Forum Index > Trail Talk > Mount Washington wind chill hits minus-108, snapping U.S. record
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Gil
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Gil
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PostMon Feb 13, 2023 11:44 am 
The records on Mount Washington have to be considered with the knowledge that places that are far colder and just as windy have no long-term weather stations. An interesting look at the weather station that operated at Denali Pass: https://journals.ametsoc.org/view/journals/apme/59/12/jamc-d-20-0082.1.xml

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thunderhead
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PostMon Feb 13, 2023 8:17 pm 
Ya, thats a good paper. The trials and tribulations of the wind sensors especially looked challenging. Lacking much observational data, and being curious about the extremes that are out there, I wrote a quick script to dig through ECMWF reanalysis(basically a very short range computer model forecast in this context) data, which I happen to have on hand every 6 hours globally at standard pressure levels going back to 1995, though a couple years are missing. Modern computer modelling is accurate enough, especially over such short periods, that I suspect it is just as accurate as the stations themselves would be in such harsh conditions(the paper Gil posted gives some of those details). I applied appropriate tweaks in the data to go from modelled free air to summit conditions, especially accelerating wind speed to account for venturi effects of high terrain and also to account for the difference in temporal resolution between the ECWMF and the Mt Washington obs. I calculated wind chill every 6 hours for 3 brutally cold locations, the south pole, and the summits of Denali and K2. As expected, all 3 of these locations are clearly colder than Mount Washington... but in terms of wind chill minima the first 2 are not as decisive as you might think. Denali spends about 20 hours in the average year with a wind chill below -110F. Since 1995, its minimum wind chill was about -122F. The south pole spends about 40 hours per year colder than -110F with a minimum of about -125F. K2 is the real winner when it comes to staggeringly terrible temperature and wind. Not surprising, since it sticks up straight into the mid-latitude jet stream. It spends about 13% of its time below -110F wind chill, with a minimum since 1995 of -145F.

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Forum Index > Trail Talk > Mount Washington wind chill hits minus-108, snapping U.S. record
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