• Since Wednesday, a torrent of showers has been falling on California, accompanied by very strong winds.

    The US Weather Service (NWS) forecast for Thursday gusts likely to reach 110 km / h and very intense rains with more than 10 centimeters of precipitation expected in San Francisco Bay.

  • California authorities have called on residents of certain neighborhoods to evacuate or barricade themselves.

    Wednesday morning, more than 186,000 people were still without electricity.

  • The consequences of these rains are amplified by a succession of storms which have made the soil impermeable, which can cause sudden floods, falling trees or landslides.

    20 Minutes

    takes stock of the progress of the storm.

“We are very worried.

Like San Francisco resident Deepak Srivastava, millions of Californians have been ordered to evacuate or barricade themselves in their homes since Wednesday.

A week after the passage of a "cyclone bomb", which literally froze the northern United States with temperatures below -31°C, a second full force strike in California since Wednesday, bringing violent winds and torrential rain.

Since the beginning of winter, California has suffered storm after storm.

“This could be the toughest and most impactful series of storms in California in the past five years,” said Nancy Ward, California Emergency Services Director, on CNN.

20 Minutes

returns this Thursday to this extraordinary storm.

When did these torrential rains start?

On Wednesday, the first heavy rains fell on the American west coast.

Northern California, especially around San Francisco and Sacramento, is the hardest hit region.

The United States Weather Service (NWS) has predicted winds likely to reach 110 km/h and very intense rain with up to ten centimeters of precipitation expected in San Francisco Bay, as well as more than a meter of snow on the Sierra Nevada mountains.

On Wednesday, the wind blew over 130 km/h in Nicasio Hills.

In some counties in the region (Mendocino, Santa Cruz, Santa Clara), several roads were cut due to flooding, falling trees or landslides.

During the night from Wednesday to Thursday, 178,000 homes and businesses were deprived of power.

This Thursday, at 10:30 a.m., more than 186,000 people were still without electricity, according to the PowerOutage site.

As of Wednesday, 80 flights to or from San Francisco airport were canceled, according to Flightaware.

What arrangements have been made by the local authorities?

The authorities warned the population against landslides and floods, warning that this storm was capable of killing people.

In view of the forecasts of meteorologists, the local authorities immediately called on the population to seal themselves off, or even to evacuate, as in the district of Santa Cruz.

“If you live in this red zone … you better: play it safe, evacuate and obey order,” said Santa Barbara County First District Supervisor Das Williams, referring to the dozens of deaths. caused for five years by these winter rains.

California Governor Gavin Newsom declared a state of emergency on Wednesday morning to facilitate the emergency response and streamline the reaction of authorities in the event of an incident.

San Francisco has set up an emergency operations center and halted the circulation of its famous cable cars.

"If you have no obligations to be outdoors in San Francisco, avoid going out on the road," warned Rachel Gordon, an official with the city's public works department.

Thousands of sandbags have been distributed to residents of at-risk areas.



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Bars and restaurants remained closed on Wednesday and some San Francisco residents were asked to work from home.

City firefighters reported several falling trees on Wednesday morning and some minor flooding, before the heart of the storm arrived on Thursday.

Why do these repeated rains cause so much damage?

The causes of this storm, namely a low pressure system, are fairly standard: two masses of air, one very cold and the other tropical, meet, causing the atmospheric pressure to drop.

A depression is a system of low atmospheric pressure, often synonymous with bad weather: its dynamics lead to updrafts that cause clouds and precipitation.

Unlike a simple episode of rain, here the atmospheric pressure has dropped by 24 hectopascals (hPa) in twenty-four hours, according to the NWS.

This is called an "explosive genesis" (or "cyclonic bomb").

Additionally, the rain in recent days is coming from an “atmospheric river,” a narrow, river-like band in the atmosphere that carries huge amounts of moisture from the tropics.

But in this rainy episode, the "cyclonic bomb" and the "atmospheric river" are not the only ones responsible for the consequences of the current torrential rains.

Northern California is still suffering the effects of a series of storms.

The latest swept through on New Year's Eve and caused landslides and power cuts.

At least one person has died after being trapped in their car by flooding. 

On December 31, San Francisco recorded the second rainiest day in its history since the measurement was launched, with 14 centimeters of precipitation.

However, the soils of the region, drained by the drought that has hit the American West for two decades, are struggling to absorb a new deluge, which increases the risk of flash floods.

“Usually, amounts of rain like those expected this week would not have a significant effect.

But last weekend's rains saturated the ground in much of California, meteorologists tell The

New York Times

, leaving it like a damp sponge and making it more susceptible to flooding and rapid runoff.


our dossier on global warming

How long before the rains stop?

In its latest bulletin dated Thursday morning, the National Weather Service, the equivalent of Météo-France in the United States, predicts, after a peak in precipitation on Thursday, a slight lull for the day on Friday.

However, the rains should start again on Sunday, and last until next Tuesday at least.

According to meteorologists, the series of storms currently battering California is not about to stop.

“We are expecting another over the weekend,” said meteorologist Matt Solum.

And then potentially multiple storms for the next week.

And possibly the following week too.



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