000
AXPZ20 KNHC 200951
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE APR 20 2010

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0945 UTC.

...ITCZ...

THE ITCZ AXIS EXTENDS FROM 05N77W TO 05N140W. ISOLATED MODERATE 
CONVECTION IS NOTED FROM 03N TO 08N E OF 97W AND FROM 02N TO 08N 
BETWEEN 110W AND 125W. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED FROM 03N TO 107N W OF 138W.   

...DISCUSSION...

AN UPPER TROUGH HAS ITS MEAN AXIS ALONG 32N133W TO 22N130W WITH 
A THIN BAND OF MOISTURE ROTATING THROUGH THE TROUGH ALONG 29N. 
OTHERWISE...DRY UPPER AIR IS NOTED N OF A LINE ALONG 21N140W TO 
27N120W TO 31N110W. 

AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 10N109W WITH AN 
UPPER RIDGE EXTENDING SW TO A SHARP CREST AT 06N125W...AN UPPER 
RIDGE EXTENDING E TO 11N98W...AND A SHORTWAVE UPPER RIDGE 
EXTENDING NE TO A CREST AT 32N114W. THIS SHORTWAVE RIDGE IS 
BECOMING EMBEDDED IN A LONGWAVE RIDGE EXTENDING S TO N ALONG 
115W ACROSS N AMERICA. ITCZ CONVECTION IS SLIGHTLY ENHANCED 
UNDER THE TROPICAL RIDGE BETWEEN 113W AND 123W...WITH THE DEBRIS 
MOSITURE EVAPORATING WITH A FEW HUNDRED MILES N AND S OF THE 
DISSIPATING CELLS. A WELL DEFINED TROPICAL MOISTURE PLUME... 
ORIGINATING OVER THE DEEP TROPICAL CENTRAL PACIFIC...STRETCHES 
ACROSS THE DISCUSSION AREA ALONG THE N PERIPHERY OF THE 
SHORTWAVE RIDGE...ROUGHLY WITHIN 240 NM EITHER SIDE OF LINE FROM 
15N140W TO 22N113W WHERE THE MOISTURE EVAPORATES.
 
AN UPPER TROUGH EXTENDS SW ACROSS THE W CARIBBEAN AND OVER THE E 
PACIFIC ALONG 12N92W TO THE EQUATOR AT 102W. UPPER DIFFLUENCE 
HAS ENHANCED CONVECTION ALONG 05N BETWEEN 88W AND 97W BUT IS 
DISSIPATING AT THE MOMENT. A BROAD UPPER RIDGE EXTENDS NW FROM S 
AMERICA ACROSS CENTRAL AMERICA WITH UPPER MOISTURE DEFINING ITS 
W EDGE ALONG 01N82W TO 11N83W. DRY UPPER AIR IS INDICATED 
ELSEWHERE S OF 13N E OF 135W.
 
AT THE SURFACE...A FRONTAL TROUGH EXTENDS FROM 32N128W TO 
24N140W WITH A RIDGE BUILDING E AND NOW BRIDGING THROUGH THE 
DECAYING FRONT. SURFACE WINDS ARE EXPECTED TO ROTATE 
ANTICYCLONICALLY THROUGH THIS RIDGE INTO THE NE TRADES S OF THE 
RIDGE FOR THE NEXT FEW DAYS DRIVING A NEW SERIES OF NW SWELL 
ACROSS THE SUBTROPICAL WATERS. SOUTHERLY SWELLS WILL CROSS THE 
EQUATOR BETWEEN 93W AND 125W FOR THE NEXT COUPLE OF DAYS.

$$
NELSON