South West England Cold Spell Discussion

[Dorset_Weather]

Yes I know what your saying, think the models always struggle when cold from the East is trying to establish its self, then they lend to get a grip 2 days just before its here..... hence the present mess.

Once the cold is established they seen to catch up and we tend to then have a bit more agreement.

Only my novice POV of what seems to of happened with recent easterly's.

Kev.

[03jtrickey]

Thanks Ian,

It's good to have you back on here again!

Interesting thoughts from the Met Office.

[Nights King]

Thanks Ian for your thoughts.

Looking forward to sunday and indeed interested in tuesday/wed updates later on.

[Ian Fergusson]

Thanks Ian for your thoughts.

Looking forward to sunday and indeed interested in tuesday/wed updates later on.

Hi Mullender

Tues/Wed a total mess in the medium-range output and we're not attempting to offer any real confidence at this juncture due to model disparity. Ironically, confidence is somewhat better further into the future, rather than within the 4-5 day scheme of things (doesn't happen often, but here's one such case). Based on the 00z runs, the Met Office's Global Model has consistently offered the notion of a (temporary) transition to a milder, cyclonic southwesterly through Wednesday and into Thursday and so for us in the West, we're anticipating a touch of hill snow in the Tues PPN story but essentially rain thereafter towards Thurs.... Conversely, worth noting how GFS has remained equally steadfast in wanting to retain a blocked scenario and a slow-moving occlusion draped across the British Isles. And completing the trio of (divergent) opinion, ECMWF has readily flip-flopped from the GM to GFS solutions.... and back again. ECMWF's latest prog calls for the cyclonic SW - as per GM - to appear on Thursday for a short period only, slowly nudging the occlusion up to the north with attendant risk of snow on the leading edge. But crucially, as of T+144, ECMWF now hints at a SE surface flow evolving and so the Met Office has modified their GM into line with this notion. Complex mess adequately sums it up for now, but we're currently going for the idea of a temporary 'somewhat milder' incursion into midweek ahead of things returning to a colder story by the weekend....

Edited January 30, 2010 by Ian Fergusson

[Guest North Sea Snow Convection]

Interesting about confidence being higher for the further outlook. I understand the background factors in play as to why that might be the case but equally, no short route to a cold easterly airstream such as the latest GFS suggests in terms of a negatively tilted system disrupting SE and undercutting the cold air to the NE, does allow other variables to come into play in the meatime if it is assumed that continental air might return up to 7 days away. Upstream signals seem to point to bursts of energy coming out of the states and there is plenty of time for even subtle changes in the energy distribution in the jet stream to have down stream effects on the present suggested outlook.

On that basis, such confidence, as expressed at present in the further outlook is surely subject to potential change.

Edited January 30, 2010 by North Sea Snow Convection

[Nights King]

Hi Mullender

Tues/Wed a total mess in the medium-range output and we're not attempting to offer any real confidence at this juncture due to model disparity. Ironically, confidence is somewhat better further into the future, rather than within the 4-5 day scheme of things (doesn't happen often, but here's one such case). Based on the 00z runs, the Met Office's Global Model has consistently offered the notion of a (temporary) transition to a milder, cyclonic southwesterly through Wednesday and into Thursday and so for us in the West, we're anticipating a touch of hill snow in the Tues PPN story but essentially rain thereafter towards Thurs.... Conversely, worth noting how GFS has remained equally steadfast in wanting to retain a blocked scenario and a slow-moving occlusion draped across the British Isles. And completing the trio of (divergent) opinion, ECMWF has readily flip-flopped from the GM to GFS solutions.... and back again. ECMWF's latest prog calls for the cyclonic SW - as per GM - to appear on Thursday for a short period only, slowly nudging the occlusion up to the north with attendant risk of snow on the leading edge. But crucially, as of T+144, ECMWF now hints at a SE surface flow evolving and so the Met Office has modified their GM into line with this notion. Complex mess adequately sums it up for now, but we're currently going for the idea of a temporary 'somewhat milder' incursion into midweek ahead of things returning to a colder story by the weekend....

Thanks Ian

I shall keep an eye on your blog which i find very informative, Will you be updating it this evening with latest NAE for sunday?

Chilly day here on mendip with our max so far at 0.9c which is colder than i expected to be honest with forecast temp values for towns being at around 4/5c today.

Slight dusting of snow also from one shower we had last night.

[Ian Fergusson]

Thanks Ian

I shall keep an eye on your blog which i find very informative, Will you be updating it this evening with latest NAE for sunday?

Chilly day here on mendip with our max so far at 0.9c which is colder than i expected to be honest with forecast temp values for towns being at around 4/5c today.

Slight dusting of snow also from one shower we had last night.

Hi Mullender - yes indeed, I'll update it based on the latest NAE once I see that..... obviously I focus attention on keeping it updated on the blog rather than duplicating the same information here on the thread, so you might want to subscribe to the blog updates via RSS or similar.

