000
AXPZ20 KNHC 281504
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURE...

HURRICANE HILARY WAS LOCATED NEAR 18.4N 118.4W AT 1500 UTC  
MOVING NW OR 320 DEG AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 
WAS 983 MB. MAXIMUM SUSTAINED WINDS 70 KT WITH GUSTS TO 85 KT. 
SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION WAS NOTED 
WITHIN 90 NM N SEMICIRCLE OF CENTER WHILE SCATTERED MODERATE 
CONVECTION WAS WITHIN 90 NM SE SEMICIRCLE OF CENTER. THE FIRST 
LOW LIGHT VISIBLE IMAGES SHOW THAT THE RAGGED EYE NOTED LAST 
NIGHT IS NOT WELL DEFINED IN SATELLITE IMAGERY. HILARY CONTINUES 
TO SLOWLY WEAKEN AS PORTIONS OF THE W SEMICIRCLE CONTINUE TO 
ENTRAIN DRIER AND MORE STABLE AIR FROM THE OPEN SUBTROPICAL 
PACIFIC. COOLER WATER TEMPERATURES ARE NOT FAR TO THE N AND NW 
AND HILARY WILL BEGIN A MORE RAPID RATE OF WEAKENING TONIGHT AND 
TUE AS IT TURNS TOWARD THE NORTH AND BEGINS TO MOVE OVER THE 
COLDER WATERS. HILARY IS FORECAST 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 THE COAST OF PANAMA NW TO NEAR  
12N93W TO 11N105W WHERE IT TERMINATES...THEN RESUMES SW OF  
HURRICANE HILARY FROM 15N122W TO LOW PRES 10.5N132W 1010 MB TO 
09N136W WHERE IT TRANSITIONS TO ITCZ TO 09N140W. SCATTERED 
MODERATE CONVECTION IS WITHIN 180 NM N OF AXIS BETWEEN 96W AND 
110W...AND WITHIN 60 NM OF AXIS W OF 136W. 

...DISCUSSION... 

COLLAPSING HIGH PRES WAS JUST NW OF THE AREA NEAR 29N141W WITH A 
WEAK SURFACE RIDGE EXTENDING SE TO NEAR 24N125W. A MID LEVEL 
CYCLONE OVER NRN BAJA CALIFORNIA AND NW MEXICO WAS REFLECTED AT 
THE SURFACE AS A WEAK TROUGH ALONG THE W COAST OF MEXICO N OF 
23N AND IN CONCERT WITH THE EXISTING RIDGE OVER THE NE PACIFIC 
ACTED TO FOCUS MODERATE NLY WINDS WESTWARD TO BETWEEN 120W AND 
125W. 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 18N W OF 130W. A 1010 MB LOW PRES CENTER WAS 
EMBEDDED WITHIN THE W END OF THE MONSOON TROUGH NEAR 10.5N132W 
AND IS DRIFTING SLOWLY W AND GENERATING BURSTS OF ACTIVE 
CONVECTION AND FRESH WINDS WITHIN 180 NM OF THE CENTER. LONG 
PERIOD NW SWELL OF 9 TO 11 FT 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 SLATED TO 
ENTER THE NW CORNER NEAR 30N140W LATE THU AND THU NIGHT.  

$$
COBB