Seattle's Strongest Windstorms 1950-2002 compiled by Wolf Read

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 [1]. 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.

Seattle's Top Windstorms 1950-2002: Peak Gusts Rank Date Everett Seattle City Boeing Sea-Tac Renton Tacoma Average 1 12OCT1962 81 66 [2] 66 58 100 88 76.5 2 15JAN1951 54 70 [3] 60 75 MM 65 64.8 3 20JAN1993 67 51 [4] 70 64 74 62 64.7 4 09JAN1953 60 53 [5] 53 70 MM 52 57.6 5 14NOV1981 52 65 [6] 46 67 69 46 [24] 57.5 6 24FEB1958 47 56 [7] 67 [22] 64 MM 53 57.4 7 24NOV1983 61 57 [8] 54 62 64 46 [25] 57.3 8 26OCT1950 50 54 [9] 65 65 MM 48 56.4 9 16JAN2000 60 55 [10] 54 52 53 60 55.7 10 13FEB1979 MM [1] 62 [11] 47 60 52 53 55.3 11 19JAN1964 48 56 [12] 48 64 58 58 55.3 12 03MAR1999 58 MM 52 60 51 55 55.2 13 26MAR1971 55 MM 46 60 59 55 55.0 14 28FEB1955 31 62 [13] 52 74 MM 56 55.0 15 12DEC1995 58 MM [14] 47 60 MM 52 [26] 54.3 16 15NOV1981 52 53 [15] 48 52 61   53.2 Some Lower-Ranking Events of Interest ?? 27DEC2002 58 54 [16] 48 52 49 51 52.0 ?? 22DEC1955 47 40 [17] 52 63 MM 55 51.4 ?? 03NOV1958 37 48 [18] 58 [23] 59 MM 54 51.2 ?? 14APR1957 MM 43 [19] 62 52 MM 40 49.3 ?? 27OCT1950 45 60 [20] 45 50 MM 39 47.8 ?? 20DEC1961 32 47 [21] 35 58 54 45 38.7

Table 1, notes: [1] Observations not taken 23:00 to 05:00 at Everett during the 1979 timeframe. Peak winds at many surrounding stations occurred during the time period of this daily data blackout. [2] Peak gust at the Seattle Naval Station. [3] Peak gust at the Seattle Naval Station. [4] Peak gust at the Seattle City Office. [5] Peak gust at the Seattle Naval Station. [6] Peak gust at the Seattle WSFO on Sand Point Way. [7] Peak gust at the Seattle Naval Station. [8] Peak gust at the Seattle City Office estimated from a peak fastest mile of 44 mph by using a standard 1.3 gust factor. [9] Peak gust at the Seattle Naval Station. [10] This peak from the University of Washington. [11] Peak gust at the Seattle City Office estimated from a peak fastest mile of 48 mph by using a standard 1.3 gust factor. [12] Peak gust at the Seattle Naval Station. [13] Peak gust at the Seattle Naval Station. [14] Peak gust for Seattle City Office not recorded on December 12, probably due to power outage. [15] Peak gust at the Seattle City Office estimated from a peak fastest mile of 41 mph by using a standard 1.3 gust factor. [16] Peak gust at the Seattle WSFO on Sand Point Way. [17] Peak gust at the Seattle Naval Station. [18] Peak gust at the Seattle City Office. [19] Peak gust at the Seattle Naval Station. [20] Peak gust at the Seattle Naval Station. [21] Peak gust at the Seattle Naval Station. [22] Peak gust from airport tower. Peak on WB anemometer was 58 mph. [23] Peak gust from airport tower. Peak on WB anemometer was 46 mph. [24] Peak gust at the Tacoma Narrows Airport station. [25] Peak gust at the Tacoma Narrows Airport station. [26] Peak gust at the Tacoma Narrows Airport station.

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.

References [1] 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 Page Created: January 24, 2003 You can reach Wolf via e-mail by clicking here. | Back |