A transition into moderate-to-strong negative phase Pacific North America (-PNA) index develops later this week and lasts through the remainder of February and may continue in March. The -PNA shifts the focus of U.S. weather hazards from cold to stormy.

The warmest sea surface temperature anomalies (SSTA) on record for early February stretching north-to-south off the coast of Chile and Peru exceeding 3C throughout much of this region has generated. Onset of this large and intense marine heatwave (MHW) occurred in DEC-25. Strengthening continues especially along the immediate coast of Chile during the past 2 weeks. The warming is spreading equatorward. The daily Nino12 SSTA region off the northwest coast of South America is +0.63C today and 1.27C warmer than 30 days ago.

During January, a subsurface warm Kelvin Wave shifted across the equatorial East Pacific recently reaching the northwest coast of South America. The Nino12 region off the northwest coast of South America warmed 1.1C during the past 30 days. The majority of global SSTA forecast models are forecasting El Nino onset during northern hemisphere spring. The onset of that ENSO change has occurred and may have contributed to the sensible weather pattern change across North America as mid-February approaches.

The observed heating degree days (HDD) in Cleveland during JAN-26 is 1335, much colder than the 30-year (1123) and 10-year (1082) normal. The JAN-26 cold is slightly colder than JAN-25 (1277) and JAN-22 (1273). The JAN-26 observation is 1 HDD colder than the “polar vortex winter” of JAN-14 (1334).