000
AXPZ20 KNHC 120941
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU AUG 12 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 
0930 UTC.

...SPECIAL FEATURE...

A 1008 MB LOW IS LOCATED NEAR 13N98W AND IS CURRENTLY MOVING NW 
AT 10 KT. INFRARED SATELLITE IMAGERY INDICATED SCATTERED 
MODERATE TO STRONG CONVECTION CONFINED TO WITHIN 180 NM IN THE N 
SEMICIRCLE OF THE LOW. THE CONVECTION APPEARED TO BE ORGANIZING 
IN A BAND WHICH EXTENDED WELL TO THE NE OF THE CENTER TO THE 
GULF OF TEHUANTEPEC...GENERALLY PARALLELING THE COAST OF MEXICO. 
A 0410 UTC HIGH RESOLUTION ASCAT PASS INDICATED THE STRONGEST 
WINDS OF 20 TO 25 KT ARE PRIMARILY IN THE S SEMICIRCLE. THE LOW 
CONTINUES TO BECOME BETTER ORGANIZED AND HAS A HIGH CHANCE OF 
DEVELOPING INTO A TROPICAL CYCLONE IN THE NEXT 48 HOURS AS IT 
MOVES CLOSE TO THE COAST OF MEXICO. 

...ITCZ...

ITCZ AXIS IS ALONG 11N86W TO 15N96W AND THEN FROM 12N105W TO 
12N127W TO 11N140W. SCATTERED MODERATE ISOLATED N OF 04N TO THE 
GULF OF PANAMA E OF 79W. SCATTERED MODERATE WITHIN 60 NM OF THE 
AXIS BETWEEN 126W AND 138W.

...DISCUSSION...

A SHEARED UPPER LEVEL TROUGH EXTENDS FROM WELL N OF THE AREA OFF 
THE NW COAST OF CALIFORNIA TO A DEVELOPING CYCLONIC CIRCULATION 
NEAR 32N125W. VERY DRY AIR UNDER MODERATE TO STRONG SUBSIDENCE 
IS PRESENT ACROSS THE AREA N OF THE ITCZ AND W OF A LINE FROM 
32N118W TO 12N131W.  

AN EXPANSIVE UPPER LEVEL ANTICYCLONE IS CENTERED OVER NW 
MEXICO NEAR 31N109W WITH AN UPPER RIDGE EXTENDING ACROSS CENTRAL 
BAJA CALIFORNIA TO A LARGE COL NEAR 19N135W. DIFFLUENT UPPER 
LEVEL NORTHEASTERLY WINDS AND SOME OROGRAPHIC LIFT WAS 
MAINTAINING SCATTERED STRONG THUNDERSTORMS ALONG THE SIERRA 
MADRE OCCIDENTAL AND ALONG THE COAST OF MEXICO FROM 19N TO 23N. 
THESE SAME WINDS WERE ADVECTING THE MID AND UPPER LEVEL MOISTURE 
WWD TO ALONG 125W N OF THE ITCZ TO 25N. A 1010 MB SURFACE LOW
NEAR 17N110W WAS EMBEDDED WITHIN THIS EASTERLY FLOW. 

ELSEWHERE AT THE SURFACE...A RIDGE AXIS IS OVER THE NW WATERS 
EXTENDING FROM 1032 MB HIGH PRES CENTERED WELL NW OF THE AREA 
NEAR 46N143W. THE RIDGE ENTERS THE DISCUSSION AREA NEAR 30N140W 
AND CONTINUES THROUGH 26N130W TO 23N115W. THE PRESSURE GRADIENT 
BETWEEN THE RIDGE AND LOWER PRESSURES OF THE SW U.S. HAVE 
RESULTED IN AN AREA OF NW TO N WINDS OF 20 KT N OF 25N WITHIN 
120-150 NM OF THE COAST OF BAJA CALIFORNIA. THESE WINDS WERE 
CONFIRMED BY A 0410 UTC ASCAT PASS. THESE WINDS ARE EXPECTED TO 
DROP BELOW 20 KT LATER TODAY. 

SOUTHWESTERLY WINDS OF 20 TO 25 KT AT THE SURFACE IS FEEDING 
INTO THE AREAS OF LOW PRESSURE NOTED ABOVE RESULTING IN 8 TO 10 
FT COMBINED SEAS. THE SAME CONDITIONS ARE EXPECTED TO PERSIST 
DURING THE NEXT 48 HOURS WITH A SLIGHT INCREASE IN THE SEAS. 

A NEW SET OF LONG PERIOD...17 TO 19 SECONDS...SWELL TO 8 FT 
HAS CROSSED THE EQUATOR E OF 110W AND ARE EXPECTED TO REACH THE 
COAST OF MEXICO AND CENTRAL AMERICA BY TONIGHT AND THE GULF OF 
CALIFORNIA BY LATE FRI.

$$
COBB