000
AXPZ20 KNHC 200946
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU AUG 20 2009

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0930 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS N OF 04N ALONG 87W AND IS MOVING W AT AN 
ESTIMATED 17 KT. ISOLATED TSTMS ARE CURRENTLY FLARING WITHIN 90 
NM OF COAST CENTRAL AMERICA ALONG THE WAVE AXIS.
 
A TROUGH IS EMBEDDED IN THE ITCZ AXIS NEAR 115W. BROAD CYCLONIC 
TURNING IS NOTED NEAR 11N116W BUT ONLY ISOLATED TSTMS ARE NOTED 
WITHIN 120 NM OF THE WAVE FROM 09N TO 12N.

A TROPICAL WAVE IS ANALYZED FROM 04N TO 16N ALONG 131W. UPPER 
LEVEL DIFFLUENCE IS ENHANCING CONVECTION FROM 09N TO 14N BETWEEN 
127W AND 132W.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS MEANDERING FROM 09N TO 11N 
FROM COLOMBIA TO 140W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS NOTED WITHIN 90 NM EITHER SIDE OF A LINE FROM 
07N77W TO 09N87W TO 09N110W TO 13N128W TO 07N140W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED N OF THE 
ITCZ WITHIN 90 NM OF THE PACIFIC COAST OF CENTRAL AMERICA FROM 
83W TO 106W. 

...DISCUSSION...

AN UPPER LEVEL ANTICYCLONE HAS SHIFTED W OF THE AREA TO NEAR 
27N143W WITH AN UNSTABLE RIDGE EXTENDING NE BUT COLLAPSING TO 
THE SE TO A CREST AT 31N131W. A SECOND UPPER ANTICYCLONE IS 
QUASI STATIONARY AT 23N117W WITH A RIDGE SW TO 11N130W. SQUEEZED 
BETWEEN THE UPPER ANTICYCLONES IS AN UPPER TROUGH EXTENDING FROM 
AN UPPER CYCLONE AT 31N124W TO A SECOND CYCLONE AT 18N. 
DEBRIS MOISTURE FROM ITCZ CONVECTION BETWEEN 123W AND 134W IS 
ADVECTED N ALONG THE W PERIPHERY OF THE EASTERN ANTICYCLONE TO 
NEAR 21N121W WHERE IT EVAPORATES. OTHERWISE...THE UPPER LEVELS 
ARE VERY DRY N OF 17N W OF 108W.

AN UPPER CYCLONE OVER THE NW CARIBBEAN AT 19N87W HAS A TROUGH 
EXTENDING SW ACROSS CENTRAL AMERICA TO 10N100W. BROAD UPPER 
RIDGING IS NOTED ELSEWHERE OVER THE TROPICAL PACIFIC E OF 110W 
AND IS ENHANCING CONVECTION ALONG THE ITCZ AND ALSO ALONG THE 
COAST OF CENTRAL AMERICA...ALL PREVIOUSLY MENTIONED. THE DEBRIS 
MOISTURE IS ADVECTED SW...BUT EVAPORATES ALONG 02N BEFORE 
CROSSING THE EQUATOR.   

AT LOW LEVELS A SURFACE RIDGE EXTENDS INTO THE AREA ALONG 
31N140W TO 11N112W. NW WINDS ARE EXPECTED TO PULSE AT MOSTLY 15 
KT...BUT OCCASIONALLY 20 KT ALONG THE W COAST OF THE BAJA 
PENINSULA FOR THE NEXT FEW DAYS. NE WINDS ARE EXPECTED TO PULSE 
TO ABOUT 15 KT IN AND DOWNSTREAM OF THE GULF OF PAPAGAYO FOR THE 
NEXT FEW DAYS. SOUTHERLY WINDS S OF THE ITCZ TO THE E OF 130W E
ARE IN THE 15 TO 20 KT RANGE WITH SEAS REACHING A MAX OF 9 FT IN 
SW SWELL. 

LONG PERIOD SOUTHERLY SWELLS AT A PERIOD OF 18 SECONDS ARE 
EXPECTED TO REACH THE COAST OF CENTRAL AMERICA S OF THE BAJA 
PENINSULA TONIGHT AND REACH SOUTHERN CALIFORNIA FRI NIGHT.

$$
NELSON