First Frost - September 16th

Danno

Looks like an exceptionally cold night Friday night into Saturday Morning with temperatures expected to hit a mere 1c in the wee hours.

This is certainly four to five weeks in advance of when we should expect a ground frost in Ireland.

Central Ireland looks like being most at risk. A few more of these nights and the trees will be bare by October.

I do wonder is this a precurser to a cold or a mild winter???

Mothman

Danno wrote:

This is certainly four to five weeks in advance of when we should expect a ground frost in Ireland.

My first frosts in previous Autumn/Winter

Ground frost
9th Sep 02
7th Sep 03
8th Oct 04
None this season so far

Air frost
5th Jan 03
27th Sep 03
14th Nov 04

Will be a sharp contrast to tonight with temp currently at 18C at 22:30.

daveirl

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Danno

Is that 4 or 5 per week in the winter or per season? You must be in Castletown Bere if it is per season!

daveirl

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Mothman

Perhaps I should differentiate a meterological ground frost and what we normally call ground frost.

A ground frost is when temp at grass tips falls below 0C, however in my experience, it isn't usually visible till the temp drops below -3C

So taking a figure of -3C at grass tips, and in brackets number of night with official ground frost before this date

First dates sub -3C in previous winters is.

19th Nov 2004 (15)
21st Oct 2003 (5)
17th Oct 2002 (10)

But then I don't think I'll I reach -3C tonight though sub zero is likely.

Mothman

Didn't get really cold last night at all. Min of 6.9C, plenty colder during the summer and earlier this month, though the grass min temp of 1.0C was lowest this side of Summer, though not as low as June 27th when a slight ground frost was recorded.

CerebralCortex

Did any body hear of the North Atlantic Oscillation that has something to do with air pressure in Iceland and the Azores.

Danno

Yup, it is to do with zonal weather - like what we have this week.
Low pressure over Iceland and High Pressure over the Azores.
The lower the low i.e. lower than 980 in iceland and stronger high pressure above 1024 in the said locations strengthens the wind from the west over ireland. bringing us mild - rain - cold - rain - mild - cold - rain... in that sequence.
It usually happens in Autumn and Spring. It is surprising me that it is happening so early this year. Usually October and March are the months for this weather.

Danno

Anyways, looking V Cold tonight, 0000z at Kilkenny, Mullingar and Claremorris at 2c. Rosslare at 11c - just 45miles from KK !!!

On the NRA:

Cavan 1.0c
Monaghan 0.9c
Baltinglass 0.5c
Killarney 30.5c - still summer in Kerry I guess - at least till sunday evening anyways!!!

Mothman

Lowest temp since May with 1.9C. Gmin -1.9C, first frost this side of Summer.

Kilkenny got down to zero.