[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 252353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT OCT 25 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2330 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 30W S OF 12N MOVING W NEAR 15 KT. WAVE IS
EMBEDDED WITHIN THE ITCZ AND AN AREA OF DEEP LAYER MOISTURE WITH
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM
7N-12N BETWEEN 28W-31W. POSITION OF AXIS COINCIDES WITH A REL
VORTICITY MAXIMUM AS SEEN ON THE CIMSS WAVETRAK PRODUCT.

TROPICAL WAVE IS ALONG 40W S OF 11N MOVING W NEAR 10 KT. DRY AIR
ASSOCIATED WITH AN UPPER-LEVEL TROUGH OVER THE CENTRAL ATLC IS
LIMITING CONVECTION IN THE VICINITY OF THE WAVE. POSITION OF
AXIS IS BASED ON CONTINUITY.

TROPICAL WAVE IS ALONG 62W S OF 15N MOVING W NEAR 10 KT. SFC
PRESSURES OBSERVED IN THE LESSER ANTILLES ARE BEGINNING TO RISE
FOLLOWING THE WAVE PASSAGE. STRONG SUBSIDENCE ALOFT IS
PREVENTING CONVECTIVE DEVELOPMENT.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 12N16W 8N25W 7N35W 7N45W 10N60W. IN
ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...ISOLATED
MODERATE CONVECTION IS SOUTH OF THE AXIS FROM 5N-6N BETWEEN
39W-44W.

...DISCUSSION...

GULF OF MEXICO...
DENSE CLOUD COVER WITH NUMEROUS SHOWERS AND ISOLATED
THUNDERSTORMS ARE OBSERVED OVER SOUTHERN FLORIDA AND THE SE GULF
AHEAD OF A FRONTAL BOUNDARY. AS OF 2100 UTC...THE COLD FRONT
ENTERS THE GULF NEAR EVERGLADES CITY AND STRETCHES ALONG 25N83W
TO 24N86W WHERE IT BECOMES STATIONARY TO 22N88W...JUST WEST OF A
1012 MB SFC LOW CENTERED NEAR 23N87W. SOUTHERLY WINDS NEAR 10 KT
AHEAD OF THE FRONT INCREASE AND BECOME NORTHERLY AT 15-20 KT
BEHIND THE FRONT TO 90W. EXPECT THE FRONT TO CONTINUE MOVING
TOWARD THE SE...REACHING THE FLORIDA STRAIGHTS ON SUN AND
EXITING THE REGION BY SUN NIGHT. E TO NE WINDS 10-15 KT FLOW
AROUND A WEAK SFC RIDGE THAT COVERS THE REMAINDER OF THE GULF.
AN UPPER-LEVEL HIGH OVER THE NW CARIBBEAN CONTINUES TO SUPPLY
MID-UPPER LEVEL TROPICAL MOISTURE TO THE AREA...MAINTAINING
PARTLY CLOUDY CONDITIONS ACROSS THE GULF WEST OF THE FRONT.

CARIBBEAN SEA...
A BROAD UPPER-LEVEL RIDGE COVERS THE ENTIRE CARIBBEAN ANCHORED
JUST SOUTH OF THE CAYMAN ISLANDS NEAR 19N80W. A DIFFLUENT
PATTERN ON THE NW PORTION OF THIS UPPER-LEVEL HIGH IS GENERATING
SCATTERED SHOWERS AND THUNDERSTORMS IN THE NW CARIBBEAN W OF 83W
AND N OF 15N. LOW-LEVEL WIND SPEED CONVERGENCE IS GENERATING A
SECOND AREA OF SCATTERED SHOWERS ALONG THE COASTS OF NICARAGUA
AND COSTA RICA S OF 12N AND W OF 81W. STRONG UPPER-LEVEL
SUBSIDENCE AND THE ASSOCIATED DRY...STABLE AIR MASS IS
INHIBITING DEEP CONVECTION EAST OF 78W. MODERATE EASTERLY TRADE
WINDS COVER THE BASIN.

ATLANTIC OCEAN...
HEAVY SHOWERS AND ISOLATED THUNDERSTORMS COVER THE W ATLC AHEAD
OF A COLD FRONT THAT...AS OF 2100 UTC...ENTERS THE DISCUSSION
AREA NEAR 31N77W AND EXTENDS ALONG 29N78W AND CROSSES THE
FLORIDA PENINSULA NEAR WEST PALM BEACH. AS OF 1800 UTC WINDS IN
THE VICINITY OF THE FRONT DECREASED BELOW GALE FORCE AND
SUBSEQUENTLY THE GALE WARNING WAS DROPPED. A BROAD SFC RIDGE
CONTINUES TO MAINTAIN FAIR CONDITIONS N OF 22N BETWEEN 51W-76W.
FURTHER EAST...A NARROW BUT DEEP-LAYER TROUGH EXTENDS INTO THE
CENTRAL ATLC AND STRETCHES SW TO THE NORTHERN LEEWARD ISLANDS.
THE ASSOCIATED COLD FRONT ENTERS THE AREA NEAR 31N44W AND
CONTINUES ALONG 25N50W TO 22N58W WHERE IT BECOMES STATIONARY TO
21N70W. A PRE-FRONTAL TROUGH EXTENDS FROM 26N49W TO 19N53W.
SCATTERED CLOUDS ARE OBSERVED ALONG THE ENTIRE FRONTAL
BOUNDARY...HOWEVER SHOWERS ARE LIMITED TO THE AREA N OF 24N
WITHIN 130 NM OF THE COLD FRONT. A STABLE RIDGE ANCHORED BY A
1031 MB SFC HIGH NE OF THE AZORES COVERS THE EAST ATLC.

$$
WADDINGTON





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