000
AXPZ20 KNHC 210947
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED APR 21 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 07N77W TO 07N117W TO 04N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED TO THE N 
OF 05N E OF 86W...WITHIN 90 NM OF 04N108W...FROM 02N TO 09N 
BETWEEN 115W AND 120W...WITHIN 120 NM EITHER SIDE OF A LINE FROM 
05N121W TO 03N140W.

...DISCUSSION...

AN UPPER TROUGH HAS ITS MEAN AXIS ALONG 32N123W TO 17N137W AND 
IS ACCOMPANIED DRY UPPER AIR WHICH IS INDICATED NW OF A LINE 
ALONG 18N140W TO 19N134W TO 30N108W. THERE ARE TWO THIN BANDS OF 
UPPER MOISTURE ROTATING E ACROSS THE AREA N OF 31N E OF 120W AND 
ACROSS SOUTHERN CALIFORNIA AND ARIZONA. 

AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 07N118W WITH AN 
UPPER SHORTWAVE UPPER RIDGE EXTENDING NE TO A CREST AT 32N108W. 
ASSOCIATED UPPER DIFFLUENCE IS ENHANCING ITCZ CONVECTION ALONG 
119W FROM 02N TO 09N...AND BETWEEN 120W AND 135W...AND ALSO FROM 
10N TO 12N BETWEEN 105W AND 111W. SOME OF THE RESULTANT DEBRIS 
MOISTURE IS ADVECTED S ACROSS THE EQUATOR BETWEEN 113W AND 
127W...BUT MOST OF THE DEBRIS MOISTURE IS EVAPORATING WITHIN A 
FEW HUNDRED MILES N AND S OF THE DISSIPATING CELLS. A WELL 
DEFINED TROPICAL MOISTURE PLUME...ORIGINATING FROM ITCZ 
CONVECTION W OF THE AREA BETWEEN 145W AND 165W...STRETCHES E 
ACROSS THE DISCUSSION AREA ALONG THE N PERIPHERY OF THE 
SHORTWAVE RIDGE...ROUGHLY WITHIN 360 NM EITHER SIDE OF LINE FROM 
12N140W TO 20N120W TO THE W COAST OF OLD MEXICO FROM 20N TO 27N 
WHERE THE MOISTURE EVAPORATES AS IT CROSSES THE RIDGE CREST.
 
A BROAD UPPER RIDGE EXTENDS W FROM S AMERICA ALONG 07N TO A 
GENTLE CREST AT 07N98W. UPPER DIFFLUENCE IS ENHANCING CONVECTION 
N OF 06N E OF 96W INCLUDING CENTRAL AMERICA...WITH THE DEBRIS 
MOISTURE SPREADING NE ACROSS THE S CENTRAL CARIBBEAN. 
OTHERWISE...DRY UPPER AIR IS INDICATED S OF 17N E OF 110W.

AT THE SURFACE...A FRONTAL TROUGH EXTENDS FROM 32N118W TO 
21N1350W BRIDGED BY AN AMPLIFYING RIDGE BUILDING SE ACROSS THE 
AREA FROM 32N142W TO 15N100W. SURFACE WINDS ARE ROTATING 
ANTICYCLONICALLY THROUGH THIS RIDGE WITH NE TRADES ALREADY 
ESTABLISHED S OF THE RIDGE W OF 115W. NW SWELLS WILL PROPAGATE 
SE THROUGH THE RIDGE MIXING WITH THE ASSOCIATED NEW NE SWELLS 
DEVELOPING IN THE LONG FETCH OF NORTHERLY 20 TO 25 KT WINDS. 
SOUTHERLY SWELLS ARE CROSSING THE EQUATOR BETWEEN 95W AND 135W 
MIXING WITH THE NE AND NW SWELL COMPONENTS.

$$
NELSON