[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 011756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 01 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

BROAD AREA OF LOW PRESSURE ASSOCIATED WITH A 1007 MB LOW IS
CENTERED NEAR 16N57W OR ABOUT 225 NM E OF THE LEEWARD ISLANDS
AND CONTINUES TO SHOW SIGNS OF ORGANIZATION THIS AFTERNOON. A
SURFACE TROUGH EXTENDS FROM THE LOW SW TO 11N63W. SCATTERED
STRONG CONVECTION IS DISPLACED TO THE EAST OF THE LOW-LEVEL
CENTER FROM 14N-20N BETWEEN 51W-57W. THIS SYSTEM COULD BECOME A
TROPICAL DEPRESSION OR TROPICAL STORM AT ANY TIME OVER THE NEXT
COUPLE OF DAYS AS IT MOVES WNW NEAR 8 KT. INTERESTS IN THE NRN
LEEWARD ISLANDS...THE U.S. AND BRITISH VIRGIN ISLANDS...AND
PUERTO RICO SHOULD MONITOR THE PROGRESS OF THIS SYSTEM.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 19W S OF 19N MOVING W NEAR 15 KT. UPPER
AIR TIME-SECTION ANALYSIS FROM DAKAR SENEGAL INDICATED THAT THIS
WAVE PASSED DAKAR AROUND 01/0000 UTC AND ALONG WITH VISIBLE
METEOSAT-9 SATELLITE IMAGERY HAS BEEN PLACED ON THE 01/1200 UTC
ANALYSIS. CYCLONIC CURVATURE IN THE LOW-LEVEL CLOUD FIELD IS
EVIDENT WITH CIMSS WAVETRAK MODEL GUIDANCE PLACING A BROAD AREA
OF 850 MB VORTICITY IN THE VICINITY OF THE WAVE AXIS BETWEEN
12N-20N. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
13N-18N BETWEEN 18W-24W.

TROPICAL WAVE EXTENDS FROM 9N32W TO 16N34W MOVING W NEAR 15 KT.
THIS WAVE REMAINS ALONG THE LEADING EDGE OF A DEEP LAYERED
MOISTURE MAXIMUM AS INDICATED BY TOTAL PRECIPITABLE WATER
IMAGERY. HOWEVER...THIS WAVE IS ALSO EMBEDDED WITHIN SAHARAN
DUST AND MOVING BENEATH VERY DRY AIR ALOFT...THUS LIMITING ANY
SIGNIFICANT DEEP CONVECTION OR SCATTERED SHOWER ACTIVITY.

