Saturday, November 30, 2013

Mid-November Wind

According to a News-Miner article on Wednesday, an anemometer atop the GVEA administration building in Fairbanks recorded a peak wind gust of 83 mph during the November 13-14 storm.  While the measurement is not comparable to the official history of wind measurements from the airport, the report is impressive and led me to wonder how the airport observations in the recent storm compared to past events.   The chart below shows the annual maximum wind speed in Fairbanks according to the GHCN daily data; note that various time averaging periods were reported at different times in the history.

The highest 5-second or greater wind speed in the GHCN data is 59 mph on April 18, 2003, but this report appears suspect to me because the 2-minute maximum for the same day was only 12 mph, and there does not appear to have been anything unusual about the weather situation that day; I excluded the report for the chart above.  Ignoring the 2003 event, the official measurement of 55 mph on November 14 is the highest on record for a 5-second period or greater; higher "peak gust" values were reported in July 1990 and June 1997.  The recent 2-minute report of 41 mph also narrowly exceeds the peak 1-minute values in 1970 and 1974.

It's also interesting to examine the annual values of the peak wind speeds in winter - see the chart below.  Note that I have excluded March here, because average wind speeds pick up considerably in March (see second chart below) and I thought it would be most valuable to look only at the deep winter months with similar wind behavior.  Interestingly, in 3 of the last 4 winters (including this one to date), the peak 2-minute wind speed has been at the upper end of the historical distribution - and so it appears we can say that Fairbanks has had a run of unusually strong wind events in recent winters.  The behavior of peak wind speeds in April through September (the "less calm" season) does not show any similar trend (third chart below).


  1. Excellent blog Richard as always. It's good to visualize the events versus time in months and years.

    Here's a few comments. The November-February period subjects the Tanana Valley and Fairbanks to periodic gap flow/katabatic winds from the Alaska Range to the south. These are usually isobar driven events. Fairbanks is usually spared any major wind associated impact, while other valley locations aren't so fortunate. What effects Fairbanks is W/SW flow like the fronts that passed this November.

    Beginning in March, we again see valley winds driven by pressure differential (for example High to the north, Low to the south resulting in E>W winds), plus the start of temperature differentials from solar warming to the south of the Alaska Range. That temp thing becomes an almost daily morning event into May, especially in Delta Jct and possibly Healy to south of Fairbanks. It can last into late September and early October.

    Summer wind events are usually associated with down flow from thunder storm activity, and to a smaller local scale from the effects of the "whirly winds" or miniature heat driven tornadoes. They are powerful and can easily lift aircraft and objects off the ground. The FAI tarmac area is subject to them for some reason, perhaps from all the black pavement on a hot sunny day.

    We can experience SW blasts from frontal activity but usually later in the summer.


    1. Thanks for the comments Gary. It's interesting to consider that Fairbanks may not be typical of interior AK locations, being usually less prone to winter strong winds except in these frontal passage events.

    2. That's why they call it "Fair-banks" I guess.

      Protected somewhat by hills in an arc SW-SE, the E>W valley flow bypasses us to a great extent, while the W>E flow can get a good fetch if aimed right, and probably makes use of knife edge refraction similar to radio wave propagation to pull upper winds to the valley floor.

      Next time the Tanana Valley Jet blows E>W have a good look at the IR Sat pics. You'll see warm dark air scooting to the south of town and NE>SW to the North and West of the city, while in town the windsocks will be all around the clock with the more southerly locations at valley floor pointing 90 deg towards the E>W flow. It takes some lengthy blow to scour out the inversion and let the wind into town from the SE.