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Post by Deleted on Dec 13, 2020 10:18:41 GMT -5
White Christmas in most places means snow falling. OP uses snow on the ground; the US national weather service (from my link) uses snow on the ground with a 1" threshold; snow falling seems to be the British definition Using the US definition, London's last white Christmas was in 1938, with Heathrow having never experienced one since the station opened. The only years with snow on the ground on Xmas day were 1970, 1981 and 2010 (though 1981 and 2010 did not have snow falling on Xmas day, and the total amount was less than 1").
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Post by Nidaros on Dec 13, 2020 10:38:45 GMT -5
As the title says, and please state what your criteria is. IMHO a proper White Christmas has snow lying on the ground, not just a few flakes in the air that melts the second it hits the ground. But if that is what you have data for, then snow falling is also interesting in this thread. It can be Christmas Eve (Dec 24.), as we here in the Nordics most often use, or Christmas day (25. Dec). It can be your locations, or any location that is of interest. Also, please state the altitude, as that is important information. Our met-office has been so kind to give a lot of data on their website just recently, with 1991-2019 as normal period. Also the snow depth last Christmas, 2019. So here is a few places in Norway, chance of snow on the ground on the morning of Christmas Eve (Dec.24th). Oslo (94m, Blindern): 60 %. In 2019: 0 cm on the ground (snowless) Oslo (360m, Bjørnholt): 83 %. In 2019: 37 cm Hemsedal (648 m): 100 %. In 2019: 71 cm Kristiansand (151m, Mestad): 40 %. In 2019: 0 Bergen (12m, Florida): 23 %. In 2019: 0 Voss (316m, Øvstedal): 90 %. In 2019: 7 cm (Voss is inland from Bergen) Trondheim (23m, Leinstrand S of the city): 70 %. In 2019: 4 cm (Trondheim AP Værnes: 57 %) Røros (685m, Aursund): 100 %. In 2019: 49 cm Vesterålen (8m, Alsvåg): 67 %. In 2019: 4 cm Tromsø (100m, met.office): 90 %. In 2019: 52 cm. would have expected much lower for Trondheim. Trondheim's December mean is -1.3°C; about the same as NYC (0.0°C). NYC has a 10% chance, Trondheim 57%. Must be from precipitation falling far less often as rain there in December and low variability and sun. Yes, the sun strength and variability is higher in NYC, so snow might have better chance of staying on the ground/not melting in Trondheim. The new normal 91-2020 seems to get Dec mean for Trondheim-Værnes -0.6C. Only 33% chance of snow on the ground Christmas Eve for Værnes last 15 years. PS: Leinstrand is not in the city center, but S/inland along a smaller fjord, so might be slightly colder in winter. No temperature data there, but the snow depth has been recorded there last decades, other recording in the city only started very recently, but we have data for Værnes airport. google map
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Post by Ariete on Dec 13, 2020 15:47:40 GMT -5
Using the US definition, London's last white Christmas was in 1938, with Heathrow having never experienced one since the station opened. The only years with snow on the ground on Xmas day were 1970, 1981 and 2010 (though 1981 and 2010 did not have snow falling on Xmas day, and the total amount was less than 1").
But but knot says England gets lots of snow! |
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Post by knot on Dec 13, 2020 16:03:01 GMT -5
But but knot says England gets lots of snow! Indeed, it does. London is an anomaly within England—when will you ever learn? Not only on the leeward side of the hills, but also greatly affected by UHI. Most of England, contrarywise, is windward and rural. |
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Post by Nidaros on Dec 13, 2020 16:40:48 GMT -5
Any data for other parts of the UK? Thunderstorm says snow on the ground at Christmas is extremely unlikely in Sheffield.
