000
AXPZ20 KNHC 210321
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 
0405 UTC SAT APR 21 2007

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY 
THROUGH 0315 UTC.

...ITCZ...

AXIS IS ALONG 9N78W 6N90W 6N126W 3N140W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 120 NM EITHER SIDE 
OF LINE 8N76W 9N84W 5N91W AND LINE 4N96W 6N108W AND WITHIN 60 NM 
EITHER SIDE OF LINE 6N115W 6N137W. 

...DISCUSSION...

AN UNSTABLE SHORTWAVE RIDGE CREST IS COLLAPSING SE NEAR 40N130W 
WITH ASSOCIATED ANTICYCLONIC FLOW OVER THE AREA N OF 26N W OF 
130W. OTHERWISE A BROAD UPPER LEVEL TROUGH DOMINATES DISCUSSION 
AREA N OF 20N W OF 112W. AN EMBEDDED CYCLONE IS NEAR 35N119W 
WITH A TROUGH SE TO NEAR 26N112W. THE ASSOCIATED SURFACE FRONT 
LIES ALONG 32N113W 26N125W THEN DIFFUSE TO 29N140W. UPPER LEVEL 
MOISTURE IS INDICATED N OF POINTS 32N108W 24N124W 26N139W BUT 
DRY UPPER AIR IS SPILLING SE IN THE COLLAPSING RIDGE. A BAND OF 
DRY UPPER AIR IS INDICATED WITHIN 240 NM EITHER SIDE OF LINE 
32N101W 22N123W 21N140W...AND THIS DRY BAND CONTINUES E ACROSS 
THE CENTRAL CONUS AND BACK INTO THE ATLC OFF THE SE COAST OF THE 
CONUS. 

AN UPPER LEVEL ANTICYCLONE IS JUST SW OF THE AREA AT 2S142W WITH 
ITS ENVELOPE OF ANTICYCLONIC FLOW EXTENDING N TO ALONG 10N W OF 
124W. 

AN UPPER ANTICYCLONE IS ESTIMATED NEAR 10N75W WITH A MID TO 
UPPER LEVEL RIDGE EXTENDING NW TO BEYOND 32N92W INTO A BROAD 
RIDGE THAT DOMINATES CENTRAL N AMERICA. AN UPPER TROUGH EXTENDS 
S FROM 9N105W TO AN UPPER CYCLONE NEAR THE EQUATOR AT 106W. WEAK 
UPPER DIFFLUENCE IS INDICATED IN THE CLOUD MOTION WINDS WITH 
SLIGHT ENHANCEMENT OF ITCZ CONVECTION BETWEEN 107W 135W...WITH 
MOST OF THE DEBRIS MOISTURE ADVECTED S OF THE EQUATOR IN THE 
ANTICYCLONIC FLOW DESCRIBED ABOVE. UPPER DIFFLUENCE IS ALSO
ENHANCING ITCZ CONVECTION E OF 101W WITH THE RESULTANT DEBRIS 
MOISTURE SPREADING N ACROSS CENTRAL AMERICA BUT EVAPORATING 
ALONG THE UPPER RIDGE AXIS. A MOISTURE PLUME CONTINUES THROUGH 
THE UPPER RIDGE...ROUGHLY WITHIN 300 NM EITHER SIDE OF LINE 
14N137W 17N115W 28N86W. 

A SURFACE RIDGE LIES ALONG 26N140W 13N102W.

$$
NELSON