An important thing to realize is that the figures on the previous two slide are updated in near-realtime; they are not figures that are produced months to years after the data have been processed. This means that the first Kelvin wave was noticed by scientists connected with the TOPEX/Poseidon project and the TOGA-TAO project in early February 1997. Because the Kelvin wave was large, it was expected that there would be at least a moderate El Niņo warming either in the late spring or early summer, although at that time, no one expected that it would surpass the event of 1982-1983. Thus, these scientists were not surprised when an official NOAA El Niņo advisory was issued in April.
The plots from the previous slides are still updated on a regular basis and are available over the World Wide Web. The TOGA-TAO data can be accessed from the NOAA Pacific Marine Environmental Laboratory:
The TOPEX/Poseidon data can be accessed from the University of Texas, Center for Space Research: