North Sea Low Cloud

[Bottesford]

As said in the 'today' thread...

Interesting reading about why these easterly flows do create cloud in some situations not others. I think it's worth looking at more closely in the future as it seems to be the hardest weather to predict - and one of the biggest and often unexpected spoilers to predicted nice weather.

The difference to yesterday is very marked - this time yesterday I was outside the pub in a t-shirt (admittedly I got nippy after a while!) having walked around in some lovely evening sunshine after a max just shy of 17c. There were loads of people out & about enjoying the outdoors & we got to have lots of air into the office and I needed no heating at home.

Today we reached 10.9c, there are very few people around outside, my heating is burning away right now and that wind is a pain in the backside to cycle against - especially uphill!

Synoptically things are very similar to yesterday but conditions are very different. Perhaps in these sorts of spells we need to examine the data more closely?

Would anyone like to comment on how tomorrow & the weekend may or may not be different? Do we just need to look at dew points and wind direction for the info or are there other factors to consider?

[Thundery wintry showers]

One interesting question to add to John Holmes's recent post, which I don't know the answer to, is how high do dewpoints have to be for low cloud and fog to form widely over the North Sea? I imagine the differential between SSTs and dewpoints has to be a factor here. Currently the dewpoints are around +6C in the North Sea.

The isobar charts show an anticyclonic southerly regime over the north, with a slight easterly drift covering the south. Tomorrow winds are set to be southerly everywhere, with the south losing that easterly drift, so I expect low cloud to be somewhat more restricted tomorrow- perhaps still clinging onto some of the more exposed North Sea coastal areas.

The GFS appears to be poor at modelling these areas of low cloud, as does the high resolution NMM model. That may well have a lot to do with it, most other areas of weather forecasting tend to be picked up to some extent on forecast models.

You have to be careful of going too far to the other extreme as well. I remember quite a few occasioins when there was a pronounced easterly flow and I forecast that there would be a lot of low cloud around the Tyne & Wear coast, and in reality the cloud burnt off pretty quickly giving mostly dry and sunny, if chilly, days.

[johnholmes]

not got time this evening but when I do get time I'll do a feature on what to look for and try to explain why some events happen and others don't.

in short, watch the visual sat last thing previous day, check the 00z Watnall ascent for its profile, humidity at low level etc, along with winds from surface to 2000ft; check the sat picc as early as possible next morning; stick the surface isobar flow over it, as good as any model output, better than most, as Met have commented through today on their techie bit, at least by inference.

More when I get time and also about the higher Sc type that can also muck up a nice day from the N Sea, old frontal zone, so different approach needed.

Short answer to Ian (TWS), yes check the SST off the coast and search for dewpoints in the same area, GFS not much use I don't think in this, anything at or above is a danger signal; dewpoint>sea temp that is.

hope this helps for the time being.

Friday should be different, as the loweest levels wind flow is very slowly veering so he flow will gradually come off the land not the sea, although for S Yorks, Notts, Lincs it may well be a slow process.

Saturday=different day=frontal from west!

Edited April 2, 2009 by johnholmes

[stormchaser1]

Evening everyone

I found this link if anyone is interested, might help!!

http://www.bbc.co.uk/wales/surfing/sites/f...es/seafog.shtml

NIGEL

[johnholmes]

The GFS appears to be poor at modelling these areas of low cloud, as does the high resolution NMM model. That may well have a lot to do with it, most other areas of weather forecasting tend to be picked up to some extent on forecast models.

the Met O Fine Mesh is better but far from good in my view, watched it today and its been better than their forecasts for this morning but still with boundary layer problems, so it has to be used with caution.

No reason though why they got it so wrong in my view, but then so did I until I decided to look at the visual sat picc and stick the lowest level wind flow on it!

Edited April 2, 2009 by johnholmes

[I remember Atlantic 252]

it sux! takes ages to clear here mainly between april-august, never seem to miss it when its due, 4th may 2007 very bad never cleared max 11.0oC, bbc predicted it to clear by 10am and 22oC

already rolled in again now, dosent usually roll in during the evening, often its started clear and rolled in at 8am ish and not cleared at all, sometimes clears at lunch time if lucky,

NSMLC summers day spoiler!

[multi cellular thunderstorm]

It came in really quick here earlier and now it's quick thick fog.

Here's a time lapse I made showing it rolling in...

http://s292.photobucket.com/albums/mm3/mpp...nt=Untitled.flv

[Costa Del Fal]

I hate this low cloud. It always clears later than most forecasts suggest too. Grrr.

