000
AXPZ20 KNHC 200358
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU AUG 20 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 ALONG 85W N OF 05N MOVING W AT 15 KT. SCATTERED 
MODERATE TO STRONG CONVECTION IS WITHIN 90 NM OF THE POINT 
10N86W. THIS CONVECTION IS RELATED TO DIURNAL LAND OCEAN 
INTERACTION AND IS NOT ORGANIZED.

TROUGH ALONG 115W FROM 08N TO 15N MOVING W AT 15 KT. ISOLATED 
MODERATE CONVECTION IS WITHIN 90 NM OF THE TROUGH. A SLIGHT 
CYCLONIC TURNING CAN BE SEEN IN THE CLOUDS NEAR THE TROUGH. THE 
COMPUTER MODEL MOVES THE SYSTEM LITTLE AND SLOWLY DEVELOPS A LOW 
PRESSURE AREA.

TROPICAL WAVE FROM 07N129W TO 15N126W MOVING W AT 15 KT. 
SCATTERED MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE 
WAVE AXIS. THE COVERAGE OF THE CONVECTION HAS DECREASED IN THE 
LAST SEVERAL HOURS. BROAD CYCLONIC ROTATION IS NOTED IN THE 
CLOUDS NEAR THE WAVE. THE COMPUTER MODELS DRIFT THE SYSTEM 
SLIGHTLY WEST AND DO NOT DEVELOP A LOW PRESSURE AREA.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE IS ANALYZED ALONG THE LINE... 
07N77W TO 08N105W TO 12N129W TO 08N132W TO 07N140W. SCATTERED 
MODERATE TO STRONG CONVECTION IS WITHIN 90 NM OF THE POINT 
10N86W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 60 NM 
OF THE POINT 09N90.5W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION IS WITHIN 60 NM OF THE POINT 11N121W AND THE POINT 
12N128W. SCATTERED MODERATE CONVECTION IS WITHIN 50 NM EITHER 
SIDE OF THE ITCZ AXIS W OF 134W.

...DISCUSSION...

UPPER LEVELS...
A SMALL RIDGE IS LOCATED OVER THE NORTHWEST PART OF THE AREA AND 
IS BETWEEN TWO MAJOR TROUGHS. ONE TROUGH IS WELL NORTHWEST OF 
THE AREA THE OTHER IS WEST OF A LINE THROUGH 32N110W TO 27N120W 
TO 25N130W TO 15N132W TO 12N140W. A CYCLONIC CIRCULATION IS 
CENTERED 33N123W. BOTH THE RIDGE AND THE TROUGH IS DRY AND CLOUD 
FREE IN THE MIDDLE AND UPPER LEVELS. OVERCAST STRATOCUMULUS IS 
IN THIS AREA NORTH OF 25N EAST OF 130W AND ELSEWHERE BROKEN TO 
SCATTERED STRATOCUMULUS IS OBSERVED IN THE LOWER LEVELS. THE 
LOW OFF THE UPPER BAJA AND SOUTHERN CALIFORNIA COASTS IS 
FORECAST TO PERSIST WHILE THE TROUGH IS FORECAST TO DRIFT WEST 
AND WEAKEN.

AN ANTICYCLONIC CIRCULATION IS CENTERED NEAR 20N118W AND EXTENDS 
OUT ABOUT 300 NM. THIS AREA IS ALSO DRY AND CLOUD FREE IN THE 
MIDDLE AND UPPER LEVELS. IN THE LOWER LEVELS THE NORTHWEST 
SEMICIRCLE IS OVERCAST STRATOCUMULUS AND SCATTERED STRATOCUMULUS 
OR CUMULUS IN THE SOUTHEAST SEMICIRCLE.

A TROUGH IS LOCATED JUST EAST AND SOUTHEAST OF THE ABOVE RIDGE. 
THE TROUGH IS ALONG THE WESTERN MEXICAN COAST AND EXTENDS 
SOUTHWARD ALONG 108W 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 96W. 

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 THU NIGHT...WITH 20 SECOND PERIOD SWELLS REACHING 
SOUTHERN CALIFORNIA LATE FRI.     

$$
LL