000
AXPZ20 KNHC 282135
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...SPECIAL FEATURE...

HURRICANE HILARY WAS LOCATED NEAR 19.0N 118.9W AT 2100 UTC  
MOVING NW OR 325 DEG AT 7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 
WAS 980 MB. MAXIMUM SUSTAINED WINDS WERE 70 KT WITH GUSTS TO 85 
KT. SCATTERED TO NUMEROUS STRONG CONVECTION WAS CONFINED TO 
WITHIN 90 NM IN THE N QUADRANT OF HILARY WHILE SCATTERED 
MODERATE CONVECTION WAS NOTED ELSEWHERE WITHIN 150 NM OF THE 
CENTER EXCEPT THE SE QUADRANT. VISIBLE SATELLITE AND WATER VAPOR 
IMAGERY INDICATED THAT THERE WAS SOME DRY AIR WRAPPING INTO THE 
CIRCULATION OF HILARY CONTRIBUTING TO THE OVERALL DEGRADATION OF 
THE SYSTEM. THIS TREND IS LIKELY TO CONTINUE AND AS HILARY 
BEGINS TO TRACK OVER COOLER WATER TEMPERATURES...A MORE RAPID 
RATE OF WEAKENING IS EXPECTED. HILARY IS FORECAST TO WEAKEN TO A 
TROPICAL STORM LATER TONIGHT AND TO A TROPICAL DEPRESSION WITHIN 
36 TO 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...

THE MONSOON TROUGH EXTENDS FROM THE SW CARIBBEAN ACROSS N COSTA 
RICA ENTERING THE E PACIFIC NEAR 10.5N85W EXTENDING W TO 
10.5N94W TO 10N100W TO WHERE IT ENDS NEAR 10N107W. THERE IS NO 
ITCZ OR MONSOON TROUGH FROM 107W TO 135W AS A RESULT OF THE 
CIRCULATIONS AROUND HURRICANE HILLARY AND A SMALL LOW PRESSURE 
CENTER NEAR 11N132W. THE ITCZ STARTS NEAR 10N135W AND EXTENDS W 
OF 09N140W. SCATTERED MODERATE ISOLATED STRONG WITHIN 60 NM 
EITHER SIDE OF MONSOON TROUGH AXIS BETWEEN 95W AND 100W. 
SCATTERED MODERATE WITHIN 30 NM N AND 45 NM S OF ITCZ AXIS W OF 
135W. 

...DISCUSSION... 

A NARROW RIDGE OF HIGH PRES EXTENDED FROM 32N135W SW ACROSS THE 
FAR NW PORTION OF THE AREA WITH ANOTHER AXIS EXTENDING SE TO 
NEAR 24N125W. A MID LEVEL CYCLONE OVER NW MEXICO WAS REFLECTED 
AT THE SURFACE AS A TROUGH ALONG THE W COAST OF MEXICO IN THE 
LEE OF THE SIERRA MADRE. THIS TROUGH 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 RIDGE OF HIGH PRES AND THE ITCZ WAS PRODUCING A BROAD 
ZONE OF FRESH NE TRADEWINDS AROUND 20 KT FROM 10N TO 18N W OF 
130W. THIS AREA OF TRADES WAS WELL DEPICTED IN A 1520 UTC 
WINDSAT PASS. ELSEWHERE A 1010 MB LOW PRES CENTER WAS EMBEDDED 
WITHIN THE W END OF THE MONSOON TROUGH NEAR 11N133W AND IS 
DRIFTING SLOWLY W AND GENERATING LITTLE IN THE WAY OF 
CONVECTION. 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