[Summer of 95]

I've been wondering this for ages- time and time again only the east coast counties are forecast to be affected, yet it frequently reaches as far west as here. I can more or less understand why it forms at the coast (difference between land/sea temps etc) but why/how can it spread 200 miles inland without evaporating? And why with the stronger sun of spring/summer, is is so reluctant to burn off at times (often I've seen it persist here till noon or beyond in May and June).

It's especially frustrating when in an easterly regime one day is gloriously sunny, yet the next I wake to chilly, cloudy conditions which persist till the afternoon, when the synoptic chart hasn't changed and the forecast is for fog near the east coast clearing by 10am, wall-to wall sunshine elsewhere.

[Bottesford]

It's especially frustrating when in an easterly regime one day is gloriously sunny, yet the next I wake to chilly, cloudy conditions which persist till the afternoon, when the synoptic chart hasn't changed and the forecast is for fog near the east coast clearing by 10am, wall-to wall sunshine elsewhere.

Precisely why I so dislike this kind of set up - it's very hard to predict with any accuracy where will be affected. It makes many forecasts useless and planning more summery outdoors stuff much more difficult.

I told many people it'd be a mostly warm & sunny week with very static unchanged conditions - I can usually give a rough guide to people about the week ahead and it isn't usually *too* far off having read the many useful posts & summaries here.

But it's ended up a very mixed week and nothing like as good as I'd said. The difference between having the cloud & not is very marked - it feels very very different despite the similar setup.

Still, it's interesting to follow how & why it forms - even if it is a pain in the backside!

[stormchaser1]

Evening Bottesford

im currently looking at the Custom Skew charts supplied by NW Xtra

and if im right it looks like more of the saame for my region tomorrow afternoon

According to the Skew charts the Dew point starts to rise on the 1500z then on the 18z the dew point rises further,

This starts to rise at around 950mb then starts to fall again around 900mb

Also there is a temperature inversion from 950mb rising to 800mb , so if my theory is correct , the Fog could start to move in between 1500 and 1800hrs

Looking at the skew chart might be better than my explanation

nigel

[Andy Bown]

It came in really quick here earlier and now it's quick thick fog.

Here's a time lapse I made showing it rolling in...

http://s292.photobucket.com/albums/mm3/mpp...nt=Untitled.flv

That's cool, how long did it take in real time?

[Geordiesnow]

Low cloud burnt off here around 12ish and were left with hazy sunshine yet looking at the cloud images, around the Boulmer area the low cloud has just stuck hence the 6C being recorded there at the moment.

Can't say i am fond of low cloud myself, its actually one of the most frustrating weather types to experiance here whilst everywhere else is at the mid-twenties and sunshine blazing whilst us poor folk on the East coast are stuck under cloud and sea fog with temps at the mid-teens at best. Must admit though i love sea fog, especially when you can see a bank of sea fog heading your way(simerler to MCT time lapse video but of course not as quick lol).

Edited April 3, 2009 by Geordiesnow

[Thundery wintry showers]

I have to admit I quite enjoy sea fog when it come in in patches with sunshine in between, which occasionally happens in Cleadon when the fog is mostly confined to the extreme coastal strip. However I tire of it very quickly when it persists- and I nearly always consider low cloud that doesn't produce fog unwelcome. One of the big problems with low cloud (including sea fog) is that when showers and thunderstorms head in, I cannot see the convective clouds that are producing them because the low cloud is in the way!

Fog that forms over the land is a totally different story. In both Norwich and Exeter I've experienced banks of fog (both locations seem quite prone) and generally welcomed them, as they rarely stick around for long and often produce spectacular effects (more so than sea fog usually does). There was a particularly memorable case on the UEA campus last September when a large bank of thick fog slowly cleared from the east, and standing on top of the highest hill on campus, I could see a huge mass of cloud retreating away below me and the tops of the trees sticking out- it was quite surreal.

One thing I notice with North Sea low cloud (which is another point in favour of sea fog as opposed to just low cloud) is that fog tends to be associated with slack easterly flows and often burns right back to the coast during the day. In contrast stronger easterly regimes tend to bring higher cloud in, and it tends to be much harder to break up.

[I remember Atlantic 252]

sea mist burnt off at 1pm, better than yesterday, 15.4C max

[Guest North Sea Snow Convection]

The only non descript cloud and mist that occurs in my area is the sort that is driven in on a south westerly off the English Channel. Horrible.Yet another reason why I hate southwesterlies. No coincidence that when the wind changed into the south west yesterday the muck arrived.

