5.4 Update on El Niño

A weakening El Nino trend has occurred across the Pacific Ocean so far. Figure 5.7 illustrates the behavior of the standard Southern Oscillation Index (SOI) of the Australian Bureau of Meteorology (BOM) from April 2018 to April 2019. 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 the current season, SOI decreased sharply from -0.6 in January to -13.5 in February, then increased to -6.8 in March, and increased to -1.3 in April 2019, indicating a weak El Nino condition.

Figure 5.7. Monthly SOI-BOM time series from April 2018 to April 2019

The sea surface temperature anomalies in April 2019 for NINO3, NINO3.4, and NINO4 regions are +0.7°C, +0.7°C, and +0.6°C in sequence,  a litter warmer than the 1961-1990 average according to BOM (see Figure 5.8-5.9). Both of BOM and NOAA conjecture that the warmer condition indicates a weak El Niño trend. CropWatch will keep monitoring the situation.

Figure 5.8. Map of NINO Region

Figure 5.9. April 2019 sea surface temperature departure from the 1961-1990 average

Main Sources:

[1] http://www.bom.gov.au/climate/current/soi2.shtml

[2] https://www.climate.gov/enso

[3] https://www.climate.gov/sites/default/files/Fig3_ENSOindices_SST_large.png

[4] http://www.bom.gov.au/climate/enso/wrap-up/archive/20190514.ssta_pacific_monthly.png?popup