000
AXPZ20 KNHC 290239
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED AUG 29 2012

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

...SPECIAL FEATURE...

TROPICAL STORM ILEANA NEAR 17.0N 111.1W AT 29/0300 UTC MOVING NW 
OR 305 DEG AT 9 KT. MAXIMUM SUSTAINED WINDS 50 KT GUSTS TO 60 
KT. ESTIMATED MINIMUM CENTRAL PRESSURE 997 MB. ILEANA IS 
EXPECTED TO MOVE NW WITH A SLIGHT DECREASE IN FORWARD SPEED OVER 
THE NEXT COUPLE OF DAYS. THE NHC INTENSITY FORECAST CALLS FOR 
ILEANA TO BECOME A HURRICANE EARLY ON THURSDAY THEN WEAKEN 
GRADUALLY AS IT ENCOUNTERS COOLER WATERS IN ABOUT THREE DAYS. 
SCATTERED TO NUMEROUS STRONG CONVECTION IS WITHIN 90 NM OF 
ILEANA IN THE SW SEMICIRCLE. SCATTERED MODERATE ISOLATED STRONG 
WAS NOTED ELSEWHERE WITHIN 150 NM W AND 90 NM E SEMICIRCLES OF 
THE STORM. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADER MIATCMEP4/ WTPZ24 KNHC FOR MORE DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH IS ALONG 08N78W TO 10N100W THEN RESUMES SW OF 
ILEANA NEAR 14N115W TO 1009 MB LOW PRES LOCATED NEAR 11N137W TO 
10N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 
05N TO 08N BETWEEN 80W AND 90W AND FROM 10N TO 16N BETWEEN 98W 
AND 106W. SCATTERED MODERATE TO STRONG WITHIN 60 NM EITHER SIDE 
OF LINE FROM 14N112W TO 13N117W. SCATTERED MODERATE WITHIN 120 W 
SEMICIRCLE NM OF LOW PRES NEAR 11N137W. 

...DISCUSSION...

1030 HIGH PRES LOCATED WELL NW OF THE FORECAST AREA EXTENDS A 
RIDGE SE ACROSS THE N WATERS TO NEAR 22N115W. LIGHT TO MODERATE 
WINDS ARE NOTED UNDER THE INFLUENCE OF THIS SYSTEM MAINLY N OF 
20N W OF 120W. A SMALL AREA OF ENHANCED N-NE WINDS IS PRESENT ON 
THE SOUTHERN PERIPHERY OF THE RIDGE...COVERING ROUGHLY THE 
REGION FROM 12N TO 17N W OF 130W. THESE WINDS WERE CONFIRMED BY 
A 2124 UTC OSCAT SCATTEROMETER PASS. THE PRES GRADIENT BETWEEN 
THE RIDGE AND A THERMAL TROUGH IN THE GULF OF CALIFORNIA IS 
MAINTAINING N-NW WINDS OF 15 TO 20 KT N OF 23 E OF 120W. FEW 
SHIP OBSERVATIONS WERE NOTED THIS EVENING AND A 1944 UTC OSCAT 
PASS CONFIRMED THE PRESENCE OF THESE WIND SPEEDS.

THE OSCAT SCATTEROMETER DATA INDICATED A LARGE AREA OF FRESH TO 
STRONG SW WINDS S OF THE MONSOON TROUGH BETWEEN 105W AND 122W 
ASSOCIATED WITH INTENSIFYING T.S. ILEANA. AN ACTIVE MONSOON 
TROUGH IS NOTED ACROSS THE FORECAST AREA.  

A WEAK 1011 MB LOW PRES...EMBEDDED IN THE MONSOON TROUGH...IS 
NEAR 11N137W. A 2126 UTC OSCAT PASS CAPTURED THE CIRCULATION 
ASSOCIATED WITH THIS SYSTEM WHICH IS FORECAST TO MOVE W OF AREA 
BY WED. A SMALL AREA OF MODERATE CONVECTION IS WITHIN 150 NM W 
OF THE LOW LEVEL CENTER.

CROSS-EQUATORIAL SW SWELLS WITH IMPRESSIVE 20-22 SECOND PERIODS  
ARE CURRENTLY SPREADING ACROSS THE SOUTHERN WATERS W OF 110W. THIS 
SWELL EVENT WILL RAISE SEAS TO 9 FT MAINLY S OF 06N BETWEEN 110W 
AND 135W BY LATE WED AND THU. ADDITIONALLY THE SWELLS WILL BEGIN 
TO IMPACT COASTAL REGIONS OF MEXICO AND CENTRAL AMERICA ON THU.

$$
COBB