Fierce Cold Spell from Sunday (February 1st)

29-01-2009 4:09pm

blackgold>> wrote: »

What dewpoint point do we need for snow and what do those 1000's on the chart above mean?

Dewpoints ideally need to be -1c or lower though it can snow up to +0.5c dp's in big downpours.

We could be see'ing them from -2c to -6c in the coming spell

The 1000's are just barometric pressure like in your barometer at home.
The 1040 in Scandi combined with the low over iberia is causing the initial easterly -windflow circulates clockwise round the hp and anticlockwise round the lp making the easterly.
HP blocking the entire atlantic later should bring in a NE ,North and hopefully more of the NE and drag in low pressure systems by then in place over Scandi.
I'm being as laymans terms as I can there.

Devils in the detail which we should be posting here come sunday and certainly through next week.

I hope I havent jinxed this.

darkman2 · 29-01-2009 4:10pm

blackgold>> wrote: »

What dewpoint point do we need for snow and what do those 1000's on the chart above mean?

Dewpoint - anything under 0C is acceptable for snow. The lower the better. Sometimes you can have a bit above 0 and still get snow but very rarely.

The "1000's" are pressure in hpa known as isobars. Basically anything under 1020hpa is considered low pressure which means a higher likelyhood of precipititation. Again the lower the better.

darkman2 · 29-01-2009 4:12pm

nacho libre wrote: »

the midlands and part of the southwest could also do well out of this cold period if a few troughs move south east wards across the country when the winds wing around to the northeast. the best those of us in sligo, donegal, leitrim, and mayo will likely get is a few meagre flurries. the east though will definitely be the place to be - the likes of supercell could be snowed in for days:)

Could get fronts bumping up against the cold air from the south later on too!

blackgold>> · 29-01-2009 4:20pm

Great explanations lads very nicely put.
I always look in this forum but have no idea what im looking at in the charts.
So sneachta is on the way !!!!!!!!!

cheers black and dark !

Redsunset · 29-01-2009 4:32pm

Dew And Frost
When a jug full of iced drink is taken out of the refrigerator, water droplets condense on the outside of the container (provided the jug is made of a material which is a good conductor of heat, such as metal). This happens because the jug is at a lower temperature than the dew-point of the air.
'Dew-point' is defined as the temperature at which the air, when cooled, will just become saturated. For example, on a summer's day when the air temperature reaches 18°C, the dew-point might typically be 8°C. By sunset the air temperature may have fallen to 12°C, but the dew-point will still be around 8°C. During the night the temperature continues to fall and if it reaches, say, 7°C the temperature of the ground is below the dew-point of the air and droplets of moisture begin to form - this is dew. Since the air is now being 'robbed' of some of its water vapour, the dew-point of the air will actually start to fall very slightly.
Next morning, as the incoming solar radiation gathers strength, the dew will evaporate and the grass will become reasonably dry (and suitable for sitting on during the day). However, in winter, when calm conditions prevail, the daytime evaporation may be so slow that dew may persist all day.
Hoar-frost is composed of tiny ice-crystals, 'feathery' in appearance when well developed. It is formed by the same process as dew, but occurs when ground temperatures are below freezing point. Consequently, when the grass is covered in a white hoar-frost at dawn it cannot be assumed that there has necessarily been an air frost.
Sometimes dew forms during the evening and subsequently freezes to become hoar-frost with globular ice on the grass.
Snow
[FONT=Arial, Helvetica]Snowflakes can be formed by the collision of ice crystals within clouds. This is known as the process of aggregation and usually accounts for the larger snowflakes that are seen to fall. Smaller snowflakes are formed by the Bergeron-Findeisen process. Supercooled water droplets (i.e. those with a temperature below freezing) are 'picked up' by the falling ice crystals. The ice crystals grow at the expense of the water droplets.[/FONT]
For snow to reach the ground the air temperature must be no more than 2°C. One would expect the falling snow to melt as soon as the temperature rises above freezing, but this is not so. As the melting process begins, the air around the snowflake is cooled. At temperatures above 2°C the snowflake will melt to become 'sleet' or rain. In this country, the heaviest falls of snow tend to occur when the air temperature is between zero and 2°C.

