[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 272354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 27 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 5N33W TO 16N29W MOVING W NEAR 20 KT.
BROAD LOW-LEVEL CYCLONIC TURNING IS NOTED ON SATELLITE IMAGERY
IN THE VICINITY OF THE WAVE AXIS. THE WAVE ALSO COINCIDES WITH
MAXIMUM VALUES IN TOTAL PRECIPITABLE WATER BETWEEN 27W-37W AS
NOTED ON THE TPW IMAGERY. SCATTERED SHOWERS COVER THE AREA FROM
5N-14N BETWEEN 27W-34W.

TROPICAL WAVE IS ALONG 78W S OF 19N MOVING W NEAR 20 KT. THE
WAVE CONTINUES MOVING BENEATH AN AREA OF DRY STABLE AIR ALOFT
AND THUS NO SIGNIFICANT DEEP CONVECTION IS ASSOCIATED WITH THE
WAVE. HOWEVER...SCATTERED MODERATE TO STRONG CONVECTION IS
ACROSS THE SW CARIBBEAN S OF 12N W OF 76W AND IS LIKELY
ASSOCIATED MORE WITH THE PROXIMITY OF THE E PACIFIC ITCZ AND AN
UPPER LEVEL DIFFLUENT PATTERN ALOFT.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 13N29W 9N34W 7N40W
10N62W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS ALONG
THE W AFRICA COAST FROM 8N-11N BETWEEN 12W-16W. WIDELY SCATTERED
MODERATE CONVECTION IS FROM 4N-12N BETWEEN 34W-43W. A SIMILAR
AREA OF CONVECTION IS LOCATED N OF THE AXIS E OF THE WINDWARD
ISLANDS FROM 10N-14N BETWEEN 50W-62W.

...DISCUSSION...

GULF OF MEXICO...
A SHARP UPPER LEVEL SHORTWAVE TROUGH EXTENDS ALONG THE ERN US
SEABOARD TO SRN GEORGIA AND ALONG THE GULF COAST STATES. TO THE
SOUTH OVER A MAJORITY OF THE GULF AND FLORIDA PENINSULA...AN
UPPER LEVEL RIDGE EXTENDS FROM CENTRAL MEXICO ALONG 24N TO THE
SRN FLORIDA PENINSULA AND INTO THE W ATLC BEYOND 30N73W. THE
UPPER LEVEL TROUGH SUPPORTS A COLD FRONT THAT CROSSES FLORIDA
FROM ST. AUGUSTINE TO CEDAR KEY AND INTO THE NE GULF TO NEAR
28N88W. REMAINING GENERALLY A DRY FRONT WITH ONLY A DIFFERENCE
IN SURFACE DEWPOINTS AND A SUBTLE WIND SHIFT ACROSS THE FLORIDA
PENINSULA...LOW-LEVEL CONVERGENCE COUPLED WITH UPPER LEVEL
DIFFLUENT FLOW IS GENERATING ISOLATED SHOWERS S OF THE FRONT E
OF 85W. THE REMAINDER OF THE GULF IS CONTROLLED BY A QUASI-
STATIONARY 1015 MB SURFACE HIGH CENTERED NEAR 26N91W AND AN
ASSOCIATED SURFACE RIDGE ALONG 26N. THIS RIDGE IS FORECAST TO
SHIFT S OVER THE NEXT 24-36 HOURS AS A WEAK FRONT APPROACHES THE
NRN GULF WATERS LATE MONDAY.

