[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041738
TWDAT

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

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 39W S OF 16N MOVING W 15 KT. LOW
AMPLITUDE WAVE MOSTLY EMBEDDED WITHIN THE ITCZ AND EMBEDDED
WITHIN A DEEP LAYER MOISTURE MAXIMUM AS OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY. BROAD MID LEVEL CYCLONIC TURNING CAN
BE OBSERVED IN THE VISIBLE SATELLITE IMAGERY. ASSOCIATED
CONVECTION IS BEING ENHANCED BY A BROAD E/W UPPER RIDGE THAT
EXTENDS ACROSS THE TROPICAL ATLC. SCATTERED MODERATE WITH
EMBEDDED CLUSTERS OF ISOLATED STRONG CONVECTION COVER A LARGE
AREA FROM 7N16N BETWEEN 34W-46W.

TROPICAL WAVE IS ALONG 53W S OF 15N MOVING W NEAR 15 KT. WELL
DEFINED LOW AMPLITUDE WAVE WITH A LOW LEVEL CYCLONIC CURVATURE
ALONG THE WAVE AXIS. WAVE ALSO COINCIDES WITH A DEEP LAYER
MOISTURE MAXIMUM AS INDICATED IN TOTAL PRECIPITABLE WATER
IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
8N-13N BETWEEN 52W-57W.

TROPICAL WAVE IS ALONG 77W S OF 18N MOVING W 15 KT. WAVE HAS
BECOME BETTER DEFINED OVER THE PAST 24 HOURS AS IT MOVES BENEATH
AN UPPER TROUGH. WAVE REMAINS EMBEDDED WITHIN AN AREA OF SLIGHT
MOISTURE AS INDICATED IN TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED SHOWERS/THUNDERSTORMS ARE FROM 15N-19N BETWEEN
74W-78W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N12W 7N23W 11N40W 10N46W 12N52W
9N62W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
150 NM S OF THE ITCZ FROM 32W-35W.

...DISCUSSION...

GULF OF MEXICO...
A COLD FRONT EXTENDS INTO THE W ATLC AND ACROSS N FLORIDA
BECOMING STATIONARY NEAR CEDAR KEY CONTINUING W TO INLAND OVER
SE LOUISIANA NEAR NEW ORLEANS. A BROAD UPPER RIDGE ANCHORED OVER
CENTRAL MEXICO EXTENDS ACROSS THE ENTIRE GULF NEAR TUXPAN TO S
FLORIDA PROVIDING DIFFLUENCE ALOFT TO ENHANCE SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS MOVING OFF TEXAS AND LOUISIANA N OF 27N W
OF 90W. ISOLATED SHOWERS ARE ACROSS THE REMAINDER OF THE N GULF
N OF 27N BETWEEN FLORIDA AND TEXAS. DUE TO AN UPPER TROUGH OVER
THE W ATLC AND THE BROAD UPPER RIDGE IS GIVING THE E GULF STRONG
UPPER LEVEL WINDS. THE S GULF IS ENJOYING RATHER TRANQUIL
WEATHER THIS AFTERNOON WITH RELATIVELY CLEAR SKIES.

CARIBBEAN SEA...
BROAD UPPER RIDGE THAT COVERS THE GULF EXTENDS OVER THE W
CARIBBEAN WITH A SECOND UPPER RIDGE COVERING THE E CARIBBEAN
ANCHORED OVER NW VENZUELA. THIS SCENARIO IS CREATING A SHARP
INVERTED TROUGH FROM PANAMA TO SW HAITI. THE UPPER RIDGE OVER W
CARIBBEAN IS USHERING IN DRY STABLE AIR W OF 80W GIVING THE AREA
MOSTLY CLEAR SKIES. THE INVERTED UPPER TROUGH IS GENERATING
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 12N TO
INLAND OVER COLOMBIA TO COSTA RICA W OF 75W AND ENHANCING THE
ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE ALONG 77W. A SURFACE
TROUGH IS JUST E OF THE LEEWARD ISLANDS GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS OVER THE LEEWARD ISLANDS BETWEEN
MARTINIQUE AND ANGUILLA.

ATLANTIC OCEAN...
THE BROAD UPPER RIDGE THAT COVERS THE GULF OF MEXICO EXTENDS
OVER THE FAR W ATLC W OF 77W WITH A NARROW UPPER TROUGH ENTERING
THE AREA JUST TO THE E ALONG 32N70W TO THE TURKS AND CAICOS NEAR
22N73W SUPPORTING A COLD FRONT THAT ENTERS THE REGION NEAR
32N77W CROSSING FLORIDA JUST S OF ST. AUGUSTINE AND INTO THE
GULF OF MEXICO. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE TO
THE E OF THE UPPER TROUGH WITHIN 90 NM OF LINE FROM 23N70W TO
BEYOND 32N66W. AN UPPER LOW IS IN THE CENTRAL ATLC NEAR 29N53W
WITH AN UPPER TROUGH EXTENDING SW TO 25N57W. A WEAK SURFACE
TROUGH IS TO THE E OF THE UPPER LOW EXTENDING FROM 30N44W 27N49W
TO 26N55W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
WITHIN 90/120 NM OF LINE FROM 28N40W TO 25N50W WITH SCATTERED
SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS FROM 27N-29N BETWEEN
48W-54W. A REMNANT SURFACE TROUGH REMAINS IN THE E ATLC
EXTENDING OVER THE MADEIRA ISLANDS ALONG 28N22W TO 26N35W
GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
WITHIN 200 NM W OF THE TROUGH AXIS. THE TYPICAL E/W UPPER RIDGE
DOMINATES MUCH OF THE TROPICS WITH THE AXIS EXTENDING ALONG 15N
TO 50W ANCHORED OVER THE CAPE VERDE ISLANDS AND ENHANCING THE
CONVECTION ASSOCIATED WITH THE TROPICAL WAVES. WEAK SURFACE
RIDGE CUTS A SWATH ACROSS THE REGION BETWEEN 20N-30N WITH A 1020
MB HIGH NEAR 23N43W.

$$
WALLACE





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