This past weekend, California was under warning. Not for an earthquake or wildfire, but for an approaching hurricane! It’s been 80 years since a tropical storm has made landfall in California, when a storm called El Cordonazo scored a direct hit on Los Angeles. As Hurricane Hilary made its way over the Pacific last week, it strengthened into a category 4 hurricane. Thankfully, it weakened into a tropical storm as it struck Mexico’s Baja California and moved northwards, otherwise, the devastation would have been far worse. Over the course of a single day, some desert regions of California were inundated with more than a year’s worth of rainfall. East of Los Angeles saw upwards of 11 inches of rain!
Cooler waters in the Pacific generally make it harder for strong hurricanes to hit the West Coast. When they do form, typically they travel west – closer to Hawaii. On August 8, Hurricane Dora passed nearby the Hawaiian Islands, and in its wake, dry high pressure moved into the region, funneling fast and dry winds that led to the devasting Maui fires. Hurricane Hilary was able to gather increased strength for a simple reason: higher than normal ocean temperatures. As last week’s Science Wednesday stated, 40% of the world’s oceans are undergoing marine heat waves, with the added heat due to greenhouse gas emissions from fossil fuels. Waters around Cabo San Lucas in Baja California are more than 4 degrees warmer than usual this summer. At 88.3 degrees Fahrenheit (31 degrees Celsius), it’s the same temperature as the water around Key West, Florida. As the ocean temperatures continue to rise, any storm build-up will produce more rain and stronger winds. Recent research suggests 30% more frequent eastern Pacific hurricanes if global temperatures increase by at least 2 degrees Celsius.
Though a storm hitting California may be weaker than the storms that the Gulf of Mexico consistently weathers, lack of preparation can lead to greater impacts, especially if there has been development in flood-prone areas. Our actions have been making unlikely events like Hurricane Hilary ever more likely. Climate change will continue to throw curveballs and surprises our way, as the planet adjusts to the increases in emissions of greenhouse gases. For the future, it’s worth preparing for these types of storms in California, even if they turn out to be infrequent. Currently, California faces rising flood risk from winter atmospheric river storms, which are caused by rivers of water vapor high up in the sky. Thus, flood preparation should be on the minds of all California citizens.