000
AXPZ20 KNHC 211605
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED SEP 21 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 
1530 UTC.

...SPECIAL FEATURE...

.TROPICAL STORM HILARY NEAR 13.6N 96.8W 1005 MB AT 1500 UTC SEP 
21 MOVING WNW OR 290 DEG AT 4 KT. MAXIMUM SUSTAINED WINDS 35 KT 
GUSTS 45 KT. TROPICAL STORM FORCE WINDS WITHIN 40 NM NE AND 30 
NM NW QUADRANTS. SEAS 12 FT OR GREATER WITHIN 60 NM N SEMICIRCLE 
WITH SEAS TO 12 FT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/
WMO HEADERS MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS. BROAD BANDS 
OF ACTIVE CONVECTION ARE WRAPPING AROUND THE CYCLONE CENTER AND 
COVER MOST OF THE AREA N OF 11N BETWEEN 92W AND 102W. 
 
...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM 13N87W OVER NW NICARAGUA TO 
13N91W TO T.S. HILARY...THEN RESUMES FROM 12N102W TO AN 1011 MB 
LOW NEAR 12N114W TO 14N116W TO 1011 MB LOW NEAR 12N121W TO 1011 
MB LOW NEAR 10N137W. ISOLATED MODERATE CONVECTION WITHIN 240 NM 
OF THE COASTS OF PANAMA...COSTA RICA...AND NICARAGUA. ISOLATED 
MODERATE CONVECTION WITHIN 120 NM OF TROUGH AXIS BETWEEN 103W 
AND 110W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 
120 NM W SEMICIRCLE OF LOW PRES NEAR 12N114W. 

...DISCUSSION... 

WEAK RIDGE EXTENDING SW FROM 1020 MB HIGH PRES NEAR 32N139W TO 
24N118W SUPPORTING LIGHT N-NE WINDS N OF 20N...AND LIGHT TO 
MODERATE NE TRADE WINDS N OF THE MONSOON TROUGH...W OF 115W. 
SCATTEROMETER DATA SHOWS 20 KT WINDS ASSOCIATED WITH A WELL 
DEFINED LOW NEAR 10N137W THAT LACKS DEEP CONVECTION. WINDS ARE 
LESS THAN 20 KT AROUND SURFACE LOWS EMBEDDED WITHIN THE MONSOON 
TROUGH NEAR 12N114W AND 12N121W. A LACK OF DEEP LAYER MOISTURE 
IS INHIBITING CONVECTION ALONG THE MONSOON TROUGH W OF 110W.

TROPICAL STORM HILARY IS ANCHORING A BROAD CYCLONIC CIRCULATION 
IN THE MONSOON TROUGH E OF 105W. CONVECTION REMAINS VERY ACTIVE 
OVER A LARGE PORTION OF THE AREA FROM 11N TO 17N BETWEEN 92W AND 
104W. MODEL GUIDANCE IS IN GOOD AGREEMENT...MOVING HILARY WNW TO 
NW S OF MEXICO THROUGH THE WEEKEND. LITTLE CHANGE IN THE OVERALL 
PATTERN IS EXPECTED ELSEWHERE...WITH MODERATE N-NE TRADE WINDS N 
OF THE MONSOON TROUGH AXIS...WHICH WILL EXTEND ACROSS THE ENTIRE 
BASIN ALONG 11-12N W OF HILARY.

THE GFS MODEL BUILDS SEAS TO 10 FT S OF A LOW EMBEDDED IN THE 
TROUGH NEAR 12N114W BY FRI...BUT THIS FORECAST IS NOT SUPPORTED 
BY EITHER ECMWF OR UKMET MODELS...SO DOWNPLAYING ANY SIGNIFICANT 
IMPACT FOR THIS FEATURE IN HIGH SEAS FCST. OTHERWISE EXPECT SEAS 
TO BUILD TO 11 FT IN LONG PERIOD SWELL EXTREME NW PORTION THU.

$$
MUNDELL/LANDSEA