[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 190544
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN OCT 19 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
0515 UTC.

...SPECIAL FEATURES...
NONE.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 38W S OF 18N MOVING W 10-15 KT. SATELLITE
IMAGERY DEPICTS INVERTED-V SIGNATURE IN CLOUD COVERAGE...ALONG
WITH COUNTERCLOCKWISE MOTION OF CLOUD ELEMENTS IN THE VICINITY
OF THE WAVE AXIS. COMPUTER MODEL GUIDANCE AND CIMSS WAVETRAK
PRODUCT CONFIRM PRESENCE OF LOW LEVEL COUNTERCLOCKWISE
CIRCULATION NEAR WAVE AXIS. THIS WAVE ALSO COINCIDES WITH A
BROAD WESTWARD-MOVING DEEP LAYER MOISTURE SURGE BASED ON TOTAL
PRECIPITABLE WATER PRODUCT FROM CIMSS. ISOLATED MODERATE
CONVECTION IS WITHIN 120 NM EITHER SIDE OF WAVE AXIS N OF 13N.

TROPICAL WAVE IS ALONG 56W/57W S OF 16N MOVING W NEAR 10 KT.
WAVE IS NOT PARTICULARLY WELL-DEFINED BASED ON SATELLITE
IMAGERY...THOUGH IT DOES COINCIDE WITH A NORTH-TO-SOUTH DEEP
LAYER MOISTURE MAXIMUM. ISOLATED MODERATE CONVECTION IS WITHIN
90 NM W OF WAVE AXIS FROM 9N-11N...WHICH IS BEING ENHANCED BY
LOW LEVEL CONVERGENCE NEAR THE ITCZ.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 7N12W 9N32W 9N45W 10N54W 9N61W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
ALONG FROM 3N-11N BETWEEN 11W-22W...AFFECTING W PORTIONS OF
SENEGAL...GAMBIA...AND GUINEA-BISSAU. ISOLATED MODERATE
CONVECTION IS FROM 8N-14N BETWEEN 30W-34W. ISOLATED MODERATE
CONVECTION IS ALSO FROM 9N-12N BETWEEN 59W-61W...AFFECTING THE
SOUTHERN WINDWARD ISLANDS.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH OVER THE E CONUS EXTENDS SOUTHWARD INTO THE
GULF...WITH SW TO W FLOW ALOFT COVERING MUCH OF THE GULF. THIS
TROUGH CONTINUES TO SUPPORT A COLD FRONT THAT IS DRAPED ACROSS
THE CENTRAL AND E GULF...EXTENDING FROM THE WEST CENTRAL FLORIDA
PENINSULA NEAR 27N82W TO 25N87W TO 22N91W. THIS FRONT IS
STATIONARY FROM 22N91W SOUTHWARD INTO THE BAY OF CAMPECHE NEAR
19N92W. MID/UPPER-LEVEL MOISTURE AND ATMOSPHERIC LIFT EMBEDDED
WITHIN SW FLOW ALOFT ARE JUXTAPOSED WITH THE SURFACE
FRONT...RESULTING IN CLOUDINESS AND ISOLATED SHOWERS WITHIN
90 NM EITHER SIDE OF THE COLD FRONT N OF 23N. FURTHER TO THE
NW...SUBSIDENCE AND DRY AIR IN NW FLOW ALOFT ARE RESULTING IN
FAIR WEATHER ACROSS MUCH OF THE NW GULF. ALSO...AN UPPER HIGH IS
CENTERED W OF THE YUCATAN PENINSULA NEAR 17N92W. MOISTURE
EMBEDDED IN DIFFLUENT FLOW ALOFT SE OF THIS HIGH IS SUPPORTING
SCATTERED MODERATE CONVECTION FROM 16N-20N BETWEEN 89W-92W...
AFFECTING THE W YUCATAN PENINSULA AND ADJACENT WATERS OF THE BAY
OF CAMPECHE. THIS CONVECTION IS BEING FURTHER ENHANCED BY LOW
LEVEL CONVERGENCE NEAR THE AFOREMENTIONED STATIONARY FRONT.

