Snow Risk - 8th/9th November 2008

Danno

Looking at the latest GFS output, I think there is a possibility of some snow showers overnight in the following areas:

Uplands in Munster, Inland Connacht, Western and Northern Leinster and Most of Ulster away from the southeast coast.

The upper air is expected to be around -35c. Mid level air is going to be around -4c and surface temperatures at 2c or 3c.
Dewpoints will be at zero or 0.5c
The sub 528dam air is completely over the island with a depression sitting just north of Donegal at around 980hpa.
Overland wind speeds will be from 25mph or higher driving the showers well inland.
The risk begins after dark on Saturday evening and extends to noon on Sunday. Sunday looks like being a raw day with 5c to 8c in a biting west to northwest wind.

Danno.

Deep Easterly

Danno wrote: »

Looking at the latest GFS output, I think there is a possibility of some snow showers overnight in the following areas:

Uplands in Munster, Inland Connacht, Western and Northern Leinster and Most of Ulster away from the southeast coast.

The upper air is expected to be around -35c. Mid level air is going to be around -4c and surface temperatures at 2c or 3c.
Dewpoints will be at zero or 0.5c
The sub 528dam air is completely over the island with a depression sitting just north of Donegal at around 980hpa.
Overland wind speeds will be from 25mph or higher driving the showers well inland.
The risk begins after dark on Saturday evening and extends to noon on Sunday. Sunday looks like being a raw day with 5c to 8c in a biting west to northwest wind.

Danno.

Certainly looks chilly Danno, time to bow our heads to the west wind again.

Snowbie

Looks cold zonal with no significant cold from 18Z but seems to have an active mid-north Atlantic in FI afterthat with cold trying to reload with wet and windy spells.

Looks turbulent on Saturday and disturbed into next week with very cold air never too far away.

AIR-AUSSIE

Danno wrote: »

Looking at the latest GFS output, I think there is a possibility of some snow showers overnight in the following areas:

Uplands in Munster, Inland Connacht, Western and Northern Leinster and Most of Ulster away from the southeast coast.

The upper air is expected to be around -35c. Mid level air is going to be around -4c and surface temperatures at 2c or 3c.
Dewpoints will be at zero or 0.5c
The sub 528dam air is completely over the island with a depression sitting just north of Donegal at around 980hpa.
Overland wind speeds will be from 25mph or higher driving the showers well inland.
The risk begins after dark on Saturday evening and extends to noon on Sunday. Sunday looks like being a raw day with 5c to 8c in a biting west to northwest wind.

Danno.

where do you get access to the latest GFS output?

arctictree

GFS can be seen on http://www.wetterzentrale.de/pics/avnpanel1.html

I think we are reaching that point in the year when the autumn storms really start going. The next few weeks will be interesting. If any of the lows pass close to us we could be in for some really bad weather.

I notice though that all the lows in the charts seem to originate from sub polar regions and hence seem to have a lot of cold weather associated with them...

nacho libre

in this situation we tend to get sleet rather than snow

Danno

But the upper air 500hpa is much colder this year than I can ever remembering seen since starting to look at GFS outputs a few years ago. Even in Summer it was much colder. Temperatures of -35c over Ireland in the depths of winter is excellent, in the 8th November is unreal.

Gonzo

im no weather expert but all i know is that the past October has been the coldest ive felt since the 80s and this summer was awfull like many of the summers of my childhood, we already had 2 inchs of snow last week altho i missed it, Ive a feeling we cud finally see a 1987/1991 winter again....1982 was a bit hardcore tho, dont really want one that bad lol:D

Snowbie

Danno wrote: »

But the upper air 500hpa is much colder this year than I can ever remembering seen since starting to look at GFS outputs a few years ago. Even in Summer it was much colder. Temperatures of -35c over Ireland in the depths of winter is excellent, in the 8th November is unreal.

The 500mb/hPa level is the middle atmosphere and where we look for cyclonic or trough formation. Other parameters involved but the -35C indicated is ahead of a trough which will override warmer moister air at the lower surface and increase the potential of thunderstorms moreso of indicating a cool down.

