[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 051053
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 05 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
0945 UTC.

...SPECIAL FEATURES...

TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 29W S OF 20N
MOVING W AT 20 KT. A 1011 MB LOW IS EMBEDDED ON THE WAVE AXIS
NEAR 15N28W. SATELLITE IMAGERY AND SATELLITE DERIVED WINDS
INDICATE LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE
AXIS CONCENTRATED AROUND THE LOW PRESSURE CENTER NEAR 15N. THE
WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED MODERATE
CONVECTION IS FROM 7N-9N BETWEEN 30W-33W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 14N-20N BETWEEN
28W-31W. THIS SYSTEM HAS A MEDIUM CHANCE...30 TO 50 PERCENT...OF
BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HRS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 39W S OF 20N MOVING W NEAR 13 KT. A 1012
MB LOW IS ALONG THE WAVE AXIS NEAR 14N39W. SATELLITE IMAGERY AND
SATELLITE DERIVED WINDS INDICATE LOW-LEVEL CYCLONIC FLOW IN THE
VICINITY OF THE WAVE AXIS CONCENTRATED AROUND THE LOW PRESSURE
CENTER NEAR 14N. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE
MAXIMUM OBSERVED TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE
IMAGERY ALSO SHOWS SAHARAN DUST TO THE W OF THE WAVE AXIS WHICH
IS LIMITING DEEP CONVECTION TO A SMALL AREA. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 15N-17N BETWEEN
39W-40W.

TROPICAL WAVE IS ALONG 57W S OF 17N MOVING W NEAR 13 KT. THE
WAVE REMAINS RELATIVELY LOW-AMPLITUDE WITH NO ASSOCIATED
DEEP CONVECTION DUE TO DRY SAHARAN DUST TO THE E OF THE WAVE
AXIS. THE WAVE COINCIDES WITH A NARROW DEEP LAYER MOISTURE
MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 17N16W 15N27W 13N34W 10N43W
8N50W 8N62W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FROM 13N-16N BETWEEN 16W-18W. ISOLATED MODERATE CONVECTION IS
FROM 5N-9N BETWEEN 45W-53W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH EXTENDS ACROSS CENTRAL FLORIDA FROM NEAR 28N81W
TO THE CENTRAL GULF NEAR 25N87W CONTINUING ALONG 28N91W 28N97W.
THE TROUGH IS SUPPORTED BY AN UPPER LEVEL SHORTWAVE TROUGH THAT
EXTENDS FROM THE W FLORIDA PANHANDLE NEAR 31N85W TO ERN CUBA
NEAR 22N84W CONTINUING TO THE NW CARIBBEAN. UPPER LEVEL
DIFFLUENCE BETWEEN THIS UPPER TROUGH AND A LARGE UPPER LEVEL
RIDGE IN THE NW ATLC CENTERED NEAR 34N57W...ALONG WITH LOW-LEVEL
CONVERGENCE NEAR THE SURFACE TROUGH ARE SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN CHANNEL TO CENTRAL
FLORIDA FROM 22N-28N E OF 85W. ISOLATED SHOWERS/THUNDERSTORMS
ARE ALSO IN THE NW GULF N OF 27N W OF 87W. THIS ACTIVITY IS
ENHANCED BY LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH ALONG
WITH UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE THAT
COVERS THE WRN GULF W OF 90W AND A LARGE UPPER LEVEL TROUGH OVER
THE ERN CONUS. EXPECT SHOWERS/THUNDERSTORMS TO PERSIST NEAR THE
SURFACE TROUGH AS IT DRIFTS N THROUGH TUE AND DISSIPATES.

CARIBBEAN SEA...
ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS THE FAR NW CARIBBEAN N
OF 20N BETWEEN 81W-86W IN ASSOCIATION WITH UPPER LEVEL DIFFLUENT
FLOW BETWEEN AN UPPER LEVEL TROUGH OVER THE CENTRAL GULF
EXTENDING TO THE NW CARIBBEAN TO NEAR 19N84W AND A LARGE UPPER
LEVEL RIDGE OVER THE NW ATLC CENTERED NEAR 34N57W. SCATTERED
SHOWERS/THUNDERSTORMS ARE OFF THE COAST OF NICARAGUA AND
HONDURAS FROM 15N-17N BETWEEN 79W-84W. ISOLATED SHOWERS ARE S OF
THIS AREA S OF 15N BETWEEN 72W-84W OFF THE COASTS OF COSTA
RICA...PANAMA...AND NRN COLOMBIA. THESE SHOWERS/THUNDERSTORMS
ARE ALL ASSOCIATED WITH MOIST SWLY FLOW ALOFT ALONG WITH UPPER
LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE NW
CARIBBEAN AND AN UPPER LEVEL HIGH DOMINATING THE REMAINDER OF
THE CARIBBEAN CENTERED NEAR 13N72W. SCATTERED
SHOWERS/THUNDERSTORMS ARE ACROSS HISPANIOLA AND PUERTO RICO FROM
17N-19N BETWEEN 64W-72W DUE TO SURFACE CONVERGENCE NEAR A
SURFACE TROUGH...REMNANTS OF ERIKA...THAT EXTENDS FROM 15N70W
TO 22N68W. MODERATE TRADEWINDS ARE ACROSS MUCH OF THE BASIN.
OVER THE NEXT 24 HR...EXPECT THE SURFACE TROUGH TO DRIFT NWD OUT
OF THE AREA AND A TROPICAL WAVE ALONG 57W WILL REACH THE LESSER
ANTILLES LATER TODAY AND CONTINUE TO TRACK ACROSS THE ERN
CARIBBEAN.

ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS ACROSS CENTRAL FLORIDA FROM 28N81W
CONTINUING TO 32N75W AND OUT OF THE DISCUSSION AREA. ISOLATED
SHOWERS/THUNDERSTORMS ARE WITHIN 100 NM EITHER SIDE OF THE
TROUGH AXIS. THE SHOWERS/THUNDERSTORMS ARE ALSO ENHANCED BY
UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL TROUGH OVER
THE CENTRAL GULF AND A LARGE UPPER LEVEL RIDGE OVER THE NW ATLC
CENTERED NEAR 34N57W. A SMALL UPPER LEVEL LOW CENTERED NEAR
26N64W INTRUDES INTO THE SRN EXTENT OF THE UPPER RIDGE. THIS
UPPER LEVEL LOW SUPPORTS A SURFACE TROUGH EXTENDING FROM 25N62W
TO 30N62W. ISOLATED SHOWERS ARE WITHIN 100 NM EITHER SIDE OF THE
TROUGH AXIS. ANOTHER SURFACE TROUGH...REMNANTS OF
ERIKA...EXTENDS FROM THE DOMINICAN REPUBLIC NEAR 19N69W TO
21N65W. ISOLATED SHOWERS ASSOCIATED WITH THE TROUGH ARE FROM
18N-20N BETWEEN 62W-68W. ELSEWHERE ACROSS THE ATLC...A BROAD
SURFACE RIDGE DOMINATES ANCHORED BY A 1023 MB HIGH NEAR 31N51W.
IN THE UPPER LEVELS...AN UPPER LEVEL HIGH IS CENTERED E OF THE
LESSER ANTILLES NEAR 17N54W. AN UPPER LEVEL TROUGH EXTENDS FROM
AN UPPER LEVEL LOW NEAR 32N35W TO 20N48W. AN UPPER LEVEL RIDGE
DOMINATES THE ERN ATLC CENTERED ALONG THE COAST OF AFRICA NEAR
17N14W.

$$
WALTON





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