000
AXPZ20 KNHC 042153
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT APR 04 2009

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2130 UTC.

...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG A LINE FROM 08N82W 
TO 03N100W TO 01N120W TO 02N140W. NO SIGNIFICANT CONVECTION.

...DISCUSSION...
A WEAK MID/UPPER LEVEL TROUGH EXTENDS FROM 30N127 TO 26N140W 
WITH STRONG SUBSIDENCE NOTED ACROSS MOST OF THE AREA N OF 22N W 
OF 125W. THIS TROUGH WILL BE REINFORCED BY A DEVELOPING MID TO 
UPPER LOW NEAR 41N145W DIVING SE AT 20 KT. THIS FEATURE WILL 
CONTINUE MOVING 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. ALSO...EXPECT ISOLATED SHOWERS ALONG THE FRONTAL BOUNDARY. 

THE APPROACHING COLD FRONT WILL WEAKEN THE SURFACE RIDGE IN 
PLACE EXTENDING FROM 30N128W TO 15N108W. AS A RESULT...THE TRADE 
WINDS OVER W WATERS WILL CONTINUE TO DIMINISH BELOW 20 KT IN 
ABOUT 36 TO 48 HOURS. MEANWHILE...THE 1430 UTC QSCAT PASS SHOWED 
TRADE WINDS OF 20 KT MAINLY N OF 7N AND SW OF LINE FROM 07N125W 
TO 24N140W. IN ADDITION...20 KT NORTHERLY WINDS ARE STILL 
BLOWING 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. WINDS OVER THE GULF OF CALIFORNIA 
HAVE DIMINISHED BELOW 20 KT...BUT 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 AFOREMENTIONED MID/UPPER LEVEL TROUGH THERE IS A 
LARGE AREA OF MID/UPPER LEVEL MOISTURE...COINCIDENT WITH THE 
SUBTROPICAL JET EXTENDING FROM THE CENTRAL BAJA CALIFORNIA 
PENINSULA TO 20N130W...THEN TURNING MORE W TO 20N140W. A BROAD 
UPPER-LEVEL RIDGE DOMINATES THE AREA S OF 20N WEST OF 110W... 
INCLUDING ALSO SE MEXICO...THE BAY OF CAMPECHE AND N CENTRAL 
AMERICA WHERE MOSTLY FAIR WEATHER PREVAILS. MODERATE TO STRONG 
UPPER LEVEL SUBSIDENCE AND IMPLIED DRY AIR MASS IS NOTED WITHIN 
THE RIDGE AXIS. AN UPPER LEVEL TROUGH/SHEAR AXIS LIES WEST OF 
THE RIDGE ALONG 115W.  

LOOKING AHEAD...A LATE SEASON GULF OF TEHUANTEPEC GALE EVENT IS 
FORECAST BEGINNING EARLY TUE AS A HIGH PRES BUILDS SWD ALONG THE 
EASTERN SLOPES OF THE SIERRA MADRE MOUNTAINS OF MEXICO IN THE 
WAKE OF A STRONG COLD FRONT FOR THIS TIME OF THE YEAR EXPECTED 
TO MOVE OFF THE TEXAS COAST SUNDAY AFTERNOON. ON AVERAGE...THE 
LAST TEHUANTEPEC EVENT OCCURS AROUND APRIL FIRST. 

$$
GR