This is the colder air aloft we look for Tcu or CB formation and usually does not have an impact on surface temps unless the colder air at suface is already established and more likely the 500mb temp level will have decreased and height(DAM thickness) but you would know the cold is there as you can feel it in the first place on the face. SO basically, You need to compare 500mb to 850mb for an accurate temp at surface level otherwise it means nothing.

Stratospheric temps are what we would look at over the pole. The warmer they are the effect it has on the polar vortex and basically a cooling trend creating a -NAO which is good for cold and blocking.

Danno

Downdrafts in any showers will be frigidly cold and with any intense precip, this -35 will push down through the atmosphere (heat rises, cold air falls) and help preserve ice better coming down. I agree that this is quite marginal. But the ingredients are just about there. Another few GFS model output runs will make things clearer hopefully!

Deep Easterly

Danno wrote: »

Downdrafts in any showers will be frigidly cold and with any intense precip, this -35 will push down through the atmosphere (heat rises, cold air falls) and help preserve ice better coming down. I agree that this is quite marginal. But the ingredients are just about there. Another few GFS model output runs will make things clearer hopefully!

Agree that is a hard one to call Danno, there may be snow but very localised I think. Like Snowbie, I would be looking more to big Atlantic thunderstorms spreading across the country in troughlines due to the conditions you describe. Later tonight and tomorrow looks to see the first wave of heavy showers passing over. Thunder is long overdue here, so hopefully will fill up my yearly quota soon as it has not been a good year for thunder at all.

M.T. Cranium

Looks like some hail or snow quite possible on Sunday, but the big story may be strong winds on Monday, the latest GFS run certainly indicates that potential, gusts to 70 mph in some western and northern counties.

enda1

So what does this mean if I'm climbing a mountain in the munster region in the early hours of tomorrow morning? Should I bring my skis?

kerry1960

enda1 wrote: »

So what does this mean if I'm climbing a mountain in the munster region in the early hours of tomorrow morning? Should I bring my skis?

lol :eek:, what Mountain are you thinking of climbing :eek:........

enda1

Brandon! 952m at summit.

I know it really well so not so concerned about that but could be difficult in present conditions.

Plan to be up there before sunrise. Bon voyage as they say. I'll get some pics for you all!

nacho libre

enda1 wrote: »

So what does this mean if I'm climbing a mountain in the munster region in the early hours of tomorrow morning? Should I bring my skis?

it means you shouldn't go:D

enda1

Ah but that's not an option! Its not Everest now in fairness and we (4 guys) are well prepared in terms of clothing and equipment for the most part. Just wondering what conditions to expect at that altitude?

I imagine freezing fog/snow and a terrible wind?

nacho libre

M.T. Cranium wrote: »

Looks like some hail or snow quite possible on Sunday, but the big story may be strong winds on Monday, the latest GFS run certainly indicates that potential, gusts to 70 mph in some western and northern counties.

Yes. We can experience some severe gusts for a couple of hours in these situations.
I think paddy1 might be right about the thunder. if he is you can be sure Galway city will be the first to get it:mad::

nacho libre

enda1 wrote: »

Ah but that's not an option! Its not Everest now in fairness and we (4 guys) are well prepared in terms of clothing and equipment for the most part. Just wondering what conditions to expect at that altitude?

I imagine freezing fog/snow and a terrible wind?

Yes i think so - sleet at the very least. Also, watch out for supercell and his snow rabbit. Anywhere there is a possibility of snow they are sure to be there.:D

Mr Benevolent

Yes i think so - sleet at the very least. Also, watch out for supercell and his snow rabbit. Anywhere there is a possibility of snow they are sure to be there

And if there's lightning around it could be the enda Enda

Supercell

nacho libre wrote: »

Yes i think so - sleet at the very least. Also, watch out for supercell and his snow rabbit. Anywhere there is a possibility of snow they are sure to be there.:D

Lol, unfortunately, with westerlies the snow rabbit is unlikely to make an appearance here.

Snowbie

enda1 wrote: »

Ah but that's not an option! Its not Everest now in fairness and we (4 guys) are well prepared in terms of clothing and equipment for the most part.

Famous last words :eek::D

Just wondering what conditions to expect at that altitude?

I imagine freezing fog/snow and a terrible wind?

