[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 050557
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...SPECIAL FEATURES...

TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 28W S OF 20N
MOVING W AT 20 KT. A 1012 MB LOW IS EMBEDDED ON THE WAVE AXIS
NEAR 14N28W. 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 ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE
CONVECTION IS FROM 7N-9N BETWEEN 29W-32W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 14N-18N BETWEEN
28W-30W. 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 38W S OF 20N MOVING W NEAR 13 KT. A 1012
MB LOW IS ALONG THE WAVE AXIS NEAR 13N38W. 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 13N. 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-16N BETWEEN
38W-40W.

TROPICAL WAVE IS ALONG 56W S OF 17N MOVING W NEAR 13 KT. THE
WAVE REMAINS RELATIVELY LOW-AMPLITUDE WITH LITTLE 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. WHILE NO
DEEP CONVECTION IS PRESENT...ISOLATED SHOWERS ARE FROM 11N-12N
BETWEEN 55W-56W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 19N19W 15N27W 12N33W 11N40W
8N50W 8N62W. A LARGE CLUSTER OF SCATTERED MODERATE/STRONG
CONVECTION IS APPROACHING THE AFRICAN COAST FROM 14N-18N BETWEEN
12W-16W. ISOLATED MODERATE CONVECTION IS FROM 6N-9N BETWEEN
43W-49W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0300 UTC...A SURFACE TROUGH EXTENDS ACROSS CENTRAL FLORIDA
FROM NEAR 28N81W TO THE CENTRAL GULF NEAR 26N89W. THE TROUGH IS
SUPPORTED BY AN UPPER LEVEL SHORTWAVE TROUGH THAT EXTENDS FROM
THE W FLORIDA PANHANDLE NEAR 31N86W TO THE YUCATAN PENINSULA
NEAR 20N87W CONTINUING TO CENTRAL AMERICA. UPPER LEVEL
DIFFLUENCE BETWEEN THIS UPPER TROUGH AND A LARGE UPPER LEVEL
RIDGE IN THE NW ATLC CENTERED NEAR 35N62W...ALONG WITH LOW-LEVEL
CONVERGENCE NEAR THE SURFACE TROUGH ARE SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN CHANNEL TO NRN FLORIDA
FROM 22N-32N E OF 85W. A FEW ISOLATED SHOWERS ARE IN THE NW GULF
N OF 27N W OF 90W. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL
DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE THAT COVERS THE WRN GULF
W OF 92W AND A LARGE UPPER LEVEL TROUGH OVER THE ERN CONUS.
EXPECT SHOWERS/THUNDERSTORMS TO PERSIST NEAR THE SURFACE TROUGH
AS IT DRIFTS NW AND DISSIPATES MON AND TUE.

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 S GUATEMALA NEAR 14N90W AND A LARGE UPPER LEVEL
RIDGE OVER THE NW ATLC CENTERED NEAR 35N62W. NUMEROUS
SHOWERS/THUNDERSTORMS AREA OFF THE COAST OF NICARAGUA AND
HONDURAS FROM 12N-15N BETWEEN 79W-84W. ISOLATED SHOWERS ARE ALSO
OFF THE COASTS OF COSTA RICA 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 13N71W. SCATTERED
SHOWERS/THUNDERSTORMS ARE ACROSS HISPANIOLA AND PUERTO RICO FROM
17N-19N BETWEEN 64W-73W DUE TO SURFACE CONVERGENCE NEAR A
SURFACE TROUGH...REMNANTS OF ERIKA...THAT EXTENDS FROM 15N70W
THROUGH THE MONA PASSAGE TO 21N65W. MODERATE TO FRESH 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 56W WILL REACH THE LESSER ANTILLES AND CONTINUE TO TRACK
ACROSS THE ERN CARIBBEAN.

ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS ACROSS CENTRAL FLORIDA FROM 28N81W
CONTINUING TO 32N76W AND OUT OF THE DISCUSSION AREA. ISOLATED
SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM NW OF THE TROUGH AXIS
AFFECTING MUCH OF FLORIDA AND THE ADJACENT COASTAL WATERS. 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 35N62W. A
SMALL UPPER LEVEL LOW CENTERED NEAR 25N62W INTRUDES INTO THE SRN
EXTENT OF THE UPPER RIDGE. THIS UPPER LEVEL LOW SUPPORTS A
SURFACE TROUGH EXTENDING FROM 26N63W TO 31N60W. ISOLATED SHOWERS
ARE WITHIN 100 NM EITHER SIDE OF THE TROUGH AXIS. ANOTHER
SURFACE TROUGH...REMNANTS OF ERIKA...EXTENDS FROM THE MONA
PASSAGE NEAR 19N68W TO 21N65W. ISOLATED SHOWERS ASSOCIATED WITH
THE TROUGH ARE FROM 18N-20N BETWEEN 57W-64W. ELSEWHERE ACROSS
THE ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1025 MB
HIGH NEAR 31N53W. IN THE UPPER LEVELS...AN UPPER LEVEL HIGH IS
CENTERED E OF THE LESSER ANTILLES NEAR 17N55W. AN UPPER LEVEL
TROUGH EXTENDS FROM AN UPPER LEVEL LOW NEAR 33N33W TO 19N47W. AN
UPPER LEVEL RIDGE DOMINATES THE ERN ATLC CENTERED ALONG THE
COAST OF AFRICA NEAR 18N16W.

$$
WALTON






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