000
AXPZ20 KNHC 192145
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT DEC 19 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 
2100 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...06.5N78W 
TO 07N82W TO 05N109W TO 09N120W TO 08N140W. SCATTERED MODERATE 
TO STRONG CONVECTION WITHIN 120 NM EITHER SIDE OF AXIS E OF 88W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 90 NM 
EITHER SIDE OF AXIS BETWEEN 119W AND 123W. SCATTERED MODERATE TO 
STRONG CONVECTION WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 127W 
AND 132W. 

...DISCUSSION...

ACTIVE CONVECTION IN THE ITCZ CONTINUES TO MAINTAIN UPPER LEVEL 
RIDGING ALONG THE W PART OF THE FORECAST AREA. TROUGHING 
PREVAILS ACROSS THE CENTRAL PORTION...WHILE CONVECTION IN THE 
ITCZ IN THE FAR E PART OF THE AREA IS MAINTAINING UPPER LEVEL 
RIDGING. SW FLOW E OF THE UPPER LEVEL TROUGH IS ADVECTING MID 
AND UPPER LEVEL MOISTURE FROM THE CONVECTION IN THE ITCZ FROM 
111W TO THE GULF OF MEXICO. A SHORT WAVE TROUGH N AND W OF THE 
AREA...WITH AXIS EXTENDING FROM 44N140W TO 31N145W. ASSOCIATED 
COLD FRONT HAS ENTERED THE NW PART OF THE LOCAL FA AND IS 
DISCUSSED IN THE FOLLOWING PARAGRAPH. A LONG WAVE TROUGH IS 
JUST E OF HAWAII. THE FLOW E OF THE TROUGH IS ADVECTING MID AND 
UPPER LEVEL MOISTURE ACROSS THE NW PORTION OF THE FORECAST AREA. 

A SURFACE COLD FRONT HAS MOVED INTO THE FAR NW PART OF THE 
FORECAST AREA...FROM 30N137W TO 26.5N140W. THE COLD FRONT WILL 
WEAKEN AND BECOME DIFFUSE WITHIN THE NEXT 24 HOURS...BUT LONG 
PERIOD NW SWELL THAT GENERATED BEHIND THIS FRONT WILL SPREAD S 
AND E ACROSS THE FORECAST AREA...MAINLY N OF 09N AND W OF 
115W...THOUGH MON. HIGH PRESSURE 1022 MB CENTERED NEAR 31N129W. 
THE PRESSURE GRADIENT BETWEEN THIS FEATURE AND ACTIVE CONVECTION 
ALONG THE ITCZ W OF 117W IS PRODUCING FOR FRESH TO STRONG 
TRADEWIND FLOW FROM 08N TO 13N W OF 117W. AS THE THE SHORT WAVE 
TROUGH MENTIONED IN THE PREVIOUS PARAGRAPH SHIFTS E THROUGH THE 
REST OF THE WEEKEND THE SURFACE HIGH WILL WEAKEN AND THE AREAL 
COVERAGE OF FRESH TO STRONG TRADEWIND FLOW WILL DECREASE.  

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

THE COMBINATION OF STRONG TRADE WINDS IN THE CARIBBEAN AND LOCAL 
DRAINAGE EFFECTS WILL ALLOW FOR NE TO E 20 KT WINDS THROUGH THE 
GULF OF PAPAGAYO TO PULSATE ON AND OFF WITH MAXIMUM PEAK 
OCCURRENCES IN THE MORNINGS INTO EARLY NEXT WEEK.

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