000
AXPZ20 KNHC 291004
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU SEP 29 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...

TROPICAL STORM HILARY WAS LOCATED NEAR 20.0N119.9W AT 0900 UTC 
MOVING NW OR 325 DEG AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 
WAS 994 MB. MAXIMUM SUSTAINED WINDS WERE 50 KT WITH GUSTS TO 60 
KT. NUMEROUS MODERATE ISOLATED STRONG CONVECTION WAS WITHIN 240 
NM NE QUADRANT OF CENTER WHILE ISOLATED TO SCATTERED MODERATE 
CONVECTION WAS ELSEWHERE WITHIN 90 NM OF CENTER. HILARY 
CONTINUES TO SLOWLY WEAKEN...AS COLDER WATERS AND VERTICAL WIND 
SHEAR ARE MAKING AN IMPACT ON THE STORM. GRADUALLY COOLER WATER 
AND THIS CONTINUED SW VERTICAL WIND SHEAR WILL PRODUCE AN 
INCREASED WEAKENING TREND AFTER 24 HOURS AS HILARY CONTINUES 
MOVING NW. OVERNIGHT MICROWAVE IMAGERY REVEALS THAT THE LOW 
LEVEL CIRCULATION OF HILARY HAS BECOME DECOUPLED FROM THE MID 
LEVEL CIRCULATION DUE TO THE WIND SHEAR. THIS PROCESS IS 
EXPECTED TO CONTINUE AND AFTER 24 HOURS A QUICKLY WEAKENING LOW 
LEVEL CIRCULATION CENTER WILL BEGIN TO BE STEERED BY THE LOWER 
LEVEL WINDS AND TURN W...THEN SW SUNDAY AND MONDAY. SWELLS 
GENERATED BY HILARY CONTINUE TO AFFECT THE WEST COAST OF BAJA 
CALIFORNIA...THE SOUTHERN GULF OF CALIFORNIA...AND ADJACENT 
PORTIONS OF SOUTHWEST MEXICO...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...

THE MONSOON TROUGH EXTENDS FROM THE SW CARIBBEAN NW THROUGH 
CENTRAL AMERICA ENTERING THE E PACIFIC NEAR 14N81W TO 09N109W 
WHERE IT ENDS. THERE IS NO ITCZ OR MONSOON TROUGH FROM 109W TO 
125W AS A RESULT OF THE DIFFLUENT FLOW INDUCED BETWEEN TROPICAL 
STORM HILLARY AND LOW PRES NEAR 11N133W. THE ITCZ STARTS NEAR 
14N125W TO LOW PRES 11N133W 1010 MB EXTENDING W TO BEYOND 
10N140W. SCATTERED MODERATE TO STRONG N OF 07N E OF 87W. 
SCATTERED MODERATE TO STRONG CONVECTION WITHIN 240 NM S OF 
MONSOON TROUGH BETWEEN 95W AND 109W. 

...DISCUSSION... 

A VERY WEAK RIDGE CONTINUES TO COLLAPSE ACROSS NW PORTIONS... 
WITH A 1020 MB HIGH CENTERED NEAR 27N138W EXTENDING WEAKLY SE TO 
NEAR 16N129W. A 1010 MB LOW PRES CENTER WAS CENTERED NEAR 
11N133W WITH ISOLATED MODERATE CONVECTION WITHIN 120 NM TO THE 
NE. WINDS 20 TO 25 KT ARE OCCURRING WITHIN 120 NM OF THIS LOW. 
THE CIRCULATION AROUND THIS FEATURE...COMBINED WITH THE 
CIRCULATION AROUND TROPICAL STORM HILARY HAS LIMITED THE 
COVERAGE OF THE MONSOON TROUGH AND ITCZ OVER THE AREA AS 
MENTIONED ABOVE. THE LOW IS FORECAST TO REMAIN NEARLY STATIONARY 
THROUGH THE FORECAST PERIOD WHILE GRADUALLY WEAKENING. 

LONG PERIOD NW SWELL PREVAILS ACROSS THE NW PORTION OF THE AREA 
PRODUCING SEAS TO 9 FT AND WILL CONTINUE TO PROPAGATE SE AND 
MERGE WITH SWELL FROM HILARY OVER THE NEXT FEW DAYS TO CREATE 
CONFUSED SEAS N OF 15N AND W OF 130W. NW SWELL WILL BE 
REINFORCED BY A COLD FRONT FORECAST TO ENTER THE NW PART OF THE 
AREA LATE THU AFTERNOON/EARLY EVENING.  

$$
STRIPLING