[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 42W S OF 15N MOVING W 10-15 KT. CIMSS
WAVETRAK PRODUCT DEPICTS LOW LEVEL CYCLONIC CIRCULATION
MAXIMIZED ALONG WAVE AXIS. WAVE IS AT THE LEADING EDGE OF A
BROAD WESTWARD-MOVING SURGE IN DEEP LAYER MOISTURE BASED ON
TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE
CONVECTION IS WITHIN 210 NM E OF WAVE AXIS. ALSO...ISOLATED
MODERATE CONVECTION IS WITHIN 180 NM W OF WAVE AXIS N OF 10N.

TROPICAL WAVE IS ALONG 55W/56W S OF 15N MOVING W 10-15 KT.
SURFACE OBSERVATIONS AND A RECENT QUIKSCAT PASS DEPICT CYCLONIC
CURVATURE IN SURFACE WIND FIELD NEAR WAVE AXIS. DEEP LAYER DRY
AIR WRAPPING AROUND AN UPPER HIGH OVER NW HAITI NEAR 20N73W IS
INHIBITING CONVECTION NEAR THE WAVE...THOUGH ISOLATED SHOWERS
ARE WITHIN 120 NM E OF WAVE AXIS N OF 13N.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 9N13W 5N26W 7N39W 8N49W 8N60W.
ISOLATED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 12W-18W.
SCATTERED MODERATE CONVECTION IS FROM 2N-14N BETWEEN 28W-38W...
WHICH IS BEING ENHANCED BY STRONG UPPER LEVEL DIFFLUENCE.
ISOLATED MODERATE CONVECTION IS FROM 7N-12N BETWEEN 48W-52W.

...DISCUSSION...

GULF OF MEXICO...
THE LARGE SCALE WEATHER PATTERN OVER THE GULF IS UNDERGOING A
SUBSTANTIAL PATTERN CHANGE...AS AN UNUSUALLY STRONG 1042 MB
SURFACE HIGH IN THE PLAINS OF THE CONUS BEGINS TO EXERT ITS
INFLUENCE OVER THE GULF. AT THE LEADING EDGE OF THE ASSOCIATED
MODIFIED CONTINENTAL POLAR AIRMASS IS A STRONG SURFACE COLD
FRONT THAT IS SURGING SOUTHWARD NEAR 30 KT ACROSS THE NW GULF.
THIS FRONT EXTENDS FROM THE W FLORIDA PANHANDLE NEAR 30N86W TO
28N92W TO S TEXAS NEAR 27N97W. THIS FRONT MARKS A PARTICULARLY
STRONG GRADIENT IN LOW LEVEL MOISTURE...AS SURFACE DEWPOINTS
RANGE FROM THE 60S IMMEDIATELY AHEAD OF THE FRONT TO THE 20S
WITHIN 90 NM BEHIND THE FRONT. ALSO...SURFACE TEMPERATURES RANGE
FROM THE 70S IMMEDIATELY AHEAD OF THE FRONT TO THE 50S WITHIN 90
NM BEHIND THE FRONT...WITH INCREASED NORTHERLY SURFACE WINDS
BEHIND THE FRONT. THE STRONG GRADIENT IN MOISTURE AND
TEMPERATURE ACROSS THE FRONT IS SUPPORTING BANDS OF CLOUDS AND
ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE FRONT. THIS
FRONT IS ALSO BEING SUPPORTED BY A DEEP TROUGH OVER THE E
CONUS...WITH STRONG MID/UPPER-LEVEL WESTERLY WINDS OVER THE N
GULF. RELATIVELY DRY DEEP LAYER AIR COVERS THE GULF IN THE WAKE
OF A SURFACE BOUNDARY SE OF THE GULF REGION...WHICH IS RESULTING
IN GENERALLY FAIR WEATHER ACROSS MUCH OF THE GULF.
ADDITIONALLY...STRONG NE TO E WINDS ARE BLOWING THROUGH THE
ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE E
PACIFIC REGION...WHICH ARE EXPECTED TO INCREASE TO STORM FORCE
AT 1200 UTC TUESDAY.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE AXIS EXTENDS WESTWARD FROM AN UPPER HIGH
OVER NW HAITI NEAR 20N73W TO W GUATEMALA NEAR 17N91W.
SOUTHWESTERLY FLOW ALOFT N OF THE UPPER RIDGE CONTINUES TO
TRANSPORT DEEP MOISTURE INTO THE NW CARIBBEAN. THIS MOISTURE IS
INTERACTING WITH A STATIONARY FRONT THAT EXTENDS FROM MIDWAY
BETWEEN THE S FLORIDA PENINSULA NEAR 24N80W TO 20N86W TO THE
GULF OF HONDURAS NEAR 16N88W...WHICH IS RESULTING IN SCATTERED
MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF THE SURFACE
STATIONARY FRONT. ACROSS THE CENTRAL AND E CARIBBEAN...DEEP
LAYER DRY AIR AND SUBSIDENCE S OF THE UPPER HIGH ARE RESULTING
IN GENERALLY FAIR WEATHER. HOWEVER...ISOLATED MODERATE
CONVECTION IS OCCURRING OVER THE SW CARIBBEAN FROM 8N-11N
BETWEEN 76W-81W IN RESPONSE TO WEAK UPPER LEVEL DIVERGENCE
INTERACTING WITH DEEP LAYER MOISTURE STREAMING NORTHWESTWARD
FROM NW SOUTH AMERICA. ALSO...AN UPPER TROUGH EXTENDS FROM THE
ATLC NEAR 24N46W TO THE SE CARIBBEAN NEAR 11N64W...WITH DEEP
LAYER DRY AIR EMBEDDED WITHIN THIS TROUGH IN THE SE CARIBBEAN.