Cheers

Ian

[Nights King]

Hi Mullender - yes indeed, I'll update it based on the latest NAE once I see that..... obviously I focus attention on keeping it updated on the blog rather than duplicating the same information here on the thread, so you might want to subscribe to the blog updates via RSS or similar.

Cheers

Ian

Just signed up cheers.

[Ian Fergusson]

Just signed up cheers.

A quick addition - am about to go out for a while but as an intermin note ahead of updating my blog a bit later.....

latest NAE (and our chief forecaster briefing) still bullish about feeding snow showers across from the west steadily through tomorrow AM; perhaps 1-3cm accumulation fairly widely stretching down over Wales into parts of midlands and southern-central England, Glos, north Wilts, probably Bristol / Bath and other districts.... I will add new modified NAE frames onto the blog a bit later. Incidentally our new run also keen to offer snow showers even by midnight appearing into areas adjacent to Bristol Channel, e.g., North Somerset.

More on the blog later -

Ian

[snowking]

Cheers Snowking, my language!

Now let's see if I have this right...I run a very hot bath in a cold room, this causes condensation, if I had low pressure in my bathroom then that condensation would fall as snow?

I work with 10 year olds, everything must be dumbed down into child speak. lol

Hi daisy,

Not quite but almost. Yes to the condensation example, what happens there is the warm water from your bath rises into the colder air (or touches the colder surfaces of, for example, your mirror) and condenses, forming condensation. Obviously in weather terms this would cause cloud and precipitation. Its all about nature trying to balance itself out, so for example air flows from high pressure to low pressure to try and even out the pressure, much the same here really as the warm air rises into the cold air to try and even things out (thats not 100% scientifically true but its the best way for you to think of it for now without going into the very complex physics behind why it happens). So using this analogy we can say that the colder the air is above, and the warmer the water is below, the bigger the thermal gradient (difference in temperature between the two) and therefore the stronger the convection, and therefore the heavier the precipitation that forms is likely to be

In terms of snow, whether or not the precipitation that is formed by convection is in high or low pressure does not determine whether it will be snow. In high pressure overall precipitation (be it rain, sleet, snow or hail) is less likely to form than in low pressure (again, some physics involved there but all you need to know is precipitation is more likely to form the lower the pressure is)

So then as a quick summary, pressure doesnt affect what type of precipitation forms, pressure only affects the potential for precipitation to form. This is generally why high pressure brings dry conditions

SK

A quick addition - am about to go out for a while but as an intermin note ahead of updating my blog a bit later.....

latest NAE (and our chief forecaster briefing) still bullish about feeding snow showers across from the west steadily through tomorrow AM; perhaps 1-3cm accumulation fairly widely stretching down over Wales into parts of midlands and southern-central England, Glos, north Wilts, probably Bristol / Bath and other districts.... I will add new modified NAE frames onto the blog a bit later. Incidentally our new run also keen to offer snow showers even by midnight appearing into areas adjacent to Bristol Channel, e.g., North Somerset.

More on the blog later -

Ian

Great to have you back Ian,

Yes will be very interested to see the modified GM output because the raw output available on weather-online not particularly keen on much precipitation away from the far west. 950mB temperatures also looking a little marginal come tomorrow too from their output

Look forward to your update

Kind Regards

SK

[dancing daisy]

Thanks a lot Kris

Child speak is without a doubt the way forward with me, I actually understand what has been written...for a change!

I really do want to learn about this, but I find my eyes glazing over and I start chewing my nails if there are words of more than 3 syllables that I do not understand, god alone knows how kids learn new things everyday and remain so cheerful.

Edited for a quick question> So do sea temperatures affect our weather then?

Edited January 30, 2010 by dancing daisy

[snowking]

Thanks a lot Kris

Child speak is without a doubt the way forward with me, I actually understand what has been written...for a change!

I really do want to learn about this, but I find my eyes glazing over and I start chewing my nails if there are words of more than 3 syllables that I do not understand, god alone knows how kids learn new things everyday and remain so cheerful.

Edited for a quick question> So do sea temperatures affect our weather then?

