[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 12 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.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 16N43W TO 7N48W MOVING WNW NEAR 15
KT. THE WAVE REMAINS EMBEDDED WITHIN AN AREA OF MAXIMUM TOTAL
PRECIPITABLE WATER ACROSS THE CENTRAL TROPICAL ATLC WITH
MOISTURE BEING DRAWN N-NE AS THE NRN PORTION OF THE WAVE MOVES
BENEATH THE INFLUENCE OF A MARGINALLY SHEARED ENVIRONMENT DUE TO
AN UPPER LEVEL TROUGH ACROSS THE ERN ATLC. WITH THE UPPER LEVEL
SHEAR IN PLACE...NO ORGANIZED DEEP CONVECTION ACCOMPANIES THE
WAVE...HOWEVER...ISOLATED SHOWERS ARE POSSIBLE WITHIN 200 NM
EITHER SIDE OF THE WAVE AXIS.

TROPICAL WAVE IS ALONG 83W S OF 15N MOVING W NEAR 15 KT. WAVE
REMAINS EMBEDDED WITHIN A DEEP LAYER MOISTURE MAXIMUM IN TOTAL
PRECIPITABLE WATER IMAGERY. WIDELY SCATTERED MODERATE CONVECTION
IS OCCURRING ACROSS THE SW CARIBBEAN FROM 10N-15N BETWEEN
80W-85W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 8N25W 10N44W 10N55W
10N62W. SCATTERED MODERATE CONVECTION IS FROM 4N-9N BETWEEN
14W-25W. SIMILAR CONVECTION IS FROM 9N-12N BETWEEN 30W-39W. ALSO
EMBEDDED WITHIN THE ITCZ...A SURFACE TROUGH IS ANALYZED FROM
13N51W TO 9N53W. WIDELY SCATTERED MODERATE CONVECTION IS FROM
8N-12N BETWEEN 50W-56W.

...DISCUSSION...

GULF OF MEXICO...
AT 1500 UTC...A STATIONARY FRONT REMAINS DRAPED ACROSS THE SE
CONUS AND INTO THE NW GULF ALONG THE TEXAS COAST NEAR MATAGORDA
BAY TO INLAND NEAR BROWNSVILLE. A SURFACE TROUGH EXTENDS FROM
BROWNSVILLE ALONG 24N97W TO 20N95W. LOW-LEVEL CONVERGENCE NEAR
THE BOUNDARIES ACROSS THE WRN GULF ARE GENERATING SCATTERED
SHOWERS AND ISOLATED TSTMS N OF 21N W OF 92W. MOST OF THIS
ACTIVITY IS ENHANCED ALOFT BY DIFFLUENCE DUE TO A BROAD UPPER
LEVEL RIDGE CENTERED OVER THE ERN GULF NEAR 26N83W THAT EXTENDS
UPPER LEVEL RIDGING WSW THROUGH 24N90W TO 23N100W. THE REMAINDER
OF THE GULF E OF 92W...WHILE BENEATH THE UPPER LEVEL HIGH...HAS
GENERALLY FAIR WEATHER ON STRONG SUBSIDENCE AND MOSTLY
SOUTH-SOUTHEASTERLY SURFACE WINDS OF UP TO 15 KT.

CARIBBEAN SEA...
A WEAK SURFACE TROUGH EXTENDS FROM THE BAHAMA ISLANDS NEAR
22N75W ACROSS ERN CUBA TO ERN JAMAICA NEAR 18N76W. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE OCCURRING FROM 16N-19N BETWEEN
75W-83W W OF THE BOUNDARY. FARTHER TO THE E...A SECOND SURFACE
TROUGH EXTENDS FROM THE US/UK VIRGIN ISLANDS ALONG 17N67W TO
16N73W. SCATTERED SHOWERS AND TSTMS ARE OBSERVED WITHIN 75 NM
EITHER SIDE OF THE SURFACE TROUGH. THE CONVECTIVE ACTIVITY
ACROSS THE N/CENTRAL AND NE CARIBBEAN IS LARGELY ENHANCED BY
UPPER LEVEL NELY DIVERGENT FLOW ON THE SRN PERIPHERY OF A BROAD
UPPER LEVEL RIDGE THAT COVERS MOST OF THE CARIBBEAN BASIN. S OF
15N E OF 80W...DRY AIR AND STRONG SUBSIDENCE IS NOTED ON WATER
VAPOR IMAGERY. THIS IS PROVIDING FOR GENERALLY CLEAR SKIES WITH
MODERATE TO FRESH TRADES THIS AFTERNOON.

ATLANTIC OCEAN...
A CENTRAL ATLC LONGWAVE TROUGH DIPS TO 29N BETWEEN 40W-57W AND
SUPPORTS A COLD FRONT WHICH ENTERS THE DISCUSSION AREA NEAR
32N45W AND CONTINUES ALONG 30N50W 32N62W 31N70W WHERE IT
CONTINUES WWD AS A STATIONARY FRONT TO THE NE FLORIDA COAST NEAR
JACKSONVILLE. ISOLATED SHOWERS ARE MOSTLY CONFINED TO N OF 30N W
OF 70W AS A SURFACE RIDGE BRIDGES THE FRONTAL BOUNDARY ACROSS
THE W ATLC WATERS. A 1022 MB SURFACE HIGH IS CENTERED S OF THE
FRONT NEAR 30N68W. THIS SURFACE RIDGE IS DUE LARGELY TO A BROAD
UPPER LEVEL ANTICYCLONIC CIRCULATION THAT ENCOMPASSES A MAJORITY
OF THE WRN ATLC E OF 57W. DRY AIR AND STRONG SUBSIDENCE IS NOTED
ON WATER VAPOR IMAGERY S OF 30N...INCLUDING THE BAHAMAS...
CUBA...AND HISPANIOLA. A 1010 MB LOW IS CENTERED NEAR 33N39W AND
EXTENDS A SURFACE TROUGH ALONG 30N40W 29N50W. ISOLATED SHOWERS
ARE WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH. ACROSS THE
ERN ATLC...A SHARP UPPER TROUGH DIGS SWD NEAR 32N28W S TO
15N32W. THIS TROUGH IS SUPPORTING A STATIONARY FRONT THAT ENTERS
THE REGION NEAR 32N27W CONTINUING SW ALONG 28N30W TO 24N40W. THE
BOUNDARY CONTINUES SW AND BECOMES MORE DIFFUSE AS A SURFACE
TROUGH ALONG 20N44W TO 17N57W. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE OCCURRING FROM 23N-32N BETWEEN 25W-34W IN ASSOCIATION
WITH THE STATIONARY BOUNDARY...WHILE ISOLATED SHOWERS ARE FOUND
WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH.

$$
HUFFMAN





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