Californians, on a normal year, typically celebrate New Year’s Eve with parties in backyards, beaches, or rooftop bars. Not this year. It rained, a lot. In late 2022 into early 2023, a long channel of warm moist air called an atmospheric river, flowed up from the tropics into the mid-latitudes (30-60N). It brought rain and gloomy weather to much of the west coast for weeks on end. Each day these rivers carry up to the equivalent of 20x the flow of water as the Mississippi River. This flow drops normally 30-50% of California’s annual precipitation.
Source: NOAA
What is this?
Atmospheric Rivers (ARs) can quite literally be pictured as rivers in the sky. These ARs have a thickness of only 300-400 miles yet a length of thousands of miles. Sometimes called the “Pineapple Express” in reference to their start near Hawaii, extremely humid, or air highly saturated with water vapor heads straight towards North America. The trajectory of this moist air flows West to East, like many other weather patterns in the world. It’s essentially a ribbon of exceptionally moist air that flows from the tropics to the mid-latitudes.
Atmospheric Rivers aren’t new however, these atmospheric rivers have been recorded extensively for the last 10 years. Scripps Oceanography at the University of California San Diego is leading the research on these across the globe. Below is a map of recording rivers and their intensity. They usually occur in the autumn/winter months and are VERY difficult to predict. We can use infrared satellites to look at water vapor in the atmosphere, yet it is difficult to know what to look for. They are tough to plan for because they flow low in the atmosphere, along with ordinary clouds away from where satellites can easily see and recognize them. We know when they are happening, but have a difficult time telling when they will happen next.
Source: C2W2 @ Scripps Oceanography Institute
How it impacts surfing
When these rivers make landfall, they continue east. The wet air rises, condenses, and precipitates like none other when it hits the mountains in eastern California. The precipitation falls as rain in the lower altitudes and snows up in the higher mountains. It is great news for the reservoirs and ski resorts, yet it leads to floods and mudslides closer to the coastal areas.
For example, Santa Barbara had 168% of its rainfall for January 2023. San Diego’s Brown Field Municipal Airport is at 187%. Up north, San Fransico has 192% rainfall compared to a 30-year normal. More CA cities can be seen here. This is dangerous for ocean folks because the rain runoff mixes with societal pollution.
Well, can you surf them?
The Department of Environmental Health suggests waiting 72 hours after “normal” rainfall before surfing. Atmospheric Rivers skew the “Safe Wait Time” with their prolonged rains. Sewage, industrial runoff, and other toxins are mixed constantly into the ocean as the precipitation pours. The wait time should be based on the quality report from the local authorities.
However, the waves during these ARs can be as large as 35+ feet. On January 4-5 in 2008, there was an AR that gifted California about a foot of rain in the lowlands, 6-10 feet of snow in the mountains, and 32-foot waves. The height of an Olympic high-dive. These are no joke.
While the waves of these storms might be truly gnarly after the chaos, there is a risk. Increased toxins in the water can make you gravely sick. To avoid this, pay attention to the color of the water. If there are beautiful waves, yet the water is muddy, grimy, and brown. Remember there are always going to be more waves. Don’t get sick being stoaked, surf safely.