Winter 2011/2012

Tindie

In here Streetly, Sutton Coldfield, it's cold but no snow but according to metcheck.com
I typed my post code in here, they i could be getting some sleet tomorrow and on

http://www.metcheck.com/V40/UK/FREE/today.asp?zipcode=B74%202DU
and Tue 13 Dec it saying will be getting heavy snow! (Which i don't think will happen)
Any got the molder charts for that week?

StormGazer.11

pistolpetes11 wrote: »

Just posted some charts over on the FI thread , strange is rite , the mean line gone negative on the AO, but today does seem at a maximum high on the index, and the NAO looks likely to flip before the AO which I think should be sooner rather than later , before the end of the month anyway.

You reckon the NAO is going to drop to the negatives so?

Kippure

Just a quick note for every one who watch the charts. The low pressure systems are just a little to far north at the moment but the angle they are coming in at is slowly changing. I can see soon maybe Irelands first Proper blizzard. A little southward. But not till after christmas and the new year me thinks.

ff9999

WolfeIRE wrote: »

Freeze pics from Sky News

http://galleries-news.sky.com/gallery/Big_Freeze_Anniversary

THANKS FOR SHARING, HOW MUCH NICER DOES EVERYTHING LOOK COVERED IN SNOW

bb1234567

met office say white xmas for uk is likely! saying a cold snap with snow to low levels from december 19th to jan 2nd...thats a pretty long cold snap.
http://www.telegraph.co.uk/topics/weather/8936008/Met-Office-predicts-possible-white-Christmas.html

pistolpetes11

StormGazer.11 wrote: »

You reckon the NAO is going to drop to the negatives so?

I do , some stage after mid month , well thats what some of the more seasoned experts have been moving towards.

Wild Bill

ff9999 wrote: »

THANKS FOR SHARING, HOW MUCH NICER DOES EVERYTHING LOOK COVERED IN SNOW

Well, not a rose, or a naked young woman....

Truly, in the Winter an old man's fancy lightly turns to thoughts of love

nacho libre

pistolpetes11 wrote: »

I do , some stage after mid month , well thats what some of the more seasoned experts have been moving towards.

with this in mind, it would be interesting to know how winters, which saw a record ao level and a very cold stratosphere at this time of year, turned out later in the season.

pistolpetes11

nacho libre wrote: »

with this in mind, it would be interesting to know how winters, which saw a record ao level and a very cold stratosphere at this time of year, turned out later in the season.

You could cross reference with good/bad winters off this chart.

Tom Cruises Left Nut

Quick question for anyone who paid for raintoday

Does the shannon radar update every 5 mins on it ?

The netweather extra doesn't. Really annoying !

pistolpetes11

t|nt|n wrote: »

Quick question for anyone who paid for raintoday

Does the shannon radar update every 5 mins on it ?

The netweather extra doesn't. Really annoying !

When Shannons radar is working it goes every 5 mins , bloody thing never seems to be working correctly though .

Actually a question for Su , does the constant issues with this Radar affect the Aviation industry much ? or is there a radar that is always up for you guys in that neck of the woods ?

Su Campu

pistolpetes11 wrote: »

When Shannons radar is working it goes every 5 mins , bloody thing never seems to be working correctly though .

Actually a question for Su , does the constant issues with this Radar affect the Aviation industry much ? or is there a radar that is always up for you guys in that neck of the woods ?

I can only see the same rainfall you can see, I check it on met.ie before a flight!

pistolpetes11

Su Campu wrote: »

I can only see the same rainfall you can see, I check it on met.ie before a flight!

Is it actually down much or is this more so an issue with Raintoday , seem to change every couple of frames





I think that unless you have the Staff radar, the Irish updates are every 15 minutes, so that is why the Raintoday leaves some frames out on its 5-minute updates.

The radar on the met.ie site has been fine throughout this evening, with no skips (15-minute updates). Why not watch it? OK, the UK one has better coverage in the north and northwest, so it depends what you're looking at.

nacho libre

All that snow up in Scotland:(

StormGazer.11

nacho libre wrote: »

All that snow up in Scotland:(

It sure isn't anyway fair Nacho... What did we do to deserve stupid south westerliers etc! I'd even settle for this north/ north westerly situation at this stage if it would just reach as far south as I am and be more consistent! Oh how I hate my geographical location at times haha!

