000
AXPZ20 KNHC 151546
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT OCT 15 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 16.5N 106.6W AT 15/1500 UTC
MOVING S AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. 
MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. IRWIN 
IS FORECAST TO WEAKEN TO A DEPRESSION THIS EVENING WHILE MOVING 
SW OVER THE NEXT 24 HOURS...THEN DRIFT WESTWARD AFTERWORDS. 
NUMEROUS TO SCATTERED CONVECTION WAS NOTED WITHIN 150 NM SW 
QUADRANT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO 
HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS. 
 
...ITCZ/MONSOON TROUGH...

MONSOON TROUGH EXTENDS FROM THE W CARIBBEAN ACROSS CENTRAL 
AMERICA AND ENTERS THE AREA NEAR 14N91W EXTENDING TO 13N95W 
OVER FAR S MEXICO NEAR 18N101W TO 18N105W. THERE IS THEN A BREAK 
IN THE MONSOON TROUGH AS A RESULT OF THE CIRCULATION AROUND 
TROPICAL STORM IRWIN. THE MONSOON TROUGH THEN CONTINUES FROM 
15.5N110W TO 09N130W TO 11N140W. SCATTERED TO NUMEROUS STRONG 
CONVECTION IS WITHIN 60 NM S OF THE TROUGH E OF 94W. SCATTERED 
MODERATE CONVECTION IS WITHIN 120 NM S OF AXIS BETWEEN 119W AND 
123W. 

...DISCUSSION...

A 1008 MB LOW NW OF THE AREA NEAR 33N139W EXTENDS A COLD FRONT 
INTO THE AREA NEAR 30N134W EXTENDING SW TO BEYOND 23N140W. 
LATEST WINDSAT PASS AS WELL A SHIP OBSERVATIONS INDICATE FRESH 
TO STRONG NW WINDS W OF THE FRONT. THE FRONT HAS ALSO GENERATED 
A NW SWELL WITH COMBINED SEAS TO 14 FT OVER THE NW PART OF THE 
AREA. THE LOW PRESSURE AREA WILL SLOWLY SHIFT E OVER THE NEXT 48 
HOURS...AND REMAIN ALONG OR JUST N OF 30N. THE FRONT WILL SHIFT 
SLOWLY E THEN DISSIPATE WITHIN 48 HOURS WITH ASSOCIATED WINDS 
DIMINISHING BELOW 20 KT. THE SWELL WILL CONTINUE TO PROPAGATE S 
AND SE THROUGH THE FORECAST PERIOD WITH COMBINED SEAS GRADUALLY 
SUBSIDING TO NEAR 10 FT. 

AN EXTENSIVE AREA OF FRESH TO STRONG SW MONSOONAL FLOW PREVAILS 
N OF 05N E OF 100W. THIS MONSOONAL FLOW CONTINUES TO ADVECT 
ABUNDANT MOISTURE NORTHWARD INTO THE N PART OF CENTRAL AMERICA 
AND S MEXICO WHICH WILL BRING PERIODS OF VERY HEAVY RAINFALL 
OVER PORTIONS OF THE PACIFIC COASTS OF SOUTHEASTERN 
MEXICO...GUATEMALA...EL SALVADOR...SOUTHERN HONDURAS AND 
NICARAGUA. THESE PERIODS OF HEAVY MONSOONAL RAINFALL HAS THE 
POTENTIAL TO CREATE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES 
OVER THESE AREAS.

A BROAD CYCLONIC CIRCULATION CENTERED OVER THE N PART OF CENTRAL 
AMERICA IS REMINISCENT OF A MONSOON DEPRESSION. NORTHERLY FLOW 
OVER THE SW GULF ASSOCIATED WITH THIS CIRCULATION CONTINUES TO 
FUNNEL FRESH TO STRONG WINDS THROUGH THE CHIVELA PASS INTO THE 
GULF OF TEHUANTEPEC. WITH THIS CYCLONIC CIRCULATION EXPECTED TO 
CONTINUE THROUGH THE FORECAST PERIOD...THE FRESH TO STRONG WINDS 
ARE EXPECTED TO CONTINUE. 

THE REMAINDER OF THE REGIONAL WATERS E OF 130W ARE DOMINATED BY 
MERGING NW AND SW SWELL. THIS SWELL EVENT WILL GRADUALLY SUBSIDE 
FROM THE NW TO SE THROUGH THE NEXT 48 HOURS...WITH SEAS GREATER 
THAN 8 FT LIMITED TO S OF 16N AND E OF 125W. 

$$
AL