000
AXPZ20 KNHC 202138
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE DEC 20 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH FROM 08N83W TO 08N94W. ITCZ FROM 08N94W TO 
07N100W TO 09N107W TO 07N117W TO 10N140W. SCATTERED MODERATE TO 
STRONG CONVECTION WAS NOTED WITHIN 120 NM N OF AXIS BETWEEN 107W 
AND 114W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS 
NOTED WITHIN 60 NM EITHER SIDE OF AXIS BETWEEN 114W AND 120W. 
SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 120 NM 
N OF AXIS BETWEEN 125W AND 130W.

...DISCUSSION...
HIGH PRESSURE IS CENTERED N OF THE AREA NEAR 36N140W WITH RIDGE 
EXTENDING TO 23N127W TO 22N111W. DISSIPATING LOW PRESSURE IS 
CENTERED OVER THE FAR NE PART OF THE AREA NEAR 30N118W WITH 
TROUGH EXTENDING TO 28N117W TO 25N123W. THE PRESSURE GRADIENT 
BETWEEN HIGH PRES AND THE TROUGH OF LOW PRES AS WELL AS LOWER 
PRESSURE IN THE VICINITY OF THE ITCZ IS MAINTAINING FRESH 
TRADEWIND FLOW OVER MUCH OF THE AREA N OF 10N AND W OF 130W...AS 
WELL AS FROM 09N TO 15N BETWEEN 105W AND 120W. LATEST ASCAT PASS 
INDICATES FRESH SOUTHERLY FLOW FROM 02N TO 07N BETWEEN 105W AND 
120W. THE FRESH WINDS ON EITHER SIDE OF THE ITCZ OVER THIS AREA 
ARE PRODUCING ENOUGH CONVERGENCE TO MAINTAIN THE CONVECTION 
ALONG THE ITCZ AS NOTED ABOVE. THE AREA OF HIGH PRESSURE WILL 
PREVAIL N OF THE AREA THROUGH THE FORECAST PERIOD...AND HELP 
MAINTAIN A TIGHT PRESSURE GRADIENT TO SUPPORT THE FRESH 
TRADEWIND FLOW THROUGH THE FORECAST PERIOD WHICH RUNS THROUGH 
THU AFTERNOON.

FRESH TO STRONG TRADEWINDS PREVAIL OVER THE W CARIBBEAN. THESE 
WINDS ARE FUNNELING INTO THE GULF OF PAPAGAYO FROM 10N TO 12N E 
OF 90W. WITH THE FRESH TO STRONG TRADEWINDS CONTINUING THROUGH 
THE FORECAST PERIOD...FRESH WINDS WILL MAINTAIN OVER THE GULF OF 
PAPAGAYO THROUGH THE FORECAST PERIOD. 

NW SWELL WILL PREVAIL OVER MUCH OF THE AREA W OF 110W THROUGH 
THE FORECAST PERIOD. THIS SWELL WILL START TO MIX WITH SW SWELL 
S OF 10N THAT MOVES INTO THE AREA OVER THE NEXT 24 HOURS. 

$$
AL