Extended Extreme Weather Event Cucumber May Break California Drought

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Current watches and warnings. Graphic courtesy of NOAA.

Current watches and warnings. Graphic courtesy of NOAA.

Decoded Science has named a new extreme weather event: Cucumber will affect the west coast of the United States for at least a week, and probably much longer.

The event will consist of a series of storms which will bring heavy rain to coastal areas as far south as Los Angeles, and more importantly (as far as the drought is concerned) heavy snow to the Sierra Nevada Mountains.

In addition, winds will reach hurricane force in the mountains and up to 60 miles per hour near the coast. Waves up to 20 feet high will hit the beaches of southern California.

Finally, areas affected by fires last summer will be vulnerable to mudslides and debris runoff.

The Jet Stream Has Done A 180 Degree Turnaround

The jet stream forecast for next week shows the pattern unchanged. -- more storms for the west coast. Forecast courtesy of NOAA.

The jet stream forecast for next week shows the pattern unchanged. — more storms for the west coast. Forecast courtesy of NOAA.

For the better part of a year, the jet stream has featured a high pressure ridge over the Gulf of Alaska, which in turn forced a trough (dip) in the middle of the US. When this trough became pronounced last winter, it created wild weather across the eastern two-thirds of the country.

This winter began with a continuation of the pattern, producing Extreme Weather Event Artichoke — a record-cold-producing outbreak of frigid air from Canada.

Corollary effects were many feet of snow in the lee of the Great Lakes and a nor’easter which brought snow to the northeast Megalopolis.

Now Mother Nature has flipped a switch, and the trough and ridge pattern is reversed. A massive low pressure system covers Alaska and the adjacent waters at all levels in the atmosphere.

The main branch of the jet stream has been shoved southward, and storms rippling along the axis of the stream will reach much lower latitudes.

The Precursor To Cucumber

Recent storms have inundated the west coast as far south as San Francisco, with beneficial rains down to the Mexican border. With the pattern now well-established, storms will tap the unlimited moisture of the Pacific Ocean and bring deluges even farther south.

Drought-Breaking Potential Of Cucumber

Though heavy rain has fallen in the areas hardest hit by the California drought, they have not alleviated the dryness in a significant way. That is because the water ran off quickly. Most of California’s water supply originates with snow in the Sierra Nevada Mountains — both from direct runoff and through aquifers. Recent storms have not brought substantial snow to the mountains; Cucumber will.

Precipitation total forecast for the next five days. Graphic courtesy of NOAA.

Precipitation total forecast for the next five days. Graphic courtesy of NOAA.

Who will Get The Rain From Cucumber?

Coastal portions of northern California and southern Oregon, as well as mountains up to the snow level, will receive the maximum amounts of rain. But the most trouble is likely to occur farther south, where summer fires have denuded hillsides and the water has a clear path to erode mud and debris. In the locally poorly-drained parts of cities, road flooding will also be a concern.

Who Will Get The Snow From Cucumber?

The snow level in the Sierras is currently at 8,000 feet, but as the jet stream pushes south allowing the colder air to penetrate the lower elevations, the snow level will come down to around 5,000 feet. It is very likely that heavily-traveled Interstate 80 between Reno and Sacramento will be closed in the region of Donner Pass at 7,000 feet..

Who Will Get High Wind From Cucumber?

The National Weather Service has issued Storm Warnings for the coastal waters from northern California to the Canadian border. A storm force wind is over 55 miles per hour.

Gusts to hurricane force (over 75 miles per hour) are likely along the coast or just offshore, and sustained hurricane force winds are possible in the mountains, especially where wind is funneled through passes

Because of the expected intensity of the wind and snow, the National Weather Service has issued blizzard warnings for portions of the mountains between central and northern California. A blizzard is a combination of low visibility in snow combined with high winds lasting more than three hours.

Who Will Get Destructive Surf From Cucumber?

Though the most intense winds from Cucumber will be confined to northern California and  Oregon, wave heights also depend on the contour of the bottom of the sea and the ocean currents. The highest waves from Cucumber are forecast to reach the southern California coast on Friday and measure over 20 feet. Beach erosion is expected.

Needless to say, swimming, boating, and surfing will be beyond hazardous.

Cucumber begins on the northwest coast. Analysis courtesy of NOAA.

Cucumber begins on the northwest coast. Analysis courtesy of NOAA.

When Will Cucumber Happen?

Wind and rain have begun in coastal Washington, extending south and east over the next couple of days. Rain will reach San Francisco by tonight and Los Angeles by late Thursday.

This will be a long-duration single event, lasting through Friday in most areas. And it isn’t over then.

After a brief period of quiet weather, another storm will strike late in the weekend, probably followed by others. Until the weather pattern changes again, Cucumber will continue to wallop the west coast.

Is Cucumber Connected To Global Warming?

A jet stream flow dubbed the Pineapple Express, which brings moisture from the subtropical Pacific to the west coast of the United States, is not uncommon.

However, Cucumber will be unusual for its intensity and duration; long periods of persistent weather are consistent with the climate change that is expected to accompany higher greenhouse gas levels in the atmosphere.

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