000
AXPZ20 KNHC 251003
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC SUN SEP 25 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0930 UTC.

...SPECIAL FEATURE...

HILARY CONTINUES AS A CATEGORY FOUR HURRICANE. AT 25/0900 UTC... 
HILARY WAS CENTERED NEAR 17.0N 108.4W MOVING W OR 275 DEG AT 8 
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 953 MB. MAXIMUM 
SUSTAINED WINDS ARE 110 KT GUSTS TO 135 KT. SOME MINOR 
FLUCTUATIONS IN INTENSITY ARE LIKELY IN THE SHORT TERM...BUT THE 
OVERALL TREND IS FOR HILARY TO SLOWLY WEAKEN. NUMEROUS STRONG 
CONVECTION WAS WITHIN 40 NM N AND 60 NM S OF CENTER. SCATTERED 
TO NUMEROUS MODERATE TO STRONG CONVECTION WAS ELSEWHERE WITHIN 
150 NM OF THE CENTER. SWELLS GENERATED BY HILARY ARE STILL 
AFFECTING PORTIONS OF THE COAST OF SOUTHWESTERN MEXICO AND ARE 
ENTERING THE SOUTHERN GULF OF CALIFORNIA THIS MORNING. THESE 
SWELLS ARE LIKELY CAUSING LARGE AND DANGEROUS SURF AND PRODUCING 
LIFE-THREATENING RIP CURRENT CONDITIONS. SEE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC 
FOR MORE DETAILS. 
 
...ITCZ/MONSOON TROUGH...

MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 09N90W TO 07N97W THEN 
RESUMES W OF HURRICANE HILARY NEAR 15N110W TO 13N125W TO 11N140W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WITHIN 150 NM S 
OF TROUGH BETWEEN 84W AND 90W...AND WITHIN 90 NM S OF TROUGH 
BETWEEN 96W AND 98W. ISOLATED MODERATE CONVECTION FROM 10N TO 
13N BETWEEN 120W AND 130W.

...DISCUSSION... 

A 1020 MB HIGH WAS CENTERED NEAR 27N130W WITH A WEAK RIDGE AXIS 
EXTENDING SE TO SOUTHERN BAJA CALIFORNIA NEAR 23N113W. THE 
PRESSURE GRADIENT BETWEEN THE HIGH PRES AND LOWER PRES OVER NW 
MEXICO IS RESULTING IN FRESH NW WINDS N OF 25N E OF 116W TO THE 
W COAST OF BAJA CALIFORNIA. THIS HIGH CENTER IS FORECAST TO 
REMAIN NEARLY STATIONARY FOR THE NEXT COUPLE OF DAYS AND 
MAINTAIN FRESH WINDS OFFSHORE OF BAJA CALIFORNIA. A COLD FRONT 
IS JUST NW OF THE FORECAST AREA CROSSING NEAR 31N140W. SW WINDS 
OF 15 TO 20 KT ARE NOTED OVER THE FAR NW PORTION WITH SEAS TO 8 
FT IN NW SWELL AFFECTING THE WATERS N OF 29N W OF 138W. LITTLE 
CHANGE IS EXPECTED IN ABOUT 24 HOURS WITH SEAS SUBSIDING BELOW 8 
FT IN 36-48 HOURS. LIGHT TO MODERATE N-NE TRADE WINDS DOMINATE 
THE REGION N OF THE MONSOON TROUGH W OF 115W...WITH A NARROW 
ZONE OF 15 TO 20 KT TRADEWINDS BETWEEN 13N AND 17N W OF 125W.

SEVERAL WEAK DISTURBANCES EMBEDDED WITHIN THE MONSOON TROUGH ARE 
PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS ALONG THE TROUGH 
AXIS BETWEEN 120W AND 140W. FRESH MONSOONAL FLOW PREVAILS S OF 
THE TROUGH AXIS PARTICULARLY E OF 95W. WEAK HIGH PRESSURE ACROSS 
THE W COAST OF THE GULF OF MEXICO SUPPORTING MODERATE TO FRESH N 
WINDS IN THE GULF OF TEHUANTEPEC ARE END THIS AFTERNOON. 

HURRICANE HILARY IS GENERATING LARGE LONG-PERIOD SWELL WITH SEAS 
GREATER THAN 8 FT UP TO 240 NM AWAY FROM THE CENTER. OTHERWISE 
MARINE CONDITIONS ELSEWHERE REMAIN FAIRLY BENIGN ACROSS THE 
DISCUSSION AREA. LONG PERIOD NW SWELL ARE MERGING WITH SW SWELL 
FROM THE SOUTHERN HEMISPHERE MAINLY S OF 10N. SE SWELL FROM 
HILARY WILL CONTINUE TO PROPAGATE NW THROUGH THE GULF OF 
CALIFORNIA TODAY THROUGH MONDAY AND PRODUCE LARGE SURF FOR THE 
TYPICALLY BENIGN COASTLINES.

$$
STRIPLING