000
AXPZ20 KNHC 082118
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1915 UTC.

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

THE MONSOON TROUGH AXIS WAS ANALYZED FROM 10N85W TO 12N96W TO 
11N113W TO 12N120W TO 10N130W. A TROUGH WAS BETWEEN THE MONSOON 
TROUGH AND ITCZ FROM 12N129W TO 05N135W. THE ITCZ AXIS WAS 
ANALYZED FROM 04N137W TO 04N140W. SCATTERED MODERATE WITH 
ISOLATED STRONG CONVECTION WAS WITHIN 150 NM N OF THE AXIS 
BETWEEN 89W AND 98W AND WITHIN 240 NM S OF THE AXIS BETWEEN 87W 
AND 107W. SCATTERED MODERATE CONVECTION WAS WITHIN 150 NM N OF 
THE AXIS BETWEEN 119W AND 123W. SCATTERED MODERATE CONVECTION 
WAS WITHIN 180 NM NW OF THE TROUGH FROM 07N TO 09N.
  
...DISCUSSION...

AN UPPER LEVEL ANTICYCLONE NEAR 21N116W EXTENDS RIDGE AXES 
SOUTHWESTWARD TO 13N140W AND SOUTHEASTWARD TO CABO CORRIENTES 
MEXICO. MEANWHILE...A MID TO UPPER LEVEL LOW LIES OVER BAJA 
CALIFORNIA NORTE. SOUTHERLY FLOW ON THE EASTERN SIDE OF THIS LOW 
IS PUMPING MOISTURE NORTHWARD ALONG THE W COAST OF MEXICO INTO 
THE GULF OF CALIFORNIA. PRECIPITABLE WATER IMAGERY SHOWS 
MOSITURE POOLED ALONG THE COAST NEAR CABO CORRIENTES MEXICO 
WHERE THE RIDGE AXIS ALOFT IS ABLE TO LIFT THIS MOISTURE AND 
ENHANCE THE SCATTERED MODERATE CONVECTION FOUND FROM 15N TO 20N 
BETWEEN 102W AND 108W. A 30-50 KT EASTERLY JET LIES S OF THE 
ANTICYCLONE IN THE REGION FROM 02N TO 15N BETWEEN 105W AND 120W. 
THIS SHEAR IS INHIBITING THE DEVELOPMENT OF DEEP 
CONVECTION...BUT A BROAD AREA OF DIFFLUENCE ALOFT E OF THIS JET 
IS ENHANCING THE SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION ALONG THE MONSOON TROUGH DESCRIBED IN THE SECTION 
ABOVE. AN UPPER LOW LIES ALONG THE EQUATOR SOUTH OF THE JET AND 
EXTENDS A TROUGH NORTHWESTWARD THROUGH 00N130W TO 09N140W. THE 
SURFACE REFLECTION OF THIS TROUGH AND THE CONVECTION ASSOCIATED 
WITH IT IS ALSO DESCRIBED IN THE SECTION ABOVE. THIS TROUGH IS 
EXPECTED TO MOVE W OF THE FORECAST AREA OVER THE NEXT FEW DAYS.

THE 1028 MB SUBTROPICAL HIGH WAS ANALYZED NEAR 39N154W. THE HIGH 
IS CURRENTLY BEING ENCROACHED UPON BY A FRONT TO ITS NW. THIS 
FRONT IS FORECAST TO MOVE EASTWARD AND USHER IN STRONGER HIGH 
PRES. FRESH TO STRONG TRADE WINDS ARE EXPECTED TO BUILD OVER FAR 
W WATERS JUST N OF THE SURFACE TROUGH/ITCZ ON SUN. THE 1524 UTC 
AND 1704 UTC ASCAT PASSES SHOW A REGION OF FRESH TO STRONG S-SW 
WINDS LIES S OF THE MONSOON TROUGH TO 05N BETWEEN 93W AND 
110W...FORCED BY THE PRES GRADIENT BETWEEN THE MONSOON TROUGH 
AND STRONG HIGH PRES OVER THE SOUTH PACIFIC. THESE WINDS ARE 
EXPECTED TO DIMINISH BELOW ADVISORY CRITERIA AS THE HIGH PRES TO 
THE S WEAKENS ON SUN. S SWELL TO 8 FT CURRENTLY IN THIS REGION 
OF FRESH TO STRONG WINDS WILL SHIFT NORTHWARD OVER THE NEXT FEW 
DAYS TOWARD THE MEXICAN COAST. AT THE SAME TIME...THE NUMERICAL 
GUIDANCE AGREES ON DEVELOPING A BROAD AREA OF LOW PRES S OF THE 
GULF OF TEHUANTEPEC BY MON AFTERNOON AND INCREASING WINDS TO 
FRESH TO STRONG ON ITS NORTHERN SIDE BETWEEN THE MEXICAN COAST 
AND 13N WHERE THE S SWELL WILL HAVE ALREADY BUILT THE SEAS.

$$
SCHAUER