000
AXPZ20 KNHC 282158
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

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

MONSOON TROUGH AXIS 05N77W TO 07N85W TO 05N108W. ITCZ AXIS 
05N108W TO 11N132W TO BEYOND 09N140W. SCATTERED MODERATE WITHIN 
180 NM EITHER SIDE OF TROUGH AXIS FROM 10N TO 15N. 

...DISCUSSION...

A MID TO UPPER LEVEL SHEAR AXIS EXTENDS WESTWARD FROM 32N110W TO 
30N130W THEN TURNS SW INTO A SHARP UPPER LEVEL TROUGH WITH AN 
EMBEDDED CYCLONE CUTTING OFF NEAR 17N144W. VERY STRONG MID TO 
UPPER LEVEL SUBSIDENCE WAS NOTED WITHIN 90-120 NM EITHER SIDE OF 
THE SHEAR AXIS AND SPILLING INTO THE BACKSIDE OF THE TROUGH AND 
THE SW SEMICIRCLE OF THE UPPER CYCLONE. A MID TO UPPER LEVEL 
ANTICYCLONE CENTERED NEAR 14N107W WITH A RIDGE EXTENDING NW TO 
25N133W. AN UPPER TROUGH/CYCLONE IS NOTED S OF THE EQUATOR 
RESULTING IN NORTHWESTERLY FLOW IN THE UPPER LEVELS SW OF A LINE 
FROM 10N140W TO 00N115W. THUS A LARGE AREA OF UPPER DIFFLUENCE 
EXISTS FROM 10N TO 25N BETWEEN 120W AND 138W PROVIDING ENOUGH 
LIFT ALONG A SURFACE TROUGH EXTENDING FROM 09N134W TO 16N133W TO 
SUPPORT SCATTERED MODERATE CONVECTION WITHIN 180 NM EITHER SIDE 
OF TROUGH AXIS FROM 10N TO 15N. A VAST AREA OF UPPER LEVEL 
MOISTURE/CONVECTIVE DEBRIS WAS INDICATED WITHIN AN AREA FROM 
10N TO 26N BETWEEN 115W AND 138W. 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...A SHEARED UPPER TROUGH EXTENDS SW FROM THE STRAITS 
OF FLORIDA ACROSS THE EXTREME W CARIBBEAN SEAS TO A SHEAR AXIS 
OVER THE E PACIFIC EXTENDING FROM GUATEMALA TO 10N98W. 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 SURFACE...A 1028 MB HIGH PRES AREA CENTERED NEAR 
32N132W WILL DRIFT WSW THROUGH THU. A BROAD LOW LEVEL TROUGH 
EXTENDING FROM 09N134W TO 16N133W IS MOVING W WITH TIME. THE 
TIGHT PRESSURE GRADIENT BETWEEN THIS TROUGH AND THE SURFACE HIGH 
TO THE NORTH IS MAINTAINING NE TO E 20 TO 25 KT TRADEWINDS OVER 
THE AREA BETWEEN 09N TO 20N W OF 120W. THE SURFACE TROUGH AND 
AREA OF ENHANCED TRADES WILL SHIFT W OF 140W THU NIGHT AND FRI. 
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...THE EDGE OF A 1638 UTC ASCAT PASS AND 
SURFACE OBSERVATIONS FROM AROUND THE GULF OF TEHUANTEPEC SUGGEST 
NORTHERLY WINDS HAVE DIMINISHED BELOW GALE FORCE. THESE WINDS 
ARE EXPECTED TO 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 
EARLY THU. 

GULF OF PAPAGAYO...FRESH TRADEWINDS OVER THE WESTERN CARIBBEAN 
WILL CONTINUE TO FUNNEL INTO THE GULF OF PAPAGAYO AT 20-25 KT 
THEN SLOWLY SUBSIDE TO AROUND 20 KT THU AND FRI WITH WINDS 
PEAKING DURING THE EARLY MORNING HOURS.

$$
COBB