000
AXPZ20 KNHC 180246
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE OCT 18 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC.

...ITCZ/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM 18N103W TO 1008 MB REMNANT LOW OF 
IRWIN NEAR 15.5N109.5W TO 08N120W TO 07N130W. ITCZ FROM 07N130W 
TO 11N140W. ISOLATED TO SCATTERED MODERATE CONVECTION FROM 10N 
TO 14N BETWEEN 92W AND 102W.

...DISCUSSION...

THE REMNANT LOW OF IRWIN IS EMBEDDED IN THE MONSOON TROUGH NEAR 
15.5N109.5W. SATELLITE IMAGERY SHOWS A SWIRL OF LOW CLOUDS 
ASSOCIATED WITH THIS SYSTEM. SW MONSOONAL FLOW EXTENDS FROM S OF 
THIS FEATURE TO THE COAST OF CENTRAL AMERICA AS DEPICTED BY THE 
MOST RECENT SCATTEROMETER DATA AND FEW SHIP OBSERVATIONS. THIS 
EXTENSIVE AREA OF FRESH TO STRONG SOUTHWESTERLY MONSOONAL FLOW 
CONTINUES TO ADVECT ABUNDANT TROPICAL MOISTURE INTO SECTIONS OF 
CENTRAL AMERICA AND SOUTHERN MEXICO. PERIODS OF HEAVY RAINFALL 
WILL OCCUR IN SECTIONS OF THE PACIFIC COASTS OF SOUTHEASTERN 
MEXICO...GUATEMALA...EL SALVADOR...SOUTHERN HONDURAS AND 
NICARAGUA. THE PERIODS OF HEAVY MONSOONAL RAINFALL HAVE THE 
POTENTIAL TO CREATE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES 
IN SOME AREAS.

WINDS HAVE DIMINISHED BELOW 20 KT IN ASSOCIATION WITH A 1012 MB 
LOW PRESSURE CENTERED NEAR 31N136W. A TROUGH EXTENDS FROM THE 
LOW CENTER TO 23N140W. COMBINED SEAS UP TO 9 FT IN N SWELL CAN 
BE FOUND OVER THE NW PART OF THE AREA BEHIND THE TROUGH AXIS.  
THIS SWELL WILL CONTINUE MOVING S AS IT SLOWLY SUBSIDES TO 8 FT 
OVER THE NEXT 48 HOURS. HIGH PRES WILL BEGIN TO BUILD ACROSS THE 
N WATERS AS THE LOW PRES MOVES AWAY FROM THE FORECAST REGION AND 
DISSIPATES.

CLIMATOLOGICALLY OCTOBER MARKS THE BEGINNING OF THE TEHUANTEPEC 
WIND EVENTS. THE FIRST GALE-FORCE EVENT OF A SEASON TYPICALLY 
OCCURRED IN MID OCTOBER WITH THE FINAL GALE-FORCE EVENT 
OCCURRING IN LATE MARCH OR EARLY APRIL. ON AVERAGE 11.9 
GALE-FORCE EVENTS AND 6.3 STORM-FORCE EVENTS OCCUR IN THE GULF 
OF TEHUANTEPEC EACH COLD SEASON. CURRENTLY...MARINE GUIDANCE 
SUGGESTS A GALE FORCE WIND EVENT ACROSS THE GULF OF TEHUANTEPEC 
BY WED. THE STRONG WINDS WILL BUILD SEAS UP TO 15 FT BASE ON 
WAVEWATCH MODEL...WITH SEAS UP TO 9 FT PROPAGATING AS FAR 
DOWNSTREAM AS 11N98W BY WED EVENING. THIS NE SWELL WILL MERGE 
WITH SW SWELL ALREADY IN THE AREA RAISING SEAS TO 11-12 FT N OF 
09N BETWEEN 90W AND 100W. THIS GAP WIND EVENT WILL BE ASSOCIATED 
WITH A STRONG COLD FRONT MOVING ACROSS THE GULF OF MEXICO 
TUESDAY AND RAPIDLY SPREAD S AND E. THE FRONT WILL REACH THE BAY 
OF CAMPECHE LATE TUE. NLY WINDS WILL FUNNEL THROUGH THE CHIVELA 
PASS INTO THE GULF OF TEHUANTEPEC REACHING GALE FORCE WED 
MORNING. A GALE WARNING IS IN EFFECT FOR THAT AREA. THE FNMOC 
EFS GALE PROBABILITY ALSO SUPPORTS THIS FORECAST.

$$
GR