000
AXPZ20 KNHC 081549
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT SEP 08 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 WESTWARD FROM THE NORTHERN COAST OF 
COSTA RICA AT 10N85W TO 12N109W TO 10N130W. THE ITCZ AXIS FORMS 
AT 05N135W AND EXTENDS W TO BEYOND 05N140W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION...WITH FREQUENT LIGHTNING...IS 
OBSERVED WITHIN 240 NM OF COAST OF CENTRAL AMERICA FROM COLOMBIA 
AT 05N78W TO THE PACIFIC COAST OF MEXICO AT 106W. SIMILAR 
CONVECTION IS OBSERVED FROM 07N TO 14N BETWEEN 93W AND 100W AND 
FROM 118W TO 133W...AND WITHIN 60 NM EITHER SIDE OF A LINE FROM 
10N100W TO 10N118W.
  
...DISCUSSION...

AN UPPER SHORTWAVE TROUGH APPROACHES THE NW PORTION PRECEDED BY 
A SOUTHWESTERLY UPPER 50 KT JET OVER THE EXTREME NW PORTION OF 
THE DISCUSSION AREA. A BROAD UPPER RIDGE DOMINATES MOST OF THE 
AREA W OF 100W WITH LARGE EMBEDDED UPPER ANTICYCLONES OBSERVED 
NEAR 32N107W AND 25N123W AND 22N112W. THE MEAN RIDGE AXIS 
EXTENDS ROUGHLY FROM 30N117W TO BEYOND 13N140W. UPPER MOISTURE 
IS NOTED FROM 28N TO 36N BETWEEN 124W AND 116W...AND IS 
SPREADING E ACROSS SOUTHERN CALIFORNIA...AND ACROSS THE SOUTHERN 
TWO THIRDS ARIZONA AND NEW MEXICO...THEN NARROWING AS IT 
CONTINUES E ACROSS NORTHERN TEXAS. A BAND OF UPPER MOISTURE IS 
OBSERVED OVER AND WITHIN 175 NM INLAND THE W COAST OF MEXICO TO 
THE N OF 20N. OTHERWISE...THE UPPER LEVELS APPEAR VERY DRY N OF 
20N W OF 110W. THE UPPER LEVELS ARE SLIGHTLY DIFFLUENT OVER THE 
DEEP TROPICS S OF THE LARGE UPPER RIDGE...AND SUPPORTING THE 
CONVECTION PREVIOUSLY DESCRIBED ALONG THE MONSOON TROUGH. THE 
DEBRIS MOISTURE IS ADVECTED W BETWEEN 100W AND 120W...THEN FANS 
OUT NW AND N TO NEAR 20N123W WHERE IT EVAPORATES.

A RIDGE AXIS EXTENDS SE FROM 32N135W TO 15N112W. NORTHEAST 
TRADES S OF THIS SURFACE RIDGE ARE EXPECTED TO INCREASE TO 20 KT 
ON SUN IN THE AREA FROM 09N TO 16N BETWEEN 132W AND 140W...WITH 
SEAS BUILDING TO 9 IN MIXED NE AND SE CROSS EQUATORIAL SWELL. 
CROSS EQUATORIAL SE SWELL WITH SEAS TO 8 FT IS NOTED S OF 03N 
BETWEEN 125W AND 135W BUT IS EXPECTED TO SUBSIDE BELOW 8 FT 
LATER TODAY. SOUTHWESTERLY MONSOONAL WINDS ARE INCREASING TO 15 
TO 20 KT...SEAS BUILDING TO 8 FT...IN THE AREA FROM 05N TO 10N 
BETWEEN 94W AND 107W...WITH LITTLE CHANGE FORECAST THROUGH 
SUN...THEN THE WINDS SHOULD DIMINISH TO 15 KT AND THE SEAS 
SUBSIDE BELOW 8 FT.   

$$
NELSON