The Atlantic tropical season runs from June 1st to November 30th each year, when tropical storms and hurricanes are most prone to developing over the northern Atlantic, Caribbean and Gulf of Mexico. A hurricane is a tropical cyclone with maximum sustained winds of 74 mph or greater. In an average year, there are 6 hurricanes and it’s not uncommon for one or more of these hurricanes to make landfall on a Gulf Coast or East Coast state. In recorded history, hurricanes have impacted all Atlantic and Gulf states from Texas to Florida, including up to Maine and nearby Canada.
But what about the West Coast of the United States, which is adjacent to the Pacific Ocean? The eastern Pacific has an active tropical season as well. The season runs from May 15th to November 30th with 8 hurricanes in an average year. With the eastern Pacific having more hurricanes than the Atlantic, why do we never hear about a hurricane hitting California, Oregon or Washington state? It boils down to two key factors that determine where hurricanes form and track: ocean water temperature and upper-level wind flow.
Ocean Water Temperature
Several elements contribute to hurricane formation and track. Perhaps the most important element needed is warm ocean water temperatures of around 80 degrees F or warmer. In the North Atlantic Ocean during peak hurricane season, these warm ocean waters are located in the Gulf of Mexico, Caribbean and Atlantic Ocean waters along the U.S. East Coast up to the Carolinas. This allows for potential hurricane formation in these areas making all nearby states susceptible to hurricane impacts.
However, in the eastern Pacific Ocean, the ocean waters along the U.S. West Coast are very cold by comparison. The warm ocean waters that hurricanes need to develop and survive are normally kept well south of the California/Mexico border by southward flowing ocean water currents. For this reason, hurricane development is generally limited to areas south of Baja California, well away from the West Coast.
Upper-Level Wind Flow
Once a hurricane develops, it tracks generally where the upper-level wind flow pattern steers it. Over the tropical regions of the Pacific and Atlantic Oceans, the Trade Winds prevail with a general east-to-west flow. This wind flow tends to steer Atlantic hurricanes on a general motion towards the Caribbean and eastern U.S. Meanwhile, over the Pacific Ocean, this east-to-west flow tends to steer most hurricanes out into the open ocean, away from the mainland.
On occasion, an eastern Pacific hurricane will break away from the trade winds and track northwestward along or near Baja California and towards the state of California. However, once the hurricane tracks north of Cabo San Lucas, it encounters the much colder ocean waters. This causes the hurricane to weaken before getting close to California.
We may never see Jim Cantore broadcasting live hurricane coverage from Los Angeles in our lifetimes. But while a hurricane landfall on California is very unlikely, it’s not impossible. In fact, there was one in 1858 which became known as the San Diego Hurricane after making landfall in California and producing significant wind damage. Other instances since then involved weakened tropical cyclones that had fallen below hurricane strength. One in 1939 became known as the Long Beach Tropical Storm which produced major flooding. Then in 1976, Hurricane Kathleen made landfall along northern Baja California, bringing heavy rain and flooding to southern California.
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