For the first times since 2012, the cool “horse shoe” SSTA pattern stretching from the Gulf of Alaska to just-off the West Coast of North America and southwestward to the south of Hawaii toward the Dateline in the Pacific tropics has emerged. Presence of the cool “horse shoe” SSTA pattern coupled with La Nina normally increases the risk and amplitude of La Nina climate signals which includes heavy precipitation during NOV/DEC/JAN in the Northwest U.S., dryness leading to drought in the Mid-south States and a general warmer-than-normal national pattern.

NOAA/CPC announced yesterday (Oct. 14) that La Nina onset developed in October 2021. The surface/subsurface cool anomalies in the equatorial East Pacific suggest La Nina Modoki. The projected ENSO West-East index (WEI) for October suggests La Nina Modoki. The La Nina episode is forecast to last into early northern hemisphere spring 2022.

Record warm SSTA in the South Atlantic tropics is the catalyst for a wet climate which defeats Brazilian drought into the summer 2021-22 season. The wet pattern is compensated for by a dry climate in Southeast Brazil to northeast Argentina where drought develops. Meanwhile regenerating La Nina brings a wet climate to Australia.

The Climate Impact Company constructed analog ENSO phase forecast using Nino34 SSTA reveals a short-term evolution of La Nina followed by mostly neutral ENSO by next March lasting into mid-2023.