000
AXPZ20 KNHC 231600
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI SEP 23 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 
1545 UTC.

...SPECIAL FEATURE...

HURRICANE HILARY WAS NEAR 16.1N 102.5W AT 1500 UTC MOVING W OR 
275 DEG AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 944 MB. 
MAXIMUM SUSTAINED WINDS ARE 125 KT WITH GUSTS TO 150 KT MAKING 
HILARY A CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON SCALE. 
SATELLITE PRESENTATION CONTINUES TO BEA RATHER IMPRESSIVE AS
A SMALL WARM EYE OF ABOUT 15 NM IS OBSERVED ON FIRST VISIBLE
SATELLITE IMAGERY FROM THIS MORNING...AND NUMEROUS STRONG 
CONVECTION IS WITHIN 75-80 NM OF THE CENTER IN ALL QUADRANTS.
LARGE CLUSTERS OF SCATTERED TO NUMEROUS STRONG CONVECTION ARE
NOTED TO THE W AND NW OF HILARY N OF 15N AND BETWEEN 104W AND 
106W. HILARY REMAINS UNDER A BROAD UPPER LEVEL ANTICYCLONE...OVER
VERY WARM SEA SURFACE TEMPERATURES...AND IN A LOW VERTICAL WIND
SHEAR ENVIRONMENT. ALL FACTORS CONDUCIVE FOR IT TO MAINTAIN
ITS CURRENT INTENSITY. HILARY IS THE FOURTH MAJOR HURRICANE OF 
2011 EAST PACIFIC HURRICANE SEASON. HILARY IS EXPECTED TO 
MAINTAIN A WNW MOTION THROUGH THE NEXT COUPLE OF DAYS BEFORE IT 
ENCOUNTERS GRADUALLY DECREASING SSTS...LESS UNSTABLE AIR...AND 
INCREASING VERTICAL SHEAR SHOULD LIKELY RESULT IN A WEAKENING 
TREND. SEE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.
 
...ITCZ/MONSOON TROUGH...

MONSOON TROUGH AXIS EXTENDS FROM 10N83W TO 6N91W...THEN RESUMES
FROM 17N110W TO 10N140W. SCATTERED MODERATE/ISOLATED STRONG 
CONVECTION EXISTS FROM 2N-8N E OF 80W...WITHIN 60 NM OF 
5N91W...WITHIN 45 NM OF 10N90W...WITHIN 90 NM OF A LINE 13N105W 
TO 15N112W...WITHIN 30 NM OF A LINE FROM 14N122W TO 14N128W.
SIMILAR ACTIVITY IS S OF THE MONSOON TROUGH WITHIN 75 NM OF
LINE FROM 10N123W 10N126W.

...DISCUSSION... 

A NARROW UPPER LEVEL TROUGH EXTENDS FROM AN UPPER CYCLONE OFF 
THE SW COAST OF CALIFORNIA NEAR 32N122W TO A SECOND UPPER 
CYCLONE NEAR 24N140W. BROAD MID/UPPER LEVEL RIDGING COVERS THE 
REMAINDER OF THE AREA ANCHORED BY AN ELONGATED ANTICYCLONE 
EXTENDING FROM HURRICANE HILARY EASTWARD TO A SMALL ANTICYCLONE
OVER THE NW YUCATAN PENINSULA AND EXTENDING W-SW TO 13N136W. 
WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE OVER THE 
AREA N OF 20N. S OF 20N AMPLE DEEP MOISTURE IS NOTED ALONG AND 
WITHIN 480 NM S OF THE MONSOON TROUGH. AT THE SURFACE...A
1020 MB HIGH IS ANALYZED NEAR 31N132W WITH A RIDGE SE TO NEAR
23N118W. HIGH PRESSURE COVERS THE AREA N OF 15N W OF 118W.
SPORADIC LIGHT TO MODERATE TRADEWINDS CONTINUE N OF THE MONSOON 
TROUGH AND W OF 120W. SW 20 KT WINDS ARE WITHIN 300 NM SE OF 
LINE FROM 16N104W TO 09N125W WITH SEAS TO 8 FT IN SW SWELL. BY 
48 HOURS...WINDS WILL BE LESS THAN 20 KT WITHIN 240 NM S OF 18N 
BETWEEN 100W AND 110W AND REMAINDER AREA S OF 05N BETWEEN 95W 
AND 130W WITH SEAS TO 8 FT IN MIXED NW AND SW SWELL. A COLD
FRONT IS FORECAST TO ENTER THE NW PORTION OF THE AREA FROM 
30N138W TO 29N140W IN 48 HOURS. NE WINDS OF 20 KT CAN BE 
EXPECTED NW OF THE FRONT.

ELSEWHERE WITH REGARDS TO MARINE IMPACTS...SOUTHERN HEMISPHERE
SW SWELL DOMINATES THE REMAINDER OF THE AREA THIS MORNING 
YIELDING SEAS GENERALLY 5 TO 7 FT. THESE TWO SWELLS ARE FORECAST 
TO MERGE S OF 10N DURING THE NEXT FEW DAYS TO RAISE SEA HEIGHTS 
TO POSSIBLY AS HIGH AS 10 FT TO SPREAD INTO THE SOUTHERN GULF
OF CALIFORNIA THIS WEEKEND.    

$$
AGUIRRE