000
AXPZ20 KNHC 202154
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN DEC 20 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE FLUCTUATES FROM 05N TO 08N E 
OF 110W THEN EXTENDS NW TO 10N120W AND CONTINUES W ALONG 10N TO 
140W. ISOLATED MODERATE CONVECTION IS NOTED FROM 904N TO 108N 
BETWEEN 80W AND 87W AND SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS DISSIPATING WITHIN 60 NM OF 08N135W.

A CLUSTER OF STRONG CONVECTION IS OBSERVED ALONG THE COAST OF 
GUATEMALA AT 92W.


...DISCUSSION...

A POSITIVE TILT SHORTWAVE TROUGH IS MOSTLY W OF THE AREA WITH 
ITS MEAN AXIS ALONG 32N135W TO 28N143W INTO AN UPPER CYCLONE AT 
23N154W WHERE CONVECTION IS ENHANCED. SOME OF THE ASSOCIATED 
DEBRIS MOISTURE IS ADVECTED NE OVER THE DISCUSSION AREA NEAR 
27N140W. A SECOND UPPER TROUGH DOMINATING EASTERN N AMERICA 
EXTENDS INTO THE AREA ALONG 32N96W TO 22N102W TO A BASE IN THE 
DEEP TROPICS AT 08N105W. DRY UPPER AIR IS INDICATED WITHIN 240 
NM OF THE TROUGH AXIS. SEPARATING THESE UPPER TROUGHS IS AN 
UPPER ANTICYCLONE CENTERED AT 06N124W WITH A RIDGE EXTENDING N 
THROUGH 22N125W TO WELL BEYOND 32N120W. CONVECTION WAS ENHANCED 
ALONG THE ITCZ BETWEEN 130W AND 140W WITH THE DEBRIS MOISTURE 
ADVECTED N BETWEEN 130W AND 140W TO BEYOND 32N WITH SOME OF THE 
MOISTURE ALSO TURNING NE OVER THE SUBTROPICAL PACIFIC INTO THE 
RIDGE AXIS SPILLING OVER THE SW CONUS. AN UPPER ANTICYCLONE OVER 
COLOMBIA HAS A RIDGE EXTENDING NW ACROSS CENTRAL AMERICA TO A 
CREST OVER OLD MEXICO AT 20N100W. DEBRIS MOISTURE ORIGINATING 
FROM ITCZ CONVECTION E OF 100W IS ADVECTED NE ACROSS CENTRAL 
AMERICA AND THE GULF OF MEXICO AND THE WESTERN CARIBBEAN.    

AT THE LOW LEVELS...A STATIONARY FRONT EXTENDS FROM 32N129W TO 
25N140W. A WEAK SURFACE HIGH PRES IS NEAR 31N127W. 

GAP WINDS...N TO NE WINDS OF 20 TO 25 KT ARE OCCURRING THROUGH 
THE GULF OF TEHUANTEPEC AND ARE EXPECTED TO CHANGE LITTLE 
THROUGH MON NIGHT THEN DIMINISH TO LESS THAN 20 KT BY MIDDAY 
TUE.

GAP NE TO E WINDS OF 20 KT ARE OCCURRING IN THE GULF OF PAPAGAYO 
REGION AND ARE FORECAST TO DIMINISH BELOW 20 KT MON.

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