000
AXPZ20 KNHC 261601
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 26 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...
ITCZ AXIS IS ALONG 07N77W TO 03N100W TO 08N115W TO 05N140W. 
SCATTERED MODERATE TO STRONG CONVECTION IS NOTED WITHIN 150 NM 
OF 05N79W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS 
OBSERVED WITHIN 30 NM EITHER SIDE OF A LINE FROM 05N85W TO 
05N91W TO 04N95W.

...DISCUSSION...
AN UPPER LEVEL TROUGH DISSECTS THE DISCUSSION AREA FROM NE TO SW 
WITH ITS MEAN AXIS ALONG 32N108W TO 16N123W TO 03N140W. AN UPPER 
ANTICYCLONE NEAR 09N142W HAS A RIDGE EXTENDING NE ALONG 23N130W 
TO NEAR 32N 117W. THE UPPER LEVEL FLOW IS NEARLY ZONAL N OF 22N 
W OF 120W AND APPEARS MOIST. DRY UPPER AIR IS INDICATED 
ELSEWHERE W OF A LINE FROM 30N103W TO 00N130W.

THE SOUTHERN EXTENSION OF AN ATLC UPPER TROUGH DISSECTS THE 
CARIBBEAN AND CONTINUES SW ACROSS PANAMA INTO A MID TO UPPER 
CYCLONE OVER THE PACIFIC AT 04N78W. THE PACIFIC ITCZ MEANDERS 
THROUGH THE SAME AREA WHERE SOUTHERLY MONSOONAL FLOW INTERSECTS 
WITH NORTHERLY FLOW BRIDGING ACROSS PANAMA MAKING IT DIFFICULT 
TO DETERMINE HOW MUCH REFLECTION OF THE UPPER FEATURE IS EVIDENT 
IN THE LOW LAYERS. IN ANY EVENT...LOW LEVEL CONVERGENCE AND 
UPPER DIFFLUENCE E OF THE UPPER TROUGH IS SUPPORTING A 
CONVECTIVE BURST IN THE VICINITY OF THE ITCZ AND PREVIOUSLY 
DISCUSSED. THE UPPER LEVELS ARE VERY DRY TO THE NW AND THE 
DEBRIS MOISTURE IS IMMEDIATELY EVAPORATING.

AN UPPER ANTICYCLONE IS CENTERED NEAR 12N91W WITH A RIDGE 
EXTENDING SW TO A SHARP CREST AT 04N110W. A RIDGE ALSO EXTENDS 
NE TO A CREST OVER CENTRAL CUBA. CONVECTION PREVIOUSLY MENTIONED 
IS ENHANCED ALONG THE SOUTHERN PERIPHERY OF THE RIDGE NEAR 
04N90W...BUT THE DEBRIS MOISTURE REMAINS IN THE SAME AREA. 
DEBRIS MOISTURE FROM FORMER ITCZ CONVECTION IS CONFINED IN A 
TROPICAL PLUME ALONG THE NW PERIPHERY OF THIS UPPER 
RIDGE...ROUGHLY WITHIN 180 NM OF LINE 10N120W TO 20N105W. THE 
MOISTURE FANS OUT OVER THE UPPER LEVELS OF THE GULF OF MEXICO 
AND FLORIDA. OTHERWISE DRY UPPER AIR IS INDICATED OVER THE 
DISCUSSION AREA S OF 18N E OF 105W.
 
AT THE SURFACE...A 1018 MB HIGH PRES CENTERED NEAR 26N123W IS 
BEGINNING TO BLOCK THE EASTWARD PROGRESSION OF A COLD FRONT 
CURRENTLY EXTENDING FROM 32N128W TO 21N140W. EASTERLY TRADES OF 
20 KT CONTINUE ALONG THE SOUTHERN PERIPHERY OF THE RIDGE. 
SUBSIDING NW SWELLS ALREADY PROPAGATING OVER MOST OF THE AREA W 
OF 112W ARE ALREADY BEING REINFORCED BY ANOTHER TRAIN OF LARGE 
NW SWELLS IN THE WAKE OF THIS COLD FRONT AND A SECONDARY SURGE 
EXPECTED TO MOVE INTO THE NW PORTION ON SUN. A LOW PRES IS 
EXPECTED TO MOVE SE INTO THE N CENTRAL WATERS LATE SUN AND 
DEEPEN TO A MINIMAL GALE CENTER EARLY MON.    

GULF OF TEHUANTEPEC...NORTHERLY WINDS ARE EXPECTED TO INCREASE 
TO 20 KT IN THE GULF OF TEHUANTEPEC LATE SUN AND CONTINUE TO 
GRADUALLY INCREASE REACHING MINIMAL GALE MON NIGHT THROUGH 
MIDDAY TUE. 

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE
  
$$
NELSON