8 months ago
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We begin today with Ned Kleiner writing for the Los Angeles Times explaining why Southern California and portions of the Southwest are going through the region's first tropical storm warning ever.
What has kept the hurricanes away from California for so long? The answer lies in two factors that fend off hurricanes: cold sea surface temperatures and high vertical wind shear.
Cold sea surface temperatures suppress hurricane formation because hurricanes get their energy and moisture by evaporating surface waters, which is much harder to do when the water is cold. Because of ocean currents, the waters of the eastern Pacific are far colder — by as much as 9 degrees — than the same latitude in the western Pacific or the Gulf of Mexico. [...]
So why has Hurricane Hilary grown stronger given the conditions of the eastern Pacific? Mostly because current conditions are not as hostile to hurricanes as usual. July was the hottest month in recorded history, and since the Earth’s surface is mostly water, a lot of that heat has gone into the oceans. At the moment, the waters around Cabo San Lucas are 88.3 degrees — more than 4 degrees hotter than normal and basically the same temperature as the water around Key West.
Meanwhile, a growing El Niño event (which occurs when the cold waters that usually rise from the Atacama Trench off Peru are prevented from reaching the ocean’s surface ) has decreased vertical wind shear in the eastern Pacific, allowing more hurricanes. These conditions have led to a string of storms in the region, including Hurricane Dora, which was one of the longest-lived Pacific hurricanes on record and was responsible for the strong winds that added to the devastating wildfires on Maui, Hawaii.
It's all connected.
