000
AXPZ20 KNHC 281015
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED SEP 28 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...

HURRICANE HILARY WAS LOCATED NEAR 17.7N 118.1W AT 0900 UTC  
MOVING NW OR 305 DEG AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 
WAS 975 MB. MAXIMUM SUSTAINED WINDS 80 KT WITH GUSTS TO 100 KT. 
NUMEROUS MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 120 NM 
NW SEMICIRCLE OF CENTER WHILE SCATTERED MODERATE CONVECTION WAS 
WITHIN 90 NM SE SEMICIRCLE OF CENTER. A RAGGED EYE WAS EVIDENT 
EARLY TONIGHT BUT HAS SINCE BECOME DIFFICULT TO DISCERN IN 
SATELLITE IMAGERY. HILARY CONTINUES TO SLOWLY WEAKEN THIS 
MORNING AS PORTIONS OF THE NW SEMICIRCLE CONTINUE TO ENTRAIN 
DRIER AND MORE STABLE AIR FROM THE OPEN SUBTROPICAL PACIFIC. 
COOLER WATERS TEMPERATURES ARE NOT FAR TO THE N AND NW AND 
HILARY WILL BEGIN A MORE RAPID RATE OF WEAKENING WITHIN 24 HOURS 
AS IT TURNS TOWARD THE NORTH AND BEGINS TO MOVE OVER COLDER 
WATERS. WEAKENING IS FORECAST DURING THE REMAINDER OF THE LIFE 
CYCLE OF HILARY...AND IT IS EXPECTED TO WEAKEN TO A TROPICAL 
STORM WITHIN 24 HOURS AND TO A TROPICAL DEPRESSION WITHIN 48 
HOURS. SWELLS GENERATED BY HILARY ARE AFFECTING 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...

MONSOON TROUGH EXTENDS FROM PANAMA NW TO NEAR 11N86W TO 12N93W 
TO 11N103W TO 13N111W WHERE IT TERMINATES...THEN RESUMES SW OF  
HURRICANE HILARY FROM 12N123W TO LOW PRES 10.5N131.5W 1010 MB TO 
09N134W WHERE IT TRANSITIONS TO ITCZ TO 09N140W. ISOLATED TO 
SCATTERED MODERATE CONVECTION IS FROM 180 NM S AND 120 NM N OF 
AXIS BETWEEN 95W AND 109W.

...DISCUSSION... 

COLLAPSING HIGH PRES WAS JUST NW OF THE AREA NEAR 29N141W WITH A 
WEAK SURFACE RIDGE EXTENDING SE TO NEAR 26N122W. A MID LEVEL 
CYCLONE OVER NRN BAJA CALIFORNIA AND NW MEXICO HAS CARVED A WEAK 
SURFACE TROUGH OFF THE W COAST OF THE BAJA PENINSULA N OF 27N 
AND ACTED TO PUSH MODERATE NLY WINDS TO W OF 120W. A MODEST PRES 
GRADIENT S OF THE COLLAPSED HIGH AND THE ITCZ WAS PRODUCING A 
BROAD ZONE OF FRESH NE TRADEWINDS AROUND 20 KT FROM 10N TO 19N W 
OF 130W. A 1010 MB LOW PRES CENTER WAS EMBEDDED WITHIN THE W END 
OF THE MONSOON TROUGH NEAR 10.5N131.5W AND IS DRIFTING SLOWLY W 
AND GENERATING BURSTS OF ACTIVE CONVECTION AND FRESH WINDS 
WITHIN 180 NM OF THE CENTER. LONG PERIOD NW SWELL HAS MOVED INTO 
NW PORTIONS OF THE AREA OVERNIGHT AND WILL BEGIN TO 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 ENTER THE NW CORNER NEAR 30N140W IN 48 HOURS.  

$$
STRIPLING