This year, La Niña will play a significant role in the winter weather outlook, and we already see widespread cooler-than-normal water temperatures in the equatorial Pacific Ocean. The cool-water anomalies will peak in intensity toward the end of 2020 — before the water gradually warms up in late winter and spring. This timing all but ensures that the atmosphere will continue to respond to La Niña conditions throughout the winter season.
To help businesses understand, prepare for, and mitigate the risks associated with winter weather hazards, DTN meteorologists Jeff Johnson, Nathan Hamblin, and Stephen Strum recently hosted a webinar to provide a winter weather risk assessment. The team reviewed the 2019-2020 winter season, examined recent and longer-term trends, the costliest winter hazards, the El Niño-Southern Oscillation (ENSO) outlook and selected analog patterns, and computer model projections. The team wrapped up the webinar with a discussion of the 2020/2021 winter outlook for November 2020 to March 2021. Below are a few highlights from the presentation.
Watch the video to get the full report on the winter forecast.
Winter 2019-2020 in review
The 2019-2020 winter season was unique. A weak El Niño kept the main jet stream and storm track from the southwestern United States through the Midwest and Northeast. The polar vortex was unusually strong, which kept the majority of the cold air well to the north. These two features provided above-average temperatures for most of the United States except for the western part of the nation. The Southwest, Southeast, and the Ohio and Tennessee Valleys saw above-average precipitation. The heating demand, measured by the number of heating degree days, was higher than average in the north-central United States, but less heating demand occurred for the east, south, and west. December 2019 was in the list of top 10 warmest Decembers for most of the south-central/southeast United States. By January, most of the nation experienced widespread above-normal temperatures. In February, near-record monthly rainfall fell in the Southeast. Twenty-two states experienced their top 10 warmest March temperatures.
The year-to-year trends in the winter temperatures have been highly variable. Chilly winters have been followed by milder winters, and then, the patterns have tended to flip back the other way. Looking at other years when there was a La Niña, you can see that the north-central United States saw much colder winters, with the single exception of 2011-2012, which was much warmer.
The costliest winter events
DTN meteorologists examined the costliest winter events. In the early 2000s, there were no billion-dollar winter events due to milder conditions, but more recently, there have been one or more of these events every year. The northeast has seen most of these events, which can be attributed to the fact that there is more infrastructure, more people, and more problems that can result from significant winter weather events in the region.
2020-2021 winter outlook highlights
A preview of the winter season forecast for the United States has several primary influencers. ENSO, polar vortex behavior, shorter sub-seasonal patterns, and recent trends all influence the long-range winter forecast. We put all these factors together to estimate the upcoming seasonal outlook.
This winter season, you can expect mainly above-normal temperatures across the south and east with brief, but potentially strong, cold snaps. Below-average temperatures will be more prevalent in the north-central and northwest United States. Near to above-normal precipitation and snow are also expected across the north and drier than normal conditions across the south. Drought conditions will grow and expand, especially in the southwestern and south-central states.
Get more insights
To learn more about the 2020-21 winter weather outlook, watch the DTN Webinar.