November 13, 2022

A Very Dry Week When It Should Be Wet

The weather gods are being extra kind to us this year, providing a usually dry period during the climatologically wettest time of the year.

To illustrate, here is the climatological probability of receiving a hundredth of an inch or more in Seattle over the year.  The climatological probability of rain each day is over 60% from November 7 through mid-December.  This is typically the wettest time of the year!


The forecast for this week?    Absolutely dry with plenty of sun.   Take a look at the forecast precipitation total through Saturday at 4 PM.  No rain over the Northwest and California.

The reason for these dry conditions?   The big West Coast ridge is back, as shown by an upper-level map (500 hPa, about 18,000 ft) on Tuesday around 4 PM.   The solid lines are heights, but you can think of them as the pressure at around 18,000 ft. 


To get a better view of the upper-level situation, the following map is at the same level, with the shading showing the anomalies from climatology (normal).  Red colord indicate above-normal 500-hPa heights and blue/green are the opposite.  

You can see our ridge has "bookend" troughs of low pressures/heights.   This is a very stable pattern, called an omega block.  We will be dry, but the eastern half of the U.S. will be cold and wet.




It does appear that this pattern is destined to breakdown next Sunday, with the 72hr precipitation totals ending on Wednesday the 23rd being quite soggy (see forecast below).

My advice...enjoy the pleasant weather this week, with highs in the lowlands around 50F.   It won't last.





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8 comments:

  1. John F. HultquistNovember 13, 2022 at 8:33 PM

    Wind tower blades were motionless today NW of Ellensburg. The BPA 5-minute chart- likewise.

    ReplyDelete
  2. Steve PNWNovember 13, 2022 at 10:41 PM

    Time to revisit the European model forecast (10/27 blog post)? November was tracking below normal even before this now entirely dry week up ahead. We've had so little rain for so long, hoping that this is the last dry stretch for a long time!

    ReplyDelete
    Replies
    1. DispenserNovember 17, 2022 at 7:41 AM

      Have you already forgot the many inches of rain we got just a week and a half ago?

      Delete
  3. JonNovember 14, 2022 at 9:33 AM

    The air quality around Seattle has unfortunately been sub par the past 3-4 days thanks to what I've heard are fires burning down by Mt. Rainier.

    ReplyDelete
  4. GlacierBakeNovember 14, 2022 at 10:51 AM

    Everything I've seen suggests that there have been similar periods - weather patterns - in the 1940's and 1980's. How do those relate to Nino's and Nina's? I'm not sure when those ocean current patterns (cycles) were named and recognized - wouldn't mind learning more about that topic. For the moment, I'm still enjoying the break from constant wet-wet-wet. (Note that I've often observed "early cold" starts becoming "warm-wet winters," for the balance of the season (Jan-April).)

    ReplyDelete
    Replies
    1. CodiiNovember 14, 2022 at 10:37 PM

      You had like the last 4-5 months of record breaking dry. I think it’s time we get back to “wet-wet-wet”

      Delete
  5. StaniNovember 14, 2022 at 12:32 PM

    It wouldn't be Thanksgiving week without sloppy weather😂 The only item missing is the regulation windstorm to usher in the 1/2 cooked turkey...

    ReplyDelete
  6. AnselNovember 14, 2022 at 2:40 PM

    Blame it on La Nina. BTW, Is it true what I suspect: That La Nina and El Nino are happening closer together than in the late 20th century, with less time in between for La Nada (i.e., "normal") conditions?

    ReplyDelete

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