Have You Had An Air Frost Yet?

[Terminal Moraine]

The minimum of -2.2c last night was the lowest temperature of the winter so far here. Between -4 and -6c in the local valleys.

[Polar Continental]

Saturday 14th January 2012:

Very cold and clear overnight with a widespread severe frost, low –5.6c with –9.5c on the grass. The morning to observation, very cold, severe frost, freezing fog patches on near by fields.

Today's readings for the 24 hrs up to 09:00 GMT:

0 Oktas: Clear.

Visibility: about 400 yards.

Temperature: -5.6°C

Humidity: 90%

Dew point –7.0°C

Wind Direction: Force 1 SE

Barometer 1032mb falling slowly.

Maximum temperature to 18:00 GMT yesterday: 5.6°C

Minimum temperature overnight: -5.6°C

24-hour maximum = 5.6°C

24-hour minimum: -5.6°C

Minimum temperature on grass: -9.5°C

Rainfall total: tr mm

Yesterday:

Clear overnight with a widespread slight frost, the temperature was up and down by one or two degrees as the wind mixed the air. Low –1.2c with –4.5c on the grass. The morning to observation has been cold and frosty with shallow mist and fog patches on the near by fields. A sunny day followed, feeling chilly though, top temperature 5.6c.Ground frost quickly returned around dusk.

Edited January 14, 2012 by Polar Continental

[Polar Continental]

Quite a few air frosts this winter, all slight till today, but -5.6c here this morning, -9.5c on the grass

Edited January 14, 2012 by Polar Continental

[reef]

I reached a low of -1.8C here this morning, meaning its the first air frost of the month and the third of the Autumn/Winter (and the coldest).

Its already down to 1.7C now, so another looks pretty likely.

To give an idea how poor January has been for cold temperatures here in recent years, tonight only has to fall to -3.4C to make it the 4th coldest January min in the last 25 years! That would be the coldest since 2002 aswell.

[Optimus Prime]

To give an idea how poor January has been for cold temperatures here in recent years, tonight only has to fall to -3.4C to make it the 4th coldest January min in the last 25 years! That would be the coldest since 2002 aswell.

Wow that is quite shocking. I'm surprised January 2009/2010 didn't produce something much colder than this.

[reef]

Wow that is quite shocking. I'm surprised January 2009/2010 didn't produce something much colder than this.

January 2011 reached -3.3C twice and January 2010 managed -3.1C.

Since 1982 its dropped below -5C here 5 times in January. January 1982 managed it 7 times on its own.

[Aaron]

Very odd reef.. there's such great variability with air frosts in this country even excluding frost hollows.. somewhere in E Yorks got to -19C in December 2010 yet you can barely manage -3C

Edited January 14, 2012 by Aaron

[reef]

Very odd reef.. there's such great variability with air frosts in this country even excluding frost hollows.. somewhere in E Yorks got to -19C in December 2010 yet you can barely manage -3C

In December 2010 it dropped to -11.4C - the coldest temperature here in 32 years. Bear in mind theres the Estuary 2 miles to the south-west and North Sea 9 miles to the north-east.

The anomoly is how rare low January minima have been in recent years. February, March and even November have had much colder temperatures.

[Optimus Prime]

Very odd reef.. there's such great variability with air frosts in this country even excluding frost hollows.. somewhere in E Yorks got to -19C in December 2010 yet you can barely manage -3C

The stats are strictly January based. I seem to recall Reef reporting a low of around -10c in December 2010. Could well be wrong (but unlikely I think)

[Terminal Moraine]

-7c is the 'magic' figure here. There were numerous occasions during the winters of the late 70s and early to mid 80s when this figure was breached but the last time it occurred in January was in 1993, in February, 1991 and in December 1981.

[Osbourne One-Nil]

Already down to -4.3º here tonight.

The highest minimum yearly temperature for me was -6.8º in 2008. Three of the last eight years have produced at least one minimum in minus double-digits.

[The PIT]

Just had our third air frost and in the process of having the fourth. Considering we only had one morning of lying snow it shows how bad this winters been.

Edited January 14, 2012 by The PIT

[Uncle_Barty]

First air frost of the winter this morning - minimum of -0.6c, andn the first since early last March

[damianslaw]

-7c is the 'magic' figure here. There were numerous occasions during the winters of the late 70s and early to mid 80s when this figure was breached but the last time it occurred in January was in 1993, in February, 1991 and in December 1981.

Isn't it more difficult to achieve particularly cold mins on higher ground - thanks to inversion conditions under high pressure, generally lowest ground achieves coldest temps in still conditions. You really need very cold uppers to bring very low temps to higher ground and deep snow cover, but also importantly light winds which is a hard combination for higher ground. I am surprised though you didn't achieve this figure in Jan 2010 - mind the lowest we achieved was only about -10 degrees.

