Friday, November 15, 2019

A little rain, followed by the big dry

November should be one of the stormiest, wettest months of the year in our region.

Not this year.

So far this month, we have only had about .76 inches, roughly 2.5 inches below normal.  Here is the plot of cumulative precipitation at Seattle (cyan is normal, purple--what actually fell)...pretty pathetic.
This weekend, a modest atmospheric river will bring substantial rain to British Columbia, but only the norther portion of Washington will get much moisture. Another storm comes in Monday.  But then it all dries out for an extended period of time....let's call it the big dry.  Very unusual considering the time of the year--with the last two weeks of the November being the wettest climatologically for our region.

The incoming atmospheric river looks mighty impressive on the latest infrared satellite imagery, drawing moisture all the way from the tropics.  Since it passes near Hawaii, I guess we can also call this a pineapple express.


The total precipitation through 4 AM on Monday is very impressive in British Columbia (over 5 inches in places),  but it fades progressively to the south.


But after one more storm late Monday/early Tuesday, things dry out.  Here is the total precipitation for the three days ending Friday at 4 PM.  Nothing over western WA and southwest BC.

And the highly prized European Center ensemble prediction  of accumulated precipitation anomaly (difference from normal) for the next 15 days, indicates much drier conditions than typical--by 2-6 inches.  Good for raking leaves (I hate soggy leaves).

Why this dry boon?   Persistent ridging (high pressure) over the West Coast (see below for 500 hPa--about 18,000 ft).  Orange shows much higher than normal heights/pressures.

Why is this happening?   The answer is clear: you have to expect fine weather after the Seattle Times does a big story on how gloomy it is here in Seattle.


10 comments:

  1. cliff i don't know if you know were lake roesiger is but it is showing towards near december 42 low 28 and snowing do and update on it

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  2. Are we going to see alot of fog under this high pressure ridge? It appears that this December will start off the same way as November did-bone dry. It seems we have had quite a few dry December's over the past 10 years or so. For sure Decembers 2009, 2011, 2013, and 2017 were drier than average. It looks like there's a good chance we can add 2019 to that list!

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  3. YAAAAAY! Seems like October and November are doing a flip-flop this year.

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    1. Not really. October at SeaTac was only .19" above normal for precipitation due to a 10-day wet period mid-month and temperature was a bit below normal for the entire month. The current pattern began the last third of October.

      https://www.wrh.noaa.gov/climate/monthdisp.php?stn=KSEA&year=2019&mon=10&wfo=sew&p=temperature

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  4. Cliff, Gloomy isn't the word I would choose especially if I was the city's newspaper. Instead, I always thought Seattle days can look like living inside a black and white photograph with fog, cloud cover, etc. (a favorite art form of mine).

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  5. Plastic microscopic sludge the size of the west coast residing around the mid Pacific slows down and deflects northward the surface currents. This puts the squeeze on the returning, northern Pacific currents producing a Bernoulli speedup towards our coast towards a bottle neck. (Basic fluid physics.) I suspect these Northern currents sheer into eddies and retain heat which maintains warm air currents in the Northern Pacific; air temperature moderation by the ocean is compromised. Developing storms follow the path of least resistance - further North than is normal.
    Let us also include in our models the Russian diverging of two rivers into the Arctic waters to open up shipping and the subsequent effects upon the Bering Sea temperatures. Anyone punching this into their (history based) models?
    Fukushima? egad! Does anyone know? What about the fifteen mile wide, 250 mile long rift in the Pacific that wrecked Fukushima? To my knowledge no one has looked at it for volcanic activity (heat) since the day.

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  6. "A little rain"? Back to: "Location is everything." I was stunned to find .98" in the gage this morning - but, hey-ho (and it's not over - I just looked at the radar).

    Dr. Mass - I'm curious: Is there a "rain shadow" map, and papers on the precipitation patterns of the Pacific Northwest?

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  7. PS - In respect to "rain shadow" records and research, if what exists is based on the samey-sameo LIMITED (banana belt) locations-sites, I suggest the matter is ripe for research. There's never been more credible data available in every respect (radar data, satellite data, GIS, SNOTELS, CoCoRaHS).

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  8. Is this the return of the Blog phenomena that was much written about in 2015? if so what does this mean for snow season in Washington and BC for 2019

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