000
AXPZ20 KNHC 210256
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI AUG 21 2009

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...TROPICAL WAVES...

TROPICAL WAVE PREVIOUSLY ALONG 90W IS RELOCATED TO ALONG 95W 
NORTH OF 08N BASED ON SATELLITE DERIVED PRECIPITABLE WATER AND 
CLOUD MOTIONS. IT IS ESTIMATED THE WAVE WILL MOVE WEST 15 KT. 
SCATTERED MODERATE TO STRONG CONVECTION IS OVER THE ISTHMUS OF 
TEHUANTEPEC WHICH IS DUE TO DIURNAL HEATING. THERE IS ONLY 
ISOLATED CONVECTION IN THE ITCZ.
 
TROPICAL WAVE ALONG 117W FROM 07N TO 17N MOVING W AT 10 KT. 
BROAD CYCLONIC TURNING IS NOTED NEAR THE WAVE AXIS. ISOLATED 
CONVECTION IS NORTH OF THE ITCZ NEAR THE WAVE AXIS AND SHOWS NO 
SIGNS OF ORGANIZATION.

TROPICAL WAVE ALONG 131W.132W FROM 09N TO 16N MOVING W AT 10 KT. 
A  1008 MB LOW IS LOCATED NEAR 14N131W. SCATTERED MODERATE  IS 
LOCATED WITHIN 120 NM OF THE AXIS SOUTH OF 15N AND SHOWS BROAD 
CYCLONIC TURNING.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG 07N77W TO 
09N105W TO 11N125W TO 09N140W. SCATTERED MODERATE WITH ISOLATED 
STRONG CONVECTION IS WITHIN 100 NM OF THE POINT 11N124W.

...DISCUSSION...

UPPER LEVELS...
A SMALL RIDGE IS LOCATED OVER THE NORTHWEST PART OF THE AREA.

A LARGE CYCLONIC CIRCULATION IS CENTERED NEAR 21N141W AND 
EXTENDS OUT ABOUT 400 NM. THE AREA IS DRY AND CLOUD FREE IN THE 
MIDDLE AND UPPER LEVELS EXCEPT FOR A PLUME OF MOISTURE EMANATING 
FROM ITCZ CONVECTION ALONG THE EASTERN FLANK OF THE CIRCULATION 
IN A BAND ABOUT 240 NM WIDE ALONG 134W. ANOTHER LARGE CYCLONIC 
CIRCULATION IS CENTERED NEAR 32N123W AND EXTENDS OUT ABOUT 500 
NM. THIS AREA IS ALSO DRY AND CLOUD FREE IN THE MIDDLE AND UPPER 
LEVELS. BROKEN TO OVERCAST STRATOCUMULUS IS IN THIS AREA NORTH 
OF 25N EAST OF 130W WITH CLEAR SKIES WITHIN 120 NM OF THE COAST 
OF BAJA CALIFORNIA. THE LOW OFF THE UPPER BAJA AND SOUTHERN 
CALIFORNIA COASTS IS FORECAST TO PERSIST WHILE THE OTHER 
CIRCULATION IS FORECAST TO DRIFT WEST AND WEAKEN.

AN ANTICYCLONIC CIRCULATION IS CENTERED NEAR 19N121W AND EXTENDS 
OUT ABOUT 400 NM. THIS AREA IS ALSO DRY AND CLOUD FREE IN THE 
MIDDLE AND UPPER LEVELS. 

A TROUGH IS LOCATED JUST EAST AND SOUTHEAST OF THE ABOVE RIDGE. 
THE TROUGH IS ALONG THE WESTERN MEXICAN COAST AND EXTENDS 
SOUTHWARD ALONG 110W TO THE ITCZ. WEST OF THE TROUGH AXIS THE 
AREA IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER LEVELS. EAST 
OF THE TROUGH AXIS THE AREA IS MOIST. CONVECTION OVER MAINLAND 
MEXICO EXTENDS FROM THE CENTRAL GULF OF CALIFORNIA TO NEAR 97W. 

THE AREA EAST OF THE TROUGH IS DIFFLUENT ALOFT WITH WIDESPREAD 
MULTI LEVEL CLOUDS AND EMBEDDED AREAS OF CONVECTION. IT INCLUDES 
A TROUGH THAT EXTENDS FROM NORTH OF THE AREA ACROSS EASTERN 
MEXICO AND NORTHERN CENTRAL AMERICA SOUTHWARD TO THE ITCZ.

SURFACE...
WEAK SURFACE RIDGE IS NORTH OF 17N WEST OF 115W. 
ELSEWHERE BROAD TROUGH IS ANALYZED AT THE SURFACE.

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.   

$$
LL