000
AXPZ20 KNHC 222131
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU SEP 22 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 NEAR 15.6N 99.8W 973 MB AT 2100 UTC SEP 22 
MOVING WNW OR 300 DEG AT 9 KT. MAXIMUM SUSTAINED WINDS HAVE 
INCREASED TO 90 KT WITH GUSTS TO 110 KT MAKING HILARY A STRONG 
CATEGORY TWO HURRICANE ON THE SAFFIR-SIMPSON SCALE. VISIBLE 
SATELLITE IMAGERY SHOWS A SMALL BUT WELL ORGANIZED TROPICAL
CYCLONE CONSISTING OF A SMALL EYE FEATURE SURROUNDED BY A 60 NM 
WIDE RING OF NUMEROUS STRONG CONVECTION. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS ELSEWHERE WITHIN 120 NM OF THE 
CENTER MAINLY IN THE W SEMICIRCLE. A LARGER CLUSTER OF 
SCATTERED TO NUMEROUS CONVECTION EXISTS TO THE NW OF HILARY IN 
AN AREA FROM 15N TO THE COAST OF MEXICO BETWEEN 104W AND 107W. 
HILARY IS UNDER A LARGE ANTICYCLONE...AND OVER VERY WARM SEA 
SURFACE TEMPERATURES IN ADDITION TO BEING IN A LOW SHEAR 
ENVIRONMENT. BASED ON THESE FAVORABLE CONDITIONS THE LATEST NHC 
FORECAST ADVISORY HAS THE CYCLONE INTENSIFYING TO A MAJOR 
HURRICANE WITHIN 12 HOURS. IF SO...HILARY WOULD BE THE FOURTH 
MAJOR HURRICANE OF 2011 EAST PACIFIC HURRICANE SEASON. 
SEE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS 
MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.
 
...ITCZ/MONSOON TROUGH...

MONSOON TROUGH AXIS EXTENDS FROM 08N81W TO 06N93W AND THEN FROM 
15N104W TO 16N110W TO 12N119W TO 12N130W. SCATTERED MODERATE 
ISOLATED STRONG WITHIN 75 NM EITHER SIDE OF A LINE FROM 09N113W 
TO 08N120W AND FROM 09N136W TO BEYOND 10N140W.       

...DISCUSSION... 

A NARROW BUT SHARP UPPER LEVEL SHARP TROUGH EXTENDS FROM THE 
SW COAST OF CALIFORNIA AND ENTERS THE REGION THROUGH 32N123W 
29N130W TO A DEVELOPING UPPER LOW NEAR 24N140W. BROAD MID/UPPER 
LEVEL RIDGING COVERS THE REMAINDER OF THE AREA ANCHORED BY 
AN ELONGATED ANTICYCLONE EXTENDING FROM NEAR THE GULF OF 
TEHUANTEPEC ALONG 17N TO 105W. SATELLITE WATER VAPOR IMAGERY 
SHOWS MODERATE TO STRONG SUBSIDENCE OVER JUST ABOUT THE ENTIRE 
AREA WITH THE EXCEPTION OF THE MONSOON TROUGH AND NEAR HURRICANE 
HILARY WHERE THE UPPER LEVEL OUTFLOW IS CHANNELING MOISTURE IN 
THE FORM OF CIRRUS OUTFLOW FROM THE CYCLONE. AT THE SURFACE...A 
TROUGH EXTENDS FROM 14N137W TO 08N142W. THE TROUGH NOTED EARLIER 
FROM FROM 15N124W TO 12N128W HAS BECOME ABSORBED INTO THE 
LARGER MONSOON TROUGH. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION WAS NOTED WITHIN 60 NM OF THE TROUGH NEAR 140W. 
A WEAK RIDGE EXTENDS FROM A 1024 MB HIGH NEAR 33N134W SE TO NEAR 
21N125W. AN AREA OF NE 20 KT WINDS EXISTS TO THE SE OF THE RIDGE 
FROM 14N-19N BETWEEN 120W-130W. THESE WINDS ARE FORECAST TO 
DIMINISH TO LESS THAN 20 KT IN ABOUT 18 HRS.

DIVERGENCE ALOFT ASSOCIATED WITH A SHARP UPPER TROUGH OVER 
SOUTHERN CENTRAL AMERICA CONTINUES TO SUSTAIN THE SCATTERED 
MODERATE CONVECTION WITHIN 120 NM S OF THE MONSOON TROUGH 
BETWEEN 86W-88W.

NW SWELLS WITH HEIGHTS TO 11 FT AND PERIODS OF 16-18 SECONDS 
CONTINUE TO PROPAGATE SE OVER THE NW PORTION OF THE MARINE AREA.
THESE SWELLS ARE FORECAST TO EXTEND FROM SW BAJA CALIFORNIA
TO THE EQUATOR AT 135W AND MERGE WITH ANOTHER LONGER PERIOD
SWELL TRAIN ORIGINATING FROM THE SOUTH PACIFIC BY LATE FRI ALONG
THE COAST OF MEXICO. PERIODS IN THIS SWELL TRAIN ARE 20 TO 22 
SECONDS.   

$$
AGUIRRE/COBB