000
AXPZ20 KNHC 200310
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN DEC 20 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...07.5N78W 
TO 06N106W TO 08N120W TO 08N140W. SCATTERED MODERATE ISOLATED 
STRONG WITHIN 120 NM EITHER SIDE OF AXIS E OF 87W. SCATTERED 
MODERATE ISOLATED STRONG WITHIN 150 NM S OF AXIS BETWEEN 115W 
AND 118W. SCATTERED MODERATE WITHIN 270 NM S OF AXIS BETWEEN 
127W AND 133W. SCATTERED MODERATE ISOLATED STRONG WITHIN 90 NM S 
AND 30 NM N OF AXIS W OF 136W. 

...DISCUSSION...

UPPER LEVEL RIDGING PREVAILS ALONG THE W PART OF THE FORECAST 
AREA...TROUGHING PREVAILS ACROSS THE CENTRAL PORTION...WHILE 
RIDGING PREVAILS IN THE FAR E PART OF THE AREA. SW FLOW E OF THE 
UPPER LEVEL TROUGH IS ADVECTING MID AND UPPER LEVEL MOISTURE 
FROM THE ITCZ NEAR 112W TO THE GULF OF MEXICO. A SHORT WAVE 
TROUGH N AND W OF THE AREA...WITH AXIS EXTENDING FROM 46N138W TO 
35N140W TO 30N147W. ASSOCIATED COLD FRONT IS IN THE NW PART OF 
THE LOCAL FA AND IS DISCUSSED IN THE FOLLOWING PARAGRAPH. A LONG 
WAVE TROUGH IS JUST E OF HAWAII. THE SOUTHWESTERLY FLOW E OF THE 
TROUGH AXIS IS ADVECTING MID AND UPPER LEVEL MOISTURE ACROSS THE 
NW PORTION OF THE FORECAST AREA. 

A SURFACE COLD FRONT IS IN THE FAR NW PART OF THE FORECAST 
AREA...FROM 30N136W 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 08N AND W OF 
117W...THOUGH MON. WEAKENING HIGH PRESSURE 1018 MB CENTERED NEAR 
28N132W. THE PRESSURE GRADIENT BETWEEN THIS FEATURE AND THE ITCZ 
IS PRODUCING FRESH TO STRONG TRADEWIND FLOW FROM 08N TO 13N W OF 
132W. AS THE THE SHORT WAVE TROUGH MENTIONED IN THE PREVIOUS 
PARAGRAPH CONTINUES TO SHIFT E THROUGH THE REST OF THE WEEKEND 
THE SURFACE HIGH WILL CONTINUE TO 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 
MON 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