33 replies to this topic

[Thundery wintry showers]

Continental air is fundamentally dry and stable, and as it passes over the North Sea it picks up moisture, and the contrast between the cold air and the warm North Sea de-stabilises the airmass near the surface, resulting in convection. If the airmass is very cold at upper levels, the contrast with the warm North Sea may be sufficient to de-stabilise the airmass up to well beyond the cloud condensation level, resulting in towering cumulus and cumulonimbus clouds. The updraughts within the convective clouds are accompanied by sinking air around their periphery, thus producing the characteristic mix of sunny intervals and snow showers. But if not, then the upper atmosphere remains stable and the convective cloud encounters an inversion, spreading out into stratocumulus. Hence, most half-hearted (in terms of cold) easterly incursions just bring an endless stream of stratocumulus in off the North Sea.

However, easterlies tend to be sunny in sheltered western areas all year around because the cloud cover, be it a layer of stratocumulus or cumulonimbus cells interspersed with clear intervals, tends to fizzle out as it passes over the land, especially if it has to pass over high ground. Note "sheltered western areas" though- sometimes in central areas you can get orographic enhancement resulting in even cloudier conditions than near the coast, e.g. during February 1947 Durham managed 42.8 hours of sunshine, about 35% below the local average, but at inland Sheffield the total was a remarkably meagre 18.5 hours, roughly 70% below normal.

[Terminal Moraine]

My location has been on the dividing line between the relatively sunny east and the cloudy west so far this winter.
December had 36.4 hrs of sunshine ( 72% of the 30 year average ) whereas Buxton ( Met' Office site ) had 26.1 hrs and Brierlow Bar a few miles to the south of the town and only 16 miles from here had just 17.7 hrs.
The second half of December was particularly cloudy with just 11.8 hrs of sunshine here from the 16th-31st.
So far January has been sunnier than average with 41.6 hrs in the first 20 days ( 115% of the average for the period) and almost as much as in the whole of January 2011 which had 44.3 hrs. Still some way to go though to equal Jan 2010 which recorded 61.7 hrs.
Both December and January ( so far ) have been wetter than average. December recorded 159.7 mm ( 139% of average ) and January is on 81.6 mm (120% of average for the first 19.5 days).

[AderynCoch]

You've got to be kidding me. We had a good four or five days straight of crisp sunshine earlier this week, but other than that sunny days have been few and far between since October.

Better to get dullness now than in summer though. I don't think I could handle another July 2010 this year.

[Aaron]

'Sunny days have been few and far between'

No, they haven't. Perhaps in your back yard.

[reef]

Aaron, on 21 January 2012 - 07:32 , said:

'Sunny days have been few and far between'

No, they haven't. Perhaps in your back yard.

They probably have been pretty hard to come by Liverpool, as the current dominant westerly pattern encourages an east/west split.

http://www.metoffice...y_1971-2000.gif

Liverpool averaged around an hour of sunshine per day in December and that easily could have come across a few days, so I can understand AderynCoch's point of view.

[Jackone]

reef, on 21 January 2012 - 12:04 , said:

They probably have been pretty hard to come by Liverpool, as the current dominant westerly pattern encourages an east/west split.

http://www.metoffice...y_1971-2000.gif

Liverpool averaged around an hour of sunshine per day in December and that easily could have come across a few days, so I can understand AderynCoch's point of view.

A cloudy winter here so far, the Christmas period was especially cloudy, but apart from that a mix with some sunny intervals, but no wall to wall sunshine like Dec 10.

http://www.metoffice...y_1971-2000.gif

http://www.metoffice...y_1971-2000.gif

A tricky one, but can anyone spot the difference between these 2 maps.

Although according to Philip Eden, January has been sunnier than normal, which surprises me a little. Certainly sunnier than Dec, but I didn't think that sunny.

http://www.climate-uk.com/page2.html

[Bottesford]

Another partly sunny day here and feeling very pleasant out of the wind (which is quite strong).
It really has been an 'easy' winter this time for the first time in some years. Looking forward to spending the gas money on fun stuff this summer!

[Milhouse]

Today has been characterised by cloudy periods but also a good deal of bright or sunny spells. In any lengthy sunshine a t-shirt is quite acceptable to go outside in.

Very satisfied with sunshine amounts so far this winter which have been well above average.

[Terminal Moraine]

Milhouse, on 21 January 2012 - 13:41 , said:

Today has been characterised by cloudy periods but also a good deal of bright or sunny spells. In any lengthy sunshine a t-shirt is quite acceptable to go outside in.

Very satisfied with sunshine amounts so far this winter which have been well above average.

Blimey it sounds like a different world to here. Very little sunshine today, just a few fleeting intervals, and a W/NW wind averaging between 30 and 38 mph with a temp' around 5c making it feel decidedly cold. The walking fraternity in the area are clad in full windproofs/ waterproofs with hoods up and secured.

Bottesford, on 21 January 2012 - 12:52 , said:

Another partly sunny day here and feeling very pleasant out of the wind (which is quite strong).
It really has been an 'easy' winter this time for the first time in some years. Looking forward to spending the gas money on fun stuff this summer!

Don't get spending that gas money just yet, Botty, there's still February and March to go yet!

[Milhouse]

Milhouse, on 21 January 2012 - 13:41 , said:

Today has been characterised by cloudy periods but also a good deal of bright or sunny spells. In any lengthy sunshine a t-shirt is quite acceptable to go outside in.

Very satisfied with sunshine amounts so far this winter which have been well above average.

I spoke to soon. Now 100% cloud cover and looking quite dull.

[Bottesford]

Oh no I'll keep the gas money going in as normal and hope to claim some back in summer! It ain't over till the fat lady sings - I remember many a freezing cold March. Spring is a long way off yet.
Still it's solstice + 1 month now - we're out the darkness pit of the year now - the steady climb begins...

[reef]

Following on from a sunny December here which saw 73 hours (155%) of sunshine, January was very sunny indeed with 89 hours (162%).

It's certainly going to be a very sunny winter. Even if February is the dullest on record the total will be above the 1971-2000 mean.

[Eugene]

Plenty of sunshine since Feb 1st with easterly winds too.

[Bottesford]

Yes absolutely - despite my earlier fears and moaning about easterlies so far this one has been great!
This winter so far has been almost perfect for me. If we get a good dumping of snow today and a reasonable sunny couple of weeks of a freeze (then a warm up) it'll make it spot on.