000
AXPZ20 KNHC 201600
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC WED OCT 20 2010

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...
AXIS FROM 08N90W TO 08N119W TO 10N129W TO 09N140W. SCATTERED 
MODERATE CONVECTION WAS NOTED E OF LINE FROM 03N78W TO 08N83W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED FROM 
09N TO 11N BETWEEN 138W AND 143W.

...DISCUSSION...
A DEEP LAYERED UPPER TROUGH IS APPROACHING THE NW CORNER OF THE 
DISCUSSION AREA ALONG 32N145W TO 28N150W WITH THE ASSOCIATED 
COLD FRONT EXTENDING FROM 32N142W TO 28N145W. SOUTHWESTERLY 
SURFACE WINDS AT 15 TO 20 KT AND SEAS TO 8 FT WILL PRECEDE THE 
FRONT BY ABOUT 150 NM. WINDS WILL VEER TO N AT 20 KT WITH SEAS 
BUILDING TO 11 FT IN NW SWELL W OF THE FRONT TILL IT STALLS FROM 
32N128W TO 28N133W ON FRI. 

AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 11N120W WITH AN 
UPPER RIDGE EXTENDING NW TO A CREST AT 35N135W. UPPER DIFFLUENCE 
IS ENHANCING CONVECTION ALONG THE ITCZ BETWEEN 128W AND 135W 
WITH THE RESULTANT MOISTURE ADVECTED N AND NE WITHIN 150 NM 
EITHER SIDE OF A LINE FROM 11N132W TO 16N127W TO 20N117W WHERE 
THIS MOISTURE PLUME EVAPORATES. CONSIDERABLE DEBRIS MOISTURE... 
ORIGINATING FROM THE ITCZ CONVECTION BETWEEN 138W AND 143W...IS 
ADVECTED N MERGING WITH A WELL ESTABLISHED TROPICAL 
PLUME...ORIGINATING IN THE CENTRAL PACIFIC...WITH THE COMBINED 
MOISTURE PLUME CONTINUING N AROUND THE W PERIPHERY OF THE UPPER 
RIDGE...ALL WITHIN 480 NM EITHER SIDE OF A LINE FROM 13N150W TO 
24N140W TO 27N127W WHERE THE MOISTURE BEGINS TO EVAPORATE. 

A MID TO UPPER LEVEL CYCLONE IS CENTERED AT 31.5N116W WITH AN 
UPPER TROUGH EXTENDING SE TO A BASE AT 17.5N110W. UPPER DEBRIS 
MOISTURE IS ROTATING CYCLONICALLY WITHIN 240 NM OF THE CENTER 
WITH SOME MOISTURE SPREADING NE OVER SOUTHERN NEW MEXICO AND 
WESTERN ARIZONA. AN UPPER LEVEL ANTICYCLONE IS ESTIMATED 
AT 18N104W WITH A RIDGE EXTENDING N OVER OLD MEXICO TO A CREST 
OVER SW TEXAS AT 32N102W WITH UPPER MOISTURE NOTED ALONG RIDGE 
CREST. OTHERWISE...THE UPPER LEVELS ARE VERY DRY W OF 97W AND 
SUPPRESSING CONVECTION ALONG THE THE ITCZ.

AN UPPER TROUGH IS SWEEPING THROUGH EASTERN N AMERICA AND 
EXTENDS S ACROSS THE GULF OF MEXICO FROM 32N90W TO A BASE OVER 
THE GULF OF TEHUANTEPEC AT 15N95W. AN UPPER ANTICYCLONE CENTERED 
OVER THE N CENTRAL CARIBBEAN RIDGES W ACROSS CENTRAL AMERICA TO 
A SHARP CREST OVER THE TROPICAL PACIFIC AT 12N110W. THE 
ASSOCIATED UPPER DIFFLUENCE IS ENHANCING SIGNIFICANT CONVECTION 
OVER A SURFACE LOW PRESSURE SYSTEM...SHOWING SIGNS OF TROPICAL 
CYCLONE DEVELOPMENT...IN THE NW CARIBBEAN BUT THE DEBRIS 
MOISTURE IS ADVECTED NE FURTHER AWAY FROM THE DISCUSSION AREA. 
CONVECTION IS ENHANCED OVER THE SW CARIBBEAN AND OVER COLOMBIA 
AND A FEW CELLS ARE NOW DEVELOPING WITHIN 60 NM OF THE PACIFIC 
COAST OF CENTRAL AMERICA. THE UPPER DEBRIS MOISTURE FROM THESE 
CONVECTIVE AREAS IS SPREADING W OVER THE DISCUSSION AREA E OF 
90W.

ELSEWHERE AT THE SURFACE...1020 MB HIGH PRES CENTERED AT 28N132W 
HAS A RIDGE EXTENDING SE TO 20N110W. NW WINDS AT 15 TO 20 KT ARE 
NOTED ALONG THE MEXICAN COAST NEAR 20N107W. NE TRADES AT 15 TO 
20 KT ARE NOTED S OF THE RIDGE AND N OF THE ITCZ IN THE AREA 
FROM 10N TO 14N W OF 135W. SOUTHWESTERLY MONSOON FLOW IS 
EXPECTED TO INCREASE TO 15 TO 20 KT OVER THE WATERS FROM 02N TO 
07N E OF 100W THROUGH FRI WITH SEAS INCREASING TO 8 FT IN SW 
CROSS EQUATORIAL SWELL THAT WILL COVER MOST OF THE PACIFIC 
WATERS S OF 08N BETWEEN CENTRAL AMERICA AND 140W. 

$$
NELSON