000
AXPZ20 KNHC 211517
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON DEC 21 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 
1500 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...08N78W TO 
03N100W TO 06N120W TO 08N140W. SCATTERED MODERATE CONVECTION IS 
WITHIN 75 NM OF THE POINT 04.5N77.5W. SCATTERED MODERATE 
CONVECTION IS WITHIN 120 NM OF THE POINT 07N86W.

...DISCUSSION...

FULL LATITUDE TROUGH MOSTLY WEST AND NORTHWEST OF THE AREA 
EXTENDS OVER THE NORTHWEST PART OF THE AREA NW OF A LINE THROUGH 
32N129W TO 23N140W. ASSOCIATED WEAK SURFACE COLD FRONT IS ALONG 
LINE THROUGH 32N127W TO 28N130W AND DIFFUSE TO 23N140W. A PLUME 
OF UPPER LEVEL MOISTURE WITH BROKEN TO OVERCAST MIDDLE AND HIGH 
CLOUDS IS ALSO ASSOCIATED WITH THE TROUGH AND COVERS THE ENTIRE 
PACIFIC OCEAN AREA NORTH OF 25N AND THE AREA WITHIN 900 NM 
SOUTHEAST OF THE TROUGH AXIS. MOISTURE AND THIN HIGH CLOUDS ARE 
OVER MEXICO NORTH OF 25N. THE MOISTURE EMANATES FROM ITCZ 
CONVECTION BOTH WEST OF THE AREA AND THE ITCZ CONVECTION WEST OF 
130W AND ALSO DUE TO THE GENERAL RISING MOTION ON THE EAST FLANK 
OF THE TROUGH. A SHORTWAVE JUST NORTH OF THE NORTHWEST PART OF 
THE AREA IS FORECAST TO TRACK EAST REACHING CENTRAL AND SOUTHERN 
CALIFORNIA TONIGHT. THE LARGER TROUGH IS FORECAST TO DRIFT EAST 
AND WEAKEN SLIGHTLY THROUGH THE NEXT COUPLE OF DAYS.

ANOTHER TROUGH IS OVER EASTERN MEXICO WITH A NEGATIVELY TILTED 
TROUGH AXIS FROM THE SOUTHWEST GULF OF MEXICO NEAR 20N95W TO THE 
ITCZ NEAR 87W. SOUTHERLY FLOW EAST OF THE TROUGH AXIS IS 
BRINGING MOISTURE FROM ITCZ CONVECTION NORTH OVER THE YUCATAN 
PENINSULA OF MEXICO ALL OF CENTRAL AMERICA. SOME DRYING IS NOTED 
OVER WESTERN GUATEMALA AS THE TROUGH SWINGS EAST. IN THIS MOIST 
REGION MULTIPLE LEVEL OVERCAST TO BROKEN CLOUDS ARE NORTH OF THE 
ITCZ WITH SOME EMBEDDED CONVECTION.  

WEST OF THE TROUGH AXIS AND EAST OF THE MOISTURE MENTIONED IN 
THE FIRST PARAGRAPH...THAT IS THE AREA BETWEEN THE TWO TROUGHS 
...IS A LARGE SCALE DEEP LAYER RIDGE WITH MOSTLY DRY AND CLOUD 
FREE MIDDLE AND UPPER LEVELS. 

OTHER THAN THE COLD FRONT MENTIONED ABOVE A WEAK RIDGE IS NORTH 
OF 15N. ELSEWHERE A BROAD TROUGH CENTERED ON THE ITCZ IS 
ANALYZED AT THE SURFACE.

GAP N TO NE WINDS OF 20 TO 30 KT ARE OCCURRING THROUGH THE GULF 
OF TEHUANTEPEC AND ARE EXPECTED TO CHANGE LITTLE THEN DIMINISH 
TUESDAY.

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

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