November 28, 2011

Climatologically, The Worst of Winter is Over!

Yes, you read that right.

The last week or two of November is climatologically the worst period of the year by many measures.   For example, consider the average precipitation per day at Sea-Tac Airport (below).  It peaks in last November and most of December is a drier.


Or how about extreme daily precipitation at the same location?


Big peaks in November and a radical reduction in extreme precipitation in December. 

Just like clockwork there is going to be a major break in the coming up this week, but first we have to get through one more storm. A low center and accompanying clouds and precipitation is moving towards us from the northwest and should bring precipitation to the region late tomorrow and Wednesday AM.  You can see it off our coast in this satellite image:


This system should be unremarkable. After that a very strong ridge will build northward into the eastern Pacific and will remain in place for at least a week.  You heard me...a week.

Like Wednesday morning

Thursday morning


 Friday morning
Saturday morning


You get the idea.  And we will have lots of sun...and some fog in the AM.  The biggest threat to your life and safety will be ice on the roadways.  Will we have another big storm...of course we will. And a good chance of some lowland snow.  But ON AVERAGE things typically improve as we move out of late November into December.

The National Weather Service has this regime going into next week...here is their latest 6-10 day precipitation forecast:  below normal in the West.


 This looks like a good time for local meteorologists to go on vacation.  Or to rake some leaves.

PS:  I know "official" winter starts on December 22 and ends in March.   The point is that calendar winter is really quite different than meteorological winter in many parts of the country...and we are a good example of that.    Around here the end of February could really be considered the end of winter....sun is much stronger, far less weather systems, chance of flooding goes to near zero, etc.  And the grass starts growing again on the west side of the Cascades.  When I have to mow my lawn, winter is over..period.

18 comments:

  1. Chilly at night and bright during the day. Should be good star gazing weather and a good time to get in some lowland hiking. Good news.

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  2. The worst of winter might be over... but it will take until next July to have consistently nice weather!

    Upcoming dry period notwithstanding.

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  3. This comment has been removed by the author.

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  4. Wished we could see the next storm coming in, but what's been up, or rather 'down', with the Langley Hill Radar? It's gone down several times over the last few weeks. Since it's from one of those 'pre-owned' lots, did we buy a Lemon? ;^)

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  5. The sooner the Meteorologists take the vacation the sooner the snow will fall. Or that suprise blizzard. Get to the vacation guys!!

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  6. Excellent blog, but I have to point out that technically winter hasn't even started yet. We've got another three weeks or so of fall.

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  7. Regarding the end of winter in the NW: I've often thought the weather better in February than March. I don't know if weather records bear that out.

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  8. My observation as to what is a serious winter snow storm:

    Foot or more of snow, that lasts upward a week

    School cancelled for two or more days

    Cold enough that pipes freeze for the unprepared

    Second observation: At my elevation of 400 feet this does not happen after the end of January, at friends place at the 1000 foot level it can happen into March.

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  9. Cliff, what's the deal with the Langley Radar? Just as a previous post by Jamesdeanreeves, I'm wondering, did we get burned with a 'Lemon Radar unit'?

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  10. I was just wondering if the Coastal Radar has been reset to zero degree elevation angle yet?

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  11. Last year winter was definitely not over after February though! Geeawd, April was terrible.....

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  12. Cliff,
    I couldn't help noticing that this blog was almost the exact same blog that you wrote one year ago.
    We had just got off a big week of storms like this year (except last year was snow) and we were looking at a dry stretch (except this year it looks longer and more sun).
    I hope that just like last year the worst of winter isn't over and there will be plenty of rainy, windy, snowy, and cold spells in the following months. The point of winter is to listen to the wind howl at night or pray for the temperature to drop two degrees so you can get snow.
    If I see bright suns in every spot on the long range forecasts for the remainder of the year, I might go crazy.

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  13. I don't care that the "worst" is over. I'd rather have some weather events (read: variety) than the never-ending wretched sameness we seem to increasingly endure here in the fourth corner.

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  14. Here are some wet streaks,
    I brought up consecutive days with five hundredths or more for Sea-Tac, interesting is the wet streak in October and ending in April this past spring.

    SEATTLE TACOMA INTL AP (KSEA)
    Consecutive Days
    Precipitation > 0.05 inches
    Years: 1948-2011

    Rank # Days End Date
    1 18 10/31/1956
    2 18 2/ 7/1953
    3 17 11/19/1963
    4 16 1/ 3/2006
    5 16 2/11/1990
    6 15 4/ 7/2011
    7 13 12/27/1972
    8 12 11/13/2006
    9 12 3/ 4/1994
    10 11 2/ 4/2006
    11 11 1/23/1999
    12 11 2/ 2/1992
    13 11 12/22/1982
    14 11 12/ 2/1955
    15 11 12/24/1950
    16 10 1/ 2/2009
    17 10 1/14/2006
    18 10 3/16/2003
    19 10 12/18/2002
    20 10 12/13/1996

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  15. Correction--that query was for more than five hundredths. I'd meant to bring up greater than or equal to 0.05" but no matter...
    The point was that if you measure winter only by periods of persistent rain, you can get these long stretches Oct-April, shorten the query to a week or ten days maybe Sept-June.

    That said...my own feeling about what constitutes winter in Seattle, is when the metro area is most likely to see some snow. I'd peg that as December through mid-February, but then you have outlier events such as November
    '85. Cliff mentions prolonged events like that come along once a decade...
    http://cliffmass.blogspot.com/2010/11/is-seattle-ready-for-snow.html
    --I seem to remember pulling up in the database about twenty stretches of genuine prolonged winter weather at Sea-Tac. You can lose events from the list too, say, if you query days of consecutive snow on the ground--and then one day in the middle of a streak it happens to melt off at Sea-Tac etc etc. But I digress.

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  16. I was listening to KOMO today and heard you tell Ken Schram that the extended models are "hinting" at cooler weather and "possible" lowland snow towards the end of next week? Can this be so? Please say it is!!!!! I'll be watching for your updates with much anticipation! ;)

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  17. Cliff,

    I live in Aberdeen and first want to thank you for your efforts to bring Langley Hill Doppler Radar to reality. It's a fantastic resource for those of us living along the coast.

    I have a question regarding the reflectivity image presented by Langley. This afternoon (Wednesday, Nov 30th) the sky is clear and we are enjoying a beautiful sunset from horizon to horizon. But Langley shows what appears to be light rain all around. Why is this?
    Thank you.

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