000
AXPZ20 KNHC 241556
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT SEP 24 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 NEAR 16.6N 106.2W AT 1500 UTC MOVING W OR 270 
DEG AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 946 MB. 
MAXIMUM SUSTAINED WINDS ARE 120 KT GUSTS TO 145 KT...A CATEGORY 
FOUR HURRICANE ON THE SAFFIR-SIMPSON SCALE. SATELLITE IMAGERY 
INDICATES HILARY HAS PEAKED IN INTENSITY AND CONTINUES TO HAVE A 
SMALL EYE. SHORT-TERM MOTION HAS BEEN SW OVER THE PAST FEW HOURS.
HILARY IS EXPECTED TO SLOWLY DECREASE IN INTENSITY OVER THE NEXT 
TWO TO THREE DAYS AS THE HURRICANE MOVES WNW OVER WARM WATERS 
AND MINIMAL UPPER WIND SHEAR. NUMEROUS STRONG CONVECTION IN 
BANDS WITHIN 75 NM N AND 45 NM S OF CENTER. SCATTERED TO 
NUMEROUS MODERATE TO STRONG CONVECTION ELSEWHERE WITHIN 150 NM 
NW AND 90 NM SE QUADRANTS. SEE LATEST NHC FORECAST/ADVISORY 
UNDER AWIPS/WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.
 
...ITCZ/MONSOON TROUGH...

MONSOON TROUGH AXIS EXTENDS FROM 09N84W TO 10N98W...THEN RESUMES 
W OF HURRICANE HILARY NEAR 15N112W TO 12N125W TO 10N140W. 
SCATTERED MODERATE TO STRONG CONVECTION WITHIN 180 NM S OF AXIS 
BETWEEN 92W AND 98W...AND WITHIN 120 NM OF AXIS BETWEEN 114W AND 
130W. SCATTERED MODERATE ISOLATED STRONG CONVECTION N OF 04N E 
OF 85W TO THE COAST OF PANAMA. 

...DISCUSSION... 

A 1019 MB HIGH IS CENTERED NEAR 28N129W WITH A WEAK RIDGE AXIS 
EXTENDING SE TO SOUTHERN BAJA CALIFORNIA NEAR 24N113W. THE 
PRESSURE GRADIENT IS PRODUCING FRESH NW WINDS FROM 23N TO 28N W 
OF BAJA. A COLD FRONT OFF THE WEST COAST OF THE U.S. EXTENDS TO 
JUST NW OF THE DISCUSSION AREA. OVER THE NEXT 24 HOURS THE HIGH 
IS EXPECTED TO REMAIN NEARLY STATIONARY WHILE THE COLD FRONT 
WEAKENS AND BRUSHES PAST THE EXTREME NW PORTION WHILE BUILDING 
SEAS TO 8-9 FT IN NW SWELL...WITH 20 KT WINDS CONTINUING NEAR 
BAJA CALIFORNIA.

A FEW WEAK PERTURBATIONS ARE EMBEDDED WITHIN THE MONSOON TROUGH 
ACROSS THE AREA. SCATTEROMETER DATA SHOWS A CYCLONIC CIRCULATION 
NEAR 12N123W THAT IS PRODUCING SCATTERED SHOWERS AND ISOLATED 
TSTMS. LIGHT TO MODERATE S TO SW MONSOONAL FLOW PREVAILS S OF 
THE TROUGH PRODUCING PATCHY CONVECTION ALONG THE TROUGH BETWEEN 
114W AND 130W. WEAK HIGH PRESSURE ACROSS THE W COAST OF THE GULF 
OF MEXICO IS SUPPORTING FRESH N WINDS IN THE GULF OF TEHUANTEPEC 
WHICH ARE EXPECTED TO LAST THROUGH EARLY SUNDAY MORNING.

HURRICANE HILARY IS GENERATING LARGE LONG-PERIOD SWELL WITH SEAS 
GREATER THAN 8 FT EXTENDING 200 TO 300 NM AWAY FROM THE CENTER. 
MARINE CONDITIONS ELSEWHERE REMAIN BENIGN ACROSS THE DISCUSSION 
AREA. LONG PERIOD NW SWELL WILL MERGE WITH SW SWELL FROM THE 
SOUTHERN HEMISPHERE TODAY S OF 10N. AS HILARY CONTINUES MOVING 
WNW...SE SWELL WILL BEGIN TO MOVE INTO SOUTHERN PORTIONS OF THE 
GULF OF CALIFORNIA SUNDAY THROUGH MONDAY.

$$
MUNDELL/COBB