000
AXPZ20 KNHC 201515
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN DEC 20 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...06N77W TO 
06N115W TO 08N140W. SCATTERED MODERATE TO STRONG CONVECTION IS 
WITHIN THE AREA FROM 07N TO 09N WEST OF 135W. OTHERWISE THERE IS 
NO SIGNIFICANT CONVECTION ALONG THE ITCZ AT THIS TIME.

...DISCUSSION...

FULL LATITUDE SHORTWAVE IS WEST AND NORTHWEST OF THE AREA AND 
EXTENDS OVER THE AREA NW OF A LINE THROUGH 32N133W TO 24N140W. 
ASSOCIATED SURFACE COLD FRONT IS ALONG LINE THROUGH 32N131W TO 
25N140W. A PLUME OF UPPER LEVEL MOISTURE WITH BROKEN TO OVERCAST 
MIDDLE AND HIGH CLOUDS IS ALSO ASSOCIATED WITH THE TROUGH AND 
COVERS THE AREA WEST OF 135W SOUTH OF 20N AND WEST OF 115W NORTH 
OF 20N. THE MOISTURE EMANATES FROM ITCZ CONVECTION WEST OF THE 
AREA AND GENERAL RISING MOTION ON THE EAST FLANK OF THE TROUGH 
WEST OF THE AREA. THE SHORTWAVE JUST NORTH OF THE NORTHWEST PART 
OF THE AREA IS FORECAST TO TRACK EAST REACHING CENTRAL 
CALIFORNIA LATE TODAY. THE LARGER TROUGH IS FORECAST TO 
REMAIN STATIONARY AND WEAKEN THROUGH THE NEXT COUPLE OF DAYS.

ANOTHER TROUGH IS OVER THE MEXICO WITH A TROUGH AXIS ALONG A 
LINE THROUGH 27N95W TO 23N100W THEN SOUTH TO THE ITCZ NEAR 105W. 
SOUTHERLY FLOW EAST OF THE TROUGH AXIS IS BRINGING ITCZ MOISTURE 
NORTH OVER MEXICO EAST OF THE TROUGH AXIS AND ALL OF CENTRAL 
AMERICA. MULTIPLE LEVEL OVERCAST TO BROKEN CLOUDS ARE NORTH OF 
THE ITCZ WITH SOME ISOLATED 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 THE ITCZ WEST OF 118W. ELSEWHERE A BROAD TROUGH CENTERED ON 
THE ITCZ IS ANALYZED AT THE SURFACE.

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

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

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