NOAA/CPC identifies many June historic weather and climate events occurring during June 2021. The June 2021 upper air pattern provided by the International Research Institute for Climate and Society helps to explain the super warmth.

The deep tropics of the North Atlantic basin are becoming somewhat warmer than normal. SSTA of >1C is considered a moderate warm anomaly and much of the deep tropics have recently reached that threshold. Robust warm anomalies of >2C rest on the equator. Anomalous warm SSTA in this region are generally well-correlated with increased convection (and tropical cyclone/hurricane risk) especially if the proper atmospheric conditions are present.

More confident is a return of La Nina by quarter 4 of 2021 by most forecast models. Interestingly, several models are indicating potential for the coolest SSTA associated with the returning La Nina near or just east of the Dateline while waters are near normal off the northwest coast of South America. This condition is representative of a La Nina Modoki and most prominently forecast by NCEP CFS V2 by October.

The Climate Impact Company July 2021 ENSO forecast reveals potential for a moderate-to-strong La Nina event returning later in 2021. The moderate La Nina strength atmosphere has lingered despite oceanic ending of La Nina in April. For this reason, the atmosphere is likely to regenerate conditions to propel the return of La Nina for quarter 4 of 2021.