000
AXNT20 KNHC 231141
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN DEC 23 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN 
SECTIONS OF SOUTH AMERICA...AND THE 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC

...ITCZ...
ITCZ AXIS ALONG 7N12W 4N26W 4N40W 7N58W.  SCATTERED MODERATE 
CONVECTION WITHIN 90 NM OF AXIS FROM 39W-48W.  ISOLATED 
MODERATE CONVECTION WITHIN 150 NM N OF AXIS FROM 23W-33W.

...DISCUSSION...
GULF OF MEXICO...
STRONG COLD FRONT EXTEND FROM 30N89W TO 21N97W THEN NWD ALONG E 
SLOPES OF SIERRA MADRE TO 23N100W.  FRONT SUPPORTED BY LARGE 
AMPLITUDE LONGWAVE TROUGH ACROSS CENTRAL PLAINS PRODUCING VERY 
WINTRY WEATHER ACROSS ITS PATH.  WELL DEFINED LINE OF CONVECTION 
MARKS FRONTAL BOUNDARY.  N GALE FORCE WINDS EXPECTED W OF COLD 
FRONT THROUGH THIS AFTERNOON.  BROKEN LOW LEVEL STRATIFIED 
CLOUDINESS AND ISOLATED SHOWERS ASSOCIATED WITH DISSIPATED WARM 
FRONT LINGERS AHEAD OF COLD FRONT.  E GULF APPEARS QUIET FOR 
TIME BEING...BUT TRANQUILITY WILL NOT LAST AS COLD FRONT SHOULD 
BRING STRONG NLY WINDS TONIGHT THROUGH MON.  HIGH PRES BUILDS 
BEHIND FRONT AND MAINTAINS COOL DRY NE FLOW THROUGH REMAINDER OF 
FORECAST PERIOD. 

CARIBBEAN SEA...
MID TO UPPER RIDGE WELL ANCHORED OVER W CARIBBEAN WITH CREST 
REACHING CENTRAL FLORIDA HAS FLOW ALOFT BECOMING ZONAL E OF 60W. 
ABUNDANT MODERATE TO STRONG SUBSIDENCE ACROSS ENTIRE BASIN 
MAINTAINS IT DRY AND STABLE CURTAILING VERTICAL DEVELOPMENT EVEN 
WHEN SURFACE UPLIFT IS AVAILABLE LIKE WITH SURFACE TROUGH ALONG 
72W OFF LAKE MARACAIBO.  ISOLATED DEEPER PRECIP IN SW CARIBBEAN 
S OF 11N W OF 80W AS TRADES COLLIDE WITH MOUNTAIN RANGE IN 
PANAMA AND COSTA RICA.   

ATLANTIC OCEAN...
MAIN FEATURE IN W ATLC IS LOW PRES AT 28N69W...1011 MB...WITH 
COLD FRONT EXTENDING FROM 29N66W TO 20N70W AND A TROUGH TO 
23N74W TO 24N77W.  LOW PRES WELL SUPPORTED BY LONGWAVE TROUGH 
RUNNING ALONG CENTRAL ATLC AND SHORTWAVE TROUGH NEAR 26N63W.
MODELS AGREE WITH SE MOVEMENT OF LOW PRES TO 25N60W IN 24 HRS 
WITH VERY TIGHT GRADIENT OVER NRN SEMICIRCLE CAUSING GALE FORCE 
WINDS WITHIN 300 NM N OF LOW PRES.  MOST DEEP CONVECTION... 
SCATTERED TSTMS...REMAIN E OF CENTER UNDER DIFFLUENT ZONE ALOFT 
ASSOCIATED WITH SHORTWAVE AND COLD FRONT.  LITTLE SIGNIFICANT 
CONVECTION ASSOCIATED WITH SURFACE TROUGH.

TAIL END OF OLD FRONTAL BOUNDARY 31N40W 27N46W MOVING E 
FORECAST TO BE OUT OF AREA WITHIN 24 HRS BY MODEL ENSEMBLE. 
LITTLE SIGNIFICANT CLOUDINESS ALONG THIS WEAK BOUNDARY.  

E ATLC UNDER UMBRELLA OF LARGE HIGH PRES RIDGE KEEPING LOW 
PROFILE WITH STRONG ZONAL FLOW ALOFT DOMINATING WEATHER PATTERN.

$$
WALLY BARNES