000
AXPZ20 KNHC 180937
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0645 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 1011 MB LOW 
PRES...REMNANTS OF IRWIN...NEAR 16N110W TO 10N119W TO 10N125W TO 
09N129W. THE ITCZ AXIS WAS ANALYZED FROM 09N129W TO 09N140W. NO 
SIGNIFICANT CONVECTION LIES ALONG THE AXIS.

...DISCUSSION...

THE REMNANT LOW OF IRWIN IS EMBEDDED IN THE MONSOON TROUGH NEAR 
16N110W. SATELLITE IMAGERY CONTINUES TO SHOW A SWIRL OF LOW 
CLOUDS ASSOCIATED WITH THIS SYSTEM. THE MOST RECENT ASCAT PASS 
MISSED THIS LOW...BUT THE RUN FROM 1626 UTC SHOWED A CLOSED LOW 
LEVEL CIRCULATION WITH WINDS AS HIGH AS 15 KT. FRESH TO STRONG 
SW MONSOONAL FLOW EXTENDS FROM S OF THIS FEATURE TO THE COAST OF 
CENTRAL AMERICA AS DEPICTED BY THE 0332 UTC AND 0512 UTC ASCAT 
PASSES AND FEW SHIP OBSERVATIONS. THIS EXTENSIVE AREA OF FRESH 
TO STRONG SOUTHWESTERLY MONSOONAL FLOW CONTINUES TO ADVECT 
ABUNDANT TROPICAL MOISTURE NORTHWARD. THE MOST SIGNIFICANT DEEP 
CONVECTION NOTED OVER THE ENTIRE FORECAST AREA LIES WITHIN OR 
JUST N OF THIS BELT...WITH SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION FOUND WITHIN 75 NM OF THE MEXICAN COAST BETWEEN 95W 
AND 100W AND ISOLATED MODERATE FOUND FROM 07N TO 14N BETWEEN 93W 
AND 110W.

1014 MB LOW PRES NEAR 31N135W IS IMPINGING ON THE 1020 MB HIGH 
PRES SYSTEM NEAR 30N125W. THIS SURFACE LOW IS FORECAST TO WEAKEN 
AND SHIFT NE AS ITS ASSOCIATED UPPER LEVEL LOW IS CAPTURED BY 
THE LEADING EDGE OF A MID LATITUDE TROUGH...CURRENTLY N OF 
HAWAII...AS THE TROUGH PUSHES E. THE PRES GRADIENT BETWEEN THE 
SUBTROPICAL HIGH AND TROUGHING OVER NW MEXICO AT THE SURFACE IS 
STRONG ENOUGH TO SUPPORT A SMALL AREA OF FRESH N WINDS OFF THE 
COAST OF BAJA CALIFORNIA NORTE ACCORDING TO THE 0518 UTC ASCAT 
PASS AND SEAS TO 8 FT ACCORDING TO SHIP DQVG NEAR 28N116W AT 
0600 UTC. FRESH NW TO N WINDS ARE EXPECTED TO CONTINUE HERE 
THROUGH AT LEAST THU MORNING.

CLIMATOLOGICALLY...OCTOBER MARKS THE BEGINNING OF THE 
TEHUANTEPEC WIND EVENTS. THE FIRST GALE-FORCE EVENT OF A SEASON 
TYPICALLY OCCURS 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...FORECAST GUIDANCE 
SUGGESTS A GALE FORCE WIND EVENT ACROSS THE GULF OF TEHUANTEPEC 
WILL BEGIN WED MORNING AFTER A STRONG COLD FRONT MOVES ACROSS 
THE GULF OF MEXICO TODAY AND REACHES THE ISTHMUS OF TEHUANTEPEC 
OVERNIGHT TONIGHT...WITH NLY WINDS THEN EXPECTED TO FUNNEL 
THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. A GALE 
WARNING IS IN EFFECT FROM AROUND SUNRISE WED UNTIL THE END OF 
THE FORECAST PERIOD EARLY THU MORNING.

$$
SCHAUER