I searched the WWW for some time for El Nio information, and then in this
week's TIME magazine I found probably the best summary. Here's some info,
for any of you who haven't fully grokked this phenomenon yet.

from TIME, Feb. 16, 1998

"The way El Nio works, scientists are now convinced, is that high pressure
in the eastern Pacific sends trade winds blowing to the West. Because these
winds push water before them like an invisible plow, the sea's surface
actually measures about a foot and a half higher around Indonesia and
Australia than it does off the coast of Peru. When the pressure drops and
trade winds slacken, the water sloshes back downhill, to the east.

This eastward flow is central to the physics that drive El Nio, says
Scripps' Nicholas Graham. The sloshing sends waves across the ocean like
ripples in a pond. These waves, in turn, push down on the so-called
thermocline, a layer of cooler water that normally mingles with the warmer
waters at the surface. As the thermocline sinks to greater depths, the
mixing stops, temperatures at the sea's surface rise, and an El Nio
begins.

These ripples can be thousands of miles slong, but since they travel 100
ft. or more beneath the surface they're hard to detect directly. So
scientists use satellites to pick up the subtle undulations in sea level
produced as the ripples pass by. That's how NASA oceanographer Anthony
Busalacchi could see early last spring that swarms of undersea waves had
started to head out across the Pacific toward the coast of Peru; he
followed them as they slammed into the continental shelf, then split,
heading sharply south toward Chile and north toward Alaska.

The warm water created by the south-moving ripples created a heat wave that
sent residents of Santiago flocking to nearby beaches in the middle of
winter, while the north-moving waves triggered a sharp rise in ocean
temperatures off California and Washington State, delighting sportfishermen
by attracting tropical species like marlin to usually frigid waters."

Dennis Paulson, Director phone 253-756-3798
Slater Museum of Natural History fax 253-756-3352
University of Puget Sound e-mail dpaulson at ups.edu
Tacoma, WA 98416
http://www.ups.edu/biology/museum/museum.html