Weather Watch

1977 sandstorm: Get a wind of this story

Cliff Trotter and Don Weeks, both of Nipomo, came by my office the other day and had a fascinating weather story to tell.

Cliff was the engineer-manager of the Arvin-Edison Water Storage District in Kern County on Dec. 20, 1977, when a terrible windstorm struck that part of the state 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 penetrating 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 even 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 cooled and became 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 very steep pressure gradient through the Central Valley.

The air flowed in a clockwise direction around the high pressure system, forcing cool 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 very 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!

Trotter said, “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 criss-crossed 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.

Thankfully, El Niño made its appearance that winter, and the storm track shifted southward, producing above-normal rainfall and ending the severe California drought.

This week’s forecast

A weak 1,018 millibar low-pressure system will pass just north of our area today. This low pressure will produce extensive low to mid-level clouds along with fog and drizzle along the beaches.

Today’s temperatures will be on the cool side, only reaching the mid- to high 60s in the interior and coastal valleys. The northwesterly facing (Los Osos) beaches will range from the high 50s to low 60s, while the southerly facing (Avila Beach and Cayucos) beaches should reach the mid-60s with a little bit of sunshine. These temperatures are well below seasonal norms.

An upper-level trough will cross our area Monday morning, producing a deep marine layer with areas of drizzle. Monday will see another day of below- normal temperatures.

A steep pressure gradient will develop in the wake of this upper-level trough, producing strong to gale-force (25-38 mph) northwesterly (onshore) winds Tuesday.

A ridge of high pressure will build over the state Wednesday, producing night and morning northeasterly (offshore) winds.

This condition will produce a sharp warming trend with readings climbing over ten degrees Wednesday.

Building high pressure will bring temperatures to near to slightly above normal with widespread clear skies Thursday and Friday. Temperatures will range from the mid- to high 70s immediately inland from the coast to near 90 degrees across the interior. A cooling trend should develop next weekend.

Surf and sea report

Today’s 3- to 4-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 11-second period) will continue at this height and period through Monday morning.

The wind fields or wind fetch will shift further northward and will produce a 5- to 7-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 9-second period) Monday afternoon through Tuesday morning. Increasing northwesterly winds will generate a 7- to 9-foot (310-degree deep-water) sea and swell Tuesday afternoon and night.

A 4- to 6-foot northwesterly (300-degree deep-water) sea and swell (with a 5- to 9-second period) will develop Wednesday and will continue at this height and period through Friday.

Arriving from the Southern Hemisphere: A 1- to 3-foot Southern Hemisphere (190-degree deep-water) swell (with an 18- to 20-second period) will arrive along our coastline on Friday, increasing to 3 to 4 feet (with a 16- to 18-second period) next Saturday and Sunday.

Seawater temperatures will range between 48 degrees and 51 degrees through Friday.

Conservation tip

Green vehicles: For nearly two decades, Pacific Gas and Electric Co. has pushed for cleaner, more efficient vehicles for our customers. For information, please visit www.pge.com.

John Lindsey is a communications representative for Pacific Gas and Electric. He is also a local weather expert and has lived on the Central Coast for more than 23 years. If you have a question, send him an e-mail at pgeweather@pge.com.

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