000
AXNT20 KNHC 031810
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI OCT 03 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 
1545 UTC.

...TROPICAL WAVES...

A NEW TROPICAL WAVE HAS BEEN ANALYZED ALONG 18W BETWEEN 8N AND 
17N MOVING W AROUND 10-15 KT.  SCATTERED MODERATE/ISOLATED 
STRONG CONVECTION EXISTS WITHIN 120 NM OF THE WAVE AXIS.  THIS 
WAS DIAGNOSED VIA SURFACE STATIONS IN WEST AFRICA...MODEL 
ANALYSES...AND THE CIMSS WAVETRAK VORTICITY.
 
TROPICAL WAVE IS ALONG 46W BETWEEN 10N AND 18N MOVING W AROUND 
10 KT.   WAVE CONTAINS ONLY ISOLATED SHOWERS WITHIN 120 NM OF 
THE WAVE AXIS.  WAVE IS WELL-DEFINED VIA MODEL ANALYSES...CIMSS 
WAVETRAK VORTICITY...AND TOTAL PRECIPITABLE WATER IMAGERY.  

TROPICAL WAVE IS ALONG 58W BETWEEN 9N AND 18N MOVING W 10-15 KT. 
NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS OCCURRING 
WITHIN 120 NM ON EITHER SIDE OF THE WAVE AXIS SOUTH OF 16N.  
WAVE IS WELL-DEFINED ON VISIBLE SATELLITE IMAGERY...CIMSS 
WAVETRAK VORTICITY...AND TOTAL PRECIPITABLE WATER IMAGERY...BUT 
NOT IN THE MODEL ANALYSES.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 13N17W 7N25W 5N32W 7N45W 
11N61W.  SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 
120 NM N OF THE AXIS AND 240 NM S OF THE AXIS FROM THE WEST 
AFRICAN COAST TO 32W.  NUMEROUS MODERATE/SCATTERED STRONG 
CONVECTION WITHIN 120 NM ON EITHER SIDE OF THE AXIS FROM 53W 
WESTWARD TO THE SOUTH AMERICAN COAST.  

...DISCUSSION...

GULF OF MEXICO...
THE GULF OF MEXICO IS DOMINATED BY POST-FRONTAL...DRY STABLE 
AIR.  WINDS ARE WEAK AND TURNING ANTICYCLONICALLY AT THE SURFACE 
UNDER THE INFLUENCE OF A MODEST HIGH OVER THE SE UNITED STATES.  
IN THE UPPER LEVELS...SUBSIDENT AND RELATIVELY ZONAL WEST TO 
WEST- SOUTHWESTERLY MID TO UPPER FLOW EXISTS ACROSS THE GULF 
WITH A WEAK MID-LEVEL VORT MAX JUST SOUTH OF LOUISIANA.


CARIBBEAN SEA...
A WEAK 1009 MB LOW IS LOCATED IN THE GULF OF HONDURAS.  A 
SURFACE TROUGH EXTENDS FROM NEAR SOUTHERN CUBA...THROUGH THE 
LOW...AND INTO HONDURAS/NICARAGUA.  NUMEROUS MODERATE/SCATTERED 
STRONG CONVECTION EXISTS BETWEEN 80W AND 84W IN ASSOCIATION WITH 
THE LOW/TROUGH.  ADDITIONAL CONVECTION IS OCCURRING NEAR THE 
WINDWARD ISLANDS IN ASSOCIATION WITH THE AFOREMENTIONED TROPICAL 
WAVE NEAR 58W.  WINDS ARE EASTERLY 10 TO 20 KT IN THE EASTERN 
CARIBBEAN...SOUTHEASTERLY UP TO 20 KT IN THE WESTERN CARIBBEAN 
EAST OF THE TROUGH AXIS...AND NORTHEASTERLY UP TO 20 KT WEST OF 
THE TROUGH AXIS.  IN THE UPPER LEVELS...A HIGH PRESSURE IS 
CENTERED OVER THE TROUGH AXIS IN THE WESTERN CARIBBEAN.  IN THE 
EASTERN CARIBBEAN EASTERLY FLOW ALOFT DOMINATES UP THE INFLUENCE 
OF A STRONG RIDGE IN THE WESTERN ATLANTIC.  HOWEVER...A 
WELL-DEFINED CLOSED LOW CENTERED OVER THE WINDWARD ISLANDS IS 
CAUSING UPPER LEVEL SOUTHWESTERLIES OVER THE LEEWARD ISLANDS.  
THIS MAY BE FORCING THE ENHANCED CONVECTION IN ASSOCIATION WITH 
THE EASTERLY WAVE AT 58W.

ATLANTIC OCEAN...
A COLD FRONT BEGINNING AT A WEAK 1013 MB LOW CENTERED AT 32N75W 
EXTENDS SOUTHWESTWARD TO THE FLORIDA STRAITS.  SCATTERED SHOWERS 
EXIST WITHIN 120 NM EAST OF THE FRONTAL BOUNDARY.  EARLIER...THE 
FRONT HAD BEEN DIAGNOSED AS A STATIONARY FEATURE...BUT HAS BEEN 
RECHRISTENED A COLD FRONT DUE TO ITS PROGRESSIVE NATURE TODAY.  
FARTHER EAST...A SURFACE TROUGH IS OBSERVED ALONG 44W FROM 20N 
TO 31N.  SCATTERED MODERATE CONVECTION EXISTS WITHIN 120 NM ON 
EITHER SIDE OF THE TROUGH AXIS SOUTH OF 24N.  SCATTERED MODERATE 
CONVECTION IS ALSO OCCURRING WITHIN 120 NM OF A LINE FROM 12N36W 
TO 19N41W.  THIS APPEARS TO BE DUE TO THE BOUNDARY OF A MOIST 
AIRMASS AND SAHARAN AIR LAYER COUPLED WITH UPPER LEVEL 
SOUTHWESTERLIES.  IN THE UPPER LEVELS...A LARGE STRONG UPPER 
RIDGE DOMINATES THE WESTERN ATLANTIC FROM 50 TO 72W.  WESTWARD 
OF 72W...STRONG SOUTHWESTERLY WINDS EXIST BETWEEN UPPER RIDGE 
AXIS AND THE STRONG LONG WAVE OVER THE EASTERN UNITED STATES.  
EASTWARD OF 50W...A DEEP LOW IS OBSERVED NEAR 24N44W...WHICH IS 
ASSOCIATED WITH THE EARLIER MENTIONED SURFACE TROUGH AT THE SAME 
LONGITUDE.

$$
LANDSEA