The evolution of the 1991-92 El Nino/Southern Oscillation event was unusual: Warm SST anomalies in the equatorial cold tongue region switched to colder than climatology in the last half of 1992, but waters warmer than 30°C remained displaced eastward just west of the dateline, continuing to fuel anomalous convection there during the IOP (Figure 2; Figure3; Figure 4). Fortunately, SST in the IFA remained warmer than 29°C during most of the IOP, and convective activity was observed over the IFA (Figure 5). The Southern Oscillation Index (Figure 6), which had relaxed to near zero prior to the experiment, decreased during the IOP, reflecting sea level pressure changes associated with renewed westerly wind activity. In response to these westerly wind events, the warm pool migrated back into the central equatorial Pacific, leading to a reintensification of the ENSO warm SST anomalies east of the dateline.

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Last modified: November 3, 1997