Tindie

Just woke UP to dusting of snow on the roofs, cars and sticking little on the ground! (Will take the dog for in it for bit
in Streetly ,Sutton Coldfield , also i am on Hill (Which is highest part of the west midlands i have been told)

Now got the feeling that winter will very be like the winter we had in 09/10

Tindie

it took really long for me to do this lol

hatrickpatrick

I'm a little late to the party here folks, two questions:

1: Where are people looking at proper worldwide high/low charts? All I can find are ones which zoom in on particular parts of the world which are obviously no use here when you're trying to look at an area including the Arctic AND the UK/Ireland. What links are you looking at?

2: Would someone mind explaining (again excuse the ignorance) why is it that snow is always more likely on hills and mountains than it is at ground level? Is it just because it's already cold up that high so it has more chance of staying on the ground instead of melting?

Deep Easterly

hatrickpatrick wrote: »

I'm a little late to the party here folks, two questions:

1: Where are people looking at proper worldwide high/low charts? All I can find are ones which zoom in on particular parts of the world which are obviously no use here when you're trying to look at an area including the Arctic AND the UK/Ireland. What links are you looking at?

2: Would someone mind explaining (again excuse the ignorance) why is it that snow is always more likely on hills and mountains than it is at ground level? Is it just because it's already cold up that high so it has more chance of staying on the ground instead of melting?

A couple of links
Wetterzentralie (ECMWF,UKMO, GFS, GME and other NWP charts)
http://www.wetterzentrale.de/topkarten/fsecmeur.html

ECMWF - via Vedur.is (European Centre for Medium Range Forecasts) 6 hr Wind, 850 hPa temps and rainfall charts in 6 hr increments:
http://www.vedur.is/vedur/sjovedur/atlantshafskort/#teg=atlant_hiti

GFS charts via Netweather:
http://www.netweather.tv/index.cgi?action=nwdc;sess=


In cooler polar air masses, temperature normally decreases with height hence why any snow that falls will tend to stick around for longer on higher ground.

WolfeIRE

Plenty of snow in the Scottish Highlands

webcams
http://www.snoweye.com/?page=uk

WolfeIRE

Unusual winter weather may be connected to rapid Arctic climate change, report warns

http://www.washingtonpost.com/blogs/capital-weather-gang/post/unusual-winter-weather-may-be-connected-to-rapid-arctic-climate-change-report-warns/2011/12/04/gIQAUdQYUO_blog.html

Tom Cruises Left Nut

WolfeIRE wrote: »

Unusual winter weather may be connected to rapid Arctic climate change, report warns

http://www.washingtonpost.com/blogs/capital-weather-gang/post/unusual-winter-weather-may-be-connected-to-rapid-arctic-climate-change-report-warns/2011/12/04/gIQAUdQYUO_blog.html

:eek:

Su Campu

hatrickpatrick wrote: »

I'm a little late to the party here folks, two questions:

1: Where are people looking at proper worldwide high/low charts? All I can find are ones which zoom in on particular parts of the world which are obviously no use here when you're trying to look at an area including the Arctic AND the UK/Ireland. What links are you looking at?

2: Would someone mind explaining (again excuse the ignorance) why is it that snow is always more likely on hills and mountains than it is at ground level? Is it just because it's already cold up that high so it has more chance of staying on the ground instead of melting?

Snow is more common on high ground for two reasons:

1) Generally the air temperature falls with altitude (but not always!), so obviously snow will melt less up high in the colder temperatures.

2) Even say the temperature is the same for the lowest 1,000 m (eg. +1 °C from ground level to 1,000 m - it is possible, but not that common). Imagine a snowflake falling through the air from above this layer (where it's colder). As it falls into the top of the warm layer, it takes some time for it to start to melt. So if it soon hits a hill top, it will still be fairly frozen. If it has to fall all the way through the layer to reach the ground then it has so much more time to melt as it does so, so therefore it will be a lot more sleety by the time it reaches low ground. So in this case it is not colder up high that leads to more snow up there, it the TIME TAKEN for the snow to fall to lower levels that causes it to melt.