No problems at all daisy, ive been viewing the charts (as i realised in the shower this morning) for almost 9 years now, and it really does take time. I learn new things every day, and you start to find that once youve mastered the charts you start looking elsewhere - medium and long range forecasting, the latter of which im still very much working on

In answer to your question yes, instrumentally in numerous ways. For example low pressure is more likely to form over warm seas (conversely high pressure is more likely to form over cooler seas). If you look at el nino/la nina, which is simply defined by the temperature of water just off the coast of peru in the pacific ocean, which has been found to affect global weather patterns on a monumental scale. Theres also the far more localised effects of convection (as we've discussed) and also modification of air masses. Basically if the seas are too warm the air just above them is likely to me warmer too. This can affect a cold air mass by mixing it with the warmer air just aloft of the sea and making the overall air mass warmer

SK

[Nights King]

A quick addition - am about to go out for a while but as an intermin note ahead of updating my blog a bit later.....

latest NAE (and our chief forecaster briefing) still bullish about feeding snow showers across from the west steadily through tomorrow AM; perhaps 1-3cm accumulation fairly widely stretching down over Wales into parts of midlands and southern-central England, Glos, north Wilts, probably Bristol / Bath and other districts.... I will add new modified NAE frames onto the blog a bit later. Incidentally our new run also keen to offer snow showers even by midnight appearing into areas adjacent to Bristol Channel, e.g., North Somerset.

More on the blog later -

Ian

Interesting to see how each update seems to suggest more widespread shower activity for tomorrow and now even a slight covering of snow cannot be ruled out. Thanks Ian i look forward to the update later on your blog.

Getting cold outside now -1.6c and todays high was a scorching 0.9c

[dancing daisy]

No problems at all daisy, ive been viewing the charts (as i realised in the shower this morning) for almost 9 years now, and it really does take time. I learn new things every day, and you start to find that once youve mastered the charts you start looking elsewhere - medium and long range forecasting, the latter of which im still very much working on

In answer to your question yes, instrumentally in numerous ways. For example low pressure is more likely to form over warm seas (conversely high pressure is more likely to form over cooler seas). If you look at el nino/la nina, which is simply defined by the temperature of water just off the coast of peru in the pacific ocean, which has been found to affect global weather patterns on a monumental scale. Theres also the far more localised effects of convection (as we've discussed) and also modification of air masses. Basically if the seas are too warm the air just above them is likely to me warmer too. This can affect a cold air mass by mixing it with the warmer air just aloft of the sea and making the overall air mass warmer

SK

and this is why I see lots of complaints about snow fizzling out over the Channel, North sea etc... Ahhh, it is slowly clicking in to place. I will look into el nino/la nina later on.

Thanks again Kris for your help and patience.

Right time for a disco nap now.

Edited January 30, 2010 by dancing daisy

[snowking]

and this is why I see lots of complaints about snow fizzling out over the Channel, North sea etc... Ahhh, it is slowly clicking in to place. I will look into el nino/la nina later on.

Thanks again Kris for your help and patience.

Right time for a disco nap now.

Yep if its heading into high pressure, or especially if its convective as it heads inland (obviously once its not moving over the warm water any more it will have little or no moisture to keep taking water from) it is likely to fizzle out

SK

[littlemissy]

Yep if its heading into high pressure, or especially if its convective as it heads inland (obviously once its not moving over the warm water any more it will have little or no moisture to keep taking water from) it is likely to fizzle out

SK

I too am very grateful for the explanations .I am hoping to be able to understand more and be able to contribute something more useful than "it's chilly" .I was thinking of getting a little weather gadget which reads temps and tells you the humidity etc.

Anyway thanks again.

[Jonesywilliteversnow]

hello ladies and gentle back to the cold it seems then and my return to visting netweather 20 times a day :lol:

[Valhalla]

Just came back home from Stockwood and the car temp read - 4

As we got back home to Brislington - 2

[Ian Fergusson]

Hellooooo

Have update the blog as promised...... re tomorrow's prospects

Cheers

Ian

[Jonesywilliteversnow]

Hellooooo

Have update the blog as promised...... re tomorrow's prospects

Cheers

Ian

Thanks

[dancing daisy]

hello ladies and gentle back to the cold it seems then and my return to visting netweather 20 times a day

So, where are your facebook updates then?

Just to be awkward, I am actually getting excited about the prospect of snow now. I am already planning my snow zoo, I could also do with a few days off work, I have worked for 2 full weeks this term, it is surely time for a break!

[Ian Fergusson]

So, where are your facebook updates then?

Just to be awkward, I am actually getting excited about the prospect of snow now. I am already planning my snow zoo, I could also do with a few days off work, I have worked for 2 full weeks this term, it is surely time for a break!

Daisy: NO...... do not get excited, about any of this, yet.

Tomorrow is still hours away and next week, frankly could be light years away.

Keep the school open for now...

[Thundersquall]

Any chance of those snow showers over N Wales reaching Bristol and

other locations in the West Country?

Edited January 30, 2010 by Thundersquall

[Ian Fergusson]

Pls note latest blog update (for tomorrow) now published based on very latest NAE etc........ ta.

[dancing daisy]

Daisy: NO...... do not get excited, about any of this, yet.

Tomorrow is still hours away and next week, frankly could be light years away.

Keep the school open for now...

Ian, do you actually understand the gravity of this situation? I need time off, I have been working too hard, you're a weatherman, so sort it out! I also have this fabulous plan for a snow giraffe.