000
AXPZ20 KNHC 211539
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED DEC 21 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 
1545 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS EXTENDS FROM 08N78W TO 05N93W TO 09N102W. 
09N102W. ITCZ AXIS EXTENDS FROM 09N102W TO 11N112W TO 08N125W TO 
09N140W. SCATTERED MODERATE TO STRONG WITHIN 150-180 NM EITHER 
SIDE OF AXIS BETWEEN 110W AND 125W. 

...DISCUSSION...
THE UPPER PATTERN FEATURES A MEAN TROUGH OVER NW MEXICO AND A 
RIDGE EXTENDING FROM AN ANTICYCLONE CURRENTLY LOCATED NEAR 
14N94W THROUGH 12N115W THROUGH 26N140W. THIS ANTICYCLONE WILL 
DRIFT N INTO THE ISTHMUS OF TEHUANTEPEC OVER THE NEXT FEW DAYS. 
RIDGING AT THE SURFACE LIES OVER MUCH OF THE NORTHERN HALF OF 
THE FORECAST AREA ANCHORED BY A 1031 MB HIGH PRES NEAR 38N139W. 
THE PRES GRADIENT BETWEEN THIS RIDGING AND TROUGHING ALONG THE 
ITCZ IS GENERATING A LARGE SWATH OF FRESH TRADE WINDS THAT 
EXTENDS AS FAR E AS 110W. THESE TRADE WINDS WILL REMAIN 
RELATIVELY UNCHANGED THROUGH THU. AS THE MEAN TROUGHING OVER NW 
MEXICO RELOADS OVERNIGHT THU NIGHT...THE SURFACE RIDGING OVER NE 
WATERS WILL WEAKEN AND TRADE WINDS WILL BEGIN TO SHIFT WESTWARD.

A CLUSTER OF SCATTERED MODERATE TO STRONG CONVECTION WAS NOTED 
WITHIN 75 NM OF 14N138W AND WAS DISPLACED TO THE N OF THE ITCZ
IN AN AREA ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE 
AFOREMENTIONED RIDGE AXIS ALOFT AND AN UPPER TROUGH AXIS ALIGNED 
FROM 12N145W TO 06N120W. A SURFACE TROUGH EXTENDING FROM 11N138W 
TO 07N141W REPRESENTED THE SURFACE REFLECTION OF THE UPPER LEVEL 
TROUGH. 

GAP WINDS...
GULF OF PAPAGAYO...THE PRES GRADIENT ACROSS CENTRAL AMERICA 
BETWEEN HIGH PRES OFF THE SE U.S. COAST AND THE MONSOON TROUGH 
CONTINUES TO SUPPORT FRESH TO STRONG WINDS IN THE GULF OF 
PAPAGAYO. A SHIP WITH CALL SIGN DGSE REPORTED 24 KT WINDS NEAR 
10N87W AT 0600 UTC. THE SURFACE RIDGE THAT EXTENDS FROM THE HIGH 
PRES SYSTEM INTO THE NW CARIBBEAN IS EXPECTED TO WEAKEN TODAY AS 
A COLD FRONT IN THE NW GULF OF MEXICO INCHES EASTWARD...BUT IT 
WILL TAKE THE NEXT COLD FRONT EXPECTED IN THE GULF OF MEXICO 
LATE THU TO FINALLY REDUCE THE GRADIENT ENOUGH TO DIMINISH WINDS 
BELOW 20 KT. WINDS WILL BE STRONGEST IN THE EARLY MORNING HOURS 
WITH THE ASSISTANCE OF DRAINAGE FLOW OFF THE LAND.

GULF OF CALIFORNIA...HIGH PRES BUILDING IN THE GREAT BASIN OF 
THE CONUS WILL DRIVE NW TO N WINDS IN THE GULF OF CALIFORNIA N 
OF 29N BY LATE THU. THESE WINDS SHOULD RAMP UP TO GALE FORCE 
OVER THE GULF OF CALIFORNIA N OF 25N BY EARLY FRI. NWP MODEL 
GUIDANCE AND IN-HOUSE DIAGNOSTICS SUPPORT THE ISSUANCE OF A GALE 
WARNING N OF 25N EARLY FRI. 

$$
COBB