Umiat's Dubious February 1955 Records

*** Update on April 2, 2014: Rick has uncovered a note from the observer on the original microfiche that states the temperature observations are 17°F too low (cold). Between 5 and 5 p.m. on 2/18/55, the temperature was corrected by the observer and appear reasonable afterward. I have placed a before and after chart at the end of the blog post. ***

Last week we had a blog post that discussed wind chills and even wind chill records. At one point in the post there was a reference to a possible -106°F wind chill. After doing a little digging around, it appears that the -106°F wind chill is not credible. Specifically, I am talking about the Umiat station and the year was 1955. As many readers know, Umiat is probably the coldest station in Alaska with respect to winter temperatures. However, the data listed for Umiat in 1955 stretches credulity. In the GHCN database, there are two entries for Umiat, 1) Umiat (USW00026508), and 2) Umiat AFS (USW00026537). Unfortunately, the station history is quite a bit more complicated that just two station entries and other people are better equipped to discuss those differences.

The data for Umiat AFS only runs from 1953 to 1955 (it stops after Feb 22, 1955) – there is no overlapping data between the two stations. In Februray 1955, the data for Umiat AFS is exceptionally cold. As a comparison, I pulled all available February data for Barrow, Umiat, and Barter Island. All comparable years with data during that time period for those three locations was charted. There were 20 years in the comparison (1949-1955; 1976-1988). In addition, I plotted the 850 mb temperature from the Barrow upper air sounding during those time periods.

Fig. 1. Temperatures for 1949-1955 and 1976-1988 for Barrow, Barter Island, and Umiat. Barrow 850 mb temperature also plotted. The 1955 data is for February 1 to February 22 for all stations.

As you can see in Figure 1, the February 1955 data for Umiat is a significant outlier. In most years, the February temperatures are 5°to 8°F colder in Umiat than the other stations. However, in 1955 Umiat (AFS) was over 20°F colder. That discrepancy is far greater (by over 2x) than any other year. A good analog year for temperatures was 1984. In that year, the temperatures at Barrow and Barter Island were about 10°F warmer than Umiat – not 20°F+ like 1955. Again, that is a strong indicator that the 1955 temperatures in Umiat are not reliable.

The 1955 data for Umiat AFS is also colder than the acknowledged coldest month in Alaska's climate record (Ft. Yukon in December 1917). Figure 2 shows the list of every month in Alaska that has a monthly temperature lower than -40°F/C. Deering in December 1917 is crossed out due to the fact that its geographic location is not conducive to such an extreme monthly temperature and since the monthly LCD makes no mention of the station. In 1955, the second coldest month in Alaska was Barter Island with a monthly average temperature of -26.4°F.

Fig. 2. List of coldest months in Alaska.

Based on all available information, it appears that the measured temperatures for Umiat AFS in 1955 were approximately 10°F-15°F colder than the actual temperatures.

If the temperatures from Umiat AFS in February 1955 are no to be believed, then the -106°F wind chills from that month are also not to be believed. Figure 3 shows the time period with the minimum temperature and wind chill from based on the February 1955 data from Umiat AFS. Again, this data is now considered unreliable. If the temperatures are 10°F to 15°F too low, then the -106°F wind chill should be between -88°F and -94°F. These values are warmer than the statewide wind chill record. *** Update on 4/2/2014: The values are now considered to be 17°F too cold. Figure 4 shows the temperature and wind chill chart using the revised temperature values. ***

Fig. 3. Three-day temperature and wind chill chart for Umiat during February 1955 showing -106°F values. *** Modified on 4/2/2014 ***

Fig. 4. Three-day temperature and wind chill chart for Umiat during February 1955 accounting for the 17°F error identified by the original observer. The minimum wind chill is now -85°F. *** Added on 4/2/2014 ***