000
AXPZ20 KNHC 282210
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT APR 28 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N85W 7N98W 4N113W 6N123W 3N140W. 
SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 
120 NM EITHER SIDE OF LINE 5N78W 8N87W 6N97W AND ALSO WITHIN 60 
NM EITHER SIDE OF LINE 8N115W 8N127W 6N137W.

...DISCUSSION...

AN UPPER SHORTWAVE RIDGE CONTINUES OVER THE W PORTION OF THE 
DISCUSSION AREA CRESTING ALONG 23N133W 28N125W 26N118W. AN UPPER 
ANTICYCLONE IS ALSO NOTED NEAR 9N129W. UPPER MOISTURE IS 
OBSERVED MOSTLY UNDER THE LARGER RIDGE....ROUGHLY WITHIN 390 NM 
EITHER SIDE OF 12N140W 24N122W. 

AN UPPER SHORTWAVE TROUGH...ACCOMPANIED BY CONSIDERABLE UPPER 
MOISTURE...IS APPROACHING THE EXTREME NW CORNER. A SMALL UPPER 
CYCLONE HAS FORMED AHEAD OF THE TROUGH NEAR 27N133W...AND IS 
SURROUNDED BY DRY UPPER AIR...ROUGHLY WITHIN 330 NM OVER ITS SE 
SEMICIRCLE AND 120 NM OVER THE NW SEMICIRCLE.

AN UPPER CYCLONE HAS STALLED OVER THE BAJA PENINSULA NEAR 
28N112W WITH AN UPPER TROUGH EXTENDING SW TO NEAR 12N119W. DRY 
UPPER AIR IS INDICATED OVER THE DISCUSSION AREA N OF 20N BETWEEN 
120W AND 99W...AND FROM 10N TO 20N BETWEEN 120W AND 95W. UPPER 
DIFFLUENCE N OF THE CYCLONE IS ENHANCING CONVECTION WITHIN 90 NM 
OF 30.5N109W...WITH LIGHTNING DATA SUGGESTING INTENSE TSTMS. THE 
DEBRIS MOISTURE IS FANNING N OVER OVER SOUTHERN ARIZONA AND NEW 
MEXICO.      

UPPER ANTICYCLONES ARE NOTED NEAR 17N96W AND 11N106W. THE 
ASSOCIATED COMBINED FLOW CREATES A NE TO SW ORIENTATED UPPER 
RIDGE FROM 20N92W TO 9N110W...AND LIKELY CONTRIBUTING TO THE 
LARGE AREA OF SUBSIDENCE DESCRIBED ABOVE. 

AN UPPER ANTICYCLONE E OF THE AREA NEAR 6N61W RIDGES W ALONG 
11N83W TO A SHARP CREST OVER THE ITCZ AT 11N91W. THERE IS A 
SLIGHT ENHANCEMENT OF CONVECTION ALONG THE E PAC ITCZ E OF 96W. 
THE DEBRIS MOISTURE SPREADS NE ACROSS CENTRAL AMERICA BUT SEEMS 
TO EVAPORATE OVER THE CARIBBEAN TO THE S OF 17N AND W OF 72W.

AT THE LOW LEVELS A RIDGE EXTENDS ALONG 32N137W 12N107W. LOCALLY 
BROKEN STRATA CUMULUS IS NOTED N OF 12N W OF 112W.  

GAP WINDS...BRISK ELY TRADES OVER THE W CARIBBEAN CONTINUE TO  
SURGE INTO THE GULF OF PAPAGAYO AT 20 TO 25 KT AND EXPECTED TO 
CONTINUE FOR AT LEAST A COUPLE MORE DAYS.

$$
NELSON