TROPICAL WAVE IS ALONG 84W S OF 16N MOVING W NEAR 18 KT. THIS
WAVE CONTINUES TO BE ILL-DEFINED AS IT TRACKS WWD BENEATH DRY
AND SUBSIDENT WLY UPPER LEVEL FLOW ALOFT. NO SIGNIFICANT SHOWERS
OR CONVECTION ARE OBSERVED ON SATELLITE IMAGERY ASSOCIATED WITH
THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 14N20W 10N31W 8N34W 7N39W
10N47W. THE ITCZ IS DISCONTINUOUS DUE TO THE LOW IN THE SPECIAL
FEATURES SECTION ABOVE. WIDELY SCATTERED MODERATE CONVECTION IS
WITHIN 150 NM S OF THE AXIS BETWEEN 34W-47W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A STATIONARY FRONT IS DRAPED ACROSS THE NRN
FLORIDA PENINSULA FROM SAINT AUGUSTINE FLORIDA TO CEDAR KEY
ALONG THE FLORIDA BIG BEND AND INTO THE NE GULF ALONG 29N86W
28N90W TO CORPUS CHRISTI TEXAS. A SURFACE TROUGH IS ANALYZED
ACROSS THE SRN FLORIDA PENINSULA ENTERING THE SE GULF NEAR
NAPLES TO NEAR 25N83W. ABOVE THE SURFACE FORCING FEATURE...A
BROAD UPPER LEVEL RIDGE ANCHORED OVER CENTRAL MEXICO NEAR
22N101W EXTENDS RIDGING EWD ALONG 24N TO THE STRAITS OF FLORIDA.
A LONGWAVE UPPER TROUGH IS LOCATED ACROSS THE SE CONUS AND DIPS
SWD ACROSS THE FLORIDA PANHANDLE AND PORTIONS OF THE FAR NE GULF
N OF 28N. LOW-LEVEL CONVERGENCE ALONG THE STATIONARY FRONT AND
MIDDLE TO UPPER LEVEL DIFFLUENCE S OF UPPER TROUGH ARE PRODUCING
SCATTERED SHOWERS AND ISOLATED TSTMS PRIMARILY N OF 26N AND E OF
92W. POSSIBLE ISOLATED SHOWERS ARE ALSO WITHIN 120 NM EITHER
SIDE OF THE STATIONARY FRONT W OF 92W. ELSEWHERE ACROSS THE SRN
GULF...NELY SURFACE WINDS OF 10 TO 15 KT AND DRIER NLY WINDS
ALOFT PREVAIL WITH RELATIVELY FAIR WEATHER S OF 25N. A FEW
ISOLATED SHOWERS HOWEVER ARE OBSERVED ON SATELLITE IMAGERY
ACROSS THE WRN BAY OF CAMPECHE.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE COVERS THE WRN CARIBBEAN W OF 75W AND IS
ANCHORED IN THE GULF OF HONDURAS NEAR 18N85W. DIFFLUENCE ALOFT
OVER THE NW CARIBBEAN IS GENERATING ISOLATED SHOWERS N OF 16N W
OF 82W TO INLAND OVER BELIZE AND NRN GUATEMALA. AN UPPER TROUGH
OVER THE W/CENTRAL ATLC EXTENDS S OVER HISPANIOLA TO THE COAST
OF NRN COLOMBIA BETWEEN 65W-75W. WATER VAPOR IMAGERY SHOWS THE
CENTRAL CARIBBEAN TO BE UNDER STRONG SUBSIDENCE AND VERY DRY AIR
ALOFT...THIS INHIBITING ANY DEEP CONVECTION OR SHOWER ACTIVITY.
TO THE EAST ACROSS THE FAR ERN CARIBBEAN AND LESSER ANTILLES...
THE LOW MENTIONED IN THE SPECIAL FEATURES IS EXPECTED TO TRACK
WNW TO THE NE OF THE LEEWARD/VIRGIN ISLANDS OVER THE NEXT FEW OF
DAYS. UPPER LEVEL RIDGING EXTENDS FROM THE TROPICAL NORTH ATLC
ACROSS THE ERN CARIBBEAN TO 75W. UPPER LEVEL DIFFLUENCE
ASSOCIATED WITH THIS UPPER RIDGING AND THE APPROACH OF THE
SURFACE LOW TO THE NRN LEEWARD ISLANDS IS GENERATING SCATTERED
SHOWERS AND ISOLATED TSTMS FROM 13N-16N E OF 65W WITH ISOLATED
SHOWERS ELSEWHERE OVER THE REMAINING LESSER ANTILLES.

ATLANTIC OCEAN...
THE MAIN FOCUS FOR THE ATLC BASIN IS THE LOW E OF THE LESSER
ANTILLES THAT HAS THE POTENTIAL FOR TROPICAL CYCLONE
DEVELOPMENT. SEE SPECIAL FEATURES ABOVE. IN THE W ATLC...A
STATIONARY FRONT ENTERS THE DISCUSSION AREA NEAR 32N77W AND
EXTENDS TO NEAR SAINT AUGUSTINE FLORIDA. A PRE-FRONTAL TROUGH IS
ALSO ANALYZED S OF THE FRONTAL BOUNDARY FROM 32N77W TO WEST PALM
BEACH FLORIDA. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN
150 NM E OF THE SURFACE TROUGH N OF 27N. FARTHER TO THE E...AN
UPPER LEVEL LOW IS CENTERED N OF THE AREA NEAR 33N61W AND
EXTENDS TROUGHING SW TO OVER HISPANIOLA AND INTO THE CENTRAL
CARIBBEAN. A SURFACE TROUGH IS ANALYZED FROM 27N76W TO THE
WINDWARD PASSAGE. SCATTERED SHOWERS AND ISOLATED TSTMS ARE
OCCURRING E OF THE SURFACE TROUGH FROM 20N-26N BETWEEN 67W-73W.
ELSEWHERE ACROSS THE REMAINDER OF THE CENTRAL AND ERN ATLC...THE
BASIN REMAINS FAIRLY BENIGN AS A SURFACE RIDGE CONTROLS N OF 20N
E OF 65W AND IS ANCHORED BY A 1031 MB SURFACE HIGH CENTERED N OF
THE REGION WSW OF THE AZORES NEAR 37N36W.

$$
HUFFMAN



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