000
AXPZ20 KNHC 040243
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN SEP 04 2011

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH IS INLAND ALONG THE PACIFIC COAST OF CENTRAL 
AMERICA THEN RESUMES AT 15N104W TO 14N120W TO 13N140W. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION IS NOTED FROM 09N TO 11N 
BETWEEN 104W AND 111W. SCATTERED MODERATE CONVECTION IS WITHIN 
120 NM S OF THE MONSOON TROUGH BETWEEN 125W AND 137W.

...DISCUSSION...
A BROAD MIDDLE TO UPPER LEVEL TROUGH COVERS THE AREA N OF 18N W 
OF 122W WITH A CUT-OFF LOW NEAR 32N130W. UPPER LEVEL RIDGE 
EXTENDS FROM AN UPPER ANTICYCLONE CENTERED NEAR 26N115W ESE 
ACROSS MEXICO TO THE BAY OF CAMPECHE. SOUTH OF THIS RIDGE...NE 
TO E FLOW ALOFT PERSISTS...YIELDING MODERATE VERTICAL WIND SHEAR 
ACROSS THE DEEP TROPICS. A SIGNIFICANT PATTERN CHANGE ACROSS THE 
FORECAST REGION IS EXPECTED NEXT WEEK AS THE UPPER TROUGH WILL 
EVENTUALLY WEAKEN AND LIFT OUT TO THE NE. 

AT THE SURFACE...WEAK RIDGE DOMINATES THE NW CORNER OF THE AREA 
PRODUCING MAINLY GENTLE BREEZE. A NEARLY STATIONARY 1012 MB LOW 
IS ALONG THE COAST OF NORTHERN CALIFORNIA WITH A FRONTAL TROUGH 
APPROACHING 30N. THE TROUGH WILL CLIP THE NW PORTION OF THE 
FORECAST AREA THIS SUNDAY AND WILL WEAKEN LATE MON. N SWELLS ARE 
EXPECTED IN THE WAKE OF THE FRONTAL TROUGH RAISING SEAS TO 8 FT 
PARTICULARLY N OF 28N W OF 132W. TRADEWINDS REMAIN BELOW 20 KT E 
OF 140W UNDER THE INFLUENCE OF THIS WEAK RIDGE...WITH SEAS TO 7 
FT IN MODERATE NLY SWELL. 

DISORGANIZED CLOUDINESS AND A FEW SHOWERS IN ASSOCIATION WITH 
THE REMNANTS OF T.D. EIGHT-E ARE EVIDENT ON VISIBLE SATELLITE 
IMAGERY ACROSS THE MOUTH OF THE GULF OF CALIFORNIA. THIS SYSTEM  
REMAINS EMBEDDED WITHIN THE S END OF THE SEMI-PERMANENT BAJA 
CALIFORNIA TROUGH AND IS FORECAST TO GRADUALLY WEAKEN DURING THE 
NEXT 24 HOURS.  

FURTHER SOUTH...BROAD MONSOONAL FLOW IS OCCURRING ACROSS THE 
AREA S OF THE MONSOON TROUGH TO THE COASTS OF CENTRAL AMERICA 
AND COLOMBIA...AND IS GENERALLY LESS THAN 20 KT BUT WITH A FEW 
VERY SMALL AREAS OF 20 KT DEPICTED BY SCATTEROMETER PASSES.  
THIS WEATHER PATTERN IS FORECAST TO PERSIST THROUGH THE NEXT 
FEW DAYS.

LONG PERIOD CROSS EQUATORIAL SWELL CONTINUES TO DOMINATE THE 
REGIONAL WATERS. ADDITIONAL PULSES ARE EXPECTED TO SPREAD ACROSS 
THE SOUTHERN WATERS TODAY.  

$$
GR