000
AXPZ20 KNHC 082158
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE DEC 08 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 ITCZ AXIS IS ALONG 05N77W TO 05N100W TO 09N116W TO 08N130W TO 
07N140W. SCATTERED MODERATE TO ISOLATED STRONG WITHIN 150 NM N OF 
AXIS FROM 122W TO 125W. SCATTERED MODERATE IS WITHIN 120 NM S OF 
AXIS BETWEEN 115W AND 125W. SIMILAR CONVECTION IS NEAR 07N140W.

...DISCUSSION...
A BROAD UPPER-LEVEL RIDGE ANCHORED ON A HIGH NEAR ACAPULCO MEXICO 
DOMINATES A LARGE PORTION OF THE DISCUSSION AREA. THE RIDGE AXIS 
EXTENDS W-NW TO NEAR 24N125W. DRY AND STABLE AIR EXISTS S OF 18N E 
OF 110W WITH STRONG SUBSIDENCE IN PLACE AS INDICATED ON WATER VAPOR 
SATELLITE IMAGERY. W OF THE RIDGE...ABUNDANT MID TO UPPER LEVEL 
MOISTURE IS BEEN ADVECTING FROM THE ITCZ TO THE N AND NE AROUND THE 
NW PORTION OF THE ANTICYCLONE. AT THE SAME TIME...THE RIDGE IS 
ENHANCING CONVECTION ALONG THE ITCZ WEST OF 115W. AN UPPER-LEVEL 
TROUGH IS MOVING ACROSS THE NW PORTION OF THE REGION. THE ATTENDANT 
COLD FRONT EXTENDS FROM 30N138W TO 26N140W. S TO SW WINDS OF 20 TO 
25 KT ARE NOTED WITHIN 150 NM AHEAD OF THE FRONT WITH NW WINDS 15 KT 
BEHIND THE FRONT. THE FRONT WILL TRACK ACROSS THE FAR NORTHERN 
WATERS REACHING FROM 30N131W TO 26N135W TO 22N140W WED AFTERNOON 
WHERE IT WILL BEGIN TO DISSIPATE AS IT ENCOUNTERS SURFACE HIGH PRES 
W OF THE BAJA PENINSULA. LARGE AND LONG PERIOD NW SWELL WILL FOLLOW 
THE FRONT AND GRADUALLY INVADE THE FORECAST REGION REACHING THE 
EQUATOR W OF 110W IN ABOUT 48 HOURS. 

NW WINDS OF 20 KT ARE BLOWING N OF 25N E OF 120W TO THE COAST OF 
BAJA CALIFORNIA PENINSULA BEHIND A COLD FRONT THAT IS ALREADY INLAND 
OVER THE SW CONUS AND NW MEXICO. THIS WINDS ARE EXPECTED TO DIMINISH 
BELOW 20 KT SHORTLY. NW SWELL OF 8 TO 13 FT IS PROPAGATING INTO THIS 
AREA. 

A 1011 MB LOW PRESSURE SYSTEM IS EMBEDDED WITHIN THE ITCZ... 
POSITIONED NEAR 13N116W...ALONG A SURFACE TROUGH EXTENDING FROM 
15N115W TO 09N118W. AN ASCAT PASS FROM AROUND 1700 UTC INDICATED NE 
WINDS OF 20 KT JUST W OF THE TROUGH AXIS AND N OF THE LOW CENTER. 
MODEL GUIDANCE ALSO SUGGESTS AN AREA OF TRADE WINDS OF 20 KT FROM 
11N TO 15N BETWEEN 120N AND 132N. AN ASCAT PASS FROM 1838 UTC 
CONFIRMED THESE WIND SPEEDS. 

GAP WINDS...
GULF OF PAPAGAYO...EASTERLY TRADES IN THE W CARIBBEAN WILL CONTINUE 
TO PASS OVER NICARAGUA AND COSTA RICA LEADING TO NE-E WINDS TO 20 KT 
IN THE GULF OF PAPAGAYO AND DOWNSTREAM TO 89W THROUGH WED 
AFTERNOON.  THE WINDS WILL BE STRONGEST DURING THE MORNING HOURS 
WITH THE AID OF DRAINAGE FLOW OFF THE LANDMASS.

$$
GR/JL