Individual ice crystals and snowflakes can be the shape of prisms, plates or stars - but all have 6 sides.
30cm of fresh fallen snow has about the same water equivalent as about 25mm of rainfall

Redsunset · 29-01-2009 4:57pm

Another cold snap is heading for the UK, as forecasters warn of the chilliest winter for 13 years.
Icy winds from the continent will be felt in the south and east of the UK in the next few days, followed by a "blast of bitterly cold air" from Russia.
Temperatures in some areas are forecast to plunge from up to 7C (45F) on Saturday daytime, to between -1C (30F) and -3C (27F) on Sunday night. BBC weather experts said snow was likely in some parts early next week.
ITS ALMOST WRITTEN IN STONE FOLKS.ALL WE NEED IS LOADS OF PRECIP.:D

nacho libre · 29-01-2009 5:00pm

520 dam thickness.

to be honest i'm still not fully sure what this is:o
does this refer to the optimum temperature along with moisture content at a certain height in the atmosphere in order for snow to occur??

an explanation would be appreciated

29-01-2009 5:28pm

I am liking the use of the term "fierce" in this thread.

How much of a go is this, arent we a good few days out yet?
Im ready to get excited for some *real* snow but how long will this last?
What kind of day time temperatures? What of lying snow at ground level?
I see night time temps of -1c and -3c but what if day time temps are higher will the snow drive them down?
oh oh I`ll be doing climatology again this semester - maybe I`ll begin to understand some of those charts a bit better

Supercell · 29-01-2009 5:32pm

nacho libre wrote: »

520 dam thickness.

to be honest i'm still not fully sure what this is:o
does this refer to the optimum temperature along with moisture content at a certain height in the atmosphere in order for snow to occur??

an explanation would be appreciated

Here's an explanation of thicknesses (dam) better than I could ever do

In an continental easterly we don't need super low dam's by the way, though they help.

Supercell · 29-01-2009 5:40pm

Deleted User wrote: »

I am liking the use of the term "fierce" in this thread.

How much of a go is this, arent we a good few days out yet?
Im ready to get excited for some *real* snow but how long will this last?
What kind of day time temperatures? What of lying snow at ground level?
I see night time temps of -1c and -3c but what if day time temps are higher will the snow drive them down?
oh oh I`ll be doing climatology again this semester - maybe I`ll begin to understand some of those charts a bit better

I'm liking it too!, If snow falls well at even sea level there could be lying snow for several days, up here it should be ...interesting to say the least.
Anywhere snow is lying will have cooler nights and days, Inland some really low overnight temperatures are possible over snowfields and a bit inland.
If the pressure is lowish -<1015 (and it is forecast to be around ) and the winds are ene- ne then Dublin and Wicklow are likely to get huge dumpings of snow in any unstable air. Our best snowfalls occur in these types of setups.
That said these thing often go titus uppes so lets just enjoy the charts.
If they look the same on Saturday..i'm stocking up on supplies..seriously as here may be cut off!!

29-01-2009 5:43pm

Deleted User wrote: »

I am liking the use of the term "fierce" in this thread.

How much of a go is this, arent we a good few days out yet?
Im ready to get excited for some *real* snow but how long will this last?
What kind of day time temperatures? What of lying snow at ground level?
I see night time temps of -1c and -3c but what if day time temps are higher will the snow drive them down?
oh oh I`ll be doing climatology again this semester - maybe I`ll begin to understand some of those charts a bit better

Impossible to say how long it will last but it is looking good when there are so many snow-fest charts to choose from now that I can't agree which one to post.

I like the suggestion of part of the polar vortex [really cold snowy area of low pressure folks] drifting into Scandinavia in FI [the further out you go the less reliable the forecast-we call it FI or fantasy island because it's usually where the good stuff stays and never materialises...not this time though hopefully...]as it can only slide all the way from there to Valentia if it verifies like that.

This is quite exciting

kerry1960 · 29-01-2009 5:45pm

Any hope i can come visit this weekend uncle SC.... cousin BB.....ANYONE......:D , just look at this chart.......
must be dreaming :P.

patneve · 29-01-2009 5:47pm

mmmmm, tasty!:eek: reminds me of the chart from the last big snow event in 2001 (dublin)

Supercell · 29-01-2009 5:48pm

kerry1960 wrote: »

Any hope i can come visit this weekend uncle SC

Lol, sure!, these charts are looking rather special. I'm frankly starting to worry that I wont be able to make it to the airport on February 9th!!

29-01-2009 5:51pm

kerry1960 wrote: »

Any hope i can come visit this weekend uncle SC.... cousin BB.....ANYONE......:D , just look at this chart.......
must be dreaming :P.

Lol
That type of set up is actually snowier than january '87...
I'd be expecting snow drifts widely over the East and a covering over much of the country and welll chaos!