CARIBBEAN SEA...
SHARP UPPER LEVEL TROUGHING EXTENDS FROM THE SW NORTH ATLC OVER
THE MONA PASSAGE TO CENTRAL AMERICA NEAR THE NE COASTLINE OF
NICARAGUA. THIS UPPER LEVEL TROUGHING SPLITS THE BASIN WITH THE
NW CARIBBEAN HAVING VERY DRY AND SUBSIDENT NELY UPPER LEVEL FLOW
AS NOTED ON WATER VAPOR IMAGERY. THE SOUTH CENTRAL AND ERN
CARIBBEAN HAVE MOIST SWLY UPPER LEVEL FLOW THAT IS PROVIDING
NOTICEABLE MIDDLE TO HIGH LEVEL TROPICAL MOISTURE E OF 70W. A
FEW AREAS OF ISOLATED SHOWERS ARE ACROSS THE ERN CARIBBEAN...ONE
FROM 14N-20N BETWEEN 62W-69W...INCLUDING PUERTO RICO AND THE
US/UK VIRGIN ISLANDS. THE SECOND AREA OF SCATTERED SHOWERS IS
OVER THE SE CARIBBEAN S OF 13N E OF 65W...INCLUDING PORTIONS OF
THE WINDWARD ISLANDS. ELSEWHERE...THE SW CARIBBEAN IS INFLUENCED
BY A DIFFLUENT PATTERN ALOFT AS WELL AS A TROPICAL WAVE
POSITIONED ALONG 78W S OF JAMAICA. SCATTERED SHOWERS AND TSTMS
ARE S OF A LINE FROM 14N83W TO NRN COLOMBIA NEAR 11N74W. FRESH
TO STRONG ELY TRADE WINDS CONTINUE ACROSS MUCH OF THE BASIN THIS
EVENING.

ATLANTIC OCEAN...
A SHARP UPPER LEVEL SHORTWAVE TROUGH EXTENDS ALONG THE ERN U.S.
SEABOARD TO SRN GEORGIA WHILE A BROAD UPPER RIDGE EXTENDS FROM
THE SRN FLORIDA PENINSULA NEWD TO BEYOND 32N68W. THE UPPER LEVEL
TROUGH SUPPORTS A COLD FRONT THAT ENTERS THE DISCUSSION AREA
NEAR 32N79W AND CONTINUES SW TO ST. AUGUSTINE FLORIDA AND INTO
THE NE GULF OF MEXICO. A PRE-FRONTAL SURFACE TROUGH IS ANALYZED
FROM THE FLORIDA COAST NEAR FORT LAUDERDALE TO BEYOND 32N76W.
LOW-LEVEL CONVERGENCE NEAR THE COLD FRONT AND SURFACE TROUGH ARE
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS N OF 25N W OF
73W ACROSS PORTIONS OF THE W ATLC. UPPER LEVEL DIFFLUENCE
ASSOCIATED WITH THE UPPER LEVEL RIDGING IS FURTHER ENHANCING
THIS CONVECTION. FARTHER E...AN UPPER LEVEL TROUGH IS LOCATED IN
THE CENTRAL ATLC THAT EXTENDS FROM 32N54W THROUGH AN UPPER LEVEL
LOW NEAR 24N63W TO OVER THE MONA PASSAGE AND INTO THE CARIBBEAN
SEA. MOIST SWLY UPPER LEVEL FLOW AND LIFT ASSOCIATED WITH THE
TROUGHING IS GENERATING AN AREA OF WIDELY SCATTERED SHOWERS FROM
18N-32N BETWEEN 50W-65W. THE UPPER LEVEL TROUGH ALSO SUPPORTS
THE TAIL END OF A COLD FRONT THAT ENTERS THE REGION NEAR 32N44W
TO 28N50W. SCATTERED SHOWERS AND POSSIBLE ISOLATED TSTMS ARE
WITHIN 200 NM SE OF THE FRONT. A SURFACE TROUGH IS ANALYZED
ALONG 40W FROM 15N-21N. POSSIBLE ISOLATED SHOWERS ARE WITHIN 200
NM EITHER SIDE OF THE TROUGH N OF 17N. THE REMAINDER OF THE E
ATLC IS DOMINATED BY A SURFACE RIDGE N OF 22N E OF 36W.

$$
HUFFMAN





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