000
AXPZ20 KNHC 212200
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE JUL 21 2009

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 
2145 UTC.

...TROPICAL WAVES...
TROPICAL WAVE N OF 04N ALONG 87W HAS MOVED W AT 20 KT OVER THE 
PAST 24 HOURS AND HAS AVERAGED ABOUT 17 KT OVER THE PAST COUPLE 
OF DAYS. THE WAVE IS PROGRESSING WESTWARD UNDER A LARGE AREA OF 
UPPER LEVEL DIFFLUENCE THAT IS ENHANCING CONVECTION WITHIN A FEW 
HUNDRED MILES W OF THE WAVE AXIS.

TROPICAL WAVE FROM 05N TO 14N ALONG 120W HAS BEEN MOVING W AT  
15 KT. THIS WAVE IS ALSO SITUATED UNDER AN AREA OF DIFFLUENCE 
THAT ENHANCED DEEP CONVECTION EARLIER WITH THE DEBRIS MOISTURE 
FANNING OUT OVER THE AREA FROM 03N TO 20N BETWEEN 115W TO 125W.
BROAD LOW TO MID LEVEL CYCLONIC TURNING IS NOTED ALONG THE WAVE 
AXIS NEAR 09 TO 12N. 
 
...ITCZ...
THE AXIS MEANDERS FROM 08N TO 10N FROM THE PANAMA TO 140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED FROM 04N 
TO 12N BETWEEN 86W AND 140W WITH THE MOST CONCENTRATED CLUSTERS 
SURROUNDING THE TWO TROPICAL WAVES.

...DISCUSSION...
THE UPPER LEVEL PATTERN IS SOMEWHAT COMPLEX OVER THE AREA W OF 
110W. AN UPPER RIDGE EXTENDS W TO E INTO THE DISCUSSION AREA 
ALONG 17N150W TO 22N134W AND IS ACCOMPANIED BY UPPER DEBRIS 
MOISTURE THAT ORIGINATES FROM ITCZ CONVECTION IN THE CENTRAL 
PACIFIC. AN UPPER LEVEL TROPICAL ANTICYCLONE IS CENTERED NEAR 
12N119W. AS MENTIONED ABOVE...ITS ASSOCIATED UPPER DIFFLUENCE 
HAS BEEN ENHANCING ITCZ CONVECTION BETWEEN 112W AND 132W. AN 
UPPER ANTICYCLONE CENTERED OVER ARIZONA HAS ITS ANTICYCLONIC 
ENVELOPE EXTENDING S OVER THE AREA N OF 27N BETWEEN 105W AND 
115W.  ANOTHER UPPER ANTICYCLONE CENTERED OVER THE SW CARIBBEAN 
HAS A RIDGE EXTENDING SW ACROSS CENTRAL AMERICA AND OVER THE 
DEEP TROPICAL PACIFIC TO A RIDGE CREST AT 10N94W. CONVECTION 
ALONG THE E PACIFIC ITCZ IS ENHANCED E OF 105W WITH SOME OF THE 
DEBRIS CIRRUS ADVECTED NE ACROSS CENTRAL AMERICA.

SEPARATING THESE UPPER RIDGES IS A SERIES OF SHORTWAVE TROUGHS. 
THE WESTERNMOST TROUGH EXTENDS FROM SW CANADA TO 32N135W TO 
28N145W AND IS ACCOMPANIED BY A 120 NM WIDE BAND OF DRY UPPER 
AIR. AN UPPER CYCLONE IS CENTERED NEAR 26N123W WITH A TROUGH 
EXTENDING SW TO 17N131W. UPPER MOSITURE IS INDICATED N OF 25N 
BETWEEN 110W AND 136W. ANOTHER UPPER TROUGH EXTENDS S ALONG THE 
E COAST OF THE UNITED STATES TURNING SW DISSECTING THE GULF OF 
MEXICO AND OVER THE E PACIFIC ALONG 16N98W TO 08N99W. 

GAP WINDS...NE TO E WINDS IN THE GULF OF PAPAGAYO AND JUST 
DOWNSTREAM WILL PULSE TO 20 KT OVER THE NEXT 30 HOURS THE 
DIMINISH BELOW 20 KT. 

LONG PERIOD SOUTHERLY SWELLS OF 18 TO 20 SECONDS RESULTING IN 
MAX SEAS OF 8 TO 13 FT ARE CROSSING THE EQUATOR AND ARE FORECAST 
TO MOVE THROUGH THE TROPICAL E PACIFIC REACHING THE PACIFIC 
COAST OF CENTRAL AMERICA LATE THU.

$$
NELSON