Why La Nina Could Be Stronger

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05/21/2020, 12:00 pm EDT
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05/31/2020, 2:19 pm EDT
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Global SSTA models are forecasting a major contrast between ocean surface temperatures across the eastern equatorial Pacific (cool) versus the far western Pacific and eastern Indian Oceans (warmer). The contrasting ocean temperatures lead to stronger trade winds across the eastern Pacific tropics possibly increasing La Nina strength and duration.

Most (not all) ENSO phase forecast models indicate La Nina is likely to form mid-to-late quarter 3 of 2020. Interestingly, the evolution of cold ENSO occurs simultaneously with developing negative Indian Ocean Dipole (-IOD). Indicated is a much warmer than normal ocean surface in the far eastern Indian Ocean/western Pacific Ocean (32C) compared to the cool equatorial East Pacific (26C). The temperature differential is 6C about twice normal. The (very) strong thermal gradient from east-to-west across the equatorial Pacific implies strong trade winds in the east/central equatorial Pacific which upwell cool waters that strengthen La Nina. Given this increasingly expected dynamic La Nina could be stronger and last longer (into 2021).