CARIBBEAN SEA...
AN UPPER RIDGE EXTENDS FROM AN UPPER HIGH NEAR 20N57W TO
N COLOMBIA...AND A WEAK UPPER TROUGH IS PRESENT OVER THE
NW CARIBBEAN. ALSO...A SURFACE TROUGH EXTENDS FROM W HONDURAS
NEAR 16N88W TO A 1009 MB SURFACE LOW NEAR 18N87W TO 16N81W TO A
1011 MB SURFACE LOW LOCATED S OF JAMAICA NEAR 17N77W. LOW LEVEL
CONVERGENCE FROM THE SURFACE TROUGH...COMBINED WITH DIVERGENCE
ASSOCIATED WITH AN UPPER HIGH NEAR 19N82W AND AMPLE MOISTURE
OVER THE W CARIBBEAN...IS SUPPORTING SCATTERED MODERATE/ISOLATED
STRONG CONVECTION WITHIN 150 NM EITHER SIDE OF THE SURFACE
TROUGH W OF 84W. FURTHER TO THE E...CONVECTIVE COVERAGE IS
LIMITED AS A RESULT OF DRY AIR EMBEDDED WITHIN CONFLUENT SW FLOW
ALOFT...WITH ISOLATED MODERATE CONVECTION OCCURRING WITH 210 NM
EITHER SIDE OF THE SURFACE TROUGH BETWEEN 78W-84W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION OVER PORTIONS OF COSTA
RICA...PANAMA...AND NW COLOMBIA IS IMPACTING THE NEARBY
SW CARIBBEAN WATERS. THIS CONVECTION IS BEING ENHANCED BY A
1008 MB SURFACE LOW OVER THE VENEZUELA-COLOMBIA BORDER NEAR
9N73W AND GREATER INSTABILITY OVER HIGHER TERRAIN.

ATLANTIC OCEAN...
AN UPPER TROUGH OVER THE E CONUS IS BRINGING SW FLOW ALOFT TO
THE W ATLC...AND IS SUPPORTING A SURFACE COLD FRONT THAT EXTENDS
FROM A 1010 MB SURFACE LOW NEAR 34N75W TO 29N78W TO THE
E CENTRAL FLORIDA PENINSULA NEAR 28N80W. DRY AIR WRAPPING AROUND
THE BASE OF THE UPPER TROUGH...COMBINED WITH SUBSIDENCE IN NW
FLOW ALOFT W OF THE UPPER TROUGH AXIS...IS LIMITING CONVECTION
OVER THE W ATLC. FURTHER TO THE E...A SURFACE TROUGH EXTENDS
FROM 31N51W TO 28N55W TO 26N59W. HOWEVER...MAINLY DRY AND STABLE
CONDITIONS AROUND AN UPPER HIGH CENTERED NEAR 20N57W ARE
PREVENTING CONVECTIVE DEVELOPMENT WITH THE SURFACE TROUGH.
FURTHER TO THE E...A 1026 MB SURFACE HIGH IS CENTERED NEAR
30N32W...AND A SURFACE RIDGE EXTENDS FROM THIS HIGH TO THE
S NEAR 13N30W... WHERE SUBSIDENCE AND STABLE CONDITIONS
PREDOMINATE OVER MUCH OF THE E ATLC. ALSO...AN UPPER TROUGH IS
PRESENT OVER THE NE ATLC N OF 18N AND E OF 19W...WITH DEEP LAYER
DRY AIR EMBEDDED WITHIN THIS TROUGH. OVER THE TROPICAL ATLC...AN
UPPER RIDGE EXTENDS ALONG 12N BETWEEN W AFRICA AND 29W. THE
W PORTION OF THIS RIDGE IS DRAWN NORTHWESTWARD TO NEAR 23N34W
DUE THE COUNTERCLOCKWISE CIRCULATION AROUND A COMPACT N-TO-S
UPPER TROUGH EXTENDING FROM 24N46W TO AN UPPER LOW NEAR 17N45W
TO 11N46W. DEEP LAYER DRY AIR EMBEDDED WITHIN THESE FEATURES IS
GENERALLY LIMITING ANY CONVECTIVE DEVELOPMENT.

$$
COHEN



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