[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041040
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN OCT 04 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.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 37W S OF 15N MOVING W NEAR 18 KT.
PARTIALLY EMBEDDED WITHIN THE ITCZ...A BROAD SWATH OF DEEP LAYER
MOISTURE SURROUNDS THE WAVE FROM 5N-14N BETWEEN 33W-43W AS
OBSERVED IN THE TOTAL PRECIPITABLE WATER IMAGERY. LOW-LEVEL
CYCLONIC TURNING IS NOTED PRIMARILY W OF THE WAVE AXIS ON
SATELLITE IMAGERY AND IS ENHANCING SCATTERED STRONG CONVECTION
FROM 7N-16N BETWEEN 33W-44W.

TROPICAL WAVE IS ALONG 52W S OF 16N MOVING W NEAR 15 KT. RATHER
WELL DEFINED ON SATELLITE IMAGERY...THIS WAVE EXHIBITS A MAXIMUM
IN 850 MB RELATIVE VORTICITY ALONG THE WAVE AXIS NEAR 10N
ACCORDING TO THE LATEST CIMSS WAVETRAK MODEL GUIDANCE. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 8N-14N BETWEEN
48W-52W.

TROPICAL WAVE IS ALONG 76W S OF 19N MOVING W NEAR 10 KT. WEAK
CYCLONIC CURVATURE IS NOTED IN THE LOW-LEVEL CLOUD FIELD OVER
THE CENTRAL CARIBBEAN. THE WAVE ALSO LIES BENEATH UPPER LEVEL
TROUGHING BETWEEN 72W-80W. SCATTERED MODERATE CONVECTION IS FROM
13N-16N BETWEEN 73W-78W AND IS LIKELY ENHANCED BY THE UPPER
LEVEL TROUGH.


...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N11W 8N34W 9N39W 9N51W 9N54W
8N61W. ASIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...NO OTHER SIGNIFICANT AREAS OF DEEP CONVECTION ARE NOTED
ON SATELLITE IMAGERY.

...DISCUSSION...

GULF OF MEXICO...
A STATIONARY FRONT EXTENDS ACROSS ALONG THE NRN GULF COAST FROM
TALLAHASSEE TO NEW ORLEANS AND INTO INTERIOR SRN TEXAS NEAR
GALVESTON. MOSTLY SELY WINDS OF UP TO 20 KT ARE OBSERVED OVER
MUCH OF THE CENTRAL AND WRN GULF. THIS MOIST LOW-LEVEL SLY
RETURN FLOW ALONG WITH LOW-LEVEL CONVERGENCE NEAR THE FRONTAL
BOUNDARY IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS N OF
27N W OF 86W. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL
ANTICYCLONIC FLOW AND DIFFLUENCE FOUND ACROSS MUCH OF THE GULF
AS AN UPPER LEVEL HIGH IS CENTERED NEAR 21N97W. ELSEWHERE...THE
GULF REMAINS RATHER TRANQUIL THIS MORNING AS THE NLY FLOW REGIME
ALOFT KEEPS STABLE ATMOSPHERIC CONDITIONS OVER THE GULF S OF 27N.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH COVERS THE CENTRAL CARIBBEAN FOCUSED ON AN
UPPER LOW CENTERED NEAR 13N77W. COMBINED WITH THE UPPER LEVEL
RIDGE LOCATED OVER THE GULF OF MEXICO...NLY WINDS ALOFT ARE
PROVIDING DRY STABLE AIR W OF 80W AND OVER A LARGE PORTION OF
CENTRAL AMERICA. THE UPPER LEVEL TROUGHING COUPLED WITH THE
TROPICAL WAVE ALONG 76W IS GENERATING CLUSTERS OF SCATTERED
SHOWERS AND ISOLATED TSTMS S OF 17N BETWEEN 70W-79W. E OF THE
UPPER LEVEL TROUGH...A LARGE AREA OF MOIST SWLY FLOW AND UPPER
LEVEL DIFFLUENCE ARE NOTED ON WATER VAPOR IMAGERY WHICH IS
GENERATING ISOLATED SHOWERS BETWEEN 63W-74W. A SURFACE TROUGH IS
ALSO ANALYZED TO THE E OF THE LESSER ANTILLES FROM 21N58W TO
15N59W. LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH IS
GENERATING SCATTERED SHOWERS AND TSTMS WITHIN 170 NM W OF THE
BOUNDARY WHICH IS IMPACTING THE LEEWARD ISLANDS.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH EXTENDS OVER THE W ATLC WATERS WITH AXIS
ALONG 73W. THIS TROUGHING EXTENDS SWD INTO THE CENTRAL CARIBBEAN
TROUGH ACROSS ERN CUBA...THE WINDWARD PASSAGE AND HISPANIOLA AND
SUPPORTS A COLD FRONT THAT IS POSITIONED ALONG THE ERN U.S.
SEABOARD TO SAVANNAH GEORGIA. VERY LITTLE PRECIPITATION IS
OBSERVED WITH THIS FRONT...HOWEVER SURFACE DEWPOINTS ARE
NOTICEABLY LOWER ON THE BACK SIDE OF THE BOUNDARY. E OF THE
UPPER LEVEL TROUGH AXIS...A LARGE AREA OF UPPER DIFFLUENCE IS
NOTED ON WATER VAPOR IMAGERY N OF 22N BETWEEN 63W-73W. ISOLATED
SHOWERS ARE FOUND OVER THIS AREA...WITH SCATTERED SHOWERS FOUND
MAINLY N OF 28N BETWEEN 67W-73W WHERE THE UPPER LEVEL FORCING IS
STRONGEST. FARTHER TO THE E...A WEAKNESS IN THE CENTRAL ATLC
SUBTROPICAL RIDGE IS NOTED BY A SURFACE TROUGH THAT EXTENDS FROM
28N45W TO 25N54W. SUPPORTED ALOFT BY A SHORTWAVE UPPER LEVEL
TROUGH...MOST OF THE SCATTERED SHOWERS AND ISOLATED TSTMS BEING
GENERATING ARE FROM 26N-30N BETWEEN 42W-48W. THE UPPER LEVEL
TROUGH EXTENDS SW FROM 24N50W TO E OF THE LESSER ANTILLES AND
SUPPORTS ANOTHER SURFACE TROUGH EXTENDING FROM 21N58W TO 15N59W.
SCATTERED SHOWERS AND TSTMS ARE OCCURRING FROM 15N-21N BETWEEN
58W-62W...INCLUDING PORTIONS OF THE LEEWARD ISLANDS. ELSEWHERE
OVER THE REMAINDER OF THE ERN ATLC...UPPER LEVEL ZONAL FLOW
DOMINATES N OF 24N E OF 45W. EMBEDDED WITH THIS FLOW ALOFT IS A
SURFACE TROUGH ANALYZED FROM 32N30W TO 27N36W. CLUSTERS OF
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING WITHIN 120 NM
EITHER SIDE OF THE SURFACE TROUGH. THE TYPICAL E/W UPPER RIDGE
DOMINATES MUCH OF THE TROPICS EXTENDING TO 50W...WITH THE
ANTICYCLONIC CIRCULATION ANCHORED OVER THE CAPE VERDE ISLANDS.
THIS UPPER LEVEL FEATURES CONTINUES TO ENHANCE THE CONVECTION
ASSOCIATED WITH THE TROPICAL WAVES ACROSS THE TROPICAL CENTRAL
ATLC.

$$
HUFFMAN



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