A whole lot windier/gusty at height and very risky to life, personally to climb 1km high mtn tomorrow is asking for trouble, best option/advice is not too.:)

nacho libre

Snowbie wrote: »

Famous last words :eek::D



A whole lot windier/gusty at height and very risky to life, personally to climb 1km high mtn tomorrow is asking for trouble, best option/advice is not too.:)

exactly how windy/gusty do you think would it be at a height of 650 metres, say if it is gusting to 60 miles per hour at sea level

nacho libre

from met.ie:
Saturday night will be cold and windy with clear spells and showers, the showers heaviest and most frequent in western counties. Southwest winds will remain fresh to strong for much of the night, preventing frost. Showers will continue in many places on Sunday but drier and clearer conditions will develop in most parts of the country later; southwest winds will moderate during the day also but it will stay rather cool. The early part of Sunday night will be cold, with a slight ground frost in places; however, showers in the west will tend to become more widespread overnight. Monday will be another rather cool day with a mixture of sunny spells and scattered showers, the showers again most frequent in western counties; southwest winds will strengthen during the day also. Monday night will remain cold, windy and showery but eastern areas will have dry periods. During Tuesday, winds will veer west to northwest and will stay strong and gusty for much of the day. While southeastern and eastern counties will have only isolated showers, towards the west and especially the north, showers will become heavier, with hail and isolated thunderstorms likely.

So it seems Tuesday could be our best chance for wintry showers.

Snowbie

nacho libre wrote: »

exactly how windy/gusty do you think would it be at a height of 650 metres, say if it is gusting to 60 miles per hour at sea level

On a 650metre summit be gusting closer to 80mph or perhaps higher depending on friction from mtn slopes (trees and terrain) Winds become stronger with height with lower pressure in general.

squonk

Plenty of other weekends for climbing Enda. Not sure I'd be venturing up a mountain tomorrow unless I really had to. Mind you I'm not sure I'll be venturing anywhere tomorrow by the looks of the day. Seriously though tomorrow's winds do sound like a big enough deal to err on the side of caution....

Mr Benevolent

So are we looking at sleet or active CBs in Dublin?

arctictree

Just looking at the GFS temp chart for now:

http://www.wetterzentrale.de/pics/Rtavn0617.png

Does GFS over estimate temperatures? Looking at my location, temps are somewhere between 8 and 10c. I am currently reading 4.8c. This seems quite cold for a southerly wind...

A

Snowbie

arctictree wrote: »

Just looking at the GFS temp chart for now:

http://www.wetterzentrale.de/pics/Rtavn0617.png

Does GFS over estimate temperatures? Looking at my location, temps are somewhere between 8 and 10c. I am currently reading 4.8c. This seems quite cold for a southerly wind...

A

That GFS output is the US 60km low resolution and does not take topography (hills mtns) into consideration. For Ireland it assumes all the land is flat and at sea level. Pretty poor and the 60km is stoneage and a rough but guideline for sea level but useless for higher elevations.

I think you may find the in my attach below far more accurate using the GFS 12km hi res for the same time.
Hope the comparison details it a bit more for you.:)

Edit:The attach i forgot to add is from 12Z and not 18Z. Hi res only released in 12hr outputs(12Z and 00Z) unfortunately though.

kerry1960

enda1 wrote: »

Ah but that's not an option! Its not Everest now in fairness and we (4 guys) are well prepared in terms of clothing and equipment for the most part. Just wondering what conditions to expect at that altitude?

I imagine freezing fog/snow and a terrible wind?

Enda1 (is he takin the pizz outta us ), if you are reading this then it means 2 things , you survived the trip / or you didn't go , and hopefully its the latter .

Having some experience of hill walking myself (not questioning your expertise) but on an exposed Mountain like Brandon its mad going climbing in present conditions , driving sleety rain in a gale at 4c is not a nice experience , you'd actually be better off if it was snowing , easier to keep dry.

One of the pleasures of hillwalking for me is to enjoy the experience and admire the views and not to turn the day into a survival course,more than likely the hills will be shrouded in cloud Saturday so the opportunities for photos may be limited .

Well done if you did complete the climb i'm curious as to how things went;).

kerry1960

Now this is hillwalking , Austrian Alps/July 06/scenery/nature , and yes this is me , suitably camouflaged to protect those of a more nervous disposition .....:P