[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231053
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED SEP 23 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1000 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 43W S OF 17N MOVING WNW NEAR 15 KT.
SATELLITE IMAGERY INDICATES A WELL DEFINED INVERTED-V STRUCTURE
IN THE LOW LEVEL CLOUD PATTERN. A LARGE AREA OF SAHARAN DUST IS
E OF THE AXIS MAINLY E OF 35W WHICH IS CURRENTLY CONFINING
CONVECTION TO THE ITCZ EXCEPT FOR A SMALL CLUSTER OF
MODERATE/STRONG CONVECTION NEAR 17N42W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N16W 7N28W 9N40W 11N50W 9N64W
11N64W. SCATTERED MODERATE/STRONG CONVECTION IS JUST OFF THE
COAST OF AFRICA FROM 11N-17N BETWEEN 17W-21W MOST LIKELY
ASSOCIATED WITH THE NEXT TROPICAL WAVE. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-8N BETWEEN
29W-39W...AND FROM 7N-10N BETWEEN 44W-51W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...A STATIONARY FRONT EXTENDS ACROSS THE NW GULF
FROM  LAKE CHARLES LOUISIANA NEAR 30N93W ALONG 27N96W TO THE SRN
TIP OF TEXAS NEAR 26N97W. A PRE-FRONTAL SURFACE TROUGH IS AHEAD
OF THE FRONT FROM 29N91W ALONG 27N93W TO 26N95W. SURFACE
CONVERGENCE NEAR THE FRONT/TROUGH IS SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS NW OF A LINE FROM 30N87W TO 24N98W.
SURFACE WINDS ARE UP TO 20 KT NW OF THE FRONT. A WEAK
SURFACE TROUGH EXTENDS THROUGH THE YUCATAN PENINSULA FROM 24N85W
TO 22N85W AND INTO THE NW CARIBBEAN. THE TROUGH IS SUPPORTING
ISOLATED SHOWERS/THUNDERSTORMS S OF 25N BETWEEN 85W-87W.
SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE SW GULF S OF
19N BETWEEN 93W-95W. IN THE UPPER LEVELS...AN ELONGATED UPPER
LEVEL RIDGE COVERS THE MAJORITY OF THE BASIN CENTERED OVER
MEXICO NEAR 21N100W WITH AXIS TO 31N87W. SHOWERS/THUNDERSTORMS
ASSOCIATED WITH THE FRONT IN THE NW GULF ARE ALSO ENHANCED BY
DIFFLUENT FLOW BETWEEN THE UPPER LEVEL RIDGE AND AN UPPER LEVEL
LOW OVER THE CENTRAL CONUS. EXPECT THE FRONT TO REMAIN
STATIONARY FOR THE NEXT COUPLE OF DAYS.

CARIBBEAN SEA...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE WRN CARIBBEAN
THIS MORNING N OF 17N W OF 75W. THE ACTIVITY IS ENHANCED BY
UPPER LEVEL DIFFLUENT FLOW BETWEEN THE UPPER RIDGE OVER THE GULF
OF MEXICO AND A BROAD UPPER LEVEL TROUGH COVERING THE CARIBBEAN
CENTERED WELL N OF THE BASIN NEAR 30N64W. A WEAK SURFACE TROUGH
EXTENDING FROM THE SE GULF TO THE NW CARIBBEAN FROM 22N85W TO
18N84W IS ALSO SUPPORTING THE SHOWER ACTIVITY.
SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE SW CARIBBEAN FROM
10N-13N BETWEEN 76W-84W DUE TO SURFACE CONVERGENCE NEAR A 1007
MB LOW OVER COLOMBIA NEAR 10N75W...AND THE CLOSE PROXIMITY OF
THE E PACIFIC ITCZ. THE REMAINDER OF THE CARIBBEAN REMAINS CALM
UNDER THE INFLUENCE OF DRY AIR ALOFT. FRESH TRADEWINDS ARE
ACROSS MUCH OF THE BASIN.

ATLANTIC OCEAN...
AS OF 0900 UTC...A SURFACE TROUGH LINES THE E COAST OF FLORIDA
FROM 31N80W TO 27N80W SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS
N OF 28N BETWEEN 79W-81W. ISOLATED SHOWERS/THUNDERSTORMS ARE S
OF 23N TO THE NRN CARIBBEAN BETWEEN 74W-81W DUE TO UPPER
DIFFLUENT FLOW BETWEEN THE UPPER LEVEL RIDGE ACROSS THE GULF AND
A BROAD UPPER LEVEL TROUGH CENTERED NEAR AN UPPER LOW AT 30N64W.
THE UPPER LEVEL LOW IS ALSO SUPPORTING A SURFACE TROUGH
EXTENDING FROM 30N56W TO 27N61W ENHANCING SCATTERED
SHOWERS/THUNDERSTORMS N OF 25N BETWEEN 55W-64W. A CLUSTER OF
SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO E OF THE UPPER TROUGH
AXIS FROM 17N-20N BETWEEN 55W-58W. ANOTHER SURFACE TROUGH
EXTENDS FROM 22N49W TO 14N50W. SURFACE CONVERGENCE NEAR THE
TROUGH IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM
20W-23W BETWEEN 42W-50W. THE REMAINDER OF THE ATLC IS RELATIVELY
CALM UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE. A BROAD UPPER
LEVEL RIDGE DOMINATES THE BASIN E OF 50W E OF THE AFOREMENTIONED
UPPER LEVEL TROUGH CENTERED NEAR 30N64W. UPPER DIFFLUENT FLOW
BETWEEN THESE UPPER LEVEL FEATURES IS ENHANCING CONVECTION NEAR
THE SURFACE TROUGH ALONG 49W/50W. A LARGE AREA OF SAHARAN DUST
IS ACROSS THE ERN ATLC MAINLY E OF 35W.

$$
WALTON





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