000
AXPZ20 KNHC 141552
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI OCT 14 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 FEATURES...

TROPICAL STORM IRWIN CENTERED NEAR 18.6N 106.8W AT 14/1500 UTC 
OR 165 MI W OF MANZANILLO MEXICO MOVING S OR 180 DEG AT 3 KT. 
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED 
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC FORECAST 
/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE 
DETAILS. NUMEROUS STRONG CONVECTION IS WITHIN 75 NM OF THE 
CENTER...WITH SCATTERED MODERATE TO STRONG CONVECTION ELSEWHERE
WITHIN 120 NM IN THE SE AND 75 NM IN THE NW SEMICIRCLES OF 
IRWIN. LITTLE CHANGE IN STRENGTH IS EXPECTED THROUGH 48 HOURS AS 
IRWIN MOVES S-SW...WITH WEAKENING TO A TROPICAL DEPRESSION 
FORECAST FROM 72-120 HOURS AS IRWIN TURNS MORE TO THE W-NW AND 
ENCOUNTERS COOLER WATERS AND DRIER AND MORE STABLE AIR ALOFT.
 
...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM STATIONARY 1004 MB LOW PRES 
OVER CENTRAL GUATEMALA NEAR 16N89.5W TO 14.5N100W THEN RESUMES 
FROM 15N123W TO 1010 MB LOW PRES NEAR 12N125W TO 09N130W TO 
08N140W. NUMEROUS MODERATE TO STRONG CONVECTION IS MAINLY S OF 
THE MONSOON TROUGH FROM 10N TO 15N BETWEEN 89W AND 101W. 
SCATTERED MODERATE CONVECTION IS N OF 05N E OF 80W.

...DISCUSSION...

A FRONTAL TROUGH IS IN THE NW PORTION OF THE WATERS EXTENDING 
FROM 28N127W TO 22N130W. MODEL GUIDANCE CONTINUES TO INDICATE 
NORTHERLY 20 KT WINDS BEHIND THE FRONTAL TROUGH ALONG WITH 8-10 
FT SEAS IN NW SWELL. THE FRONTAL TROUGH WILL WEAKEN AND STALL 
OVER THE NW PORTION THROUGH SAT WHILE A RATHER SIGNIFICANT LOW 
PRES SYSTEM MOVES BY JUST N OF THE DISCUSSION AREA FROM 24-48 
HOURS. W-NW WINDS OF 20-30 KT WITH POSSIBLE HIGHER GUSTS ARE 
EXPECTED TO MATERIALIZE NEAR THE LOW AND BEHIND THE FRONTAL 
TROUGH IN 24 HOURS WITH SEAS BUILDING TO 12 FT...WITH WINDS 
DIMINISHING TO 20-25 KT IN 48 HOURS.

1010 MB LOW PRES IS EMBEDDED IN THE MONSOON TROUGH NEAR 12N125W. 
20 KT SOUTHERLY WINDS WILL CONTINUE IN THE S SEMICIRCLE OF THE 
LOW S OF THE MONSOON TROUGH WITH SEAS UP TO 10 FT IN MERGING SW 
AND NW SWELL. THIS LOW WILL WEAKEN AS IT MOVES NE-E THROUGH 24 
HOURS TO NEAR 13N119W WITH 20 KT WINDS PERSISTING...THEN WILL 
DISSIPATE BY 48 HOURS.

A RECENT WINDSAT SCATTEROMETER PASS INDICATED 20-25 KT NORTHERLY 
WINDS IN AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC AROUND A 
BROAD AREA OF 1004 MB LOW PRES CENTERED OVER CENTRAL GUATEMALA 
NEAR 16N89.5W...WITH SEAS TO 11 FT S OF THE MONSOON TROUGH. 
THESE WINDS AND SEAS WILL PERSIST AS THE BROAD AREA OF LOW PRES 
REMAINS NEARLY STATIONARY.

AS THIS LOW PRES AREA OVER GUATEMALA LINGERS...VERY HEAVY 
RAINFALL WILL CONTINUE OVER PORTIONS OF THE PACIFIC COASTS OF 
SOUTHEASTERN MEXICO...GUATEMALA...EL SALVADOR...SOUTHERN 
HONDURAS AND NICARAGUA RESULTING IN LIFE-THREATENING FLASH 
FLOODS AND MUD SLIDES.

THE REMAINDER OF THE DISCUSSION WATERS ARE DOMINATED BY MERGING 
NW AND SW SWELL. THIS SWELL WILL GRADUALLY SUBSIDE FROM THE NW 
TO SE THROUGH THE NEXT 24-48 HOURS...WHILE THE NEW SET OF NW 
SWELL DISCUSSION IN THE PARAGRAPH ABOVE ATTEMPTS TO PROPAGATE TO 
THE S.

$$
LEWITSKY