[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161742
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 16 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1700 UTC

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 15N77W TO 9N78W MOVING W NEAR 12 KT.
THIS WAVE REMAINS LOW AMPLITUDE AND COINCIDES WITH A BROAD AREA
OF DEEP LAYER MOISTURE OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY. ISOLATED MODERATE CONVECTION IS FROM 9N-12N BETWEEN
75W-80W.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N15W 10N26W 7N37W 10N50W
10N63W. SCATTERED STRONG CONVECTION IS FROM 14N-16N BETWEEN
17W-20W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
6N-11N BETWEEN 20W-23W...AND FROM 6N-10N BETWEEN 25W-30W.
SIMILAR CONVECTION IS ALSO FROM 10N-13N BETWEEN 56W-63W.

...DISCUSSION...

THE GULF OF MEXICO...
AS OF 1500 UTC...A DYING STATIONARY FRONT EXTENDS FROM LOUISIANA
NEAR 29N91W TO 26N94W. THE FRONT IS SUPPORTED BY AN UPPER LEVEL
TROUGH OVER THE NW GULF WITH AXIS ALONG 97W. SCATTERED
SHOWERS/THUNDERSTORMS ARE AHEAD OF THE FRONT FROM 24N-30N
BETWEEN 86W-92W. A SURFACE TROUGH IS IN THE FAR SW GULF FROM
22N92W TO 17N93W. SURFACE CONVERGENCE NEAR THE TROUGH IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS S OF 22N BETWEEN
92W-95W. BOTH AREAS OF SHOWER ACTIVITY ARE SUPPORTED BY UPPER
LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH IN THE NW GULF
AND AN UPPER LEVEL HIGH OVER THE YUCATAN CHANNEL NEAR 22N86W. A
FEW ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ALONG THE SW COAST
OF FLORIDA AND THE STRAITS OF FLORIDA FROM 23N-25N BETWEEN
81W-82W. EXPECT THE DYING FRONT TO DISSIPATE LATER TONIGHT AS A
NEW FRONT ENTERS THE NW GULF.

THE CARIBBEAN SEA...
THE NW CARIBBEAN REMAINS FAIRLY CALM UNDER THE INFLUENCE OF DRY
AIR AND SUBSIDENCE ALOFT ASSOCIATED WITH AN UPPER LEVEL HIGH
OVER THE YUCATAN CHANNEL NEAR 22N86W. HOWEVER...A FEW ISOLATED
SHOWERS ARE N OF 18N BETWEEN 75W-80W OVER PORTIONS OF CUBA. A
TROPICAL WAVE ALONG 77W/78W IS SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS IN THE SW CARIBBEAN FROM 9N-12N BETWEEN
75W-80W...SEE ABOVE. THIS ACTIVITY IS ALSO ENHANCED BY SURFACE
CONVERGENCE NEAR THE E PACIFIC ITCZ. AN UPPER LEVEL LOW NEAR
15N68W IS SUPPORTING A LARGE AREA OF DISTURBED WEATHER ACROSS
THE ERN CARIBBEAN. ISOLATED SHOWERS/THUNDERSTORMS ARE N OF 15N
BETWEEN 64W-71W AFFECTING THE LEEWARD ISLANDS...PUERTO
RICO...AND ERN HISPANIOLA. SCATTERED SHOWERS/THUNDERSTORMS ARE S
OF 15N E OF 14W AFFECTING THE WINDWARD ISLANDS. MODERATE TRADE
WINDS ARE ACROSS MUCH OF THE BASIN. EXPECT THE TROPICAL WAVE IN
THE WRN CARIBBEAN TO CONTINUE WWD.

THE ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS FROM A 1011 MB SURFACE LOW NEAR 32N71W
TO THE CENTRAL BAHAMAS NEAR 24N75W. SCATTERED
SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM AHEAD OF THE TROUGH. THE
SHOWERS ARE ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN A
BROAD UPPER LEVEL TROUGH OVER THE WRN ATLC AND AN UPPER LEVEL
RIDGE BETWEEN 60W-70W. THE UPPER LEVEL LOW OVER THE ERN
CARIBBEAN NEAR 15N68W IS SUPPORTING A FEW ISOLATED SHOWERS S OF
21N BETWEEN 62W-69W. A 1013 MB LOW...THE REMNANTS OF FRED...NEAR
20N51W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM
21N-25N BETWEEN 51W-55W. THE SURFACE LOW IS SUPPORTED BY AN
UPPER LEVEL LOW NEAR 19N52W. A SECOND 1013 MB SURFACE LOW IS
NEAR 14N32W SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS FROM
14N-17N BETWEEN 30W-37W. A FEW ISOLATED SHOWERS ARE ALSO FROM
27N-31N BETWEEN 26W-31W IN ASSOCIATION WITH ANOTHER UPPER LEVEL
LOW NEAR 29N28W. AN UPPER LEVEL RIDGE DOMINATES THE TROPICAL
ATLC S OF 21N ENHANCING CONVECTION ALONG THE ITCZ.

$$
WALTON





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