Heavy Precipitation and the Mid-Winter Water Update for Our Region

Note: My next blog will be on the sudden stratospheric warming over the Arctic and the implications for the long-term weather forecast. Major changes in the large scale weather circulation in the offering!
__________________________________________

As promised, a potent atmospheric river has hit our region, with very heavy precipitation on the upwind (windward) sides of regional terrain.

Let be begin by showing you a satellite-based view of total atmospheric moisture from late yesterday.  Purple and red are the highest amounts.   Satellites can sense water vapor content based on the emission of radiation by water vapor.  

You can see the plume of moisture heading into us from the southwest.  Amazingly,  our moisture plume can be traced back thousands of miles to the western Pacific near the Philippines and Indonesia: the region of the warmest water on the planet, known as the warm pool. 

The map below shows the precipitation for the past 24 h (ending 8 AM).  Some locations on the south and southwest side of the Olympics have gotten 5-6 inches so far, as have some rain gauges in the mountains of SW Washington.  Around Seattle about 1.5 inches have fallen, while only a few tenths of an inch have wet the ground over northern Whidbey Island in the rain shadow.  Seattle already has had 5.12 inches this month and by the end of the day we will reach the typical monthly total (5.57 inches).  A whole month's rain in less than half a month!


Weather radars can be used as remotely sensing rain gauges by making some assumptions.  Here is the "storm total" for the past two days from the Camano Island radar.  You can see the profound rainshadow to the northeast of the Olympics, with about a tenth of an inch at its core.   But 3-5 inches not far away west of the Hood Canal.



Several of you have emailed me, asking about the current level of our reservoirs.  As of yesterday, Seattle's water supply was in good shape (see below), with above-normal cumulative precipitation, above normal snowpack, and much above normal water storage.   Today will provide a substantial water addition.



But what about the drought-sensitive Yakima River Reservoir System, so critical for agriculture in the east? (see below).  Currently above normal and WAY above last year.


And Washington State's snowpack is in good shape, as shown below and noted in previous blogs, and Oregon is just slightly below normal.


The bottom line:  water resources and snowpack are in good shape for our region at this point, something not surprising for a La Nina Year.

Many of you are asking about cold and snow in the lowlands.   I will talk about this in future blogs, but the latest forecasts are projecting a turn to radically cooler conditions by the end of the month.  As a teaser, here is the predicted 7-day snowfall ending January 29th.  Yes, lowland snow.  But don't get too excited yet.... forecast skill is marginal that far out.   Seattle and other municipalities should make sure the plows and salt supplies are in good order.

Comments

Post a Comment

Popular posts from this blog

The Time of Year You Can See the Air Move

Image
  Most of the time, you can not see the air move.   You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere.   Cottonwood season.  And we right in the middle of it.   Being cottonwood aware is of particular value this year.  It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers.   A million seeds weigh about 3 pounds.  Yes, each seed and tuff weights about .000003 pounds.   And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly.   So slowly that they are excellent markers for the three-dimensional flow of the
Read more

Why so little lightning in the Pacific Northwest? And a very nice weekend ahead.

Image
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why?    My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers:     Like the podcast? Support on Patreon 
Read more

Strong Atmosphere River Heads into British Columbia and Southeast Alaska

Image
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska.   And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor.  You can see the current of moisture extending from near Hawaii into central BC.  This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California.   A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
Read more