Band of rain/sleet/snow pushing up from the south 29th+30th Dec - Snowstorm or not?

Chicken Run

redsunset wrote: »

All high ground folk are in bother in my view

I live halfway up a mountain - so YAYYY.
Also I don't have to go anywhere major over the next few days apart from out to the shed for more turf and the odd can of cider.... bring it on.

Currently 1.5C here in East Clare (don't have a DP thing) and breezy

digme

WolfeIRE wrote: »

dew points have dropped by 0.5 to one degree C in the last half hour in most places as have air and ground temps.

What dew point do we need to get snow around sea level?

WolfeIRE

digme wrote: »

What dew point do we need to get snow around sea level?

look at post 344.

thecretinhop

gally74 wrote: »

i have a headache, but its more to do with last night and arthur guinness

I have a headache too thats from me bet celebrated that and chrimbo a bit too much, was all for having a quite night untill my ould lad showed up with jameson special reserve!! nice one... by the way been well on it for last few days did I see that RTE weather girl wearing what looked like a spacesuit mini dress that was bursting to get out or was that the ale:)

Redsunset

nacho libre wrote: »

to be honest i think we are all aware high ground is likely to get a pasting between tomorrow evening and wednesday. however, if weathercheck's prediction is correct he deserves the plaudits because few here and in met eireann are backing his opinion of how this will pan out at lower levels

Well yes one is always reluctant to call lower level snow in such marginal conditions.
Not looking for a medal here was only highlighting to some who still choose to believe its all rain.

Weathercheck shall receive a salute should it pan out the way he sees it.

digme

WolfeIRE wrote: »

look at post 344.

sound

Supercell

digme wrote: »

What dew point do we need to get snow around sea level?

You generally need a dew point of <0.0 for snow, thought very wet sleety snow is possible up to DP of 0.3 or so (there is much more to it than that, but for the current spell it should hold true)
If you are based in Dublin or the east coast keep an eye on the M2 buoy dew point - http://www.met.ie/latest/buoy.asp , if that goes below zero you are pretty much guaranteed snow even at sea level in this current spell in Dublin.

pistolpetes11

redsunset wrote: »

Well yes one is always reluctant to call lower level snow in such marginal conditions.
Not looking for a medal here was only highlighting to some who still choose to believe its all rain.

Weathercheck shall receive a salute should it pan out the way he sees it.

Did he not call it for later on Wednesday , maybe thursday ? lower levels that is.

Sligome

well i have been snowed in for the past two weeks with god awful road conditions, 4 inches of snow, not a bit of melting and no snow has fallen in the last week, we hit minus ten the last three nights and i now cant even walk outside as i will fall on my behind. where is the weather report for that i ask.

digme

Thanks a lot the m4 one has a dp of 0.7
Temp is 7 degrees though.

WolfeIRE

Supercell wrote: »

You generally need a dew point of <0.0 for snow, thought very wet sleety snow is possible up to DP of 0.3 or so (there is much more to it than that, but for the current spell it should hold true)
If you are based in Dublin or the east coast keep an eye on the M2 buoy dew point - http://www.met.ie/latest/buoy.asp , if that goes below zero you are pretty much guaranteed snow even at sea level in this current spell in Dublin.

supercell - dewpoint is at 0.5 and dropping steadily in the past 90 mins. Air temp is between 0 and 0.5c. Do you anticipate that temps will rise as the front approaches clare? i guess we will probably see precipitation around 3-4am.

Su Campu

pistolpetes11 wrote: »

Did he not call it for later on Wednesday , maybe thursday ? lower levels that is.

I think you're mixing it up with my post

northtipp

currently 1.9 here in nenagh i think we will get snow tomorrow they got it wrong in 1982 and i remember that one well have been waiting since for a snowfall like that to occur again i hope my wait is over all will be revealed tomorrow i guess /hope

Deep Easterly

WolfeIRE wrote: »

dew points have dropped by 0.5 to one degree C in the last half hour in most places as have air and ground temps.

Dp reading here has remained just slightly above freezing over the last while.

Current Readings:



Cloud base thickening a little and does not feel all that cold outside despite the breeze.

Shane Slv

out of interest what do they use to measure dew points some kind of thermometer?

currently at shannon airport:
temperature:4C
dew point 1C

North Cork

Why does it actually get warmer when it snows? [FONT=Verdana,Arial,Helvetica][SIZE=-1]
Snowing does not cause the warmth, the relative warmth causes the snow.
During very cold weather the capacity of the air to contain moisture is greatly reduced. What water vapor remains is deposited as frost. At the same time, evaporation is reduced and therefore air humidity remains low. In these conditions snow cannot form.

Warmer air can hold more moisture before saturation point is reached and the water vapor begins to condense out. So when warmer air moves into cooler areas, not only do we feel the increase in temperature, but the excess vapor precipitates as snow.
[/SIZE][/FONT]

Supercell

WolfeIRE wrote: »

supercell - dewpoint is at 0.5 and dropping steadily in the past 90 mins. Air temp is between 0 and 0.5c. Do you anticipate that temps will rise as the front approaches clare? i guess we will probably see precipitation around 3-4am.

You have faux cold as the easterly is travelling over land to Clare. I would be amazed if you got any snow there tonight, DP to your north are still far too high, which means the local ones are shallow and not likely to reflect upper air conditions with much accuracy (as they might if there was a a stronger easterly wind blowing). For example I had negative DP earlier but as soon as a light breeze came up the temp shot up as did the DP - faux cold, the true cold air isnt where the precip is currently.

So unless you live about 600 metres up or higher then its rain until tomorrow evening at the earliest I think, and rising temps , probably around 3-5°C there by dawn would be my guess.

