[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 010533
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT NOV 01 2008

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 10N14W 9N20W 10N35W 9N52W 10N63W.
TWO SURFACE TROUGHS REMAIN EMBEDDED WITHIN THE ITCZ. ONE TROUGH
EXTENDS FROM E OF THE CANARY ISLANDS NEAR 16N22W TO 13N24W TO
8N25W.  THIS TROUGH COINCIDES WITH A WESTWARD-MOVING SURGE IN
DEEP LAYER MOISTURE BASED ON TOTAL PRECIPITABLE WATER PRODUCT
FROM CIMSS. ISOLATED MODERATE CONVECTION IS WITHIN 180 NM EITHER
SIDE OF THE TROUGH FROM 10N-14N...WHICH IS BEING ENHANCED BY
UPPER LEVEL DIVERGENCE. THE SECOND TROUGH EXTENDS FROM 18N46W TO
14N46W TO 10N46W AND COINCIDES WITH ANOTHER WESTWARD-MOVING
SURGE IN DEEP LAYER MOISTURE. THIS TROUGH IS SUPPORTING
SCATTERED MODERATE CONVECTION FROM 9N-16N BETWEEN 38W-48W...
WHICH IS ALSO BEING ENHANCED BY UPPER LEVEL DIVERGENCE.
ELSEWHERE...ISOLATED MODERATE CONVECTION IS FROM 4N-12N BETWEEN
13W-21W...AFFECTING W PORTIONS OF GUINEA AND W GUINEA-BISSAU.
ALSO...SCATTERED MODERATE CONVECTION IS FROM 9N-16N BETWEEN
27W-38W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE OF HIGH PRESSURE IS AFFECTING MUCH OF THE GULF
REGION. THIS SURFACE RIDGE IS ANCHORED BY A 1033 MB SURFACE HIGH
NEAR THE E COAST OF N CAROLINA. SUBSIDENCE IN THE VICINITY OF
THE RIDGE IS RESULTING IN FAIR WEATHER CONDITIONS ACROSS MUCH OF
THE GULF REGION. ALOFT...UPPER LEVEL MOISTURE EMBEDDED WITHIN
THE BASE OF AN UPPER LEVEL TROUGH OVER THE W GULF CONTINUES TO
RESULT IN HIGH CLOUDINESS OVER THE SW GULF. ACROSS THE N AND E
GULF...DEEP LAYER DRY AIR AND STRONG MID/UPPER-LEVEL WESTERLY
FLOW ARE PRESENT. THE UPPER LEVEL PATTERN IS FORECAST TO CHANGE
OVER THE NEXT DAY AS A CLOSED UPPER LEVEL LOW AND ASSOCIATED
UPPER TROUGH AND UPPER MOISTURE...CURRENTLY OVER W TENNESSEE...
APPROACH THE N GULF. HOWEVER...COMPUTER MODEL GUIDANCE INDICATES
THAT THESE FEATURES COULD WEAKEN AS THEY POTENTIALLY BECOME
OVERTAKEN BY AN EASTWARD-MOVING UPPER RIDGE CURRENTLY OVER THE
PLAINS OF THE CONUS. ADDITIONALLY...STRONG N TO NE SURFACE WINDS
ARE BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE
FORCE WINDS IN THE E PACIFIC REGION.

CARIBBEAN SEA...
ANTICYCLONIC FLOW AROUND AN UPPER HIGH CENTERED NEAR 15N76W
COVERS MUCH OF THE CARIBBEAN...WITH DEEP MOISTURE OVER THE W
CARIBBEAN. UPPER LEVEL DIVERGENCE SW OF THE UPPER HIGH IS
SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER
THE W CARIBBEAN FROM 9N-18N BETWEEN 76W-85W...AFFECTING PORTIONS
OF PANAMA AND COSTA RICA WHERE LOW LEVEL CONVERGENCE NEAR THE E
PACIFIC ITCZ IS ENHANCING THE CONVECTION. ADDITIONALLY...A
SURFACE TROUGH EXTENDS FROM W OF HAITI NEAR 20N73W TO 18N79W TO
E NICARAGUA NEAR 14N83W. A RECENT QUIKSCAT PASS DEPICTS NE WINDS
OF 20 TO 25 KT NW OF THE SURFACE TROUGH...AND NE WINDS NEAR 15
KT SE OF THE SURFACE TROUGH. THE CORRESPONDING LOW LEVEL
CONVERGENCE NEAR THIS TROUGH...COMBINED WITH DEEP MOISTURE...IS
SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER
SIDE OF THE SURFACE TROUGH. DEEP LAYER DRY AIR E OF THE UPPER
HIGH IS RESULTING IN MAINLY FAIR WEATHER ACROSS THE E CARIBBEAN.

ATLANTIC OCEAN...
DEEP LAYER DRY AIR EMBEDDED WITHIN A BROAD UPPER LEVEL TROUGH
COVERS THE W ATLC...WHERE GENERALLY FAIR WEATHER IS PRESENT. AT
THE SAME TIME...A SURFACE RIDGE OF HIGH PRESSURE...ANCHORED BY A
1033 MB SURFACE HIGH NEAR THE E COAST OF N CAROLINA...IS
RESULTING IN SUBSIDENCE ACROSS MUCH OF THE W ATLC. FARTHER TO
THE E...A SURFACE STATIONARY FRONT EXTENDS FROM 32N53W TO 27N59W
TO 24N65W...AND A SURFACE TROUGH EXTENDS FROM 24N65W TO 21N71W
TO W HAITI NEAR 20N73W. ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY
FLOW ALOFT IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM EITHER
SIDE OF THE SURFACE STATIONARY FRONT AND SURFACE TROUGH N OF
22N...WHICH ARE BEING SUPPORTED BY UPPER DIFFLUENCE NEAR AN
UPPER RIDGE FROM 24N-30N BETWEEN 51W-60W. FARTHER TO THE E...A
COMPACT UPPER LEVEL TROUGH IS PRESENT WITH AN AXIS THAT EXTENDS
FROM 30N45W TO 31N47W TO 12N49W. ALSO...A DEEP LAYER TROUGH IS N
OF 24N E OF 42W...WHICH IS SUPPORTING A SURFACE COLD FRONT
EXTENDING FROM 32N11W TO 30N20W TO 32N28W THAT IS APPROACHING
THE CANARY ISLANDS FROM THE NORTH. ISOLATED SHOWERS ARE
OCCURRING WITHIN 90 NM EITHER SIDE OF THE COLD FRONT E OF 15W.
OVER THE TROPICAL ATLC...AN EAST-TO-WEST UPPER RIDGE IS ALONG
11N BETWEEN THE AFRICAN COAST AND 42W. UPPER LEVEL DIVERGENCE
NEAR THIS RIDGE IS ENHANCING THE CONVECTION ASSOCIATED WITH THE
SURFACE TROUGHS THAT ARE EMBEDDED WITHIN THE ITCZ.

OF NOTE...NOVEMBER IS THE LAST MONTH OF THE ATLANTIC HURRICANE
SEASON. SO FAR...FIFTEEN NAMED STORMS HAVE DEVELOPED...OF WHICH
SEVEN BECAME HURRICANES...WITH FOUR OF THE HURRICANES ATTAINING
MAJOR HURRICANE STATUS. IN ADDITION...A SHORT-LIVED TROPICAL
DEPRESSION FORMED IN OCTOBER. THE MOST POWERFUL HURRICANES SEEN
THIS SEASON ARE GUSTAV AND IKE...BOTH CAT 4 ON THE SAFFIR
SIMPSON SCALE.

$$
COHEN/GR



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