A strong Christmas atmosphere. There’s no drought in California this year — is Watt surprised?

From Cliff Mass Weather Blog

cliff mass

One of the most commonly used terms in the media is “atmospheric river.” Yes, even more hyped than Bomb Tornado. But there will be one atmospheric river of note this week… which I'll discuss below.

Atmospheric river overuse

Although the term “atmospheric river” was first used in the late 1990s, the phenomenon has been known for decades: a stream of warm, moist air guiding cold fronts associated with midlatitude cyclones.

Virtually every midlatitude cyclone/low center has such moist air. To understand how ubiquitous atmospheric rivers are, here is a map of today's water vapor plume (red and orange) and its altitude at a pressure of 700 hPa (think of it as a pressure of 10,000 feet). Many atmospheric rivers, most of which are associated with the low center and its associated fronts.

But not all atmospheric rivers are the same size.

Some particularly heavy rainfall will hit northern California and southern Oregon this week, unleashing intense amounts of precipitation as regional topography forces moist areas to rise.

One of the best measurements of the strength of atmospheric rivers is Integrated Water Vapor Transport (IVT), which is calculated by determining the amount of water vapor transported by atmospheric rivers over a period of time (essentially wind speed multiplied by the amount of water vapor in the air). .

Here's a picture from Wednesday night's IVT. Wow…that’s such an atmospheric river!

The result this week of this atmospheric river and some of its weakened cousins ​​will be a lot of rain on the West Coast.

In the 72 hours ending at 4 p.m. Thursday, large precipitation totals will occur (according to the University of Wisconsin model) from northern California to British Columbia, with northern California/southwestern Oregon being the hardest hit (more than 5 inches ).

Here are the totals for Eurocentric models as of the end of the year. More than a foot of rain could fall in many places.

Remember all the talk of permanent drought in California during global warming.

Well, such predictions did not turn out well.

Most California reservoirs are above normal now…and that was before this week's heavy rains (see proof below). With the coming rains, reservoir levels will soar.

Snow conditions are good across the West Coast. (see below).

In short, the water supply situation looks very good for the coming year.

Relevant