“West Coast Hurricanes”

by Caleb, KE0FOE

Did you know that hurricanes only strike the East Coast and Gulf Coast of the United States but never the West Coast?

There are two main reasons for this. The first reason is ocean water temperature. During hurricane season, water in the Gulf of Mexico and along the Atlantic Coast is often above 79 degrees Fahrenheit which is the minimum temperature needed for hurricane formation. Meanwhile, waters along the northeastern Pacific Coast from Washington down through northern Baja California are much colder and cannot support the formation of a hurricane nor can they sustain a hurricane passing over and heading toward the U.S. West Coast.

The second reason is wind direction. Hurricanes which form in the tropics in the northern hemisphere generally move toward the west-northwest. These winds usually steer hurricanes toward the  East Coast and away from the West Coast.

However, there are exceptions to this rule, and as we speak, Hurricane Ophelia is a current example. Instead of forming over the Atlantic Ocean and moving westward toward the U.S., Hurricane Ophelia is moving northeastward toward Europe and is expected to slam into Ireland early tomorrow morning. While it will be post-tropical once it hits the Emerald Isle on Monday, Ophelia is still expected to bring hurricane-force winds and several inches of rain. It could even bring tropical storm-force winds as far north as Norway later this week!

Has this movement direction exception ever happened on our West Coast? Yes, it has. Since 1850, seven tropical cyclones have hit the southwestern United States. However, because of the aforementioned cold Pacific Ocean temperatures, none of these systems have been hurricanes – only tropical storms.

For more information about this topic, please check out this article by Scientific American. For a listing of tropical cyclones which have affected California and the Southwestern United States, please visit this article on Wikipedia.