000
AXPZ20 KNHC 261555
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON SEP 26 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1530 UTC.

...SPECIAL FEATURE...

HILARY REMAINS A POWERFUL HURRICANE. AT 1500 UTC...THE EYE OF 
HURRICANE HILARY WAS LOCATED ABOUT 420 NM SSW OF CABO SAN LUCAS 
NEAR 16.7N 113.1W MOVING W OR 265 DEG AT 9 KT. ESTIMATED MINIMUM 
CENTRAL PRESSURE IS 953 MB. MAXIMUM SUSTAINED WINDS ARE 110 KT 
GUSTS TO 135 KT. MINOR FLUCTUATIONS IN INTENSITY ARE POSSIBLE 
DURING THE NEXT DAY OR SO...BUT THE OVERALL TREND IS FOR HILARY
TO SLOWLY WEAKEN DURING THE NEXT 48 HOURS BEFORE TURNING NORTH 
WEDNESDAY. NUMEROUS STRONG CONVECTION WITHIN 60 NM OF CENTER. 
SCATTERED MODERATE CONVECTION ELSEWHERE WITHIN 90 NM E AND W 
QUADRANTS..150 NM N AND S QUADRANTS. SWELLS GENERATED BY HILARY 
ARE AFFECTING THE SOUTHERN HALF OF BAJA CALIFORNIA AND THE GULF 
OF CALIFORNIA S OF 25N...CAUSING HIGH SURF AND 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 NORTHERN COSTA RICA NEAR 10N85W 
TO 15N102W...THEN RESUMES W OF HURRICANE HILARY FROM 14N117W TO 
10N128W TO 10N140W. SCATTERED MODERATE CONVECTION WITHIN 120 NM 
N OF AXIS BETWEEN 88W AND 93W...AND BETWEEN 120-300 NM S OF AXIS 
BETWEEN 90W-96W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
WITHIN 90 NM N AND 30 NM S OF AXIS BETWEEN 125W AND 128W.

...DISCUSSION... 

HIGH PRES RIDGE EXTENDS SE FROM A 1020 MB HIGH CENTERED NEAR 
28N130W TO NEAR 24N116W. THE PRESSURE GRADIENT BETWEEN THE HIGH 
PRES AND A PERSISTENT TROUGH OVER WESTERN MEXICO IS SUPPORTING 
FRESH NW WINDS N OF 25N NEAR THE W COAST OF BAJA CALIFORNIA. 
LITTLE CHANGE IS EXPECTED IN THE GENERAL SYNOPTIC PATTERN DURING 
THE NEXT 24 HOURS AS THE HIGH REMAINS NEARLY STATIONARY. HOWEVER 
AFTER 24 HOURS THE HIGH WILL BEGIN TO RETREAT SLOWLY TO THE NW 
AND ALLOW WINDS TO DIMINISH E OF 120W. THE PRES GRADIENT BETWEEN 
THE HIGH AND HURRICANE HILARY IS RESULTING IN AN AREA OF FRESH NE
ALMOST 600 NM TO THE NW OF HILARY. AS THE HIGH RETREATS DURING 
THE WEEK...THIS PRESSURE GRADIENT WILL REMAIN INTACT...AND BEGIN 
TO FRESHEN THE NE TRADEWINDS S OF 20N AND W OF 125W...BUILDING 
SEAS TO AROUND 8 FT. 

A WEAK FRONT CROSSING THE AREA NEAR 30N140W WILL BECOME DIFFUSE 
THEN DISSIPATE BY TUE NIGHT. MODERATE SW WINDS WITH SEAS TO 8 FT 
WILL SLOWLY SUBSIDE TODAY...BUT WILL INCREASE AGAIN TO 8 TO 10 
FT TUE NIGHT AS A NEW PULSE OF NW SWELL MOVES INTO NW PORTIONS. 
THE LONG-PERIOD NW SWELL WILL MERGE WITH MIXED SWELL GENERATED 
BY HILLARY ON WED TO CREATE A LARGE AREA OF SEAS GREATER THAN 8 
FT...ROUGHLY BOUNDED BY N OF 10N AND W OF 105W.

CONVECTION ASSOCIATED WITH THE MONSOON TROUGH HAS DIMINISHED OVER
THE PAST FEW HOURS...AND SHIFTED W OF 140W. SCATTEROMETER DATA 
SHOWS LIGHT TO MODERATE S-SW WINDS S OF THE MONSOON TROUGH EXCEPT
FOR A SMALL AREA OF ENHANCED SOUTHERLY WINDS S OF 07N BETWEEN 
95W AND 103W. SWELL GENERATED IN THE SOUTHERN HEMISPHERE EVIDENT
S OF 09N BETWEEN 90W AND 105W ARE PRODUCING SEAS TO 9 FT IN THE 
AREA OF ENHANCED SOUTHERLY FLOW.

$$
MUNDELL