000
AXPZ20 KNHC 311511
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON DEC 31 2007

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 
1545 UTC.
 
...ITCZ...
INTERTROPICAL CONVERGENCE ZONE AXIS 7N77W 8N110 8N120W 7N140W. 
SCATTERED MODERATE ISOLATED STRONG WITHIN 80 NM EITHER SIDE AXIS 
EAST OF 88W...AND BETWEEN 95W AND 103W.

...DISCUSSION...
A CUT-OFF LOW IS OVER THE NW CORNER OF THE FORECAST AREA NEAR 
24N130W WITH AN UPPER-LEVEL TROUGH EXTENDING SOUTH TO NEAR 10N. 
DRY UPPER AIR IS NOTED BEHIND THE TROUGH AXIS N OF 20N WHILE 
AMPLE UPPER LEVEL MOISTURE IS SEEN E AND S OF THE TROUGH AXIS 
COVERING MOST OF THE AREA W OF 110W. AN UPPER-LEVEL RIDGE 
ANCHORED ON A HIGH LOCATED OVER THE CENTRAL CARIBBEAN DOMINATES 
SOUTH MEXICO AND THE EPAC E OF 110W. THIS FEATURE IS ENHANCING 
CONVECTION ALONG THE ITCZ PARTICULARLY SOUTH OF PANAMA AND COSTA 
RICA.   

AT THE LOW LEVELS...HIGH PRES DOMINATES THE AREA N OF THE ITCZ W 
OF 110W WITH THE EASTERLY TRADES S OF THE RIDGE IN THE 20-25 KT 
RANGE AND EXPECTED TO DIMINISH TO ABOUT 20 KT AS THE RIDGE 
WEAKENS AND SHIFTS EASTWARD IN ADVANCE OF A WEAK COLD FRONT THAT 
WILL MOVE INTO THE NW CORNER TUE AFTERNOON. A STRONGER COLD 
FRONT IS EXPECTED TO ENTER THE NW WATERS ON THU. THIS COLD FRONT 
WILL BE ACCOMPANIED BY A FRESH NW SWELL TRAIN THAT WILL DRIVE 
SEAS TO ABOUT 16 FT IN THE AREA NEAR 30N140W LATE WED INTO THU. 

GAP WINDS ARE DEVELOPING THIS AFTERNOON TO ABOUT 20 KNOTS IN AND 
DOWNSTREAM OF THE GULF OF TEHUANTEPEC AND THE GULF OF PAPAGAYO  
WITH SEAS TO MAX AT 7 FT. THE GRADIENT WILL TIGHTEN TO 20 TO 25 
KT TONIGHT IN THE GULF OF TEHUANTEPEC AND GRADUALLY INCREASE TO 
GALE FORCE ON TUE. THESE NLY WINDS WILL CONTINUE TO INCREASE TO 
STORM FORCE TUE NIGHT AND FURTHER INCREASE TO MINIMAL HURRICANE 
FORCE EARLY WED MORNING WITH SEAS BUILDING TO ABOUT 24 FT NEAR 
13N96W. NE WINDS WILL ALSO FURTHER INCREASE TO 30 KT IN THE GULF 
OF PAPAGAYO IN 48 HOURS. 

NW WINDS IN THE GULF OF CALIFORNIA WILL FLUCTUATE AROUND 20 KT 
THIS AFTERNOON THEN INCREASE BRIEFLY TO 20 TO 25 KT TUE THEN 
DIMINISH TO 20 KT WED. SEAS MAX WILL MAX AT 6-7 FT IN THE 
CENTRAL EXPOSED WATERS.

$$
GR