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Post by knot on Dec 13, 2020 16:47:09 GMT -5
Any data for other parts of the UK? Thunderstorm says snow on the ground at Christmas is extremely unlikely in Sheffield. Might I remind you, that I do not believe in such nonsense? Using one petty holiday to determine how much snow a region gets during the winter…is fraudulent, at best. Ariete had attempted to score a "gotcha" point with me after B87 confirming that London doesn't usually get snow on "Christmas"—well, I never mentioned "Christmas"! I use the entire winter instead, like a rational person would. |
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Post by Nidaros on Dec 13, 2020 16:54:19 GMT -5
This thread is about the chance of a White Christmas.
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Post by knot on Dec 13, 2020 17:00:57 GMT -5
This thread is about the chance of a White Christmas. And this is the post I was replying to, in case you haven't noticed:  Pathetic attempt at a "gotcha" by Ariete. |
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Post by Babu on Dec 13, 2020 17:04:00 GMT -5
I think the normal probability for Umeå is about 95%. I think like 4 of the last 6 or so christmases have been without snow cover at some point during Christmas Eve.
This Christmas I'd give it about a 50/50 chance.
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Post by Strewthless on Dec 13, 2020 17:11:41 GMT -5
Media are saying the highest probability for a long time. Usually christmas always seems to be chilly and with clear golden skies due to the latitude, but I think I've only seen snow once or twice on Christmas, definitely in 2010, when it was -14C on Christmas Day.
I actually recall more snowy birthdays, and my birthday is in November.
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Post by Ariete on Dec 13, 2020 17:50:04 GMT -5
Media are saying the highest probability for a long time. Usually christmas always seems to be chilly and with clear golden skies due to the latitude, but I think I've only seen snow once or twice on Christmas, definitely in 2010, when it was -14C on Christmas Day. I actually recall more snowy birthdays, and my birthday is in November.
Christmas Eve 2010 was the 3rd coldest in Helsinki's history with a low of -22.4C. Coldest was 1915 with a low of -25.4C.
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Post by Strewthless on Dec 13, 2020 18:15:36 GMT -5
Media are saying the highest probability for a long time. Usually christmas always seems to be chilly and with clear golden skies due to the latitude, but I think I've only seen snow once or twice on Christmas, definitely in 2010, when it was -14C on Christmas Day. I actually recall more snowy birthdays, and my birthday is in November. Christmas Eve 2010 was the 3rd coldest in Helsinki's history with a low of -22.4C. Coldest was 1915 with a low of -25.4C.
Funnily enough, it was also our 3rd coldest, two times before that we'd recorded -18C. |
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Post by Deleted on Dec 13, 2020 18:55:11 GMT -5
Chance of a white Christmas in Europe.  |
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Post by Deleted on Dec 13, 2020 19:02:45 GMT -5
Most of England has between 10-20 days per year with sleet falling, though commonly below 10 days in the south.  |
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Post by knot on Dec 13, 2020 19:16:42 GMT -5
^Exactly! That's well and truly snowy.
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Post by Deleted on Dec 13, 2020 19:20:10 GMT -5
^Exactly! That's well and truly snowy. It's less snowy than the vast majority of Europe or the US, bearing in mind that those numbers are mostly inflated by the inclusion of sleet. |
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Post by knot on Dec 13, 2020 19:23:57 GMT -5
It's less snowy than the vast majority of Europe or the US, bearing in mind that those numbers are mostly inflated by the inclusion of sleet. Yep, but it's still snowy. Sleet is the same thing as snow, just wetter. |
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Post by Deleted on Dec 13, 2020 19:24:45 GMT -5
It's less snowy than the vast majority of Europe or the US, bearing in mind that those numbers are mostly inflated by the inclusion of sleet. Yep, but it's still snowy. Sleet is the same thing as snow, just wetter. The US doesn't include sleet in their definition of snow falling days. |
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Post by knot on Dec 13, 2020 19:26:08 GMT -5
The US doesn't include sleet in their definition of snow falling days. Because in the US, sleet = ice pellets. Whereas in the UK and AU, sleet = wet snow. Entirely different definitions! |
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Post by Deleted on Dec 13, 2020 21:32:46 GMT -5
The chance of having at least 1 inch of snow on the ground on Christmas Day here, based on 1971-2019, is 71%.
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