[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE OCT 21 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.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 21W/22W S OF 15N MOVING W NEAR 5-10 KT.
AN ELONGATED CYCLONIC CIRCULATION IS OBSERVED ON SATELLITE
IMAGERY WITH A WEAKLY SHEARED INVERTED-V CLOUD SIGNATURE. AN
AREA OF SCATTERED MODERATE CONVECTION IS FROM 11N-15N BETWEEN
17W-21W.

A TROPICAL WAVE IS ALONG 49W S OF 20N MOVING W NEAR 10-15 KT.
THE SSMI-TPW PRODUCT FROM CIMSS INDICATES A NORTHWARD SURGE OF
MOISTURE ALONG THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 18N-21N BETWEEN 43W-46W AND FROM 20N-23N
BETWEEN 48W-51W. THIS ACTIVITY IS BEING DRAWN NORTHWARD BY A
SHARP UPPER-LEVEL TROUGH AXIS ALONG 51W.

A TROPICAL WAVE IS ALONG 74W S OF 15N MOVING W NEAR 10 KT. THE
WAVE IS LOCATED WITHIN STRONG EASTERLY SURFACE FLOW ACROSS THE
CARIBBEAN. NO SHOWERS OR DEEP CONVECTION OBSERVED WITH THE WAVE.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N15W 10N20W 9N23W 7N34W 9N47W
9N51W 9N62W. IN ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL
WAVES...SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN
17W-21W AND FROM 5N-10N BETWEEN 40W-47W. SIMILAR CONVECTION IS
FROM 11N-13N BETWEEN 54W-61W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER-LEVEL HIGH CENTERED IN THE CENTRAL CARIBBEAN SEA
EXTENDS WEAK RIDGING ACROSS THE ENTIRE GULF. MODERATE TO STRONG
SUBSIDENCE/DRY AIR IS NOTED OVER THE GULF. AT THE SURFACE...A
1025 MB HIGH PRESSURE CENTERED OVER CENTRAL ALABAMA EXTENDS A
RIDGE ACROSS THE NRN GULF N OF 25N. A SECOND 1021 MB HIGH IS
CENTERED JUST SOUTH OF TAMPICO MEXICO NEAR 21N98W. WEAK LOW TO
MIDDLE LEVEL CYCLONIC FLOW IS ACROSS THE S/CENTRAL GULF AND
YUCATAN PENINSULA WHICH IS GENERATING POSSIBLE SHALLOW SHOWERS
FROM 21N-25N BETWEEN 89W-94W. EXPECT THE RIDGE ACROSS THE GULF
TO WEAKEN IN ADVANCE OF A WEAK FRONTAL BOUNDARY FORECAST TO MOVE
INTO THE FAR NW GULF WATERS BY LATE WED.

CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS ACROSS CENTRAL CUBA W-SW TO THE GULF OF
HONDURAS INTO A 1011 MB SURFACE LOW NEAR 16N87W. THIS LOW IS
PRODUCING DISORGANIZED SCATTERED SHOWERS AND TSTMS OVER A LARGE
PORTION OF THE WRN CARIBBEAN SEA W OF 77W. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 11N-14N BETWEEN 77W-82W IN
THE SW CARIBBEAN AND FROM 14N-21N BETWEEN 80W-87W IN THE NW
CARIBBEAN. SUPPORTING THIS CONVECTION IS UPPER-LEVEL DIFFLUENCE
ASSOCIATED WITH AN UPPER-LEVEL HIGH LOCATED SOUTH OF HISPANIOLA
NEAR 16N71W WHICH DOMINATES THE ENTIRE CARIBBEAN SEA. THE
PRESSURE GRADIENT BETWEEN THIS SURFACE LOW AND HIGH PRESSURE
OVER THE W ATLC AND GULF OF MEXICO IS PRODUCING MODERATE TO
STRONG ELY WINDS ACROSS THE ENTIRE CARIBBEAN BASIN. ELSEWHERE...
A FEW SCATTERED SHOWERS ARE NOTED ACROSS THE SRN WINDWARD
ISLANDS AND SE CARIBBEAN DUE PRIMARILY TO LOW-MID LEVEL MOISTURE
CONVERGENCE AND UPPER-LEVEL DIFFLUENCE.

ATLANTIC OCEAN...
A DEEP LAYERED TROUGH IS OVER THE W ATLC AND SUPPORTS A COLD
FRONT THAT ENTERS THE AREA NEAR 32N54W...TURNING STATIONARY NEAR
23N65W...AND EXTENDS ACROSS THE SRN BAHAMAS TO INLAND ACROSS
CENTRAL CUBA. A BAND OF MULTILAYERED CLOUDS WITH EMBEDDED
SHOWERS IS WITHIN 150 NM OF THE COLD FRONT N OF 24N. ELSEWHERE
ALONG THE FRONTAL BOUNDARY MULTILAYERED CLOUDS ARE OBSERVED WITH
POSSIBLE SCATTERED SHOWERS ACROSS THE BAHAMAS...STRAITS OF
FLORIDA AND WRN CUBA. SUBSIDENCE/DRY AIR AND A STABLE ATMOSPHERE
ARE IN PLACE ACROSS THE W ATLC N OF 26N AND W OF THE COLD FRONT.
IN THE E ATLC...A 1025 MB HIGH IS NEAR 32N38W AND EXTENDS A
SURFACE RIDGE OVER THE NE ATLC E OF 43W. A SHARP UPPER-LEVEL
TROUGH WITH AXIS ALONG 51W AND AN AMPLIFIED UPPER-LEVEL RIDGE
WITH AXIS ALONG 40W CONTINUES TO FUNNEL DEEP-LAYERED TROPICAL
MOISTURE NORTHWARD INTO THE CENTRAL ATLC. UPPER-LEVEL DIFFLUENCE
BETWEEN THIS LOW AND THE UPPER-LEVEL HIGH LOCATED OVER THE
CARIBBEAN SEA IS ENHANCING CONVECTION ALONG THE ITCZ EAST OF THE
WINDWARD ISLANDS TO 51W. ANOTHER UPPER-LEVEL TROUGH EXTENDS
BETWEEN THE CANARY AND CAPE VERDE ISLANDS E OF 28W.

$$
HUFFMAN




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