[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200524
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN SEP 20 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
0430 UTC.

...SPECIAL FEATURES...

A 1012 MB LOW IS CENTERED E OF THE WINDWARD ISLANDS NEAR 15N45W
MOVING TO THE WNW NEAR 9 KT. ISOLATED MODERATE CONVECTION IS
FROM 11N-20N BETWEEN 40W-43W...AND FROM 15N-17N BETWEEN 43W-48W.
WHILE THE SYSTEM REMAINS POORLY ORGANIZED...IT HAS A MEDIUM
CHANCE...30 TO 50 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HRS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 31W S OF 18N MOVING W NEAR 10 KT. THE
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN
TOTAL PRECIPITABLE WATER IMAGERY AS WELL AS A MAXIMUM IN 850 MB
RELATIVE VORTICITY SEEN IN THE CIMSS WAVETRAK MODEL GUIDANCE.
SCATTERED MODERATE CONVECTION IS FROM 16N-18N BETWEEN 29W-34W.

TROPICAL WAVE IS ALONG 96W S OF 20N MOVING W NEAR 12 KT. THE
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM IN THE E
PACIFIC BASIN WHERE MOST OF THE WAVE AXIS LIES. ISOLATED
MODERATE CONVECTION IS IN THE FAR SW GULF FROM 18N-21N BETWEEN
94W-96W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N12W 6N20W 11N29W 15N40W 11N53W
10N63W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
8N-12N BETWEEN 15W-18W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0300 UTC...A SURFACE TROUGH EXTENDS ACROSS THE FAR NW GULF
FROM SW LOUISIANA NEAR 30N93W TO 27N97W. NO SHOWERS ARE
CURRENTLY ASSOCIATED WITH THE TROUGH. ANOTHER SURFACE TROUGH
EXTENDS FROM THE SE GULF NEAR 26N83W TO THE YUCATAN PENINSULA
NEAR 20N89W. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM
EITHER SIDE OF THE TROUGH AXIS. THIS ACTIVITY IS ALSO ENHANCED
BY UPPER LEVEL DIFFLUENCE BETWEEN A SHORTWAVE UPPER LEVEL TROUGH
OVER THE CENTRAL GULF WITH AXIS ALONG 88W AND AN UPPER LEVEL
RIDGE OVER THE SE GULF CENTERED OVER THE STRAIGHTS OF FLORIDA
NEAR 24N81W. ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE
SW GULF S OF 23S W OF 89W IN ASSOCIATION WITH UPPER LEVEL
DIFFLUENCE BETWEEN THE SHORTWAVE UPPER TROUGH OVER THE CENTRAL
GULF AND ANOTHER UPPER LEVEL RIDGE OVER THE WRN GULF CENTERED
OVER MEXICO NEAR 20N103W. SOME OF THE SHOWERS MAY ALSO BE
ENHANCED BY SURFACE CONVERGENCE NEAR THE TROPICAL WAVE ALONG
96W. EXPECT THE TROUGH IN THE NW GULF TO LIFT N AND DISSIPATE AS
A SURFACE RIDGE BUILDS IN FROM THE E.

CARIBBEAN SEA...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE NW CARIBBEAN FROM
13N-23N BETWEEN 76W-83W WITH ISOLATED SHOWERS/THUNDERSTORMS W OF
83W TO THE YUCATAN PENINSULA. THE ACTIVITY IS ENHANCED BY UPPER
LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE OVER THE SE GULF
AND THE BAHAMAS CENTERED OVER THE STRAIGHTS OF FLORIDA NEAR
24N81W AND AN UPPER LEVEL INVERTED TROUGH OVER CENTRAL AMERICA.
THE REMAINDER OF THE CENTRAL AND E CARIBBEAN REMAINS FAIRLY CALM
UNDER THE INFLUENCE OF DRY AIR ALOFT. HOWEVER...A FEW ISOLATED
SHOWERS/THUNDERSTORMS ARE ACROSS WRN HISPANIOLA FROM 18N-19N
BETWEEN 71W-74W DUE TO UPPER LEVEL DIFFLUENT FLOW BETWEEN THE
UPPER LEVEL RIDGE OVER THE BAHAMAS AND AN UPPER LEVEL LOW N OF
THE WINDWARD ISLANDS NEAR 23N62W. FRESH TRADE WINDS ARE ACROSS
THE SRN CARIBBEAN WITH THE STRONGEST NEAR THE COAST OF COLOMBIA.
EXPECT SHOWERS/THUNDERSTORMS TO PERSIST OVER THE WRN CARIBBEAN
AS THE UPPER LEVEL TROUGH OVER THE SW CARIBBEAN SLOWLY MOVES W.

ATLANTIC OCEAN...
A FEW ISOLATED SHOWERS REMAIN ACROSS THE WRN ATLC N OF 27N W OF
73W DUE TO UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL
RIDGE OVER THE BAHAMAS CENTERED OVER THE STRAITS OF FLORIDA NEAR
24N81W AND AN UPPER LEVEL TROUGH ACROSS THE NW ATLC. A 1014 MB
SURFACE LOW IS NEAR 28N70W WITH A SURFACE TROUGH EXTENDING
THROUGH IT FROM 31N70W TO 24N70W. SURFACE CONVERGENCE NEAR THE
LOW AND TROUGH AXIS IS SUPPORTING ISOLATED SHOWERS FROM 25N-27N
BETWEEN 70W-72W...AND SCATTERED SHOWERS/THUNDERSTORMS FROM
29N-31N BETWEEN 67W-70W. SCATTERED SHOWERS/THUNDERSTORMS ARE
ALSO N OF THE WINDWARD ISLANDS FROM 18N-23N BETWEEN 61W-68W IN
ASSOCIATION WITH AN UPPER LEVEL LOW NEAR 23N62W. ELSEWHERE
ACROSS THE ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A
1026 MB HIGH NEAR 33N42W. IN THE UPPER LEVELS...AN UPPER LEVEL
RIDGE IS N OF 25N BETWEEN 35W-50W. AN UPPER LEVEL TROUGH
DOMINATES THE E ATLC WITH AXIS ALONG 33N24W TO 23N34W. A BROAD
UPPER LEVEL RIDGE COVERS THE TROPICAL ATLC ENHANCING CONVECTION
NEAR THE LOW CENTERED AT 15N45W.

$$
WALTON






This weather bulletin was brought to you by:
www.nashvilleweather.net