000
AXPZ20 KNHC 170240
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT APR 17 2010

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

...ITCZ...

THE ITCZ AXIS EXTENDS FROM 05N77W TO 06N83W TO 05.5N98W TO 
04.5N112W TO 06N123W TO 05N131W TO 05.5N136W TO 04N140W. 
SCATTERED MODERATE TO STRONG CONVECTION WITHIN 240 NM N OF AXIS 
BETWEEN 83W AND 95W. ISOLATED MODERATE TO STRONG CONVECTION 
WITHIN 120 NM S OF AXIS BETWEEN 99W AND 111W. SCATTERED MODERATE 
TO STRONG CONVECTION WITHIN 180 NM EITHER SIDE OF AXIS W OF 
113W.  
 
...DISCUSSION...

A POSITIVELY TILTED UPPER LEVEL TROUGH IS LOCATED JUST W OF THE 
AREA. FURTHER E...A HIGH AMPLITUDE UPPER LEVEL TROUGH DOMINATES 
THE E PART OF THE AREA E OF 105E...WITH AXIS EXTENDING FROM THE 
WESTERN GULF OF MEXICO ACROSS SE OLD MEXICO NEAR THE GULF OF 
TEHUANTEPEC TO NEAR 00N95W. THIS TROUGH IS ENHANCING CONVECTION 
N OF THE ITCZ BETWEEN 83W AND 95W.  

A LARGE UPPER LEVEL ANTICYCLONE COVERS THE ENTIRE AREA W OF 
113W...CENTERED NEAR 12N123W. ACTIVE ITCZ CONVECTION W OF 113W 
IS HELPING MAINTAIN THIS UPPER LEVEL ANTICYCLONE.

AT THE SURFACE...THE ABOVE MENTIONED UPPER LEVEL TROUGH W OF THE 
AREA IS SUPPORTING A 1007 MB LOW NEAR 32N141W WITH ASSOCIATED 
COLD FRONT JUST ENTERING THE NW PORTION OF THE AREA. NEAR GALE 
FORCE WINDS ARE JUST E OF THE FRONT AS A RESULT OF THE LOCALLY 
TIGHT PRESSURE GRADIENT BETWEEN THE FRONT AND HIGH PRESSURE 1020 
MB CENTERED NEAR 28N123W. AS THE UPPER LEVEL TROUGH CONTINUES TO 
SHIFT E...THE SURFACE HIGH PRESSURE CENTER WILL WEAKEN AND SHIFT 
N OF THE AREA OVER THE NEXT 24 HOURS. THIS WILL ENABLE THE 
SURFACE LOW TO MOVE SE INTO THE FORECAST AREA SAT...WITH NEAR 
GALE FORCE WINDS E AND S OF THE LOW. LONG PERIOD SWELLS 
GENERATED BEHIND THIS FRONT WILL MOVE INTO THE NW PART OF THE 
AREA OVERNIGHT...WITH COMBINED SEAS REACHING AS HIGH AS 17 FT BY 
SAT NIGHT. 

THE PRESSURE GRADIENT BETWEEN THE ITCZ AND THE SURFACE HIGH 
PRESSURE CENTER MENTIONED IN THE PARAGRAPH ABOVE IS MAINTAINING 
NE TRADES OF 20 TO 25 KT FROM 08N TO 13N BETWEEN 117W AND 135W. 
RESULTANT SHORT PERIOD NE WIND WAVES ARE COMMINGLING WITH LONG 
PERIOD NW SWELL AND CROSS EQUATORIAL LONG PERIOD SW SWELL THAT 
HAS BEEN PROPAGATING N ACROSS THE DISCUSSION AREA FOR SEVERAL 
DAYS RESULTING IN CONFUSED SEAS WHERE THE DIFFERENT WAVE GROUPS 
ARE INTERSECTING. AS THE HIGH PRESSURE CENTER WEAKENS AND MOVES 
N...THE PRESSURE GRADIENT WILL RELAX AND WINDS WILL DECREASE 
BELOW 20 KT OVER THE TRADEWIND BELT SAT. 

$$

AL