Tuesday, April 3, 2018

Thermal ups and downs

I’ve left the deserts of Arizona and California to visit the Pacific Coast for a few days. That meant a sudden elevation shift as I drove west along Interstate 8.

El Centro, California, is 40 feet below sea level. It was shorts and air conditioning weather yesterday afternoon. About 93 degrees. Then 25 miles west, at Ocotillo, the highway begins to climb into the mountains: 3,000 feet in 12 miles. And the temperature rapidly drops.

It’s a basic principle we nomads learn: as you go up the temperature usually goes down, and vice versa. So we can avoid troublesome temperatures by shifting elevation, not just latitude.

On a cloudless day (like yesterday), temperature decreases approximately 5.4°F for each 1,000 foot gain in elevation. So it should’ve been in the 70s when I pulled into Coyote’s Flying Saucer Retrievals & Repairs atop the first summit. But it was in the 60s because of another factor. Hot air rising in the desert was drawing cool ocean air over the mountains.

This is where the 5.4°F per 1,000 feet rule breaks down. It’s not going to get warmer as I drop out of the mountains to the ocean because Pacific currents coming out of the north bring colder ocean temperatures which creates a layer of colder air along the coast.

That’s why this visit to the Coast will be short. Say hi to my Los Angeles friends, stare at the ocean for a while, then head back inland in search of perfect weather. But I'll be back. More than once. Autumn is a great time to be on the West Coast.

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