[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 040545
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI SEP 04 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 SATELLITE IMAGERY THROUGH
0345 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION ERIKA WAS DOWNGRADED TO A REMNANT LOW AT
04/0300 UTC AND CENTERED NEAR 16.8N 65.6W OR ABOUT 100 NM SSE OF
SAN JUAN PUERTO RICO AND ABOUT 190 NM SE OF PUNTA CANA IN THE
DOMINICAN REPUBLIC MOVING W AT 6 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1009 MB. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH
GUSTS TO 35 KT. THIS IS THE LAST NHC PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC AND THE LAST
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
TO ISSUED BY THE NATIONAL HURRICANE CENTER. ERIKA REMAINS
POORLY-DEFINED WITH CLUSTERS OF SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS COVERS THE AREA 15N-18N BETWEEN 60W-65W INCLUDING
THE LEEWARD AND VIRGIN ISLANDS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 19W/20W S OF 18N WITH A 1009 MB LOW ALONG
THE WAVE NEAR 11N MOVING W NEAR 10-15 KT. WAVE REMAINS EMBEDDED
WITHIN A BROAD AREA OF DEEP LAYERED MOISTURE AS INDICATED BY THE
TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY SHOWERS A
BROAD LOW/MID LEVEL CYCLONIC ROTATION WITH CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ROTATING AROUND THE LOW
LEVEL CENTER FROM 8N-16N BETWEEN 20W-26W.

TROPICAL WAVE IS ALONG 33W S OF 19N WITH A 1012 MB LOW ALONG THE
WAVE NEAR 24N MOVING W NEAR 10 KT. THE WAVE COINCIDES WITH A
DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY. HOWEVER...SATELLITE IMAGERY AND THE TPW IMAGERY
INDICATE DRY SAHARAN AIR LAYER HAS BEING INJECTED INTO THE WAVE
JUST S OF THE LOW LEVEL CENTER. SMALL CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 60 NM OF LINE
FROM 16N33W TO 13N38W.

TROPICAL WAVE IS ALONG 50W/51W S OF 16N MOVING W 15 KT. WAVE
REMAINS LOW-AMPLITUDE AND EMBEDDED WITHIN THE ITCZ AT THE
LEADING EDGE OF A MOISTURE MAXIMUM AS INDICATED BY TOTAL
PRECIPITABLE WATER IMAGERY. WAVE IS ALSO EMBEDDED WITHIN SAHARAN
DUST THUS LIMITING ANY SHOWERS/CONVECTION.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N16W 11N22W 13N34W 9N44W
9N62W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
ARE WITHIN 200/225 NM S OF THE ITCZ FROM 40W-52W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH THAT COVERS THE E HALF OF THE U.S. EXTENDS S
COVERING THE ENTIRE GULF TO ACROSS THE YUCATAN PENINSULA AND S
MEXICO. A REMNANT SURFACE TROUGH EXTENDS ACROSS THE FLORIDA
PENINSULA ENTERING THE GULF NEAR TAMPA TO A WEAKENING 1011 MB
LOW NEAR 27N84W THEN S TO THE YUCATAN CHANNEL NEAR 21N86W.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE OVER THE SE GULF S
OF 26N E OF THE SURFACE TROUGH INTO THE STRAITS OF FLORIDA AND
OVER S FLORIDA. EVEN THOUGH THERE IS DRY AIR IN THE UPPER LEVELS
THERE IS ENOUGH SURFACE MOISTURE TO GENERATE ISOLATED SHOWERS
MAINLY OVER THE NE GULF N OF 26N E OF 90W.

CARIBBEAN SEA...
ERIKA IS NOW ONLY A REMNANT LOW OVER THE NE CARIBBEAN BUT
CONTINUES TO GENERATE RAINFALL FOR THE LESSER ANTILLES...SEE
SPECIAL FEATURES ABOVE. THE UPPER TROUGH OVER THE GULF OF MEXICO
COVERS THE NW CARIBBEAN N OF 15N W OF 80W WITH THE SURFACE
TROUGH EXTENDING THROUGH THE YUCATAN CHANNEL TO 21N86W AND
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 19N W
OF 80W TO ACROSS CUBA AND OVER NE YUCATAN PENINSULA. AN UPPER
RIDGE COVERS THE REMAINDER OF THE CARIBBEAN ANCHORED OVER THE SE
NEAR 13N66W DRAWING TROPICAL MOISTURE OVER THE SW CARIBBEAN AND
GENERATING SCATTERED SHOWERS/THUNDERSTORMS S OF A LINE FROM
COLOMBIA NEAR 11N73W TO NEAR 13N83W INCLUDING ALL OF PANAMA.

ATLANTIC OCEAN...
A SURFACE TROUGH ENTERS THE REGION NEAR 32N77W EXTENDING SW TO A
1012 MB LOW OFF THE COAST OF DAYTONA BEACH FLORIDA CONTINUING
ACROSS THE FLORIDA PENINSULA INTO THE GULF OF MEXICO. BROAD
UPPER RIDGE REMAINS ANCHORED OVER THE W ATLC NEAR 30N72W
PROVIDING DIFFLUENCE ALOFT TO GENERATE CLUSTERS OF SCATTERED
SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN S OF 30N W
OF 77W AND N OF 30N W OF 74W INCLUDING THE N BAHAMA ISLANDS. THE
BROAD UPPER TROUGH OVER THE E ATLC AND THE UPPER RIDGE OVER THE
E CARIBBEAN COMBINE TO PRODUCE AN AREA OF DIFFLUENCE ALOFT TO
GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS IN THE CENTRAL
ATLC WITHIN 90 NM OF LINE FROM 28N57W TO 22N49W. OTHERWISE...THE
REMAINDER OF THE ATLC IS DOMINATED BY A BROAD SURFACE RIDGE
BETWEEN 20W-70W ANCHORED BY A 1028 MB HIGH WELL N OF THE REGION
S OF THE AZORES AND A 1025 MB HIGH OVER THE CENTRAL ATLC NEAR
33N44W.

$$
WALLACE





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