000
AXPZ20 KNHC 210911
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0700 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 09N102W. THE ITCZ 
AXIS EXTENDS FROM 09N102W TO 11N111W TO 08N125W TO 09N140W. 
SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION LIES WITHIN 
180 NM N OF THE AXIS BETWEEN 108W AND 128W. 

...DISCUSSION...
THE UPPER PATTERN FEATURES A MEAN TROUGH OVER NW MEXICO AND A 
RIDGE EXTENDING FROM AN ANTICYCLONE CURRENTLY LOCATED NEAR 
12N96W THROUGH 12N115W TO 25N140W. 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 STEMMING FROM 1034 MB HIGH PRES NEAR 46N133W. 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.

MID-LEVEL ENERGY OVER SW WATERS S OF THE RIDGE AXIS ALOFT IS 
REFLECTING A SURFACE TROUGH FROM 13N135W TO 07N137W. SCATTERED 
MODERATE CONVECTION LIES JUST N OF THE TROUGH FROM 13N TO 20N W 
OF 133W. PRECIPITABLE WATER IMAGERY SHOWS MOISTURE POOLED NEAR 
THE TROUGH WHILE THE MEAN DEEP-LAYER WINDS ARE TRANSPORTING THE 
MOISTURE NORTHWARD TOWARD THE DIFFLUENT REGION ASSOCIATED WITH 
THE RIDGE AXIS ALOFT...DISPLACING THE CONVECTION N OF THE 
SURFACE TROUGH. MEANWHILE...SCATTERED MODERATE WITH ISOLATED 
STRONG CONVECTION LIES NEAR THE ITCZ AXIS OVER CENTRAL WATERS 
AND IS BEING ENHANCED BY DIFFLUENCE ASSOCIATED WITH THE 
AFOREMENTIONED RIDGE AXIS ALOFT. THIS CONVECTION IS DESCRIBED IN 
THE ITCZ/MONSOON TROUGH SECTION ABOVE. 

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. SHIP 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...LOOK FOR NW TO N WINDS IN THE GULF OF 
CALIFORNIA TO INCREASE QUICKLY LATE THU AS THE MEAN TROUGH OVER 
NW MEXICO RELOADS. NEAR GALE FORCE WINDS ARE EXPECTED BY THE END 
OF THE PERIOD ON EARLY FRI MORNING AS HIGH PRES BUILDS IN THE 
GREAT BASIN...INCREASING THE PRES GRADIENT OVER THE GULF.

$$
SCHAUER