000
AXPZ20 KNHC 281533
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON DEC 28 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ALONG THE LINE...04N77W TO 
08N126W TO 07N140W. SCATTERED MODERATE WITHIN 60 NM EITHER SIDE 
OF AXIS E OF 88W. SCATTERED MODERATE ISOLATED STRONG WITHIN 130 
NM N AND 250 NM S OF AXIS W OF 131W. 

...DISCUSSION...

ZONAL FLOW IN THE UPPER LEVELS PREVAILS ALONG MUCH OF THE 
FORECAST AREA. A STRONG SHORTWAVE TROUGH IS ALONG 117W NORTH OF 
15N. DEEP LAYER MOISTURE IS PRESENT EAST OF THE SHORTWAVE NORTH 
OF 23N WITH BROKEN TO OVERCAST MIDDLE AND UPPER LEVEL CLOUDS. 
THE SHORTWAVE IS FORECAST TO MOVE EAST ABOUT 30 KNOTS AND REACH 
BAJA CALIFORNIA LATE TONIGHT. AREAS OF RAIN AND SOME EMBEDDED 
CONVECTION IS NOTED NEAR AND WITHIN ABOUT 300 NM EAST OF THE 
SHORTWAVE. AN UPPER LEVEL RIDGE IS E OF 94W. UPPER LEVEL 
MOISTURE FROM CONVECTION IN THE ITCZ W OF 131 W IS BEING SPREAD 
IN DIFFLUENT UPPER FLOW AND COVERS FROM 01N TO 13NW OF 120W. 

A WEAK SURFACE LOW IS NEAR 24N132W WITH A CENTRAL PRESSURE OF 
1017 MB. THE LOW IS MOVING SOUTHEAST ABOUT 10 KT. SURFACE WINDS 
OF 20 KT ARE FORECAST WITHIN 300 NM FROM THE CENTER IN THE 
NORTHWEST SEMICIRCLE. THE LOW IS FORECAST TO WEAKEN TO A TROUGH 
IN 24 HOURS. 

HIGH PRESSURE 1022 MB CENTERED JUST N OF THE FORECAST AREA NEAR 
32N136W. THE PRESSURE GRADIENT BETWEEN THE HIGH AND LOW PRESSURE 
DUE TO CONVECTION IN THE ITCZ IS RESULTING IN 20 TO 25 KT 
TRADEWINDS N OF THE ITCZ TO 20N W OF 125W. WITH HIGH PRESSURE 
REMAINING JUST N OF THE LOCAL AREA...FRESH TO STRONG TRADEWIND 
FLOW CAN BE EXPECTED W OF 120W THROUGH AT LEAST WED MORNING. 

GAP WINDS...
GULF OF TEHUANTEPEC...N WINDS OF 20 KT ARE EXPECTED TO SPREAD S 
AND W AND INCREASE TO 20 TO 30 KT BY TONIGHT.

GULF OF PAPAGAYO...E WINDS OF 20 KT ARE EXPECTED TO INCREASE TO 
20 TO 30 KT AND SPREAD EAST BY TONIGHT.

SEA CONDITIONS ARE DOMINATED BY LONG PERIOD NW SWELL (WAVE 
PERIODS OF UP TO 18 SECONDS) WITH SIGNIFICANT WAVE HEIGHTS AS 
HIGH AS 16 FT PARTICULARLY OVER THE NW CORNER OF THE AREA. THIS 
SWELL EVENT WILL CONTINUE TO SPREAD SE REACHING NEAR 91W IN 
ABOUT 48 HOURS.

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE
  
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AL