Fire And Ice Impact U.S. From Coast To Coast

There are numerous severe weather events happening across the U.S. this week, from devastating wildfires on the West Coast to a major winter storm shutting down schools, businesses and travel and knocking out power across the eastern areas of the country.

Both events have been prominently covered in the news. My colleague Renny Vandewege spoke about the raging wildfires and Santa Anna winds earlier this week on Forbes Breaking News. What may be less known is that although the two distinct events are not directly related to the same weather system, they are influenced by broader atmospheric patterns and seasonal phenomena that can coexist and interact.

California Wildfires

The wildfires in California are driven by a combination of dry vegetation, low humidity, and strong Santa Ana winds. January is not a typical month for wildfires. California typically experiences its peak wildfire season June through late October, although in recent years the “season” has extended to year-round.

A warming climate complicates everything. Hotter and drier seasons mean that big fires in January, once very rare, are now more common. The lush foliage dried by scorching temperatures and high winds are a dangerous combination.

Winter Snowstorms

The winter storms sweeping across the U.S. South and Midwest are associated with a different weather phenomenon, often tied to cold air masses (polar vortex) interacting with moist air from the Gulf of Mexico. This leads to snow, sleet, or freezing rain depending on local temperatures.

Influence By Atmospheric Patterns

While these events are distinct, they can be indirectly connected through larger atmospheric patterns such as the jet stream.

The jet stream is high-altitude, west to east wind current that circulates the Northern Hemisphere. It moves weather systems along which means it plays a significant role in shaping weather systems. This NASA video is a good visual on how the jet stream flows.

Its waviness can create ridges (areas of high pressure) and troughs (areas of low pressure). For example, a ridge over the western U.S. may contribute to drier, windier conditions in California, enhancing wildfire risk, while a trough over the central and eastern U.S. can pull cold air southward, fueling winter storms in places not used to experiencing heavy snow and ice.

It is the plunging jet stream we are currently experiencing that is turbocharging the intense Santa Anna winds, clocked up to 100 mph, causing the fueling of the fires and rapidly spreading them to adjacent areas.

The same plunging jet stream is the primary cause of the current major winter storm. Cold air from the polar vortex is dipping southward, bringing significant snowfall and frigid temperatures to large parts of the United States. As you can see from the precipitation map, heavy snow and ice currently across portions of the Southeast states will spread into the Northeast over the weekend with millions in the path of this storm.

La Niña conditions have finally taken hold, bringing a more typical pattern for the rest of January. At least 2-3 additional southern storms are expected to move up the East Coast, as shown on the National Weather Service map. This first storm will track across to the Carolinas and then out to sea but will spread snow up into the Great Lakes and Northeast. The storm moving into the Northwest will move across the north-central US into the Great Lakes by Sunday, bringing the snow shown across the western and northern U.S. Most of next week looks quieter until a new storm moves in the following weekend. 

The other atmospheric pattern contributing to the fire and ice phenomenon is atmospheric blocking. Atmospheric blocking refers to a large-scale, persistent weather pattern where the normal west-to-east flow of the atmosphere is disrupted, often causing weather systems to stall over a region for days or even weeks. In blocking situations, the jet stream becomes wavy or distorted, like we are experiencing now.

While the atmospheric river flow remains shut down, it will offer some respite but prolong dry conditions in Southern California’s fire-ravaged areas.

Climate Change

I’ve written about attribution science before and how researchers use scientific methods to determine if the weather event was caused by climate change or contributed to the severity of the event. The wildfires are a good example of climate change contributing to the severity of the event.

While there is not a definitive link between the Santa Ana winds happening later than usual, there are studies that show climate change exacerbates extreme weather by making conditions for wildfires (e.g., drought, heat) more severe.

The waviness of the jet stream that contributed to the 100 mph winds is also debated within the scientific community. Some studies suggest that rapid Arctic warming, known as Arctic amplification, reduces the temperature gradient between the Arctic and mid-latitudes, potentially leading to a more meandering jet stream. This increased waviness can result in prolonged weather patterns, such as extended cold spells or heatwaves.

Another study found minimal influence of reduced Arctic sea ice on mid-latitude weather patterns.

Two Sides Influenced by the Same System

The California wildfires and U.S. winter snowstorms are separate weather events resulting from different immediate causes. However, both are influenced by large-scale atmospheric patterns and potentially by the impacts of climate change. Both have had devastating health, infrastructure and economic effects on the country and again point to weather resiliency and the imperative to further the science of weather.