Atmospheric river storms to soak Bay Area, Northern California — biggest in 9 months – Times-Herald

A series of three storms, starting late Tuesday night and expected to rain the most in nine months in the drought-stricken Northern California and Bay Area, surged off the Pacific coast this week, forecasters said. Announced on Tuesday. Two years characterized by record wildfires and dry conditions.

Two of these storms look like atmospheric rivers. A narrow, water-rich storm that plays an important role in the state’s water supply. The first to arrive late Tuesday night and set to continue into the Bay Area until Wednesday morning could be a mild storm. However, another form of Sunday night was upgraded to Category 5 on Tuesday and was the best on a 5 level scale.

Martilalph, director of the Western and Extreme Weather Center at the University of California, San Diego, said: “We are seeing prolonged rains and some heavy rains.”

According to the National Meteorological Service, a storm from Tuesday night to Wednesday morning combined with forecasts of light rain on Thursday will result in 2.5-3.5 inches of rain across the North Bay Mountains and 1-1.5 inches and 0.25 inches of rain in the Santa Cruz Mountains. It may rain. Up to 0.75 inches in most of the San Francisco Bay Area and Big Sur area.

After the largest Sunday storm of the three, total rainfall for seven days can range from 5 to 8 inches in North Bay, 3 to 5 inches in the Santa Cruz Mountains, and 1 to 3 inches in the San Francisco Bay Area. There is sex. Big sur area.

“This is definitely good news,” said Sarah McCorkle, a meteorologist at the National Weather Service in Monterey. “It’s hopeful to see something like this in October. Of course, things can change, but the fact that some systems are going through tells us how dry things were. Thinking about it, it’s a good start to winter. “

With total forecasts, storms can double or triple the average monthly rainfall in October in a few days. In San Francisco, for example, the historical average for October was .94 inches. It is 0.53 inches in San Jose and 1.13 inches in Auckland.

October is usually the beginning of the winter rainy season, but about half of the state’s rainfall falls in December, January, and February.

California desperately needs rain.

The last two years in Northern California have been the driest since 1976-77, measured by combined rainfall and snow.

Overall, 93% of California is in some drought and 87% is in extreme drought. Drought monitor in the United States, A weekly report published by the US National Oceanic and Atmospheric Administration, the US Department of Agriculture, and the University of Nebraska.

Genene Jones, a drought manager at the California Department of Water Resources, said this week’s rain wouldn’t hurt the overall water shortage because the conditions have been dry for so long.

“I don’t want to say it’s a drop in the bucket,” Jones said. “But we are just the beginning of the year of water. It’s a good start, but we need more to continue.”

According to recent estimates by the U.S. Geological Survey and the Department of Water Resources, Jones said the state would need to receive 140% of its annual rainfall this winter in order to obtain a normal runoff into the reservoir. .. It has been so dry for the past two years that much of the water seeps into the dry soil before the ground saturates and causes significant runoff into streams and rivers.

Reservoir throughout the state is dangerously scarce. The largest Shasta and the second largest Oroville were each only 22% full on Tuesday.

This week’s storm will dramatically reduce the risk of fires throughout Northern California and will probably end it in several places. They can pose a risk of landslides in some burn areas, especially the Dixie fire near Lassen Peak and the Caldor fire near South Lake Tahoe.

The rain is expected to be warm. The National Meteorological Service predicted on Tuesday that more than 6,000 feet of snow would fall 1-2 inches in central and northern Sierra until Wednesday morning. However, donor passes near Lake Tahoe, such as the Tioga Pass and Sonora Pass in Yosemite National Park, are projected to cover more than 5,500 feet of more than two feet of snow from Saturday night to Monday at 6 to 8 inches.

On Tuesday, Caltrans closed several major Sierra Nevada roads “until further notice.” Monitor Pass State Highway 89, Sonora Pass State Highway 108.

Ralph, one of the US experts on atmospheric storms, devised a scale for atmospheric rivers to be graded. This is based on the amount of water vapor in the storm and the length of time it travels over land.

In a typical year, California has about 10 to 15 significant atmospheric river storms. Ultimately, they account for up to 50% of the state’s rainfall.

Although they flow up to two miles above sea level, the atmospheric rivers, also known as the “Pineapple Express” storms when they occur in the subtropics, are the largest “rivers” on the planet. The largest atmospheric river storms carry twice as much water as the Amazon and 25 times as much water as the Mississippi River, which flows into the ocean.

California can be drought when high-pressure ridges block the river. It happened in the last drought of 2012-16. Large-scale atmospheric river storms in 2017 destroyed droughts, filled reservoirs, caused massive floods in downtown San Jose, and destroyed spillways at Oroville Dam.

Over the last two years, high-pressure ridges have deflected many of the storms from California, causing recent droughts. The last major atmospheric river storm in the Greater Bay area occurred on January 28, with 15 inches of rain on the Big Sur, 7 feet of snow on the Lake Tahoe area, and thousands of Santa Cruz Mountains. Many people have evacuated. Risk of landslides after the CZU Lightning Complex fire last summer.

Ralph said the record-breaking 2017 in most parts of California began with a flood in October.

“Of course, we can’t predict the rest of the winter,” he said. “But it certainly helps to start from a wet state.”

Atmospheric river storms to soak Bay Area, Northern California — biggest in 9 months – Times-Herald Source link Atmospheric river storms to soak Bay Area, Northern California — biggest in 9 months – Times-Herald

Related Articles

Back to top button