March 25, 2023

A Powerful Coastal Storm Approaches

On Monday and Tuesday, a powerful Pacific cyclone will intensify off the northern California/southern Oregon coasts.   A storm that would be notable in mid-winter, but very unusual in late March.

Below is the forecast sea level pressure chart for 2 AM Tuesday morning.  Also shown are the near-surface wind barbs and low-level temperature (shading).  

Just wow.   A very deep low-pressure center (985 hPa) with a huge gradient of sea level pressure, which means strong winds.  It almost looks like it has an inner eye!

A simulated cloud field for nearly the same time is downright scary (see below).  As you might suspect, the low center is in the middle of the swirling cloud bands.  Looks like something out of a science-fiction movie.

With such strong pressure gradients (pressure differences over distance), you can expect powerful low-level winds.   Below are the predicted wind gusts for the same time as the pressure analysis above.   A ring of strong winds surrounds the low, with the most powerful gusts to the west and south of the low center (as high as 60 knots, orange color).  

This structure is classic for strong marine cyclones.  The strong wind area is something called "the poisonous tail of the bent-back occlusion.'

Needless to say, if you are in the maritime industry it would be better to avoid being offshore Monday through Wednesday.

The extraordinary thing about this low is that it will spin offshore for an extended period, slowing weakening over time (the forecast map 24 h later is shown below)

As I noted above, such a low off the coast is unusual.  The map below gives some information on how unusual (colors).  The light pink indicates pressures that are more than 4 standard deviations from average (normal) values.   That is rare.

As you are probably sick of me pointing out, this situation reflects the anomalous atmospheric circulation we have "enjoyed" for the last month or so, with the jet stream going far south of its normal location.

Finally, with this low going south of us, so will the weather action for the next few days.  As a result, there will be very heavy rain over central and northern California (see below).    Yes, they are getting our water.

A few individuals were unhappy that I noted that the drought is over in California.  Well folks, the objective evidence is absolutely clear:  the drought is finished.  Kaput.  You can speculate why some people don't want to accept this.  Take a look at the graphic below if you have any doubts.  Normal is the gray, the yellow is this year.  Just stunning.

March 23, 2023

Cool air and snow showers on Friday for the western lowlands. More crazy stuff in California.

 No, there won't be accumulating snow near sea level, but don't be surprised if you see a few flakes west of the Cascade crest on Friday,

The visible satellite image this morning (below) shows a strong spring-time front about to make landfall on the coast, with a swirl of clouds associated with a low-pressure area evident offshore.  To the west, you can see the mottled, white and dark cloud areas associated with great instability, instability caused by cold air passing over warm water.    That air is our future.

This area of cold air is coming to us all the way from Alaska, as shown by a wider-area satellite image.  Call it the Aleutian Express.

The trouble for low-elevation snow lovers is that this maritime air (called a marine polar, MP, air mass) is generally too warm for any lowland snow.   But it is the perfect pattern for heavy snow in the Cascades.

Below is the forecast SNOWFALL total through 11 PM Friday. Some very light snow south of Tacoma, with more over southwest Washington.   Not only will the temperatures be marginal, but with the flow off the ocean being northwesterly,  Puget Sound will be rain shadowed (or snow-shadowed) by the Olympics.

The Columbia Basin will also be rain shadowed, but the mountains will enjoy as much as a foot of new powder.

On Friday and Saturday, the lowlands will not get above the upper 40s, substantially cooler than normal.

California Madness

It is hard to believe, but ANOTHER powerful, record-breaking spring storm is being predicted for California.  Below is the forecast sea level pressure and surface winds for 11 PM Monday, when a deep, intense low center will approach the coast north of San Francisco.

Will California get heavy precipitation from this system?   Do kids like ice cream?

Take a look at the forecast precipitation totals through Wednesday morning. 3-7 inches more precipitation over the Sierra Nevada and northern CA.   Perhaps the U.S. Drought Monitor will FINALLY drop severe drought over northern California.  Just silly.

A Powerful Coastal Storm Approaches

On Monday and Tuesday, a powerful Pacific cyclone will intensify off the northern California/southern Oregon coasts.   A storm that would be...