Sandblasted: Dust, sand and 192 mph winds slammed the San Joaquin Valley in the 1970s

If you live in California, you don’t often think of sandstorms — but they do happen.

On Oct. 30, one of the strongest and longest lasting Santa Ana wind events ever to occur during the fall season developed.

Sustained winds of between 40 and 50 mph were reported throughout Ventura and Los Angeles counties over an extended period.

A wind gust of 78 mph was reported at Boney Mountain above Naval Air Station Point Mugu. On the other side of the Tehachapi Mountains, gale-force southerly winds flowed into the southern San Joaquin Valley and screamed northward toward Sacramento.

These winds started that morning and continued through the day, and by the afternoon dust clouds that could be seen on satellites imagery looked like ghostly brown, uneven waves in the sky.

That day, the San Joaquin Valley Air Pollution District Issued an air quality emergency warning for Kern County. Blowing dust severely impacted air quality, and residents were urged to stay indoors with the windows closed to avoid extended exposure from high levels of unhealthy particulate matter in the air.

As bad as the air was that week, it was worst in Dec. 20, 1977. On that day, a terrible dust and sandstorm struck the southern San Joaquin Valley and caused a great amount of damage.

That year, the Eastern Pacific high was entrenched off the California coastline and kept the storm track far to the north. This prevented all but a few weather systems from reaching into California.

The most notable was Hurricane Doreen, which tracked northwestward along Mexico’s Baja Peninsula, came onshore as a tropical depression over Orange County and produced heavy rain and floods in parts of Southern California.

Otherwise, the position of the Eastern Pacific high produced one of the worst two-year droughts in California history, from 1975 through 1977.

The San Joaquin Valley was declared a disaster area. Its soils were more parched than normal.

The snowpack measurements performed on April 1, 1977, indicated the lowest water content in 47 years. As the winter of 1977 approached, the air over the high deserts of the western United States was cold and dense.

On Dec. 20, an exceptionally strong area of high pressure moved southward over the Great Basin. At the same time, an intense low-pressure system and its associated cold front approached the coast of Northern California.

This condition produced a steep pressure gradient through the Central Valley. The air flowed in a clockwise direction around the high-pressure system, forcing the cold and dry desert air down the Tehachapi mountain canyons toward the southern San Joaquin Valley.

As gravity pulled the air mass toward the valley floor, it funneled through the mountain passes and canyons, producing hurricane-force east-southeasterly winds.

To make matters worse, as this air mass descended, it was compressed, and its temperature increased; as air heats, its relative humidity decreases, so the air became bone dry.

Some of the strongest winds ever recorded in California history slammed into the southern San Joaquin Valley that day and, combined with the extraordinarily dry soil, produced a fearsome dust and sand storm.

Sustained winds reached 125 mph and caused extensive damage to buildings and fertile farmland.

The U.S. Geological Survey estimated that wind gusts reached 192 mph at Arvin. Vehicles that were left outside during that windstorm were literally sandblasted.

The winds carried tremendous amounts of soil that filled in many of the water canals that crisscrossed that part of the valley. It took weeks of work by heavy equipment operators to clear some those canals.

Not surprisingly, large volumes of dust were carried northward through the San Joaquin and Sacramento valleys toward the Oregon border. Dust from this storm obscured the sun as far north as Colusa County.

An outbreak of valley fever followed as spores traveled into Sacramento and Redding. Months later, hydrographers found a layer of dust embedded in the snowpack in the Mount Shasta area that was probably from this event.

I will be giving a presentation about climate change, and what it means for our local weather at the Morro Bay Library from 4:30 to 6 p.m. Tuesday. All are welcome, including families.