World Record Snowfall?

World Record Snowfall?

Last Blog (Part 3), for now, About NCDC Possible Extreme Weather Record Errors

I’ve been reporting the last few weeks about some errors in the NCDC database of extreme temperature records for a selection of various states. This blog was going to be about precipitation errors but the NCDC COOP site for the COOP/IPS data is apparently down for the time being so I am only able to present a single document (that I happened to download some months ago) so far as possible precipitation errors.
According to the NCDC site a world record 24-hour snowfall occurred at a site in Alaska back in February 1963.

The Great 78-inch snowfall of February 7, 1963 at Mile 47 Camp, Alaska

The official world record 24-hour snowfall, according to the WMO Climate Extremes Committee, was an accumulation of 75.8” at Silver Lake, Colorado on April 14-15, 1921. This record has been scrutinized in great detail, especially since an observer in Montague, New York reported a 77” fall during a 24-hour period on January 11-12, 1997 . The NCDC sent a team to investigate that report and published 50-page report refuting it. It was refuted as a result of one too many observations being made during the course of the 24 hours of accumulation. This in spite of the fact that the accumulation itself was not questioned, simply the method of the observation of such.

Remarkably, the NCDC now seems to accept without question a 78” snow accumulation on February 7, 1963 at a remote site located on the mile 47 marker of the Richardson Highway in Alaska (to its credit the WMO Climate Extremes Committee has, as of now, not published this as a new world record weather extreme). Here is the COOP form associated with the Alaska event:



The COOP form for Mile 47 Camp, Alaska showing the 78” single-day snow accumulation of February 7, 1963. Note the melted precipitation figure of 6.02” and the daily temperature range of 0°-8°F (or perhaps -4° to +8°F, it appears the '0°' is crossed out and replaced with a -4°F figure, hard to tell).

Of particular interest is the melted precipitation figure of 6.02” on February 7, 1963 along with the day’s temperature range of 0°F (low) to 8°F (high) for that day. A fall of some 6 inches of precipitation with a temperature of zero to 8°F strains the boundary of physical possibility. I would challenge anyone to conceive of how a situation could possibly evolve to create 6 inches of precipitation while the temperature at the surface was this cold. The observer’s comment for this extraordinary day simply states “overcast”.

THE SITE OF CAMP MILE 47

Camp Mile 47 on the Richardson Highway is located, obviously, 47 miles along the route heading north from the port of Valdez.



A photograph of the Richardson Highway near the site of Mile Camp 47. Photo by “TFO” from Google Earth map site.

It was a highway maintenance station associated with the construction of the oil pipeline from the North Slope of Alaska to the port of Valdez. This highway crosses over the Thompson Pass (elevation 2,800’) 27 miles north of Valdez. Thompson Pass for the period of 1952-1974 maintained a weather station (at a site located at 2,500’) which indeed did record the heaviest snowfalls ever reported from Alaska, and, in some cases, reported the most intense snow accumulations ever measured on earth. To wit:

62.0” in 24 hours on December 29, 1955
120.6” in 2 days on Dec. 29-30, 1955 (world record)
147.0” in 3 days on Dec. 28-30, 1955 (world record)
163.0” in 4 days on Dec. 27-30, 1955
175.4 in 5 days on Dec. 27-31, 1955
186.9” in 7 days on Feb. 18-24, 1953
346.1” in one calendar month in February 1964
974.1” in one winter season in 1952-1953

However, a modest 53.5” fell for the ENTIRE month of February 1963 at Thompson Pass. Kenney Lake was the only other site in the area to have records for February 1963 and it reported 17.0” for the month. Sheep Mountain, also in the area reported 7.0” for that month and Cordova Airport had 10.1” with Valdez reporting 36.0” (a relatively low value for the site for a February that averages around 50” for the month). In other words, there was no extraordinary or unusual storm associated with the snowfalls of February 1963.

The Thompson Pass COOP weather site was operational during the winter of 1963 and recorded a snowfall of 12” on February 7, 1963. Mile 47 is 20 miles beyond the pass along the Richardson Highway and some 750 feet lower. It is hard to imagine that the Mile 47 site reported a snowfall some six to seven times greater than the summit just 20 miles further down the road.

CONCLUSION

The NCDC has obviously been using the IPS COOP form database to create its extreme weather summaries as per their new web site without actually fact checking the accuracies of these forms. Although it is conceivable that some microclimate pattern was at work (a strong moist easterly flow packing the snowfall up the backside of the Thompson Pass for instance) it seems that as thorough an investigation should be made of this event as was done at Montague in New York, being a potential world weather record.