000
AXPZ20 KNHC 281551
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED DEC 28 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 
1445 UTC.

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

MONSOON TROUGH AXIS EXTENDS FROM 05N77W TO 07N84W TO 05N97W TO 
TO 08N108W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN 
ITCZ WHICH CONTINUES W TO 10N130W TO BEYOND 08N140W. SCATTERED 
MODERATE CONVECTION IS NOTED S OF THE MONSOON TROUGH WITHIN 30 
NM OF 05N79W AND ALSO ALONG THE ITCZ WITHIN 09N136W. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION HAS FLARED ALON THE ITCZ 
WITHIN 15 NM OF 08N114W.

...DISCUSSION...

AN UPPER TROUGH EXTENDS W FROM 32N110W TO 30N130W THEN TURNS SW 
INTO AN UPPER CYCLONE CUTTING OFF NEAR 17N144W. DRY UPPER AIR IS 
NOTED WITHIN 90 NM OF THE TROUGH AND OVER THE SW SEMICIRCLE OF 
THE CYCLONE. AN UPPER ANTICYCLONE IS AT 12N107W WITH A RIDGE NW 
TO 25N133W. AN UPPER TROUGH IS NOTED S OF THE EQUATOR RESULTING 
IN NORTHWESTERLY FLOW IN THE UPPER LEVELS SW OF A LINE FROM 
08N140W TO 00N123W. THUS A LARGE AREA OF UPPER DIFFLUENCE EXISTS 
FROM 10N TO 22N BETWEEN 120W AND 137W. ADDITIONALLY...DENSE 
UPPER MOISTURE IS INDICATED WITHIN THE UPPER RIDGE OVER THE 
DISCUSSION AREA FROM 10N TO 28N BETWEEN 138W AND 115W. SOME OF 
THIS UPPER MOISTURE SPREADS E IN UPPER ZONAL FLOW ACROSS THE 
UPPER RIDGE OVER NORTHERN MEXICO...ROUGHLY FROM 20N TO 30N 
BETWEEN 115W AND 108W.        

FURTHER E...AN UPPER TROUGH EXTENDS SW FROM THE SE GULF OF 
MEXICO ACROSS EXTREME EASTERN MEXICO TO OVER THE E PACIFIC NEAR 
07N97W. THE UPPER LEVELS APPEAR VERY DRY TO THE S OF 17N E OF 
106W...WITH THE DEBRIS MOISTURE FROM THE CONVECTION NEAR 05N79W 
QUICKLY EVAPORATING IN THIS DRY AIR ALOFT.  

AT THE LOW LEVELS...A 1030 MB HIGH PRES AREA CENTERED NEAR 
32N131W WILL DRIFT WSW THROUGH THU. A BROAD LOW LEVEL TROUGH 
EXTENDING FROM 09N131W TO 15N130W IS MOVING W WITH TIME. THE 
TIGHT PRESSURE GRADIENT BETWEEN THIS TROUGH AND THE SURFACE HIGH 
TO THE NORTH IS MAINTAINING NE-E 20 TO 25 KT TRADEWINDS OVER 
THE AREA BETWEEN 09N TO 20N W OF 118W. THE SURFACE TROUGH AND 
AREA OF ENHANCED TRADES WILL SHIFT W OF 140W LATE THU NIGHT.
NW SWELL WILL CONTINUE TO PROPAGATE SE OVER THE WATERS W OF 
110W...MIXING WITH NE TRADE SWELL...AND EVEN SE CROSS EQUATORIAL 
SWELL S OF 17N W OF 110W. 

GULF OF TEHUANTEPEC...NORTHERLY WINDS ARE AT MINIMAL GALE THIS 
MORNING...BUT EXPECTED TO DIMINISH BELOW GALE THIS AFTERNOON... 
AND CONTINUE TO DIMINISH TO 20 KT MOSTLY DUE TO LATE NIGHT 
DRAINAGE FLOW THROUGH EARLY FRI MORNING. A LARGE AREA OF NE 
SWELL TO 9 FT WILL PROPAGATE SW OVER THE WATERS S OF 13N BETWEEN 
95W AND 110W THROUGH THU THEN SUBSIDE FROM THE N ON FRI.

GULF OF CALIFORNIA...THE PRESSURE GRADIENT BETWEEN PERSISTENT 
HIGH PRESSURE CENTER NW OF THE GULF OF CALIFORNIA...AND 
TROUGHING OVER MEXICO WILL MAINTAIN NW 15-20 KT WINDS OVER THE 
GULF OF CALIFORNIA THROUGH TONIGHT THEN DIMINISH BELOW 20 KT 
ON THU. 

GULF OF PAPAGAYO...FRESH TRADEWINDS OVER THE WESTERN CARIBBEAN 
WILL CONTINUE TO FUNNEL INTO THE GULF OF PAPAGAYO AT 20-25 KT 
THROUGH THU NIGHT WITH WINDS PEAKING DURING THE EARLY MORNING 
HOURS.

$$
NELSON