000
AXPZ20 KNHC 101553
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT DEC 10 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 
MONSOON TROUGH EXTENDS FROM 09N84W TO 06N92W. ITCZ AXIS EXTENDS 
FROM 06N92W TO 08N108W TO 10N140W. SCATTERED MODERATE CONVECTION 
WITHIN 120 NM N OF AXIS BETWEEN 130W AND 135W.

...DISCUSSION...
A SHORT WAVE TROUGH EXTENDS FROM 16N140W TO 07N137W IS 
SUPPORTING ACTIVE ITCZ CONVECTION W OF 130W. SOME CONTINUED DEEP 
CONVECTION SHOULD BE EXPECTED AS THE UPPER TROUGH AND ITCZ 
INTERACT TODAY WITH LITTLE CHANCE OF TROPICAL CYCLONE 
DEVELOPMENT DUE TO STRONG VERTICAL SHEAR AND LACK OF 
PRE-EXISTING SURFACE TROUGH. BY SUNDAY...THE TROUGH SHOULD LIFT 
OUT TO NE AND THE DEEP CONVECTION SHOULD LIKELY DIMINISH.  
ELSEWHERE THE TROPICAL NE PACIFIC IS DOMINATED BY AN ANTICYCLONE 
CENTERED NEAR 10N111W...PROMOTING SUBSIDENCE AND DRY CONDITIONS 
IN EASTERN PORTION AS WELL AS ADVECTING UPPER LEVEL MOISTURE AND 
CLOUDINESS FROM WESTERN PORTION TOWARD NW MEXICO.

A SURFACE RIDGE EXTENDS FROM 30N140W TO NEAR 22N112W. THE 
COMBINATION OF THE RIDGE WITH ITCZ ASSOCIATED LOW PRESSURE IS 
SUSTAINING FRESH E-NE WINDS FROM 15N TO 20N W OF 130W. HIGHER 
THE GRADIENT NOT EXPECTED TO VARY MUCH OVER THE NEXT COUPLE OF 
DAYS...WITH LITTLE CHANGE IN EXPECTED WINDS.

WHILE NO OBSERVATIONS HAVE BEEN AVAILABLE RECENTLY...WINDS 
THROUGH THE GULF OF TEHUANTEPEC ARE BELIEVED TO HAVE REACHED 
GALE FORCE THIS MORNING AS THE LOCAL SURFACE PRESSURE GRADIENT 
BETWEEN THE GULF OF TEHUANTEPEC AND THE SOUTHWESTERN GULF OF 
MEXICO HAS TIGHTENED. BASED ON LATEST MODEL GUIDANCE...IT 
APPEARS THIS EVENT WILL PERSIST AT LEAST A FEW MORE DAYS... 
PERHAPS THROUGH WEDNESDAY MORNING...WITH LITTLE CHANGE OTHER 
THAN DIURNAL VARIABILITY.  FORECAST BASED PRIMARILY UPON BLEND 
OF GFS...ECMWF...UKMET...AND NAM...AS THE NOGAPS MODEL APPEARS 
TO BE SYSTEMATICALLY TOO WEAK FOR THIS EVENT.

A VIGOROUS TROUGH DIGGING SOUTHEASTWARD TOWARD THE COAST OF 
SOUTHERN CALIFORNIA AND NW MEXICO SUNDAY AND MONDAY IS EXPECTED 
TO BRIEFLY DEEPEN INTO A CLOSED LOW NEAR SAN DIEGO MONDAY 
EVENING.  PRESSURE GRADIENT BETWEEN THIS LOW AND A HIGH NEAR 
35N142W WILL INDUCE FRESH TO STRONG NORTHERLY WINDS N OF 25N 
MAINLY BETWEEN 120W AND 135W WITH N SWELLS SWEEPING INTO THE 
AREA AS WELL...WITH SEAS PEAKING NEAR 15 FT ALONG OUR NORTHERN 
BORDER EXPECTED BY MONDAY NIGHT.

THOUGH NOT EXPLICITLY INCLUDED IN THE HIGH SEAS FORECAST...NE 
WINDS IN THE GULF OF PAPAGAYO MAY REACH OUR 20 KT THRESHOLD.  
HOWEVER...THESE WINDS WILL PRIMARILY OCCUR DURING LATE 
NIGHT-EARLY MORNING HOURS AND OVER A VERY LIMITED EXTENT OVER 
THE NEXT COUPLE OF DAYS.

$$
LANDSEA