000
AXPZ20 KNHC 041524
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SAT APR 04 2009

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1515 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 07N78W 
TO 05N100W TO 02N120W TO 02N140W. NO SIGNIFICANT CONVECTION.

...DISCUSSION...
A SHEARED MID TO UPPER LEVEL TROUGH EXTENDED FROM 30N115W TO 
25N140W WITH STRONG SUBSIDENCE NOTED WITHIN 120 NM OF THE AXIS
AND ELSEWHERE N OF 22N W OF 130W. THIS TROUGH WILL BE REINFORCED 
BY THE MID LATITUDE ENERGY CUTTING OFF FROM THE NORTHERN STREAM 
WITH AN ASSOCIATED DEVELOPING MID TO UPPER LOW NEAR 41N145W 
DIVING SE AT 20 KT. THIS MID TO UPPER LOW WILL CONTINUE DIVING 
SOUTHEASTWARD THROUGH THE NE PACIFIC TOWARD CALIFORNIA OVER THE 
NEXT FEW DAYS. AT THE SURFACE...THE ASSOCIATED COLD FRONT WILL 
MOVE INTO NW WATERS EARLY SUN WITH NW SWELL OF UP TO 15 FT  
MOVING IN BEHIND THE FRONT LATE SUN INTO MON.

THE APPROACHING COLD FRONT WILL WEAKEN THE SURFACE RIDGE IN 
PLACE ALONG 38N130W TO 30N128W TO 15N118W.  TRADE WINDS OVER W 
WATERS SW OF THE AXIS WILL DIMINISH AS THE RIDGE BREAKS DOWN.  
MEANWHILE...THE 0500 UTC ASCAT PASS SHOWED 20 KT NORTHERLY WINDS 
OVER THE NE WATERS BETWEEN THE RIDGE AXIS AND LOW PRESSURE OVER 
THE SW CONUS.  THESE WINDS WILL ALSO DIMINISH OVER THE NEXT 24 
HOURS AS THE RIDGE WEAKENS AND THE LOW PRESSURE OVER THE SW 
CONUS SHIFTS EASTWARD. A 1254 UTC QUIKSCAT PASS INDICATED NW 
WINDS OVER THE GULF OF CALIFORNIA HAVE DIMINISHED BELOW 20 KT.
WINDS WILL ONCE AGAIN BRIEFLY REACH 20 KT SUN AFTERNOON THROUGH 
MON MORNING AS THE SW CONUS COLD FRONT FINALLY WORKS ITS WAY 
SOUTHWARD INTO NW MEXICO/NORTHERN GULF OF CALIFORNIA.

SOUTH OF THE ZONAL TROUGH AXIS...MID TO UPPER LEVEL MOISTURE IS 
INDUCING MULTILAYERED CLOUDINESS WITHIN 360 NM OF A LINE FROM 
24N108W TO 14N140W.  AN UPPER LEVEL TROUGH/SHEAR AXIS LIES SOUTH
OF THIS REGION ALONG 115W.  VERTICAL LIFT ASSOCIATED WITH THE 
REAR RIGHT QUADRANT OF THE SOUTHERLY UPPER JET ON THE LEADING 
EDGE OF THIS TROUGH IS ACTING ON PLENTIFUL LOW LEVEL 
MOISTURE...WITH PRECIPITABLE WATER VALUES IN EXCESS OF 2 
INCHES.  SATELLITE WATER VAPOR IMAGERY CONFIRMS THIS INCREASE IN 
MOISTURE IN THE MID TO UPPER LAYERS AND INDICATES SOME CYCLONIC 
ROTATION ALOFT CENTERED NEAR 02N117W NEAR THE ITCZ.  
HOWEVER...THERE IS NO DEEP CONVECTION NOTED WITH THE SYSTEM
AS THE REGION IS DOMINATED BY STRONG SUBSIDENCE ALOFT.
  
EAST OF THIS UPPER TROUGH...A STRONG ANTICYCLONE AND AN 
ASSOCIATED DRY AIR MASS CENTERED OVER SOUTHERN MEXICO ALLOWS 
SUBSIDENCE TO DOMINATE THE AREA S OF 20N. THIS RIDGE ENVELOPS SE 
MEXICO AND NORTHERN CENTRAL AMERICA WHERE MOSTLY FAIR WEATHER 
PREVAILS.

$$
COBB