000
AXPZ20 KNHC 170343
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT DEC 17 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH AXIS FROM 09N84W TO 05N98W TO 08N105W THEN ITCZ 
TO 08N132W TO 10N113W TO BEYOND 07N140W.  ISOLATED MODERATE 
CONVECTION WITHIN 45 NM OF AXIS FROM 110W TO 117W.  SCATTERED 
MODERATE CONVECTION WITHIN 90 NM OF AXIS W OF 132W.

...DISCUSSION...

WELL DEFINED UPPER LEVEL CYCLONE AT 30N117W REFLECTS AS HEALTHY 
SURFACE LOW PRES 1015 MB WITH FRONTAL TROUGH EXTENDING SW TO 
23N120W THEN W TO 22N134W.  CYCLONE MOVES E-NE SAT ONLY TO BE 
REPLACED BY NEW AND STRONGER CYCLONE FROM THE NW WITH ITS 
ATTENDANT FRONTAL BOUNDARY LATE SUN.  MID TO UPPER LEVEL RIDGE 
REMAINS WELL N AND W OF BASIN ALLOWING SERIES OF SHORT WAVES TO 
IMPACT NE PORTION OF E PAC.  MOISTURE LADEN AIR MASS FLOWS INTO 
BASIN FROM THE W ALONG ITCZ WITH SOME FLARE UPS W OF 132W AS 
UPPER DIVERGENCE ENHANCES CONVECTION. 

UPPER LEVEL RIDGE OVER SOUTH AMERICA ADVECTS ABUNDANT MOISTURE 
ALONG MONSOON TROUGH BUT LACKS MECHANICAL UPLIFT TO WARRANT 
SIGNIFICANT CONVECTION.  ONLY ISOLATED SHOWERS ELSEWHERE ALONG 
ITCZ.    

ELSEWHERE AT THE LOW LEVELS...
HIGH PRES CENTER 1028 MB N OF BASIN PRODUCING FRESH NE BREEZE W 
OF 130W WEAKENS IN STRENGTH AND SHRINKS IN COVERAGE AS FRONTAL 
BOUNDARIES SCRATCH NE PORTION OF E PAC SAT AND SUN.

GAP WINDS...
GULF OF TEHUANTEPEC...MODEL GUIDANCE AGREE ON BRINGING STRONG N 
WINDS ACROSS CHIVELA PASS UNTO GULF OF TEHUANTEPEC BY SAT NIGHT
...TURNING INTO GALE FORCE WINDS ACROSS GULF OF TEHUANTEPEC.  
EVENT IS SHORT-LIVED AS WIND SOURCE IS QUICKLY CUT OFF BY FAST 
MOVING HIGH PRES RIDGE OVER CONUS ATLC SEABOARD.  FRESH TO 
STRONG N WINDS BEGAN EARLIER TONIGHT PRECEDING GALE. 

GULF OF PAPAGAYO...BUILDING PRES GRADIENT OVER SOUTHERN MEXICO 
EXTEND S TO GULF OF PAPAGAYO EARLY SAT WITH FRESH NE WINDS 
EXPECTED TO INCREASE EARLY SUN AND EXTEND N ALONG NICARAGUAN 
COAST TO GULF OF FONSECA.

$$
WALLY BARNES