North Sea Cloud is a different 'animal' entirely - as are winds from an easterly/northerly quarter in general.

Edited April 4, 2009 by North Sea Snow Convection

[Bottesford]

... and that's what it comes down to - location! You're less prone to North Sea cloud but more prone to westerly stuff perhaps. Other way round here - as the gorgeous day today testifies. Looks like it's heading your way too anyway!

[johnholmes]

exactly Botte

Kent is affected by both, the NE corner = N Sea, most of the rest of the county is south coast effect.

However there is a major difference that is the 'feel' of low cloud on the south coast with a S-SW wind, be it light or moderate, and that along the N Sea coast.

Personally I would IF I had to suffer either, take the south coast over the N Sea coast any day!

I will eventually do the blog I promised on how to try and predict before it rolls in, N Sea low cloud/mist/sea fog.

Edited April 4, 2009 by johnholmes

[Nick F]

I've been affected here by both low grey cloud off the N Sea over recent days (and I live in the far west of Kent) of the depressing grey cold kind. And also, today, low grey cloud and hill fog from the SW. Both as annoying as each other, but both directions have fortunately seen the low grey cloud and mist burnt off by mid-afternoon to glorious sunshine, today without the nagging cold easterly wind which made it more comfortable not to wear a coat.

[damianslaw]

Noted the cold on the Aberdeenshire coastline yesterday with Inverbervie recording a mx of 5.7 degrees whilst Kinlochewe sheltered in the NW Highlands recorded I believe 19 degrees or thereabouts. It shows how cold the North Sea is at this time of year and how those on the North Sea coast must really despise it when a slack east wind moves in.

[johnholmes]

I've been affected here by both low grey cloud off the N Sea over recent days (and I live in the far west of Kent) of the depressing grey cold kind. And also, today, low grey cloud and hill fog from the SW. Both as annoying as each other, but both directions have fortunately seen the low grey cloud and mist burnt off by mid-afternoon to glorious sunshine, today without the nagging cold easterly wind which made it more comfortable not to wear a coat.

so are you saying Nick, that getting both types, the N Sea 'feels' the colder one?

[Nick F]

It shows how cold the North Sea is at this time of year and how those on the North Sea coast must really despise it when a slack east wind moves in.

Aye, it's not pleasant ... the easterly during the week as well as bringing uniform slate grey skies was damp and fairly cold too - Nasty. I like the outdoors and going for long walks and the difference of appeal this afternoon's clear blue skies and sun's warmth on our walk compared to one of the other morning's cold grey mizzle from the North Sea would be quite stark. Fortunately I was busy at work on those cold grey easterly mornings.

so are you saying Nick, that getting both types, the N Sea 'feels' the colder one?

Definately the case these last few days, the SWerly hill fog, drizzle and mist this morning felt less cold than its N Sea cousin during the week. Though if I was down by the coast this morning it may have felt chilly off the sea in the dampness.

[Guest North Sea Snow Convection]

Crikey, it's gang warfare now! I'm getting a mugging for my choice of airflows of one of our coastal stretches :lol:

I never thought it would matter so much. This is being taken seriously!

It's only weather guys !

[Nick F]

Crikey, it's gang warfare now! I'm getting a mugging for my choice of airflows of one of our coastal stretches :lol:

I never thought it would matter so much. This is being taken seriously!

It's only weather guys !

Don't think anyone's taking it seriously are they??? Just light-hearted observations of the last 4-5 days' grey mornings ... no melodrama intended.

[Guest North Sea Snow Convection]

I would rather have the clear skies and sunshine than the low cloud from an easterly, but it isn't such a bane or as critical to me as it obviously is for others and as I said on another thread about summer, it can bring some pleasant relief in the mornings when being out and about and refreshingly cool to be out and about in.

South westerly winds which bring the damp muggy low cloud/drizzle and mist are definitely the worst - it is the very symptom of that awful tropical maritime air that we endure during our worst winter weather and when it occurs in summer,for eg, it is often at the expense of storms or anything interesting. With easterly winds at least conditions can change from low cloud to storms from the continent, say, in no time at all

With sw'erlies in summer if it happens to be a convectional airstream,all the showers form well inland and 12 miles or so from the coast where I now live there is nothing as all the cloud bubbles up and is blown well inland. There is no improvement here in that respect to when I lived just a mile or two from the coast.

Edited April 5, 2009 by North Sea Snow Convection