Monday, November 16, 2015

Widespread Damaging Wind Storm Tuesday

In the Inland Northwest, we get several windy storms every winter.  It comes with the territory of living at this latitude, as well as being a frequent "gateway" for storms to enter the US.  But many of these windy storms aren't considered "extreme".  A typical wind storm in our area will result in gusts somewhere in the 50-60 mph.  A wind gust over 60 mph becomes much more rare.  The table below shows the wind records for the Spokane Airport.

Spokane Airport Wind Record (by month)
Fastest Mile (1949-1995)
Peak Gust (pre-1984)
Peak Gust (since 1984)
59 MPH (Jan 9, 1972) 
67 (Jan 9, 1972)
56 MPH (Jan 11, 2014)
54 MPH (1949)
58 MPH (Feb 28, 2011)
54 MPH (Mar 16, 1971) 
64 (Mar 26, 1971)
66 MPH (Mar 15, 2009)
52 MPH (Apr 17, 1987)

62 MPH (Apr 17, 1987)
49 MPH (1957)
59 MPH (May 3, 2010)
44 MPH (1986)
77 MPH (Jun 21, 2005)
43 MPH (1970)
67 MPH (Jul 23, 2014)
50 MPH (1982)
54 (Aug 9, 1982)
54 MPH (Aug 25, 2013)
38 MPH (1999)
55 MPH (Sep 6, 2009)
56 MPH (Oct 27, 1950)
65 (Oct 27, 1950)
62 MPH (Oct 16, 1991)
54 MPH (Nov 27, 1949)
65 (Nov 27, 1949)
64 MPH (Nov 16, 2010)
51 MPH (1956)
63 MPH (Dec 12, 1995)

The all-time wind speed at Spokane is 77mph, but that was caused by a thunderstorm gust front, not a widespread winter storm.  So ignoring that, a really strong winter storm will typically gust into the 60-65 mph range.  The highest non-thunderstorm wind at Spokane is 67 mph from January 1972.

The storm on Tuesday will have the potential to do that.  Here's some of the damage reported by the Spokesman Review in  January 1972:

  • Communities of Beverly, Shawana, and Mattawa (along the Columbia River south of Wenatchee) sustained extensive damage.  Six trailer houses were overturned and destroyed.  Other low-income homes were leveled.  All three towns were without power and phones.
  • Rattlesnake Mountain near Richland measured a wind gust of 150 mph, the top speed of the instrument.
  • Gusts of 60-65 mph and higher were prevalent.
  • The wind blew away the upper mechanical room of the University of Idaho Physical Science Building in Moscow.
  • Wind toppled chimneys in Colfax.

Another strong wind storm occurred on Nov 19, 2003.  Here's some reports from that storm:

  •  In the northern Idaho panhandle a dozen large pine trees fell on summer homes along Lake Pend Oreille. 
  • In the Coeur d'Alene area numerous trees fell on houses and power lines.
  • At Pomeroy a wind gust was measured at 65 mph. 
  • Over the Palouse region a wind gust blew the roof off of a barn near Colfax. 
  • Near Newport a tree was blown onto a house. 
  • The heaviest damage occurred in the Spokane area where numerous trees were toppled onto houses and power lines. Up to 16,000 people were without power in Spokane's South Hill neighborhood. 
  • Fairchild Air Force base recorded a wind gust of 68 mph which ripped the roof off of a recreation center. 
  • At Spokane International Airport a wind gust of 63 mph was recorded and at the Spokane National Weather Service office the wind gusted to 61 mph. 

There are two predominate weather patterns for high winds in the Inland Northwest.

Weather patterns for high winds in the Inland Northwest

The first pattern is where a deep low approaches the Washington/Oregon coast from the south or southwest.  This pattern is fairly common, and most storms produce high winds along the coast.  The stronger storms also deliver high winds to the inland areas of western Oregon/Washington (i.e. I-5 corridor).  But strong winds east of the Cascades in this pattern are rather rare.  Only the strongest storms of this pattern can produce damaging winds in eastern Washington.  Some of these are the Columbus Day storm of 1962, December 10th 1995, and the Hanukkah Eve storm of 2007.

Track #2 is more rare, but is the more favored pattern for high winds in eastern Washington and north Idaho.  The low tracks west-to-east across southern British Columbia.  If the low is strengthening as it does this, then high winds are more likely.

Here's what the forecast for Tuesday looks like:

GFS MSLP forecast valid 7am Tue 17 Nov 2015

GFS MSLP forecast valid noon Tue 17 Nov 2015

GFS MSLP forecast valid 6pm Tue 17 Nov 2015

The low follows Track #2 across southern BC.  The central pressure starts at 993 mb off the BC coast, and deepens to a 977 mb over Alberta.  In other words, this is a classic set up for high winds in the Inland Northwest.  

So how strong will the winds be?  Here's the current forecast:

You'll notice that the 68 mph forecast for Spokane is higher than the January 1972 storm.  We don't have the skill to predict the winds to the nearest mile-per-hour.  But we do think that this storm has the potential to rank as one of the strongest ever in the Inland Northwest. The areas in the mountainous regions have lower wind speeds forecast, but don't let that fool you.  There's a lot more trees in those locations, so there's more trees to blow over.

Be prepared for lots of downed trees, power lines, fence and roof damage, and maybe even some blowing dust in the Columbia Basin.

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