Your definition of an ice day is different to mine! (Or there's a typo)...
I take an ice day to have a max of -0.1 or less... even 0.0 isn't a guarantee, as it could be a rounded 0.01.
Talking of ice, though, it's now -0.2C out there and still misty with it. Three frosts in a row... my mum used to say "three frosts and it wets itself", and indeed tomorrow it's going to rain. There's a kernel of truth in the old sayings!
Originally Posted by: Retron
I would agree with that, but I would also say that we need to be careful about how we define our "maximum" temperature. For Edinburgh Gogarbank and the botanic gardens in Edinburgh (as is the case at other SYNOP stations throughout the UK), our temperature data will usually come from raw SYNOP/BUFR data which has been decoded. In most cases, that will be every hour, although I have recently discovered that raw SYNOP data for Edinburgh Gogarbank is also being transmitted at other times within each hour as well such as at half past the hour or 20 minutes past the hour.
If we define what an official observation day is (which is usually from 09:00 UTC on one day to 09:00 UTC on the next day), we could easily take the highest temperature reading from all of the readings within that period and call that our "maximum" temperature. As it turns out though, that is nothing more than the highest reading and will not usually be the same as the actual official "maximum" temperature.
Those official minimum and maximum temperatures will therefore come from separate raw SYNOP/BUFR codes within those same transmitted, which is only transmitted at 06:00 UTC, 09:00 UTC, 18:00 UTC and 21:00 UTC on each day. Since our observation day usually begins and ends at 09:00 UTC on each day, the important readings here will come at 09:00 UTC and 21:00 UTC.
Each of those readings cover the preceding 12 hour period, so the minimum and maximum temperature data for 09:00 UTC will cover the period from 21:00 UTC on the previous day to 09:00 UTC whereas that same data for 21:00 UTC will cover the period from 09:00 UTC on that morning to 21:00 UTC. The higher of those two maximum temperature readings will then be the official maximum temperature on that day with the lower of those two minumum temperature readings being that day's official minimum temperature.
Under that system, those official maximum temperatures will always be the same as or higher than the highest individual temperature reading for throughout that official observation day. Because of that, any official declaration of an ice day can't be made from those highest temperature readings alone because even if that is below freezing, an ice day can only be declared if the official maximum temperature from those twice daily summary readings at 09:00 UTC and 21:00 UTC is below freezing. If that comes out to be either at or above freezing, there can be no official ice day even if the highest individual temperature reading throughout that official observation day is below freezing.
Of course, different stations will operate in different ways in that regard, but this is how official Met Office weather stations usually operate.
Meanwhile here in Edinburgh, it is still overcast but in spite of that, the temperature has dropped to just below freezing once again. Today's official maximum temperature (technically, that can't officially be finalized until 09:00 UTC tomorrow morning) so far at Edinburgh Gogarbank was just 0.9°C which actually makes today our coldest day of this year so far.
Edited by user
02 December 2023 18:20:25
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Reason: Not specified
The north of Edinburgh, usually always missing out on snow events which occur not just within the rest of Scotland or the UK, but also within the rest of Edinburgh.