Another important factor though is the fact that as snow accumulates, its melts slower than individual flakes would as more energy is required from the air to melt this larger bulk of frozen water. As the snow reaching high ground is more frozen than that reaching low ground, it accumulates at a faster rate, and therefore is less likely to melt than the same snow falling lower down.

Here's a piece I did for IWO just after the first snow at the end of November 2010.

Well, what a week it's been! Rain, snow, hail, graupel, frost, thunder, blue lightning, freezing fog, freezing rain - the list goes on. For the vast majority of the country, meteorological winter has well and truly started with a flurry (excuse the pun!), with satellite pictures showing the vast majority of the country blanketed by snow and ice. But why did the snow accumulate so quickly this early in the season? Shouldn't it have melted, like it seems to do most other times? With land and sea surface temperatures still usually not at their coldest for another 6-8 weeks yet, you'd have been forgiven to think "ah yeah, but it won't stick" when you woke up last Saturday morning, but boy would you have been wrong!

Snow is an extremely complicated form of precipitation, and as such leads to a very tricky time for a forecaster. There are two "types" of snow - wet and dry, and the particular type we get is important in how it reacts when it hits the ground. Wet snow occurs when the temperature in the Planetary Boundary Layer (roughly the lowest 500-1000m of the atmosphere) is fairly constant and near zero. Partial melting means it contains some liquid water, and is therefore more dense than dry snow. It will compact quicker, so for the same amount of liquid-precipitation, it will form a thinner layer than dry snow, with a liquid equivalance of between 10:1 and 5:1. It will also fall in larger flakes, because two or more flakes will agglomerate as they fall, and it will not drift to well in wind. This type is the best for making snowballs.

Dry snow occurs when the PBL is a lot colder, inhibiting this partial melt, and therefore yielding a less dense and smaller flake. The lower liquid content makes this snow difficult to make snowballs with, and will easily drift as it blows in the wind. Its lower density means it will form deeper layers than wet snow, with a liquid equivalent of between 15:1 and 30:1. As we were affected by an Arctic airmass, with low moisture levels, most of the snow fell as dry snow.

An important factor in setting the scene for the week was the fact that the first snow fell onto frozen terrain. A hard frost had set in Friday night, with air temperatures down to -3°C in the east, and grass temperatures a few degrees lower. This meant that anything that fell remained intact, building up a layer that would then further help to keep the ground temperature low, but also insulate any further snowfall from the remaining warmth radiating up from the ground. The dry nature of the snow layer meant it contained lots of air, which is a good insulator, adding to the effect. This is also why snow accumulates more on grass than on concrete pavements, roads, etc. The grass blades are more exposed to cold air than concrete, which will stay warm for longer as it's in full contact with the ground's internal warmth. The air pockets around grass insulate the snow from the this warmth, allowing it to build quicker. Of course, the more it builds, the greater its bulk, therefore the greater the energy input required from the ground to raise its temperature and cause melting.

Another factor is that the snow fell at nightime. With nightime snow there is no uv radiation present to cause sublimation of the snow as it falls, therefore more of it reaches the ground than when it falls in daylight. Dayime uv radiation also heats the ground and other surfaces, reducing the chances of it sticking, but with a covering of snow present, this radiation doesn't get a chance to heat the ground, therefore air temperatures remain low.

Now of course the synoptics have changed, and much warmer air has moved in behind yesterday's front. Temperatures and dewpoints rose above 0°C, kicking off melting of the snow layer. Once some bare ground becomes exposed, daytime uv radiation can accelerate melting around the edges, exposing more and more ground, which means more and more melting, and so on. The depth of lying snow reported at Casement fell from 21 to 16cms in one hour Friday afternoon as temperatures rose slightly and precipitation turned to rain. It will take some time, however, for all the snow to thaw, with nightime freezing fog lingering throughout the day in places during the next few days. Further snow is expected next week, especially over high ground, so it will be interesting to observe whether this during the day or at night. And as it's a polar airmass this time, it will more than likely be wet snow, so will lead to the same depths as of late.

Maybe that's where the term "Depths of Winter" comes from?!

