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damianslaw

UK first ground and air frost watch season 2019-2020

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September marks the start of the new season and therefore apt time to start the frost watch thread for 2019-2020.

There are suggestions some parts of Scotland might see a ground frost early hours of 2nd Sept - nothing unusual, just and indication that under clear skies such a feature is always a threat as we enter September.

Please use this thread to predict and also record your first ground and air frost. Here we tend to record our first ground frost at some stage second half of September, and out first air frost by the third week of October -but in some years we have had to wait until well in November..

A ground frost occurs when temperatures are above 0 degrees, sometimes as high as 3 degrees when a light grass frost occurs, an air frost can only occur when the air temp is at or below 0 degrees. Sometimes an air frost is recorded yet there is no visible sign of it - this is a dry frost and usually happens under very dry air with low lapse rates, not a common feature in autumn, but more so in the winter.

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First frost at Aboyne with 0.0C (though I suspect it also hit 0C in the early July cold snap when it went offline).

https://eldoradoweather.com/climate/world-extremes/world-temp-rainfall-extremes.php?extremes=United%2BKtnaharra recr

Altnaharra recorded -0.4C on July 8th

https://www.ogimet.com/cgi-bin/gsynres?lang=en&ind=03044&ano=2019&mes=8&day=2&hora=8&min=0&ndays=50

Been nowhere near a frost here yet. Coldest so far 9.0C. Coldest I've seen in Yorkshire was 5.3C at Topcliffe a couple of days ago.

 

 

 

 

 

Edited by Aleman

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Last year on 31st August we had ground frost and minimum of +0.8C
Maximum was 18.5 on same day.

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8 minutes ago, Aleman said:

First frost at Aboyne with 0.0C (though I suspect it also hit 0C in the early July cold snap when it went offline).

https://eldoradoweather.com/climate/world-extremes/world-temp-rainfall-extremes.php?extremes=United%2BKtnaharra recr

Altnaharra recorded -0.4C on July 8th

https://www.ogimet.com/cgi-bin/gsynres?lang=en&ind=03044&ano=2019&mes=8&day=2&hora=8&min=0&ndays=50

 

 

 

 

 

bit like sunspots - is that -0.4 at Altnaharra a last frost from previous winter, or first frost from the upcoming one?!

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1 hour ago, JeffC said:

bit like sunspots - is that -0.4 at Altnaharra a last frost from previous winter, or first frost from the upcoming one?!

I'd probably attach it to the previous. Here statistically the 31st July and 1st August are the two warmest days, so anything after that is 'on the way down' and would be the next season.

It's pretty irrelevant here in reality though as we've never seen the first air frost before mid-October.

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1 hour ago, reef said:

I'd probably attach it to the previous. Here statistically the 31st July and 1st August are the two warmest days, so anything after that is 'on the way down' and would be the next season.

It's pretty irrelevant here in reality though as we've never seen the first air frost before mid-October.

Did we record anything decent in Sep 07? Other than though yes, it’s normally November. 2012 was probably the last October to produce decent frost.

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I remember September 1986 we had a good spell of sunny days that all started with a groundfrost,not seen anything like it since mind you it still is the coldest September in the last 70 years!

Edited by hillbilly

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6 hours ago, Aleman said:

First frost at Aboyne with 0.0C (though I suspect it also hit 0C in the early July cold snap when it went offline).

https://eldoradoweather.com/climate/world-extremes/world-temp-rainfall-extremes.php?extremes=United%2BKtnaharra recr

Altnaharra recorded -0.4C on July 8th

https://www.ogimet.com/cgi-bin/gsynres?lang=en&ind=03044&ano=2019&mes=8&day=2&hora=8&min=0&ndays=50

Been nowhere near a frost here yet. Coldest so far 9.0C. Coldest I've seen in Yorkshire was 5.3C at Topcliffe a couple of days ago.

 

 

 

 

 

One of my stations in the North York Moors fell to 2.7c yesterday morning. Rosedale Abbey, albeit a very good frost hollow.

@4wd I remember that day well last year, Goathland at 0.1c, very nearly an air frost in summer!

Edited by vizzy2004

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3 hours ago, Turnedoutniceagain said:

There was a definite mention on Sky of "a frost in the isolated glens of Scotland" for later this week

Corgarff, Aberdeenshire in the Grampians fell to 0.0c this morning.

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Back in September 2005 I recorded -1C twice on the 17th & 24th. Since then I've not had an air frost in September again, might have to check but don't think I have. Usually start getting them in October at some point. Some years later depends on a few things - air masses, little to no wind with clear sky by night etc.

Edited by Frost HoIIow

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2 minutes ago, Frost HoIIow said:

Back in September 2005 I recorded -1C twice on the 17th & 24th. Since then I've not had an air frost in September again, might have to check but don't think I have. Usually start getting them in October at some point. Some years later depends on a few things - air masses, clear sky by night etc.

Maybe 2010??

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Just now, feb1991blizzard said:

Maybe 2010??

I got down to 1C towards the end of the month but no air frost.

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We had a notable air frost around 23 Sept 2012 - it got down to -3 degrees, and the frost was still evident in lakeland valleys at half 10..

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9 minutes ago, damianslaw said:

We had a notable air frost around 23 Sept 2012 - it got down to -3 degrees, and the frost was still evident in lakeland valleys at half 10..

It was probably the 22nd Damian. I've just went through that year & we got close to -2C here on that morning. Actual reading -1.8C. So it's "only" been 7 years since I last had a September air frost & not 14.

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9 minutes ago, Frost HoIIow said:

It was probably the 22nd Damian. I've just went through that year & we got close to -2C here on that morning. Actual reading -1.8C. So it's "only" been 7 years since I last had a September air frost & not 14.

Thanks for checking.

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A chance of an air frost tonight for a few places. Ground frost a bit more widespread even in some southern parts.

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On 02/09/2019 at 20:57, damianslaw said:

We had a notable air frost around 23 Sept 2012 - it got down to -3 degrees, and the frost was still evident in lakeland valleys at half 10..

Child of Nadine? surprised there was a frost

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First air frost of the Autumn here in North Yorkshire this morning.

My weather station at Keld in the Yorkshire Dales fell to -0.7c

The station is sited at the bottom of a valley at around 327m and has proved to be a very cold location since setting up a month ago.

Coldest in the UK appears to be Corgarff again with a low of -1.6c but rumour has it Aboyne has had -2c??

 

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Quite a chilly night for some sheltered north east parts of England expected including Yorkshire - could be a few places record there first ground frost, mins down to 1 or 2 degrees.

 

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+0.8C here about 4am, some cloud came over or it may have gone lower.
It would have been at least  the 4th ground frost nonetheless.

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