I hope I don't jinx this.

Redsunset · 29-01-2009 5:59pm

Supercell wrote: »

Lol, sure!, these charts are looking rather special. I'm frankly starting to worry that I wont be able to make it to the airport on February 9th!!

Ha ha.6pm news on feb 9th reads coast guard air lifts man from an avalanche of snow so he don't miss his flight.taxpayers annoyed over wasted expense.:pac:

kerry1960 · 29-01-2009 6:00pm

Supercell wrote: »

Lol, sure!, these charts are looking rather special. I'm frankly starting to worry that I wont be able to make it to the airport on February 9th!!

Yeah SC , imagne being snowed in ,with nothing but a camera and

the lappy , my heart is bleeding

.

Gonzo · 29-01-2009 6:05pm

if this turns out to be anything like 87 or 91 this will be very special indeed. I remember both those winters well and I remember days on end of prolonged snow showers, most of the snow showers gave between one and 2 inchs of snow per hour and several of these fell in an afternoon and more of them through the night, this trend repeated withself for up to a few days were we ended up with 8 to 14 inchs of snow depending on location. I remember one whiteout shower in particular, i think it was during the 1991 spell where it snowed so heavy one afternoon that you couldnt see more than 10 feet infront of you with flakes often 2 to 3 inchs wide (snowflakes often joining with another one to produce mammoth flakes).

Trogdor · 29-01-2009 6:06pm

Things looking very very good indeed and for once its not that far out:eek: not much point looking at the details yet but gfs seems to have constant precip fringing the east coast for days...this COULD be very special indeed

ninebeanrows · 29-01-2009 6:08pm

The output so far this evening is nothing short of sensational.

Look at a chart that is just 84 hours away, unprecedented in recent times

:D

I think weathercheck.net might just be recreated for this event!

DOCARCH · 29-01-2009 6:15pm

Fantastic charts - this must be the payback for WC becoming a mod.

:

Is there/will there be enough precip to make an 'event'? Or are we relying on 'lake effect' snow?

ninebeanrows · 29-01-2009 6:17pm

DOCARCH wrote: »

Is there/will there be enough precip to make an 'event'? Or are we relying on 'lake effect' snow?

Looks like lake effect Sunday night/ Monday then perhaps organised snow during Tuesday into Wednesday.

Look far too good to be true at this stage :eek::D

Supercell · 29-01-2009 6:25pm

DOCARCH wrote: »

Fantastic charts - this must be the payback for WC becoming a mod. :

Lollers, you know I was thinking the exact same thing!

, he's got special powers now to make these things happen you see :pac::pac::pac:

Pangea · 29-01-2009 6:28pm

Im still gona be cautious ,because this sounds like the perfect letdown, keeping the snow thoughts to myself , instead of crying wolf to loved ones..... again....... lol :pac::D

DOCARCH · 29-01-2009 6:29pm

Pangea wrote: »

Im still gona be cautious ,because this sounds like the perfect letdown, keeping the snow thoughts to myself , instead of crying wolf to loved ones..... again....... lol :pac::D

+ 1......but quietly confident and currently minimising meetings next week to ensure I am close to computer!

Pangea · 29-01-2009 6:30pm

Supercell wrote: »

Lol, sure!, these charts are looking rather special. I'm frankly starting to worry that I wont be able to make it to the airport on February 9th!!

lol , where u fllying to?
I have to make the airport for feb 18th ,will i make it ? lol

200motels · 29-01-2009 6:33pm

It's really looking good for snow next week. What's the chances of snow in Waterford City?

darkman2 · 29-01-2009 6:35pm

Im gonna take a more cautious approach I think(since no one else will!). Don't be going OTT with it. Nothing is nailed yet.

The charts look good, a couple of nagging issues from Monday night for the East coast. Things look like getting a bit marginal. Still good charts and hopefully something actually materialises this time.

ninebeanrows · 29-01-2009 6:42pm

Loving the UKM 72hrs.

Show that this could actually happen, look at the cold pool. Corrrrrrrrrrr:D

UW72-7.GIF?29-18

200motels · 29-01-2009 6:45pm

darkman2 wrote: »

Im gonna take a more cautious approach I think(since no one else will!). Don't be going OTT with it. Nothing is nailed yet.

The charts look good, a couple of nagging issues from Monday night for the East coast. Things look like getting a bit marginal. Still good charts and hopefully something actually materialises this time.

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This chart looks very tasty.

Fierce Cold Spell from Sunday (February 1st)

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