000
AXPZ20 KNHC 112134
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN SEP 11 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM EXTREME SOUTHWEST CARIBBEAN WNW 
ACROSS N PORTIONS OF COSTA RICA AND ENTERS EPAC WATERS NEAR 
10N86W TO 08N91W TO 20.5N112W TO 1008 MB LOW PRES AT 16.5N116.W 
TO 1009 MB LOW PRES AT 12.5N133.5W TO 10.5N137W THEN TRANSITIONS 
TO ITCZ TO BEYOND 10N140W. SCATTERED TO NUMEROUS MODERATE TO 
STRONG CONVECTION NOTED WITH 60 NM N AND 270 NM S OF AXIS E OF 
96W...AND BETWEEN 98W AND 105W.  

...DISCUSSION...
A RIDGE/TROUGH/RIDGE PATTERN DOMINATES MOST OF THE FORECAST 
REGION. AN UPPER ANTICYCLONE IS CENTERED W OF THE AREA NEAR 
23N147W WITH A RIDGE EXTENDING NE OVER THE NW CORNER OF THE 
FORECAST REGION TO BEYOND 36N135W. ANOTHER UPPER ANTICYCLONE 
IS OVER W MEXICO AT 23N104W WITH AN UPPER RIDGE EXTENDING W OVER 
THE PACIFIC TO NEAR 18N131W...AND RIDGING TO THE N OVER THE SW 
CONUS. BETWEEN RIDGES...THERE IS AN UPPER LEVEL TROUGH WITH AXIS 
EXTENDING FROM AN UPPER LEVEL LOW OVER SOUTHERN NEVADA TO 
ANOTHER WEAK LOW NEAR 18N136W. UPPER LEVEL NE TO E FLOW 
DOMINATES THE DEEP TROPICS TO THE S OF THESE FEATURES. 

AT THE SURFACE...A WEAK HIGH PRES RIDGE CONTINUES OVER THE NW 
WATERS PRODUCING MAINLY LIGHT WINDS. ON THE SOUTHERN PERIPHERY 
OF THE RIDGE...NE TRADES OF 10 TO 15 KT CAN BE FOUND. THE 
MONSOONAL FLOW ALSO REMAINS WEAK WITH WINDS BELOW 20 KT. AS 
TROPICAL CYCLONE NATE CONTINUES TO MOVE FARTHER INLAND OVER THE 
NEXT 12-24 HOURS EXPECT NLY WINDS TO FUNNEL ACROSS THE GULF OF 
TEHUANTEPEC BEGINNING TONIGHT. MARINE GUIDANCE SUGGESTS WINDS OF 
20 TO 25 KT ACROSS THIS GAP REGION DURING THE NEXT 24 HOURS.

SHOWER ACTIVITY REMAINS MINIMAL IN ASSOCIATION WITH THE AREA OF 
LOW PRESSURE CENTERED NEAR 16.5N116.5W. DEVELOPMENT OF THIS 
SYSTEM APPEARS UNLIKELY DUE TO UNFAVORABLE UPPER-LEVEL WINDS AND 
COOLER WATER ALONG THE EXPECTED NORTHWARD TRACK. AN EARLIER 
ASCAT PASS SHOWED THE CYCLONIC CIRCULATION ASSOCIATED WITH THIS 
SYSTEM WITH WINDS OF 20 KT AND SEAS TO 8 FT WITHIN 150 NM SW 
QUADRANT OF THE LOW CENTER.  

THE SMALL AREA OF LOW PRESSURE LOCATED NEAR 12.5N133.5W 
CONTINUES TO PRODUCE DISORGANIZED SHOWERS AND THUNDERSTORMS. 
DEVELOPMENT...IF ANY...SHOULD BE SLOW TO OCCUR AS THE LOW BEGINS 
TO MOVE SLOWLY WESTWARD OR WEST-SOUTHWESTWARD. WINDS OF 20 KT 
AND SEAS TO 8 FT ARE NOTED WITHIN 90 NM NW SEMICIRCLE OF THE LOW 
CENTER.

NORTHERLY SWELLS...RESULTING IN COMBINED SEAS OF 9 FT... 
PREVAILS OVER THE WATERS N OF 25N BETWEEN 118W AND 135W. THIS 
SWELL EVENT WILL SPREAD SLIGHTLY FURTHER S BEFORE SUBSIDING 
BELOW 8 FT LATE MON. CROSS EQUATORIAL SW SWELL...WITH SEAS TO 9 
FT...WILL MOVE N OVER THE WATERS S OF 10N W OF 90W. THIS SWELL 
EVENT WILL CONTINUE TO SPREAD NORTHWARD THROUGH THE FORECAST 
PERIOD REACHING THE COAST OF MEXICO S OF SOUTHERN BAJA 
CALIFORNIA THIS MON.

$$
GR