000
AXPZ20 KNHC 291002
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

...SPECIAL FEATURE...

TROPICAL STORM ILEANA NEAR 17.6N 111.8W AT 29/0900 UTC MOVING NW 
OR 315 DEG AT 8 KT. MAXIMUM SUSTAINED WINDS 55 KT GUSTS TO 65 
KT. ESTIMATED MINIMUM CENTRAL PRESSURE 957 MB. ILEANA IS 
EXPECTED TO TRACK NW WITH A SLIGHT DECREASE IN FORWARD SPEED 
OVER THE NEXT COUPLE OF DAYS. THE LATEST NHC ADVISORY ISSUED AT 
0900 UTC FORECASTS ILEANA TO INTENSIFY INTO A HURRICANE UNDER A 
FAVORABLE UPPER ENVIRONMENT LATE TONIGHT NEAR 19.5N 113.7W...
THEN GRADUALLY WEAKEN AS IT ENCOUNTERS COOLER WATERS IN ABOUT 
THREE DAYS. SCATTERED TO NUMEROUS STRONG CONVECTION IS WITHIN 75 
NM NE AND 90 NM IN THE SE QUADRANTS. SCATTERED MODERATE TO 
STRONG ELSEWHERE WITHIN 180 NM SW AND 90 NM NW QUADRANTS. 
SCATTERED MODERATE ISOLATED STRONG WITHIN 60 NM OF LINE FROM 
15N114W TO 13N16W. SEE LATEST NHC FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADER MIATCMEP4/ WTPZ24 KNHC FOR MORE DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...THE MONSOON 
TROUGH EXTENDS FROM 09N85W TO 09N98W WHERE IT ENDS. IT RESUMES 
SW OF ILEANA AT 12N124W TO A 1010 MB LOW PRES NEAR 11N138W. THE 
ITCZ EXTENDS SW FROM THE LOW TO 09N140W. SCATTERED MODERATE 
ISOLATED STRONG WITHIN FROM 09N TO 14N BETWEEN 87W AND 103W.

...DISCUSSION...

A 1030 HIGH PRES LOCATED WELL NW OF THE FORECAST AREA EXTENDS A 
RIDGE SEWD THROUGH 32N132W AND TO NEAR 25N122W. HIGH PRES COVERS
THE AREA N OF 18N AND W OF 125W. LIGHT TO MODERATE NE 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 18N W OF 132W. THESE WINDS WERE CAPTURED BY THE 
ASCAT PASS FROM 0616 UTC THIS MORNING...AND BY AN OSCAT PASS
FROM YESTERDAY AFTERNOON. 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 AS WERE NOTED BY A FEW SHIP 
OBSERVATIONS EARLY THIS MORNING IN THAT PART OF THE PACIFIC 
DISCUSSION DOMINION.

THE ASCAT PASS FROM 0616 UTC REVEALED A LARGE SWATH OF SW 
20-25 KT MONSOON WINDS FROM 07N TO 14N BETWEEN 105W AND 120W 
IN ASSOCIATION ENHANCED BY THE STRENGTHENING TREND OF 
TROPICAL STORM ILEANA. TO THE E OF THIS AREA OF SW 20-25 KT
WINDS...CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
ARE OBSERVED FROM 09N TO 14N BETWEEN 87W AND 103W WHERE UPPER
WATER VAPOR IMAGERY SHOWS ABUNDANT MOISTURE PRESENT.

A WEAK 1010 MB LOW PRES...EMBEDDED IN THE MONSOON TROUGH...IS 
ANALYZED NEAR 11N138W. THE 0616 ASCAT  PASS CAPTURED THE 
CIRCULATION ASSOCIATED WITH THIS SYSTEM WHICH IS FORECAST TO 
MOVE W OF AREA BY WED. SCATTERED STRONG CONVECTION IS N OF THE 
LOW WITHIN 45 NM OF 12N140W.

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 
105W AND 135W LATE TONIGHT...AND S OF A LINE FROM THE EQUATOR AT 
93W TO 14N106W BY LATE THU NIGHT. THESE SWELLS MAY BEGIN TO 
IMPACT THE COASTAL REGIONS OF MEXICO AND CENTRAL AMERICA ON THU.
WITH SEAS POSSIBLY UP TO 7 FT.

$$
AGUIRRE