[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 070559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

A TROPICAL WAVE IS ALONG 20W S OF 18N MOVING W NEAR 18 KT WITH A
1008 MB LOW EMBEDDED ON THE WAVE AXIS NEAR 12N. A DEEP LAYER
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 NW OF THE LOW
CENTER FROM 12N-16N BETWEEN 20W-25W. AN E-W BAND OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION...MORE LIKELY ASSOCIATED
WITH THE ITCZ...IS FROM 7N-9N BETWEEN 20W-27W. CONDITIONS APPEAR
FAVORABLE FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL DEPRESSION
WITHIN THE NEXT DAY OR SO.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 41W S OF 17N MOVING W NEAR 15 KT. MOST OF
THE ENERGY FROM THIS WAVE FRACTURED NWD AS A SURFACE TROUGH AND
SURFACE LOW NEARLY 24 HOURS AGO...AND ANY REMAINING SIGNATURE
HAS BECOME ILL-DEFINED AND PARTIALLY ABSORBED INTO THE TROPICAL
WAVE ALONG 49W. SCATTERED SHOWERS REMAIN ASSOCIATED WITH THE
ITCZ AXIS FROM 10N-17N BETWEEN 39W-43W.

TROPICAL WAVE IS ALONG 49W S OF 21N MOVING W NEAR 15 KT. A 1012
MB LOW IS ALONG THE WAVE AXIS NEAR 16N. CIMSS WAVETRAK MODEL
GUIDANCE INDICATES A BROAD AREA OF 850 MB VORTICITY N OF 15N
BETWEEN 45W-55W SURROUNDING THE WAVE. SCATTERED MODERATE
CONVECTION IS 16N-18N BETWEEN 47W-50W.

TROPICAL WAVE IS ALONG 70W S OF 20N MOVING W NEAR 20 KT. MOVING
BENEATH DRY AIR AND MODERATE SUBSIDENCE ALOFT...A LOW-LEVEL
INVERTED-V CLOUD SIGNATURE IS EVIDENT ON SATELLITE IMAGERY
ACROSS THE CENTRAL CARIBBEAN IN THE VICINITY OF THE WAVE AXIS.
NO DEEP CONVECTION ACCOMPANIES THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 12N19W 9N22W 6N27W 11N40W
15N47W 15N50W 11N62W. BESIDE THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVES ACROSS THE TROPICAL ATLC...ISOLATED LOW-LEVEL
SHOWERS ARE FROM THE EQUATOR TO 12N E OF 28W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH IS OVER THE 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 NE OF KEY WEST NEAR 25N82W. 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.

CARIBBEAN SEA...
A TROPICAL WAVE WITH NO SIGNIFICANT CONVECTION IS OVER THE
CENTRAL CARIBBEAN ALONG 70W. AN UPPER LEVEL SHORTWAVE TROUGH
EXTENDS FROM THE W ATLC ACROSS CUBA AND JAMAICA AND IS
SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM THE CAICOS ISLANDS
INTO THE WINDWARD PASSAGE AND SW HAITI NEAR 18N74W. THIS SURFACE
FEATURE ALONG WITH UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE
UPPER TROUGH IS GENERATING SCATTERED SHOWERS AND TSTMS N OF 17N
BETWEEN 69W-82W. SCATTERED SHOWERS AND DEBRIS CLOUDINESS SPREAD
EWD OF 70W 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 13N80W TO 13N65W.
MODERATE SUBSIDENCE IS NOTED ON WATER VAPOR IMAGERY THUS
LIMITING ANY DEEP CONVECTION...HOWEVER A FEW POSSIBLE SCATTERED
SHOWERS ARE OVER THE SW CARIBBEAN S OF 13N W OF 79W.

ATLANTIC OCEAN...
A SHORTWAVE UPPER LEVEL TROUGH IS OVER THE SOUTH CAROLINA
COASTLINE AND SUPPORTS A 1014 MB SURFACE LOW CENTERED NEAR
32N78W. AS OF 0300 UTC...A SURFACE TROUGH EXTENDS SSW FROM THE
LOW ALONG 30N78W TO WEST PALM BEACH FLORIDA AND OVER THE SRN
FLORIDA PENINSULA. LOW-LEVEL CONVERGENCE COUPLED WITH UPPER
LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND ISOLATED
TSTMS N OF 25N BETWEEN 76W-81W. AN UPPER LEVEL LOW IS CENTERED
NEAR 29N68W AND EXTENDS TROUGHING ACROSS THE CAICOS ISLANDS AND
CUBA. THIS UPPER LEVEL FEATURE SUPPORTS A SURFACE TROUGH THAT IS
ANALYZED FROM 25N69W TO 18N74W. LOW-LEVEL CONVERGENCE NEAR THE
SURFACE TROUGH AND UPPER LEVEL DIFFLUENCE E OF THE UPPER TROUGH
AXIS ARE GENERATING SCATTERED SHOWERS AND TSTMS WITHIN 200 NM OF
A LINE FROM 19N69W TO 31N62W. 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 26N55W TO 31N42W. 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 17N36W THROUGH A 1012 MB LOW CENTERED NEAR
20N35W TO 23N33W. SCATTERED SHOWERS EXTEND N OF THE SURFACE LOW
FROM 20N-27N BETWEEN 28W-38W.

$$
HUFFMAN


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