000
AXPZ20 KNHC 180920
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED AUG 18 2010

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 
0800 UTC. 

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS IS ANALYZED FROM 12N107W 
TO 10N120W TO 12N128W TO 07N140W. SCATTERED MODERATE CONVECTION 
IS WITHIN 150 NM S OF THE ITCZ AXIS BETWEEN 107W AND 117W AND 
WITHIN 90 NM S OF THE ITCZ AXIS BETWEEN 131W AND 137W. 
SOUTHWESTERLY FLOW DOMINATES THE PAC WATERS GENERALLY E OF 107W 
TO A TROUGH OFF THE MEXICAN COAST FROM 17N106W TO 12N92W.  
ISOLATED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF 
THIS TROUGH.   

...DISCUSSION...

ALOFT...A BROAD UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED 
OVER THE TEXAS/LOUISIANA BORDER EXTENDS A RIDGE ACROSS THE U.S. 
DESERT SOUTHWEST TO TIJUANA MEXICO AND THEN SOUTHWEST TO AN 
ANTICYCLONE NEAR 23N132W. THE RIDGE PASSES OVER A WEAK UPPER 
TROUGH FROM THE NORTHERN GULF OF CALIFORNIA TO 24N120W...BUT 
UPPER LEVEL RIDGING COVERS MUCH OF THE AREA N OF 15N ASIDE FROM 
THE FAR NW CORNER WHERE A 40 KT SOUTHWESTERLY JET RESIDES ON THE 
LEADING EDGE OF A TROUGH WHOSE AXIS IS NW OF THE FORECAST AREA. 
MODERATE TO STRONG SUBSIDENCE DOMINATES THE AREA N OF 20N W OF 
127W. EASTERLY FLOW ALOFT PREVAILS IN THE DEEP TROPICS WITH TWO 
WEAK TROUGHS EMBEDDED IN THESE STRONG EASTERLIES. THE EASTERN 
TROUGH LIES FROM CANCUN MEXICO TO 10N91W AND THE WESTERN TROUGH 
LIES FROM 20N128W TO 08N132W. THE STRONGEST WINDS ALOFT...UP TO 
40 KT...CAN BE FOUND BETWEEN THESE TROUGHS S OF 15N.

AT THE SURFACE...A WEAK SURFACE RIDGE LIES FROM 30N140W TO 
15N125W. THE PRES GRADIENT IS FORECAST TO TIGHTEN BETWEEN THE 
RIDGE AND LOWER PRES OVER NW MEXICO OVERNIGHT THU 
NIGHT...PRODUCING NW WINDS OF 20 KT WITHIN 90 NM OF THE COAST OF 
BAJA CALIFORNIA. A TROUGH IS EMBEDDED IN THE ITCZ ALONG 130W BUT 
IS NOT ASSOCIATED WITH ANY DEEP CONVECTION. BROAD TROUGHING 
DOMINATES THE AREA E OF 120W. THE REMAINS OF THE LONG-LIVED LOW 
PRES SYSTEM THAT WAS S OF THE BAJA PENINSULA FOR SEVERAL DAYS 
HAS OPENED TO A TROUGH AND DRIFTED NORTH REACHING 25N114W TO 
20N113W. BROAD TROUGHING OFF THE W COAST OF MEXICO HAS DISRUPTED 
THE ITCZ...WITH SOUTHWESTERLY WINDS FOUND SOUTH OF THE TROUGH 
AXIS WHICH LIES FROM 17N106W TO 12N92W ACCORDING TO THE 0346 UTC 
ASCAT PASS. THESE WINDS REACH 20 KT FROM 02N TO 08N BETWEEN 90W 
AND 115W. 

CROSS EQUATORIAL SW SWELLS ARE RAISING SEAS UP TO 9 FT OVER S 
CENTRAL WATERS AND IS FORECAST TO SLOWLY MOVE NORTH OF 10N BY 
LATE WED. THIS SWELL EVENT IS BEGINNING TO MAKE ITS WAY E OF THE 
GALAPAGOS ISLANDS AND SEAS WILL REACH 8 FT OFF THE COAST OF 
WESTERN PANAMA BY THU MORNING. 

$$
SCHAUER