Many Januaries since 1988 have been devoid of long protracted cold spells associated with very cold uppers, most cold conditions have occured thanks to high pressure overhead and warmer uppers, a bit like we are seeing now. However, Jan 2010 was an exception it did see some notably cold uppers and late Jan 96 and early Jan 97 also delivered a sustained cold attack from the east with slightly less cold uppers. Cold spells in Jan 91, late Jan 92, 01 and 09 were associated with high pressure.

Up until Jan 2009, I was bemoaning January and the fact it has hardly delivered anything particularly cold since 1997, but 2009 and more especially 2010 has rescued it somewhat, mind the way it has behaved up until now has had me bemoaning it again, it is the true winter month, but on so many occasions fails to maximise just what potential it has - a bit like the way July has behaved since 2006.

[Terminal Moraine]

Isn't it more difficult to achieve particularly cold mins on higher ground - thanks to inversion conditions under high pressure, generally lowest ground achieves coldest temps in still conditions. You really need very cold uppers to bring very low temps to higher ground and deep snow cover, but also importantly light winds which is a hard combination for higher ground. I am surprised though you didn't achieve this figure in Jan 2010 - mind the lowest we achieved was only about -10 degrees.

Many Januaries since 1988 have been devoid of long protracted cold spells associated with very cold uppers, most cold conditions have occured thanks to high pressure overhead and warmer uppers, a bit like we are seeing now. However, Jan 2010 was an exception it did see some notably cold uppers and late Jan 96 and early Jan 97 also delivered a sustained cold attack from the east with slightly less cold uppers. Cold spells in Jan 91, late Jan 92, 01 and 09 were associated with high pressure.

Up until Jan 2009, I was bemoaning January and the fact it has hardly delivered anything particularly cold since 1997, but 2009 and more especially 2010 has rescued it somewhat, mind the way it has behaved up until now has had me bemoaning it again, it is the true winter month, but on so many occasions fails to maximise just what potential it has - a bit like the way July has behaved since 2006.

You're quite right regarding the difficulty of achieving low min' on high ground, unless you happen to live in a hollow or valley within a general area of high ground. Cold spells here are great for lengthy spells of 'ice days' but really low minima are as rare as hens teeth.

Contrast the following minima between here and the local valley at 140m just 1.5 miles away.

November 2010: Valley -13.4c Here -6.4c

December 2010: Valley -11.5c. Here -6.7c

Just occasionally the minima will be similar at both locations, such as Jan' 1987 when the valley recorded -11.4c and it was -10.7c here.

[Aaron]

You do better for snow however and for most people it's snow first, cold second.. I would have thought!

-5.7 here at the moment, a low of -5.8c by far the coldest of the winter season and colder then any temperature of 2011..

Edited January 15, 2012 by Aaron

[Evening thunder]

This winter must be the longest wait I can remember to get below -3C here. Not sure this spell can do it due to the SE breeze and cloud at times here. The lowest so far is -2.6C in December. January 2011 reached -7.4C here on the 31st.

We live in a frost hollow here due to being in a river valley, though the whole area towards Exeter tends to be a 'cold hollow' type area on clear nights (Exeter Airport reached -16.5C on the 26th December last year!) We had -14.0C here on the 25th. Sometimes we are colder than Exeter Airport though it often just beats me.

A station on a hill that sides the valley about 1 mile from me only got it's 1st air frost the other day! though this station is a Davis Vantage Vue that's about 8m above ground to optimize wind readings over temperature.

[reef]

I reached a low of -1.8C here this morning, meaning its the first air frost of the month and the third of the Autumn/Winter (and the coldest).

Its already down to 1.7C now, so another looks pretty likely.

To give an idea how poor January has been for cold temperatures here in recent years, tonight only has to fall to -3.4C to make it the 4th coldest January min in the last 25 years! That would be the coldest since 2002 aswell.

Ironically the min temp here was -3.3C morning, so we just missed out again. Still a hard frost though.

[jean91]

Wow that is quite shocking. I'm surprised January 2009/2010 didn't produce something much colder than this.

We managed a very good -12.5c here in Orly Airport on the 7th january 2009 with snow on ground and a clear, no wind night .This is not often that we reach -12c for here so did went for a walk!!!!!! January 2009 was a much better month for lowest temps than december 2010 . The last time we did reach -12c was on the 1st january 1997.

[AderynCoch]

You're quite right regarding the difficulty of achieving low min' on high ground, unless you happen to live in a hollow or valley within a general area of high ground. Cold spells here are great for lengthy spells of 'ice days' but really low minima are as rare as hens teeth.

Contrast the following minima between here and the local valley at 140m just 1.5 miles away.

November 2010: Valley -13.4c Here -6.4c

December 2010: Valley -11.5c. Here -6.7c

Just occasionally the minima will be similar at both locations, such as Jan' 1987 when the valley recorded -11.4c and it was -10.7c here.

January 1987 is a classic example of cold lower-level temperatures brought about by cold uppers, rather than inversion. In this instance, the air imported from the east was so cold (uppers below -20C in some parts) that clear skies and lack of wind were not required to record such low temperatures. The prevalence of snow clouds and strong winds also explains why although the low minima were not that exceptional in most areas, the low maxima certainly were.