000
AXPZ20 KNHC 071550
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI SEP 07 2012

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS NW ALONG THE PACIFIC COAST FROM THE 
PANAMA/COLOMBIA BORDER TO NW COSTA RICA TO 12N90W...THEN TURNS 
SW INTO AND EMBEDDED 1010 MB LOW PRES AT 11N94W...THEN NW 
THROUGH 10N98W TO 13N114W...THEN SW TO 08N127W WHERE LOW LEVEL 
WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES SW TO 
04N132W TO BEYOND 05N140W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 90 NM 
EITHER SIDE OF A LINE FROM 08N91W TO 09N106W TO 13N111W...AND 
ALSO WITHIN 180 NM EITHER SIDE OF A LINE FROM 15N113W TO 
07N133W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
ACCOMPANIED BY FREQUENT STRIKES WITHIN 150 NM OF PACIFIC COAST 
FROM COLOMBIA AT 03N77W TO OFFSHORE NICARAGUA AT 12N88W...AND 
ALSO OFFSHORE GUATEMALA AT 13N91W TO THE MEXICAN COAST AT 
24N108W. 

...DISCUSSION...

A UPPER SHORTWAVE TROUGH EXTENDS SW INTO THE NW PORTION OF THE 
DISCUSSION AREA FROM 35N137W TO 30N135W TO 20N137W AND INTO AN 
UPPER CYCLONE AT 17N135W. AN UPPER ANTICYCLONE IS OVER ARIZONA 
AT 33N110W...WITH A RIDGE EXTENDING SW THROUGH ANOTHER 
ANTICYCLONE AT 26N131W...TO A CREST AT 26N130W. ANOTHER UPPER 
ANTICYCLONE IS OVER THE SOUTHERN TIP OF THE BAJA CALIFORNIA 
PENINSULA AT 22N109W...WITH AN UPPER RIDGE EXTENDING SW TO A 
CREST OVER THE DEEP TROPICS AT 12N134W. UPPER MOISTURE IS 
OBSERVED OVER AND WITHIN 150 NM INLAND FROM THE W COAST OF 
MEXICO TO THE N OF 22N...AND IS SPREADING SE TO NEAR 20N100W 
WHERE IT EVAPORATES COMPLETELY. UPPER MOISTURE IS ALSO NOTED
ALONG THE NORTHERN UPPER RIDGE...ROUGHLY TO N OF 25N BETWEEN 
117W AND 127W...AND IS SPREADING NE ACROSS SOUTHERN 
CALIFORNIA...THEN EASTWARD ACROSS ARIZONA AND NEW MEXICO.

THE UPPER LEVELS APPEAR VERY DRY W OF A LINE FROM CALIFORNIA 
COAST AT 34W TO 20N130W TO 10N140W. THE UPPER LEVELS ARE 
SLIGHTLY DIFFLUENT OVER THE DEEP TROPICS AND SUPPORTING THE 
CONVECTION PREVIOUSLY DESCRIBED ALONG THE MONSOON TROUGH. THE 
DEBRIS MOISTURE IS ADVECTED W BETWEEN 85W AND 110W...THEN FANS 
OUT ALONG THE SOUTHERN TROPICAL RIDGE COVERING THE TROPICS FROM 
02N TO 17N BETWEEN 115W AND 127W. 

ELSEWHERE AT THE SURFACE...A 1014 MB LOW PRESSURE...REMNANT OF 
TROPICAL CYCLONE JOHN...IS NEAR 26N122W BUT LACKS CONVECTION. A 
RIDGE EXTENDS SE FROM 30N140W TO 15N106W. CROSS EQUATORIAL SE 
SWELL WITH SEAS TO 8 FT IS NOTED S OF 05N BETWEEN 120W AND 135W 
BUT IS EXPECTED TO SUBSIDE BELOW 8 FT ON SAT.

$$
NELSON