The Seattle Times had a front page article today saying half of Seattle's residents are depressed and by a small margin we are the most depressed major city in the U.S.!
Although we expect that the Pacific Northwest will experience a wet, cool, snowy La Nina winter, the opposite is projected for California because of La Nina. Furthermore, California is going into its "wet season" after a dry fall, and its reservoir system is well below capacity.
I will bring you up-to-date on the California water situation in this blog.
Let's start with the precipitation anomaly for the last two months: how precipitation over California differs from normal for the past 60 days. For nearly the entire state, precipitation has been below normal, but the normally arid southern portions and far western sections only down by 0 to 3 inches. In contrast, the Sierra Nevada is down 3- 9 inches and some portions of the mountainous northern portion of the State are as much as 9-15 inches less than normal.
It is interesting to look at the percentage of normal precipitation for the same period. YIKES. Much of California has received less than 25% of normal for the last two months, particularly southern CA. This shows you the dangers and potential deceptive impressions of percent of normal plots....in places of little precipitation, just a modest shortfall can create scary low percentages of normal. But the implications of such small deficits may not be significant.
And then there is the impressive California reservoir system, which has the capability of holding MULTIYEAR water supplies. Very different than our region, where our reservoir capacity if far less (generally a few months to a half year). Below is the latest CA reservoir situation. The largest reservoirs in the North (e.g., Shasta and Orovile) are significantly below normal, while the reservoirs to the south are near normal.
But to get more insight into the filling of the critical northern reservoirs, here is a plot of the current cumulative precipitation compared to normal (blue shading) for this (blue line) and other years. You see the problem-- only about 30% of normal this year and just above the historically dry 1976-1977 uber drought year. And last year was dry year as well...but considerable more than this fall.
Note: I will be having a specific online zoom session for my Patreon supporters on Saturday morning at 10 AM. I will talk about the effects of the eastern Pacific BLOB on Northwest weather and will answer your questions. Patreon information:
Our snowpack percentage of normal has declined quite a bit the last week or so, but don't be too concerned. Bountiful snow is coming.
Here is the latest percentage of normal snowpack from the wonderful SNOTEL website. Slightly below normal in Washington and generally near normal overall in Oregon. Below normal in Idaho.
Remember a few weeks ago when we are 400% of normal?...it couldn't last. Climatological snowpack is increasing and we had a dry period for a while.
If you compare our snowpack to a year ago, we are actually doing much better than 2019 (2019 is left, 2020 is on the right). Hugely more this year (you are looking at SWE, Snow Water Equivalent, the depth of liquid water that resulst from melting the snowpack at a location).
La Nina is strengthening and this has a lot of implications for our upcoming winter.
As noted in earlier blogs, La Nina is associated with colder than normal water temperatures in the central and eastern tropical Pacific. This cold water has global effects, changing the atmospheric circulation around the globe.
Let's start by looking at the current sea surface temperatures anomaly (difference from normal) around the world (below). Blue indicates cooler than normal temperatures and there is plenty of that color along the equator along the central and eastern Pacific--that is the sign of La Nina.
And the predicted snowfall for the period is bountiful.
I often get emails and questions about clouds. People are particularly interested in learning how to identify clouds and to understand what they imply about upcoming weather. What is meant by the arcane compound names, such as altostratus, cirrostratus, or the intriguing altocumulus lenticularis?
To address these questions, I am going to write series of blogs, with this being the first, the reveals the intricacies and power of cloud identification. Knowing about cloud identification will change your life...in a positive way.
Modern cloud identification goes back approximately 220 years to the work of Jean Baptiste de Monet Lamarck in France and Luke Howard in England in 1802-1803.
If there EVER was a year we needed a break from the cool, cloudy murk of the Northwest mid-winter period, this is it.
Sun and warmth that allow folks to get outside in healthful air to enjoy recreation and exercise
Sun and warmth that would facilitate outdoor eating during this COVID period when inside dining it closed.
Sun during the period of earliest sunsets (around 4:18 PM today in Seattle)
The weather gods have heard your cries and has provided deliverance, and as their close follower and scribe, let me tell you what they have done for you.
To begin, the solar radiation during the past week (November 29-December 5) has been the greatest on record for several stations (although admittedly the records are only a decade or two long for this parameter).
For example, at Seattle, the WSU AgWeather site (in the field below the UW) enjoyed more sun in this period than any other (see below), with a hefty daily average of 5.03 Megajoules per square meter (Mega=million, Joule is a unit of energy. Some years have had HALF as much!
The plot of solar radiation on top of the UW Atmospheric Building for the last three days is enough to make one smile, with the last two days being almost perfect cosines (meaning full radiation), reaching about 6.3 megajoules the last two days. No wonder some students were sunbathing on the UW quad!
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The sun was also associated with unusual warmth leading to a number of daily high temperature records being broken, such as:
Here is a plot of the some of the high temperatures yesterday around the region (click on figure to enlarge). 60F or more at several sites and even lower 60s south of the Olympics. 61F on the coast.
Looking at the temperatures in Seattle for the past two weeks compared to normal (below), shows we have exceeding the normal highs (purple lines) day after day, in some cases by 5-10F.
And the first 5 days of December was one of the driest on record!
The satellite imagery at 1 PM for the past two days shows the generally clear skies west of the Cascade crest and over high terrain. The only persistent cloudiness is found in the lower elevations of the Columbia Basin. Such low clouds are the price they pay for the heat and sun of the warm half of the year. Weather gods obviously think this is reasonable and so should you.
So why have we enjoyed this sunny, warm bounty?
Because their has been a very persistent and strong upper-level ridge of high pressure over our region. Such ridges produce sinking motion that evaporate clouds and warms the atmosphere above us.
To illustrate, here is a map of the ANOMALY (difference from normal) of the heights of the 500 hPa pressure surface (about 18,000 ft above sea level) for the past week. Yellow and red mean higher than normal (anomalous ridging). We have a nice ridge feature center centered over Washington!
But wait! It is even better than that! The upper level high is associated with high sea level pressure over eastern Washington (see sea level pressure map for yesterday afternoon below). Large difference in pressure across the Cascades that produced powerful EASTERLY (from the east) winds above the surface. As air descended the Cascades and Olympics, it warmed more by compression and prevented the development of fog and low clouds (which can happen with high pressure overhead)
My new podcast is out and I provide a detailed forecast for this weekend and next week, including Christmas Day. And then I turn to the gre...
