000
AXNT20 KNHC 170550
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST WED DEC 17 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.

...THE ITCZ...
ITCZ IS CENTERED ALONG 8N13W 5N25W 4N30W 6N40W 3N51W. NUMEROUS 
MODERATE TO STRONG CONVECTION IS WITHIN 120 NM EITHER SIDE OF 
THE AXIS BETWEEN 20W-35W.     

...DISCUSSION...

GULF OF MEXICO...
A FRONTAL BOUNDARY IS SLOWLY LIFTING BACK N OVER THE EXTREME NW 
GULF FROM 30N92W TO 25N96W TO 22N98W. THE FRONT IS GRADUALLY 
BECOMING DIFFUSE CAUSING N TO NE WINDS TO LIGHTEN W OF THE 
FRONT. E OF THE FRONT...E TO SE WINDS ARE LIGHT TO MODERATE 
EXCEPT FOR MODERATE TO FRESH WINDS OVER THE FLORIDA STRAITS. 
ONLY SCATTERED PATCHES OF LOW-LEVEL CLOUDS ARE BEING DRIVEN BY 
THE FLOW WITH EMBEDDED ISOLATED SHOWERS. THE FRONT IS EXPECTED 
TO DRIFT BACK INLAND OVER THE SE CONUS TODAY. ALOFT...THE N 
PERIPHERY OF AN UPPER HIGH OVER CENTRAL AMERICA IS PRODUCING WLY 
FLOW WHICH IS TRANSPORTING BROKEN HIGH LEVEL CLOUDINESS FROM THE 
TROPICAL PACIFIC.  

CARIBBEAN SEA...
AN UPPER RIDGE OVER CENTRAL AMERICA AND AN UPPER LOW OVER THE 
SUBTROPICAL CENTRAL ATLC IS PRODUCING NW TO W FLOW ALOFT AND 
ENHANCING SUBSIDENCE ACROSS THE REGION. THE AIR IS MOST STABLE 
IN A CONFLUENT ZONE OVER THE FAR E CARIBBEAN. IN THE LOWER 
LEVELS...THE TIGHT PRES GRADIENT N OF THE AREA IS PRODUCING 
STIFF N TO NE WINDS WHICH ARE DRIVING SCATTERED SHOWERS AND LOW 
TOPPED TSTMS OVER THE NE CARIBBEAN ISLANDS. SHOWERS BECOME MORE 
ISOLATED IN NATURE S OF 15N...BUT NEARLY ALL OF THE ACTIVITY IS 
CAPPED BY THE DRY MID-LEVEL AIR. SFC OBS AND SCATTEROMETER DATA 
REVEAL 20-25 KT NE WINDS...STRONGEST IN THE PASSAGES. 
  
ATLANTIC OCEAN...
DEEP LAYER LOW PRESSURE OVER THE CENTRAL ATLC IS CAUSING FAIRLY 
ACTIVE WEATHER TONIGHT. THE SFC CENTER IS ANALYZED 1009 MB NEAR 
26N59W WITH ITS ASSOCIATED TROUGH EXTENDING BOTH N AND S ALONG 
58W/59W. QSCAT AND ASCAT DATA SHOW A WELL DEFINED SFC 
CIRCULATION AND N WINDS TO GALE FORCE BETWEEN THE TROUGH AND 
67W. LOW-LEVEL CONVERGENCE AND INSTABILITY NEAR THE LOW IS 
PRODUCING SCATTERED SHOWERS AND TSTMS WITHIN 180 NM OF THE  
CENTER. A LARGER AND MORE INTENSE AREA OF TSTMS EXISTS FARTHER 
NE N OF 23N BETWEEN 44W-54W IN AN UPPER DIFFLUENT ZONE. THIS LOW 
IS EXPECTED TO TRACK SW FOR ANOTHER DAY OR TWO AND WEAKEN BEFORE 
GETTING PULLED BACK NE BY A SHORTWAVE TROUGH. FARTHER E...STRONG 
WLY FLOW OVER THE TROPICAL E ATLC IS TRANSPORTING WIDESPREAD 
MID-HIGH LEVEL CLOUDINESS AND ENHANCING ITCZ CONVECTION. 

$$
CANGIALOSI