000
AXPZ20 KNHC 232149
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC FRI OCT 23 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...TROPICAL LOW...
THE SOUTHERN EXTENT OF AN ATLANTIC AND CARIBBEAN UPPER TROUGH 
TERMINATES OVER THE E PACIFIC NEAR 07N89W. THE RESULTANT BROAD 
AREA OF LOW PRESSURE IS ANALYZED AS A SURFACE LOW PRESSURE AT 
09N87W AT AN ESTIMATED 1007 MB. SEVERAL CYCLONIC SWIRLS ARE 
OBSERVED S OF 10N BETWEEN 93W AND 83W AND CONVECTION REMAINS 
UNORGANIZED.   

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 10N80W TO 
06N87W TO 12N110W TO 10N140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS NOTED WITHIN 150 NM EITHER SIDE OF A LINE FROM 
07N82W TO 09N100W AND ANOTHER LINE FROM 11N111W TO 11N129W TO 
10N140W.

...DISCUSSION...
AN UPPER LEVEL ANTICYCLONE IS CENTERED AT 32N136W WITH A RIDGE 
EXTENDING SSE TO A SHARP CREST AT 26N132W. A TROPICAL 
ANTICYCLONE IS CENTERED AT 11N132W WITH A RIDGE EXTENDING N TO 
21N136W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING CONVECTION 
ALONG THE ITCZ BETWEEN 136W AND 146W. SOME OF THE DEBRIS 
MOISTURE IS ADVECTED N UNDER THE RIDGE BUT EVAPORATES BEFORE 
REACHING 20N. A THIRD ANTICYCLONE IS OVER THE S CENTRAL GULF OF 
MEXICO AT 23N88W WITH A RIDGE EXTENDING SW OVER THE THE E 
PACIFIC TO A CREST AT 11N110W...RESULTING IN A BROAD UPPER RIDGE 
OVER THE TROPICAL PACIFIC BETWEEN 90W AND 110W. DEBRIS MOISTURE 
FROM ITCZ CONVECTION BETWEEN 107W AND 120W IS ADVECTED NE ALONG 
THE NW PERIPHERY OF THIS TROPICAL RIDGE BECOMING A PLUME OVER 
OLD MEXICO FROM 20N104W TO NEAR BROWNSVILLE TEXAS.

THE DISCUSSION AREA BETWEEN THESE ANTICYCLONES IS DOMINATED BY 
THE SOUTHERN EXTENSION OF A LONG WAVE TROUGH THAT DISSECTS 
CENTRAL N AMERICA AND EXTENDING INTO THE DISCUSSION AREA ALONG 
32N105W TO 15N118W WITH THE TROUGH CONTINUING W...BUT 
WEAKENING...EVENTUALLY EXTENDING INTO AN UPPER CYCLONE AT 
19N144W. THE TROPICAL RIDGE PREVIOUSLY MENTIONED IN BUILDING 
OVER THE PORTION OF THE TROUGH W OF 130W. EXCEPT AS 
MENTIONED...VERY DRY UPPER AIR IS INDICATED N OF 17N W OF 110W 
AND OVER NORTHWESTERN OLD MEXICO. 

AT THE LOW LEVELS HIGH PRES IS CENTERED N OF THE AREA NEAR 
34N136W WITH A RIDGE EXTENDING SE TO NEAR 17N112W. THE GRADIENT 
NE OF THE RIDGE IS SUPPORTING NORTHERLY WINDS TO 20 KT WHILE THE 
GRADIENT SW OF THE RIDGE IS SUPPORTING NE TRADES AT 20 TO 25 KT. 
N AND NW SWELLS ARE MIXING OVER THE SUBTROPICAL WATERS. 

$$
NELSON