81W-85W. THE GULF W OF 85W IS UNDER
STRONG SUBSIDENCE AND DRY UPPER AIR. HOWEVER...AMPLE LOW LEVEL
MOISTURE REMAINS IN THE BAY OF CAMPECHE TO GENERATE ISOLATED
SHOWERS FROM 17N-21N BETWEEN 90W-93W.

CARIBBEAN SEA...
A WEAK UPPER LOW IS IN THE NW CARIBBEAN SOUTH OF THE CAYMAN
ISLANDS NEAR 18N80W AND REMAINS EMBEDDED WITHIN THE STRONGER
UPPER RIDGE ANCHORED IN THE W ATLC THAT COVERS THE REMAINDER OF
THE CARIBBEAN. THE UPPER RIDGE IS BRINGING STRONG SUBSIDENCE AND
DRY STABLE AIR TO THE ERN CARIBBEAN E OF 75W LEAVING THE WRN
CARIBBEAN UNDER DEEP LAYERED MOISTURE AND CLUSTERS OF SCATTERED
SHOWERS AND TSTMS FROM 15N-21N W OF 75W USHERED IN ON MODERATE
TRADE WINDS OVER THE ENTIRE BASIN. THE ITCZ EXTENDS ACROSS THE
SW CARIBBEAN ALONG 10N AND ISOLATED SHOWERS ARE WITHIN 100 NM ON
EITHER SIDE OF THE AXIS.

ATLANTIC OCEAN...
TROPICAL STORM LAURA IS LOCATED N OF THE REGION...SEE SPECIAL
FEATURES ABOVE. A BROAD UPPER RIDGE COVERS THE W ATLC ANCHORED
NORTH OF PUERTO RICO NEAR 23N67W AND A RIDGE AXIS EXTENDS NORTH
TO 32N70W DRAWING UPPER LEVEL MOISTURE FROM THE WRN CARIBBEAN
ACROSS THE SE GULF OF MEXICO AND FLORIDA INTO THE W ATLC W OF
73W. A SURFACE TROUGH EXTENDS FROM 32N77W TO NEAR BOCA RATON
FLORIDA GENERATING SCATTERED SHOWERS AND TSTMS E OF LINE FROM
DAYTONA BEACH TO ST. PETERSBURG FLORIDA AND N OF 24N ACROSS THE
NW BAHAMAS. BENEATH THE UPPER RIDGE IS A 1017 MB SURFACE HIGH
NEAR 25N66W. UPPER TROUGHING ACROSS THE N/CENTRAL ATLC EXTENDS A
SURFACE TROUGH INTO THE DISCUSSION AREA NEAR 32N57W AND EXTENDS
SW TO NEAR 29N60W. SCATTERED SHOWERS AND POSSIBLE ISOLATED TSTMS
ARE FROM 26N-29N BETWEEN 55W-61W. AN UPPER TROUGH COVERS THE NE
ATLC N OF 25N E OF 19W. THE ERN AND CENTRAL TROPICAL ATLC IS
DOMINATED BY AN E/W UPPER RIDGE ANCHORED W OF THE CAPE VERDE
ISLANDS EXTENDING W TO NEAR 50W. AT THE SURFACE...A 1033 MB HIGH
IS LOCATED N OF THE AZORES AND EXTENDS A RIDGE SWD TO NEAR 22N.

$$
HUFFMAN




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