Seattle's Strongest Windstorms 1950-2002
After many windstorms, claims are often made for the "biggest since Columbus Day 1962" or "strongest storm of the decade," or some variation on this theme. One of the main purposes of this website is to try to create a scientific basis for such comparisons--in essence, to create a method that is repeatable by someone wishing to dig into the data for themselves.
Which brings the discussion to Table 1, below . In terms of wind speeds, direct comparisons can be made among the greater Seattle area ("Seattle, Tacoma, Everett and vicinity") stations that have a long period of record: Sea-Tac, Boeing Field, Everett, Renton, Sea-Tac Airport, Seattle City Station (Seattle Naval Station and Weather Service Forecast Office used for some readings) and Tacoma McChord Field (Narrows Airport in some instances). The table lists the top eleven most powerful storms for Seattle from 1962 to 2002, and ranks them according to the strength of their averages. In some cases, peak gust data were missing, and the average represents the value for the available data.
Table 1, notes:
Only a handful of storms stand out in this Seattle area ranking. Indeed, only the top three--The Columbus Day Storm, the Inauguration Day Storm, and an event on January 15, 1951--are clearly above what appears to be a background of 53-57 mph averages for most significant windstorms. With six stations, a difference of six mph equals a full point. There's enough variance from the mean peak gust for each storm, and uncertainty in the maximum wind readings for Pre-ASOS (pre 1995-1996) events, to make rankings of just 0.1 point apart very gray, and 1.0 point quite uncertain. The rankings start having significance when the difference between two storms is about three points or greater.
The number of storms with readings below 53.0 increases quickly. The December 27, 2002 windstorm is shown as an example of one of these lower category storms. It is also included to make an observation about human memory and windstorms. After the December 27, 2002 event, statements such as, "Strongest storm since March 1999," or, "We haven't seen a windstorm like this since March 1999," circulated among Seattle area newspapers, web and TV broadcasts. This is interesting, for the January 16, 2000 sou'wester ranked slightly above the March 3, 1999 windstorm. Even if the difference between the 1999 and 2000 events is insignificant, the two storms were markedly above the December 27, 2002 storm. Thus, a more accurate comment for the Seattle area impact of the December 27, 2002 gale would have been to say, "Strongest winds since January 2000," not March 1999. This leads me to wonder what aspect of the March 3, 1999 event lead people--in this case, probably National Weather Service personnel--to remember the 1999 storm, while forgetting the January 16, 2000 gale. This could be because the March 1999 storm struck the coast with a greater ferocity than the January 2000 gale, and the March windstorm didn't initialize well in the computer models, making a bigger headache for forecasters. Also, the peak gust at Sea-Tac was clearly higher for the March 1999 event--60 mph verses 52 mph in 2000.
Which brings up an interesting fact about this table. If the storms were ranked for individual stations, different events would come out on top. For Sea-Tac, the January 15, 1951 event produced the strongest gust 1950-2002. For Boeing Field, it was the Inauguration Day storm. The Columbus Day Storm, however, dominates among the other four stations. Further down the line, like for 2nd and 3rd place, the rankings get more confused. This is why the average for six stations is used for the final ranking--it smooths out some of the variance from random factors, such as differences in observing method, wind measure, and instrument type and position.
Finally, the table above depicts just one method for ranking windstorms. Peak gust is just one important measure among characteristics like maximum sustained winds, wind direction changes and wind duration. If the duration of strong winds were factored in, some of these storms would start climbing up the ladder in comparison to others--notably the November 14, 1981 event. Methods can be devised to factor in high wind interval, but the process of adding in duration is quite time consuming in itself! When looking at the table above, it is easy to forget how much time is required to compile something as simple as this peak gust comparison.
 Peak gust data for storms from the 1962 to 1995 period is from the National Climatic Data Center, unedited surface observation forms, and Local Climatological Data monthly summaries (LCD mainly for the Seattle City Office readings, but also December 12, 1995 for Sea-Tac). Peak gust data for storms from the 1996-to-present era are from the University of Washington archived surface observations, save December 27, 2002 which was from METAR reports collected online from the National Weather Service, Portland and Seattle offices. The one datapoint from the University of Washington's station was from the University's meteogram plotting feature.
Last Modified: February 24, 2003
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