000
AXPZ20 KNHC 172121
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SUN OCT 17 2010

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2100 UTC.

...ITCZ...
THE ITCZ AXIS IS ALONG 07N78W TO 07N100W TO 08N113W TO 09N130W 
TO 08N140W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION 
WITHIN 50 NM EITHER SIDE OF AXIS E OF 81W. SCATTERED MODERATE 
CONVECTION IS NEAR 8N112W.

...DISCUSSION...
ALOFT...
A LARGE UPPER LEVEL ANTICYCLONE CENTERED NEAR 13N129W COVERS MOST
OF THE DISCUSSION AREA W OF 120W. AN UPPER LEVEL TROUGH EXTENDS 
S FROM 30N103W TO A COL NEAR 15N117W. MODERATE TO STRONG SWLY 
WINDS OF 50-70 KT IS NOTED OVER THE NW CORNER OF THE FORECAST 
AREA. THESE WINDS ARE TRANSPORTING ABUNDANT MID/UPPER LEVEL 
MOISTURE ACROSS THE N WATERS PARTICULARLY N OF 20N INTO THE BAJA 
CALIFORNIA PENINSULA. A DIFFLUENT PATTERN ALOFT IS HELPING TO 
INDUCE CONVECTION NEAR THE SURFACE TROUGH LOCATED W OF 130W AND 
ALSO E OF 90W. 

SURFACE...
A MONSOON TROUGH IS EVIDENT E OF 90W IN THE ERN PORTION OF THE 
DISCUSSION AREA. A BROAD AREA OF LOW PRESSURE...ANALYZED 1009 MB 
ON THE 18 UTC SURFACE MAP...IS PROVIDING A FOCUS FOR THE WLY 
MONSOON FLOW S OF COSTA RICA AND PANAMA...WITH FRESH WINDS OF  
15-20 KT. AN EARLIER WINDSAT PASS AND THE MOST RECENT ASCAT PASS 
BOTH CORROBORATED THESE WIND SPEED. SHIP A8IP4 LOCATED NEAR 
5N85W REPORTED SW WINDS OF 20 KT AND SEAS TO 7 FT THIS MORNING. 
A SURFACE TROUGH EXTENDS FROM THE BROAD AREA OF LOW PRESSURE IN 
THE SW CARIBBEAN INTO THE EPAC TO NEAR 9N90W. FURTHER W...A WEAK 
TROUGH EXTENDS FROM 13N133W TO 9N138W...AND HAS WINDS TO 20 KT 
NEAR TROUGH AXIS AND SEAS TO 8 FT. OTHERWISE A BROAD HIGH PRES 
RIDGE DOMINATES NW PORTION OF AREA.

GAP WINDS...
OCTOBER MARKS THE BEGINNING OF THE TEHUANTEPEC WIND EVENTS. THE 
10-YEAR CLIMATOLOGY INDICATES THAT ON AVERAGE 11.9 GALE-FORCE 
EVENTS AND 6.3 STORM-FORCE EVENTS OCCUR IN THE GULF OF 
TEHUANTEPEC EACH COLD SEASON...OCTOBER TO MAY. GALE FORCE EVENTS 
HAVE OCCURRED AS EARLY AS SEPTEMBER AND AS LATE AS MAY. 
STORM-FORCE EVENTS OCCUR MOST OFTEN IN JANUARY. HOWEVER...A 
STORM WIND EVENT HAS ALREADY DEVELOPED ACROSS THIS AREA A FEW 
DAYS A AGO. WINDS DIMINISHED BELOW GALE FORCE YESTERDAY NIGHT 
AND CURRENTLY NLY WINDS OF 20 KT ARE NOTED OVER THE GULF OF 
TEHUANTEPEC PER AN EARLIER ASCAT PASS. THE NAM MODEL ALSO 
SUGGESTS N WINDS OF 20 KT AT THIS TIME.  WEAKENING HIGH PRES IN 
THE GULF OF MEXICO AND WINDS SHIFTING TO ENE OVER THE NEXT 24 
HOURS MEANS WINDS WILL BE BELOW 20 KT THERE TONIGHT. 
    
$$
GR