000
AXPZ20 KNHC 160142
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...SPECIAL FEATURES...

TROPICAL STORM IRWIN CENTERED NEAR 15.6N 107.1W AT 15/2100 UTC 
MOVING S SW AT 8 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 AND ENTERS THE AREA 
NEAR 13N89W EXTENDING TO 12N94W TO 16N97W THEN ACROSS SW MEXICO 
TO NEAR 17N105W. THERE IS THEN A BREAK IN THE MONSOON TROUGH AS 
A RESULT OF THE CIRCULATION AROUND TROPICAL STORM IRWIN. THE 
TROUGH THEN RESUMES NEAR 14N108W TO 10N125WW TO 12N140W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WAS NOTED N OF 
THE TROUGH BETWEEN 90W AND 94W. ISOLATED MODERATE CONVECTION WAS 
NOTED WITHIN 90 NM S OF THE TROUGH BETWEEN 117W AND 121W.

...DISCUSSION...

A 1006 MB LOW NW OF THE AREA NEAR 31.5N138W EXTENDS A COLD FRONT 
INTO THE AREA NEAR 30N133W EXTENDING SW TO BEYOND 22N140W. 
LATEST WINDSAT PASS AS WELL A SHIP OBSERVATIONS INDICATE FRESH 
TO STRONG 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 9 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 PARTS 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 OF MEXICO ASSOCIATED WITH THIS CIRCULATION 
CONTINUES TO FUNNEL STRONG TO NEAR GALE WINDS THROUGH THE 
CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. JUST A SIDE NOTE OF 
INTEREST TO INDICATE THE INFLUENCE OF THIS CYCLONIC CIRCULATION 
OVER THE AREA...THE WINDS FUNNELING INTO THE GULF OF TEHUANTEPEC 
ARE TURNING NW THEN WEST AS IT MOVES FURTHER FROM THE GULF OF 
TEHUANTEPEC. TYPICALLY...THE WINDS FUNNELING INTO THE GULF OF 
TEHUANTEPEC TURN NE THEN E AS IT MOVES FURTHER FROM THE GULF OF 
TEHUANTEPEC. WITH THIS CYCLONIC CIRCULATION EXPECTED TO CONTINUE 
THROUGH THE FORECAST PERIOD...FRESH TO STRONG WINDS ARE EXPECTED 
TO CONTINUE OVER THE GULF OF TEHUANTEPEC. 

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 12N AND E OF 125W BY MON. 

$$
AL