Since late December, rainfall in California has been abundant. Round after round of heavy rain and mountain snow has slammed the pacific coast of the state. Some places have received up to 40 inches of rain or over 10 feet of snow. While the state does need rain, this much in a short period of time is causing major problems. Numerous floods and mudslides have recently ravaged the state.
California has been incredibly drought prone for several years. Widespread extreme drought and burn scars from numerous large forest fires make the ground unable to hold as much water as normal. Because of that, the heavy rain the state has seen nonstop for several weeks has nowhere to go, leading to flooding. This flooding has led to at least 17 deaths in the state, and caused extensive property damage in poor and rich communities alike. Up and down the coast, along with parts of the Central Valley, flooding has been nearly the worst it has been in at least 25 years.
In terms of the meteorology behind the prolific storms of the past few weeks, this event has not been unique. Each storm has been the result of an atmospheric river, which is essentially a long tail of moist air being pulled northward by a low pressure system. As each storm comes ashore, it brings with it a conveyor belt of moisture all the way from as far south and west as Hawaii, which is why these storms are able to produce so much rainfall. These atmospheric rivers generally happen several times a winter on the west coast, and even occur in drier years. What makes this event so unique and devastating is the repetitive and concentrated nature of the storms, coupled with the preexisting dry and burned ground; each storm came right on the heels of the previous one and targeted roughly the same part of northern and central California. This event is not itself a result of climate change, but the pattern of more extreme droughts and floods is. Math teacher and former meteorologist Jodi Pickle said, “The fascinating aspect about these events is that meteorologists predicted this at least 25 years ago due to the oceans and atmosphere warming. Since the tropical oceans are warming, more water vapor evaporates from the vast Pacific Ocean, so getting a direct infusion of this into a storm makes a stronger storm and produces more precipitation.” This combination of heavier rainfall and persistent extreme patterns is what has made the recent flooding a unique event for the region.
By the third week of January, this rainy pattern looks like it might settle down for the west coast, with a much drier few weeks to follow. This will provide a welcome respite to areas that have been oversaturated since the end of last year. While the flooding does not provide a ton of drought relief because most of the water ends up running off into lakes, rivers, and eventually the ocean, the snowfall that covers the Sierras will provide meaningful moisture in the long run. As snow melts in the spring, its runoff is more able to soak into the ground because it comes at a controlled pace, which reduces the drought more effectively. As a result, the California storms are beneficial in the long run despite all their negative impacts currently.