Breakdown: Why hurricanes are less common on the West Coast
MEMPHIS, Tenn. (WMC) - We see the coverage of major hurricanes in the Atlantic year after year. But we rarely hear about major hurricanes in the eastern Pacific.
Hurricanes in the Atlantic versus hurricanes in the Pacific are identical in every way, shape and form, but Pacific hurricanes make the news less often and do less damage than their Atlantic counterparts. Additionally, Pacific Hurricanes almost never hit the United States. Why?
There are many factors that need to play out in order for a hurricane to occur. In short, wind direction and cold water are the main reasons hurricanes aren’t as common on the West Coast.
By the time these systems travel far enough to the north to bring their associated moisture to the United States, the tropical cyclones have normally diminished below tropical storm strength over Mexico or over the colder waters of the California current that flows southward along the California coast. Rain, sometimes locally excessive, can be seen in many areas of the southwestern United States when tropical cyclone remnants enter the region.
The conditions guiding the development and movement of these storms impact whether, and where, they hit land.
Two factors explain why hurricanes very rarely form and come close to land on the west coast.
First, hurricanes in the northern hemisphere move east to west, meaning storms that form in the Atlantic head straight for the American mainland, whereas in Pacific typically move away from land and out to sea.
Secondly, hurricanes need warm water to form. Water temperatures in the Atlantic Ocean average about 80 degrees because of the warm air from the Gulf Stream. In the Pacific Ocean, they average about 60 degrees, though slightly warmer water near Hawaii would explain why that state sees the occasional hurricane. The warmer the water, the better chance the storm becomes a strong hurricane.
California lacks these warmer waters and is usually under 75 degrees, even around 60 degrees in the upper northwest.
California’s average temperatures during hurricane season are between 60 to 72 degrees over open water.
There have even been recorded sea surface temperatures around 80 degrees near San Diego’s beaches, but it is exceedingly rare. The only actual hurricane to get close to California was the 1858 San Diego Hurricane, but its still debated over whether it really made landfall.
The only known system to truly make landfall was the 1939 Long beach tropical storm. It was formerly a hurricane that formed off Central America and made a rare shift from a west movement to an eastern movement before making landfall on San Pedro.
Three other cyclones have brought tropical storm force winds to the southwestern United States during the twentieth century:
- Hurricane Joanne on 6 October 1972 in Arizona
- Hurricane Kathleen on 10 September 1976 in California and Arizona
- Hurricane Nora in September 1997 in Arizona.
Only the 1939 tropical storm made a direct landfall in coastal California, because the other three systems entered the United States after first making landfall in Mexico.
Usually only the remnants of tropical cyclones affect California.
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