ATLANTIC OCEAN...
A DEEP LAYER TROUGH OVER THE E CONUS IS APPROACHING THE W
ATLC...WITH STRONG MID/UPPER LEVEL FLOW ROTATING AROUND THE BASE
OF THE TROUGH INTO THE W ATLC. DEEP LAYER DRY AIR EMBEDDED
WITHIN THE TROUGH IS RESULTING IN GENERALLY FAIR WEATHER OVER
THE W ATLC IN THE WAKE OF A COLD FRONT THAT EXTENDS FROM 32N69W
TO 27N74W TO MIDWAY BETWEEN THE S FLORIDA PENINSULA AND N CUBA
NEAR 24N80W. DEEP LAYER MOISTURE WRAPPING AROUND THE UPPER HIGH
OVER NW HAITI NEAR 20N73W IS SUPPORTING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WITHIN 60 NM EITHER SIDE OF THE COLD
FRONT W OF 77W. A MUCH DRIER AND COOLER AIRMASS WILL BEGIN TO
PUSH ACROSS THE W ATLC TONIGHT...WHICH IS BEING USHERED IN BY A
COLD FRONT THAT IS CURRENTLY MOVING SOUTHWARD ACROSS CENTRAL
GEORGIA...THE W FLORIDA PANHANDLE...AND THE NW GULF OF MEXICO.
FURTHER TO THE E...UPPER LEVEL ANTICYCLONIC FLOW ASSOCIATED WITH
THE AFOREMENTIONED UPPER HIGH OVER NW HAITI COVERS MUCH OF THE
CENTRAL ATLC...AND A DEEP LAYER TROUGH EXTENDS FROM 32N42W TO
24N46W TO THE SE CARIBBEAN NEAR 11N64W. THIS TROUGH IS
SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 31N42W TO 24N46W
TO 20N56W. THIS TROUGH IS MARKED BY WEAK SURFACE CONFLUENCE...
WITH ISOLATED MODERATE CONVECTION OCCURRING WITHIN 60 NM EITHER
SIDE OF THE SURFACE TROUGH. FARTHER TO THE E...AN UPPER RIDGE IS
N OF 24N BETWEEN 21W-39W...AND AN UPPER TROUGH IS N OF 19N E OF
17W. GENERALLY DEEP LAYER DRY AIR IS PREVENTING DEEP CONVECTION
NEAR THESE FEATURES. ALSO...SUBSIDENCE IS OCCURRING IN THE
VICINITY OF A SURFACE RIDGE IN THE E ATLC...WHERE GENERALLY FAIR
WEATHER CONDITIONS PREDOMINATE. OVER THE TROPICAL ATLC...AN
EAST-TO-WEST UPPER RIDGE IS ALONG 12N BETWEEN THE AFRICAN COAST
AND 25W.

$$
COHEN



This weather bulletin was brought to you by:
www.nashvilleweather.net