000
AXPZ20 KNHC 291004
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU APR 29 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 
0930 UTC.

...ITCZ...
AXIS ALONG 09N79W TO 04N111W TO 06N122W TO 05N140W.  SCATTERED 
MODERATE TO STRONG CONVECTION WITHIN 120 NM N AND 180 NM S OF 
AXIS E OF 105W.  SCATTERED MODERATE CONVECTION WITHIN 90 NM OF 
AXIS W OF 131W.

...DISCUSSION...
LARGE LONGWAVE UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM  
32N110W TO 21N140W EFFECTIVELY FLATTENING CREST OF BROAD MID/ 
UPPER LEVEL RIDGE CENTERED AT ANTICYCLONIC GYRE AT 11N110W.  
WESTERLY QUASI-ZONAL DRY WIND FLOW N OF 15N E OF 1120W.
WEAK DEFORMATION ZONE BETWEEN GYRE AND MID/UPPER ANTICYCLONE 
PROMOTING MODERATE TO STRONG DIFFLUENT FLOW ALOFT OVER EXTREME 
SE OF BASIN WHERE SURFACE TROUGH CONVECTION HAS BEEN 
UNINTERRUPTED FOR SEVERAL DAYS.  MODEL GUIDANCE HAVE POOR HANDLE 
ON CONDITIONS WITH GFS MOST AGGRESSIVE WHILE NAM IS TAMER AND 
ECMWF SOLUTION PRESENT BETTER ORGANIZATION BUT WEAKER WINDS.
FORECAST MAINTAINS MEANDERING TROUGH AT THE SURFACE WITH 
INCREASING SW WINDS TONIGHT BUT DIMINISHING FRI NIGHT.  REAL 
LIFE SOLUTION MAY OSCILLATE WITH SHEAR ALOFT FOLLOWING RIDGE 
EXPANSION TO THE W.  RIDGE ADVECTS ABUNDANT AMOUNTS OF TROPICAL 
CONVECTIVE DEBRIS MOISTURE ACROSS CENTRAL AMERICA INTO EASTERN 
GULF OF MEXICO WITH LITTLE CONSEQUENCES AS LARGE HIGH PRES 1018 
MB MAINTAINS STABLE AIR MASS THERE. 

ELSEWHERE AT THE SURFACE...
DIFFUSING FRONTAL TROUGH FROM 30N115W TO 22N140W HAS ALL BUT 
LOST ITS IDENTITY.  STILL...HEALTHY HIGH PRES 1033 MB PRESSES ON 
EASTWARD TIGHTENING GRADIENT AGAINST BAJA CALIFORNIA W COAST 
PROMPTING STRONG NW BREEZE.  STRENGTHENING RIDGE INCREASES NE 
TRADES TONIGHT AND EXPANDS COVERAGE THU NIGHT.  LONG FETCH ON E 
SIDE OF RIDGE PROMPTS LARGE LONG PERIOD SWELLS TO SPREAD SE 
ACROSS BASIN AND EVENTUALLY MERGE WITH CROSS EQUATORIAL SW SWELL 
S OF 10N.  

WEAK TROUGH EMBEDDED IN ITCZ ALONG 122W FROM 02N-09W IS UNDER 
FAVORABLE ENVIRONMENT ALOFT WHICH ENHANCES DEEP CONVECTION AS IT 
TRAVELS W.  SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED 
ON IR IMAGERY BUT LITTLE OR NO ORGANIZATION EXPECTED ALTHOUGH IT 
MAY CONTINUE UNDER SIMILAR ENVIRONMENT THROUGH FORECAST PERIOD. 

$$
WALLY BARNES