[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 071057
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON SEP 07 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
1015 UTC.

...SPECIAL FEATURES...

A TROPICAL WAVE IS ALONG 22W S OF 20N MOVING W NEAR 18 KT WITH A
1007 MB LOW EMBEDDED ON THE WAVE AXIS NEAR 13N. A DEEP LAYERED
MOISTURE MAXIMUM IS NOTED IN THE VICINITY OF THE WAVE ON THE
TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY AND CIMSS
WAVETRAK MODEL GUIDANCE EXHIBITS LOW-LEVEL CYCLONIC CIRCULATION
WITH SCATTERED MODERATE TO STRONG CONVECTION W OF THE LOW CENTER
FROM 10N-16N BETWEEN 22W-26W. AN E-W BAND OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION...MORE LIKELY ASSOCIATED WITH THE
ITCZ...IS FROM 6N-9N BETWEEN 19W-29W. CONDITIONS APPEAR
FAVORABLE FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL DEPRESSION
WITHIN THE NEXT DAY OR SO.

...TROPICAL WAVES...

TROPICAL WAVE PREVIOUSLY ALONG 41W S OF 17N HAS BEEN DROPPED
FROM THE 07/0600 UTC ANALYSIS. MOST OF THE ENERGY FROM THIS WAVE
FRACTURED NWD AS A SURFACE TROUGH AND SURFACE LOW OVER 24 HOURS
AGO...AND ANY REMAINING SIGNATURE HAS BECOME FULLY ABSORBED INTO
THE TROPICAL WAVE ALONG 50W.

TROPICAL WAVE IS ALONG 50W S OF 21N MOVING W NEAR 15 KT. A 1012
MB LOW IS ALONG THE WAVE AXIS NEAR 17N. CIMSS WAVETRAK MODEL
GUIDANCE INDICATES A BROAD AREA OF 850 MB VORTICITY N OF 15N
BETWEEN 45W-55W SURROUNDING THE WAVE. SCATTERED MODERATE
CONVECTION HAS DECREASED OVER THE PAST 6 HOURS ON SATELLITE
IMAGERY AND ONLY SCATTERED SHOWERS REMAIN FROM 16N-21N BETWEEN
45W-53W.

TROPICAL WAVE IS ALONG 72W S OF 18N MOVING W NEAR 20 KT. MOVING
BENEATH DRY AIR AND MODERATE SUBSIDENCE ALOFT...THE WAVE REMAINS
ILL-DEFINED AND DIFFICULT TO TRACK. NO DEEP CONVECTION
ACCOMPANIES THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 17N16W 16N20W 8N24W 8N31W 16N47W
15N53W 11N64W. BESIDE THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVES ACROSS THE TROPICAL ATLC...ISOLATED LOW-LEVEL
SHOWERS ARE S OF 10N E OF 30W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH IS OVER THE LOWER MISSISSIPPI RIVER VALLEY
ACROSS THE ERN CONUS WHILE AN UPPER LEVEL ANTICYCLONIC
CIRCULATION IS CENTERED OVER SRN MEXICO NEAR 19N95W. STRONG
WESTERLY UPPER LEVEL FLOW BETWEEN THE TWO UPPER LEVEL FEATURES
DOMINATES ACROSS THE GULF OF MEXICO. THIS IS PROVIDING A LACK OF
ANY SIGNIFICANT SURFACE FEATURES OTHER THAN A WEAK PRESSURE
GRADIENT AND RELATIVELY LIGHT WINDS ACROSS THE GULF. HOWEVER...A
SURFACE TROUGH EXTENDS FROM THE W ATLC ACROSS THE FAR SRN
FLORIDA PENINSULA TO NEAR KEY WEST. THE UPPER LEVEL RIDGE IS
ALSO PROVIDING UPPER DIFFLUENCE TO GENERATE SCATTERED SHOWERS
AND A FEW ISOLATED TSTMS WITHIN 150 NM EITHER SIDE OF A LINE
FROM APALACHICOLA BAY THROUGH 25N90W TO VERACRUZ MEXICO. THE
MOST INTENSE ACTIVITY IS LOCATED OVER THE SW GULF AND BAY OF
CAMPECHE S OF 23N W OF 93W.

CARIBBEAN SEA...
A TROPICAL WAVE WITH NO SIGNIFICANT CONVECTION IS OVER THE
CENTRAL CARIBBEAN ALONG 72W. AN UPPER LEVEL SHORTWAVE TROUGH
EXTENDS FROM THE W ATLC ACROSS CUBA...JAMAICA AND PORTIONS OF
WRN HISPANIOLA. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE UPPER
TROUGH IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS N OF
18N BETWEEN 74W-79W. SCATTERED SHOWERS AND DEBRIS CLOUDINESS
SPREAD EWD OF 74W ACROSS THE REMAINDER OF HISPANIOLA AND PUERTO
RICO. THE UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER SRN
MEXICO NEAR 19N95W EXTENDS UPPER RIDGING ACROSS MUCH OF CENTRAL
AMERICA AND THE CENTRAL CARIBBEAN THROUGH 12N80W TO 14N65W.
MODERATE SUBSIDENCE IS NOTED ON WATER VAPOR IMAGERY THUS
LIMITING ANY DEEP CONVECTION...HOWEVER A FEW ISOLATED SHOWERS
AND TSTMS ARE OVER THE SW CARIBBEAN S OF 15N W OF 80W.

ATLANTIC OCEAN...
A SHORTWAVE UPPER LEVEL TROUGH IS OVER THE SOUTH CAROLINA
COASTLINE AND SUPPORTS A 1012 MB SURFACE LOW CENTERED NEAR
32N79W. AS OF 0900 UTC...A SURFACE TROUGH EXTENDS S FROM THE LOW
ALONG 30N79W TO FT. LAUDERDALE FLORIDA AND OVER THE SERN
FLORIDA PENINSULA. LOW-LEVEL CONVERGENCE COUPLED WITH UPPER
LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS N OF 23N
BETWEEN 75W-80W. AN UPPER LEVEL LOW IS CENTERED NEAR 27N68W AND
EXTENDS TROUGHING ACROSS THE CAICOS ISLANDS AND CUBA. UPPER
LEVEL DIFFLUENCE E OF THE UPPER TROUGH AXIS IS GENERATING
SCATTERED SHOWERS AND TSTMS FROM 20N-23N BETWEEN 73W-80W AND
FROM 21N-29N BETWEEN 61W-69W. FARTHER TO THE E ACROSS THE
CENTRAL ATLC AN UPPER LEVEL HIGH IS CENTERED NEAR 30N55W AND AN
UPPER LEVEL LOW IS CENTERED NEAR 26N45W. NELY UPPER LEVEL
DIFFLUENT FLOW IS LOCATED BETWEEN THESE TWO FEATURES AND IS
PRODUCING POSSIBLE SCATTERED SHOWERS WITHIN 120 NM EITHER SIDE
OF A LINE FROM 27N53W TO 32N43W. IN ADDITION...MOIST SWLY UPPER
LEVEL FLOW LOCATED SE OF THE UPPER LEVEL LOW NEAR 26N45W IS
SUPPORTING A FRACTURED PORTION OF ENERGY ANALYZED AS A SURFACE
TROUGH EXTENDING FROM 17N35W THROUGH A 1013 MB LOW CENTERED NEAR
20N35W TO 24N33W. SCATTERED SHOWERS AND ISOLATED TSTMS EXTEND N
OF THE SURFACE LOW FROM 21N-26N BETWEEN 30W-36W.

$$
HUFFMAN





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