Caff Caff

WolfeIRE wrote: »

Unusual winter weather may be connected to rapid Arctic climate change, report warns

http://www.washingtonpost.com/blogs/capital-weather-gang/post/unusual-winter-weather-may-be-connected-to-rapid-arctic-climate-change-report-warns/2011/12/04/gIQAUdQYUO_blog.html

I wonder how Piers would respond to that!

mcriot29

WOW AO is so high today near 6 record breaking event, even 14 days out its at plus 2.

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.obs.gif

WolfeIRE

Cold weather has its many downsides. R.I.P.



The death of a homeless man in Dublin city centre is being blamed on last night's cold weather by local representatives.
The body, believed to be a 30-year-old man who was originally from Latvia, was discovered in the garden area of Dominick Street flats this morning.
Local Independent Councillor Christy Burke said the man was one of three Latvians who had been living there with sleeping bags and cardboard boxes for a number of months.
"Every year someone dies of hypothermia in Dublin city," Cllr Burke said.

nacho libre

WolfeIRE wrote: »

Cold weather has its many downsides. R.I.P.



The death of a homeless man in Dublin city centre is being blamed on last night's cold weather by local representatives.
The body, believed to be a 30-year-old man who was originally from Latvia, was discovered in the garden area of Dominick Street flats this morning.
Local Independent Councillor Christy Burke said the man was one of three Latvians who had been living there with sleeping bags and cardboard boxes for a number of months.
"Every year someone dies of hypothermia in Dublin city," Cllr Burke said.

it's a disgrace, with all the unoccupied houses that anyone should be homeless.

on topic:

Su Campu wrote: »

2) Even say the temperature is the same for the lowest 1,000 m (eg. +1 °C from ground level to 1,000 m - it is possible, but not that common). Imagine a snowflake falling through the air from above this layer (where it's colder). As it falls into the top of the warm layer, it takes some time for it to start to melt. So if it soon hits a hill top, it will still be fairly frozen. If it has to fall all the way through the layer to reach the ground then it has so much more time to melt as it does so, so therefore it will be a lot more sleety by the time it reaches low ground. So in this case it is not colder up high that leads to more snow up there, it the TIME TAKEN for the snow to fall to lower levels that causes it to melt.

.

a quick question, if you don't mind:
what exactly is theta-e? is it a measure of the humidity of an airmass?
Also, doesn't how dry or humid the air is at certain levels, when the flake falls, play a part too in the melting process? say if a flake falls slowly and the rate of conduction is much greater than the rate of evaporation a flake, a flake would be more likely to melt?

Su Campu

nacho libre wrote: »

it's a disgrace, with all the unoccupied houses that anyone should be homeless.

on topic:



a quick question, if you don't mind:
what exactly is theta-e? is it a measure of the humidity of an airmass?
Also, doesn't how dry or humid the air is at certain levels, when the flake falls, play a part too in the melting process? say if a flake falls slowly and the rate of conduction is much greater than the rate of evaporation a flake, a flake would be more likely to melt?

Theta-e is the psuedo-Equivalent Potential Temperature. It takes into account the temperature and water vapour content of the air at a certain level. It is the temperature that a parcel of air at a certain level would have if all its moisture were removed and then the parcel brought dry-adiabatically to 1000 hPa. Higher values mean a warmer and/or more humid airmass, while lower values mean a colder and/or drier airmass. For snow to sea level, we need theta-e around 9 °C. It's going to get to around 11-12 °C on Friday, which should keep the snowline a little higher.

The relative humidity of the layer snow is falling through is an important factor, yes. For the same temperature, snow will melt more slowly falling through a drier layer, as the extra evaporation/sublimation occuring on the snowflake removes more latent heat from the air, cooling it and establishing an equilibrium at a lower temperature, hence reducing melting. This is why it is much easier for us to get snow from an easterly than a more moist polar or Arctic airmass off the Atlantic.

only one

Net weather are ment to have theyre winter forecast updated today but it's not updated yet

Musicman2000

only one wrote: »

Net weather are ment to have theyre winter forecast updated today but it's not updated yet

Their fulll Winter outlook is allready out, That update today just goes on the Cfs charts that change every day.