WolfeIRE

Deep Easterly wrote: »

Dp reading here has remained just slightly above freezing over the last while.

Cloud base thickening a little and does not feel all that cold outside despite the breeze.

Hi Deep. Forgive me if I am wrong but don't those readings favour snowfall?

edit - supercell has answered that one for me. thanks super. ps. the wind is quite strong here now and it is coming from the NE.

pistolpetes11

Weathercheck wrote: »

We expect rain tonight and into tomorrow across the south.

The cold begins to undercut as the front pushes north around midday tomorrow.

Dew points are obviously marginal but always are in snowy set-ups.

During the precip tomorrow dews will be between -1c - 1c

The snow will probably be wet at first near the coasts and then dry up as the cold digs and digs in.

Lots of snow possible from evening.

Well tomorrow evening then

ninebeanrows

Shane Slv wrote: »

out of interest what do they use to measure dew points some kind of thermometer?

currently at shannon airport:
temperature:4C
dew point 1C

It based on the 2m temperature and relative humidity reading.

Low humidity = Low dew point

Redsunset

WEATHERCHECK post,


The precip-band will begin to turn to snow during tomorrow evening across the northern sections and steadily all the band will turn to snow overnight and into Wednesday.

Granted the precip is likely to stay as sleety stuff along the coast until late tomorrow night.

The Eagle is wrong.

And i will confidently call heavy snow for a large portion of the country beginning tomorrow night and throughout Wednesday.

I'll put my cred on it. And will take defeat graciously.

Deep Easterly

WolfeIRE wrote: »

Hi Deep. Forgive me if I am wrong but don't those readings favour snowfall?

edit - supercell has answered that one for me. thanks super

Actually, they are quite borderline . Despite the "faux cold", Dp over the west of the country will probably be a bit lower than in the east due to the land fetch. (the opposite of normal). However, the general trend is a slight rise as the night goes on so really hard to say. Our best chance will be on Wednseday as that cooler airmass tries to dig in under the frontal zone. Very much nowcasting from here on.

pistolpetes11

Su Campu wrote: »

I think you're mixing it up with my post

Got my days mixed up , had it in my head it was Tuesday today ,(I know it technically is now )

Supercell

Deep Easterly wrote: »

Actually, they are quite borderline . Despite the "faux cold", Dp over the west of the country will probably be a bit lower than in the east due to the land fetch. (the opposite of normal). However, the general trend is a slight rise as the night goes on so really hard to say. Our best chance will be on Wednseday as that cooler airmass tries to dig in under the frontal zone. Very much nowcasting from here on.

No they are not borderline at all i'm afraid, the only reason your dp is low is because it is pure faux cold. You said it yourself, the trend is for it to rise, why is that? - because as the precip approaches the wind will likely increase as will humidity and cloudiness and thus less radiative cooling and so therefore your temps rise.
Its nowhere near borderline, if there was precip in your area the temps would be higher, simple as.
Of course that will all change tomorrow as the day goes on, but right now its not borderline at all, unless your very very high up.
Anyone waiting up tonight for snow is going to be sorely disappointed.
This time tomorrow night though..well we live in hope

Bog Butter

Do Met Eireann have acess to exclusive information? I mean to say do they have info that you guys don't have. Or are ye both singing from the same hymn sheet so to speak?

Shane Slv

Thanks Weathercheck.

Dew point now 0c at shannon airport

Deep Easterly

Supercell wrote: »

No they are not borderline at all i'm afraid, the only reason your dp is low is because it is pure faux cold. You said it yourself, the trend is for it to rise, why is that? - because as the precip approaches the wind will likely increase as will humidity and cloudiness and thus less radiative cooling and so therefore your temps rise.
Its nowhere near borderline, if there was precip in your area the temps would be higher, simple as.
Of course that will all change tomorrow as the day goes on, but right now its not borderline at all, unless your very very high up.
Anyone waiting up tonight for snow is going to be sorely disappointed.
This time tomorrow night though..well we live in hope

At the moment, yes, they are quite borderline. But as I said, the trend is for it to rise. I am not expecting snow, so what is your point?

Edit: Some light showers over east Galway, wonder will they head this way...?

Supercell

My point is, current conditions are nowhere near borderline in most of Ireland, its preposterious to say they are.
Its nailed on non borderline rain tonight. For the exact same reason it rained when people were having temps of -4 and dewpoints lower last weekend, 850 thicknesses are too deep, its not borderline, its not even close.
This precip might fall as snow on the very top of Carauntoohil, there its genuinly borderline. At <500 metres its not borderline, it will rain tonight if precip falls from the sky.

Deep Easterly

Supercell wrote: »

My point is, current conditions are nowhere near borderline in most of Ireland, its preposterious to say they are.
Its nailed on non borderline rain tonight. For the exact same reason it rained when people were having temps of -4 and dewpoints lower last weekend, 850 thicknesses are too deep, its not borderline, its not even close.
This precip might fall as snow on the very top of Carauntoohil, there its genuinly borderline. At <500 metres its not borderline, it will rain tonight if precip falls from the sky.

I think most of us have been aware of that for quite some time.

IMBACKLATER

new weather warning from met eireann

Issued at 29 December 2009 - 00:10
Weather warning
Rain will spread slowly northwards during Monday night, Tuesday and Tuesday night to affect much of the country (but will be slow to reach Ulster and north Connacht). It will be persistent and heavy in places, with totals of 30 mm or more in parts of the south and southeast. It will produce heavy snowfall on some mountains - with the risk of blizzard conditions at times - and may also give some falls of snow in places at lower levels.