5.4 Update on El Niño

Neutral El Nino condition prevails across the Pacific Ocean continuously. Figure 5.10 illustrates the behavior of the standard Southern Oscillation Index (SOI) of the Australian Bureau of Meteorology (BOM) from April 2019 to April 2020. Sustained positive values of the SOI above +7 typically indicate La Niña while sustained negative values below −7 typically indicate El Niño. Values between about +7 and −7 generally indicate neutral conditions. During this monitoring period, SOI decreased from 1.3 in January to -5.2 in March, then increased to -0.5 in April, 2020, indicating a neutral El Nino situation.

The sea surface temperature anomalies in April 2020 for NINO3, NINO3.4, and NINO4 regions were +0.3°C, +0.5°C, and +0.9°C, respectively, somewhat warmer than the 1961-1990 average according to BOM (see Figure 5.10 and Figure 5.11). Both BOM and NOAA conjecture that the warmer condition indicates a neutral El Niño (www.climate.gov/enso). CropWatch will keep monitoring the situation (Figure 5.12).

Figure 5.10 Monthly SOI-BOM time series from April 2019 to April 2020 (Source: http://www.bom.gov.au/climate/current/soi2.shtml)

Figure 5.11 Map of NINO Region (Source: https://www.climate.gov/sites/default/files/Fig3_ENSOindices_SST_large.png)

Figure 5.12 April 2020 sea surface temperature departure from the 1961-1990 average (Source: http://www.bom.gov.au/climate/enso/wrap-up/archive/20200512.ssta_pacific_monthly.png?popup)