It has been often said that it is darkest before the dawn.
Well folks, we have been very dark and dawn is a long way off.
The image from the Seattle SpaceNeedle at noon Wednesday, was dismal at best (see below)
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It has been often said that it is darkest before the dawn.
Well folks, we have been very dark and dawn is a long way off.
The image from the Seattle SpaceNeedle at noon Wednesday, was dismal at best (see below)
You did not have to travel to Hawaii this morning to experience subtropical warmth or tropical-intensity showers. It was here in the Pacific Northwest.
As a substantial atmospheric river interacts with our terrain, large amounts of precipitation have fallen during the last 36 h, with extreme contrasts over a few miles.
Before are the 36-h totals. Some locations over NW Oregon and SW Washington got to around 8 inches...and more is coming. 6-7 inches in the Cascades.
The air over us has felt subtropical. The temperatures this morning have gotten into low-60s (see proof below). The dewpoints (a measure of water vapor content) rose into the mid-50s.
If some folks thought that a strong El Nino would protect the region from heavy rain before the new year, they were mistaken.
A substantial atmospheric river-- a narrow current of high-water vapor content-- will be heading right into our region starting Monday evening, and the precipitation amounts will be substantial.
Let me show you.
Below is a forecast map of total water vapor content through a vertical column of the atmosphere at 10 PM Monday. The blues and light pinks indicate the largest values.
Atmospheric rivers like this tap large amounts of water vapor in the tropics and subtropics. Moisture also converges into the "river" from the sides, not unlike the water of small streams flowing into a major river along its path.
It is a measure of how much water vapor is being transported by the wind and is better correlated with rainfall potential.
Here is the IWVT at the same time as the image above (10 PM Monday). Blues indicate large values.
Below is the forecast total precipitation through Monday at 4 AM (start at 4 AM Sunday). Precipitation for the whole region, but heaviest over the Oregon terrain.
Do you want to see something very, very impressive? Go to Snoqualmie Falls on Wednesday. You won't believe what you will see.
One thing I can guarantee you. The City of Seattle will be able to bring the water level of its reservoirs way up and there won't be any talk of low water levels. Take a long shower if you like....😔
Considering that we are in a strong El Nino period, which will probably reduce snowpack in the spring, reservoir managers should try to save as much of this water as possible.
After a period of high pressure, weak winds, fog, low clouds, and little precipitation, the weather in our region is about to get quite intense and interesting.
Strong winds will soon buffet western Washington and heavy snow (multiple feet) will fall across our regional mountains.
A front went through this morning and our region is now in moist, unstable northwesterly flow as shown by the visible satellite image this morning (below). The white and dark areas offshore are convective showers and you can see the intense cloudiness on the western slopes of the Cascade associated with substantial snow showers.
White-out conditions are now occurring in the mountain passes, illustrated by the WSDOT pass cam below.
Through 4 PM the Cascades will get as much as 6-12 inches, and eastern Washington be whitened.
The total through 4 AM Saturday is much more impressive, with 1-2 feet over higher terrain.
And then there are the winds.....
Some of you will experience power outages overnight. I am charging up my devices as soon as I get home from the UW!
A low-pressure system will move eastward to our north, creating a large north-south pressure difference across western Washington (see forecast surface pressure map for 4 AM Saturday). That means strong winds.
The latest NOAA HRRR forecast (available on the City of Seattle Windwatch site built by the UW) predicts powerful winds overnight.
Below are the forecast gusts at 1 and 3 AM. First, the coast and NW Washington will get hit and then Puget Sound, some with winds exceeding 50 mph. Such winds guarantee some power outages.
The only good thing is that many trees have lost their leaves, making them less vulnerable
The visible satellite image this morning was stunning.
Low-elevation clouds covered nearly all of Washington, except for the highest elevations (see image)
And this cloudy murk was cold, with much of the state below freezing (see minimum temps this morning). Freezing fog was widespread.
Cold, cloudy, foggy and icy. Yuk.
What can you blame for this unpleasant situation?
Persistent high pressure. A strong ridge of high pressure aloft.
The upper-level map (500 hPa pressure, about 18,000 ft) on Sunday evening shows the situation (see below).
Translation: the high-pressure aloft was very strong and persistent.
In the summer, such a pattern would give us a heat wave.
But in winter we get a cold wave! But why?
High pressure is associated with sinking air aloft, which kills middle and upper-level clouds.
Without clouds, the Earth can effectively emit infrared radiation into space. There are no clouds to get in the way! Nights are very long and the sun is wimpy, so solar heating is weak.
The inversion is a very stable feature and prevents the mixing of air at lower elevations. It protects the low-level cold air from mixing out.
Want to see the inversion? Here is a plot of temperature (red) and dew point on the Washington coast at Quillayute on Tuesday morning. Temperature is increasing with height at low levels. An inversion!
And it is even worse than that. The top of the clouds reflect solar radiation back to space, enhancing cooling. Clouds are good emitters of infrared radiation. More cooling. Low clouds are cooling machines!
So if you want to blame the cold, cloudy weather on something, blame the high pressure!
We escape this run-away cooling in the summer because of the far stronger solar radiation, which is able to heat the surface and destroy the low-level inversion.
A number of media stories have been talking about King Tides and flooding during the past few days, and I have gotten several emails from worried readers.
So let's talk about the reason for King Tides and evaluate the threat.
The highest tides of the year...the King Tides... typically occur this time of the year for two reasons.
First, the astronomical setup is ideal, because the Earth is closest to the sun around the New Year.
Second, this is the stormest time of the year, with Pacific cyclones associated with low pressure, and low pressure causes the water level to rise.
Monthly high tides, also known as spring tides, occur twice each month when the sun, moon, and earth are aligned.
How much? When sea level pressure falls by 1 hPa (or 1 mb), the water level rises by about 1 cm. So a deep storm that causes pressure to fall by 25 hPa can result in a water rise of around 25 cm or roughly 10 inches.
Now let's look ahead.
Take a look at the predicted astronomical tide levels for November, December, and January below (the green line is today). For November, tides will max out during the next few days around 12.5 ft above Mean Lower Low Water (MLLW), the average level of the lowest tide for each day computed over a 19-year period.
December will have a number of days (mainly during the middle and end of the month) that will get to the same level. Mini-King tides.
Mid-January will bring max tides that are a bit higher...around 13 feet....so that will be the time of greatest vulnerability.
I am very sad to report the passing of Steve Pool, past chief meteorologist at KOMO TV, and a dear friend for many decades.
Steve was one of the most exceptional and generous individuals I have ever known.
A brilliant communicator. A kind and generous soul. A highly intuitive and insightful meteorologist. And someone who gave so much to our community.
I first got to know Steve during the mid-80s, when I got a call from KOMO-TV asking whether I would instruct him in meteorology; he had just taken on weather responsibilities at the station.
For the next year and a half, Steve and I worked together intensively to cover the essentials of meteorology, Northwest weather, and weather forecasting. An extraordinarily bright guy, Steve quickly mastered a huge volume of weather knowledge and became a very able local weather analyst and forecaster. He was determined to get his forecasts right, and we would often talk during the late evening before his 11 PM broadcast.
As I got to know him better it became clear to me that he was a preternaturally talented communicator and that I had a lot to learn from him in that domain.
And I mean much more than a smooth delivery. He had the ability to connect with people. A disarming smile, great empathy, and a personality that was upbeat and sunny. I don't think I ever heard him talk ill of another.
It has been often said that it is darkest before the dawn. Well folks, we have been very dark and dawn is a long way off. The image from th...