Winter/Spring 2013 (Model Output Discussion)

Harps

pistolpetes11 wrote: »

An important chart is the 500 - 1000 hPa thickness chart, which shows the thickness of the layer of atmosphere between the 1000 and 500 hPa pressure levels. As described above, the colder the airmass, the denser the air, and hence the closer these two levels will be. For snow in Ireland, usually we need somewhere around 528 dm or lower, as this will ensure that the airmass is probably cold enough at all levels for snow to survive the descent to the surface,

Of course, we need to also factor in conditions at the surface, which at the moment are not forecasted to be good for cold and snowy weather,


http://www.boards.ie/vbulletin/newreply.php?do=newreply&p=75404833

That's actually describing these charts



The colours on the sea level pressure charts are showing the distance between sea level and the 500hPa level (in geopotential height) in dams.

snaps

Comparing the charts and sat24 imagery this morning. That low looks amazing, really winding itself up. But on the satellite view, it looks a lot futher north west than its chart position?

derekon

Quick update from Brian Gaze over at TWO (The Weather Outlook):

"the general picture during the next couple of weeks isn’t a very cold one. The cold block out to our north east looks set to gradually sink south allowing the Atlantic to exert a greater influence on the weather over the UK. Those of you who are old enough may remember the freeze of January 1987, and what happened after it broke. High pressure to the north east of Britain gradually slipped away south, and the cold didn’t really return again during the rest of the winter. I’m not saying that will happen this winter, but slowly sinking high pressure systems to our north east can be real bed blockers as far as getting long cold spells over the UK (rather than transient cold snaps) is concerned. So during the next 2 weeks temperatures look like being much closer to the seasonal average than we’ve had recently, and in the south especially it could become quite mild. The GFS / GEFS chart below shows there are still some colder incursions on some of the runs during the Xmas period, so nothing can be completely ruled out just yet and things can change very quicklly, but……

The chances of snow seem to be receding every time I go online! I think December is now a write off for snow. We can only cross our fingers for January 2013!!

D

cyclops999

M6 Buoy @18.00 hrs, pressure 976.1 winds gusting 12 to 45 kts

John.Icy

Still have no clue how so many are writing off the next few weeks, unless by 'few weeks' they mean 2 weeks (ala Brian.G)...

Fascinating models this evening, New trends, could be gone in the morning, oh well, it doesn't mean we should pretend they don't exist . Interesting developments within Hi-res. It's only fair to give respect to these charts, considering the brash outlooks some big time weather forecasters have based on silly raging Atlantic charts +180 and further.

Raging zonality? I really don't see it tbh, never had, and it's already very interesting seeing signs of something brewing again. But no one cares at this stage after the last cold attempt flip, which had nothing on the Feb 2009 ensemble flip might I add! Toughen up boardsies

Missymoohaa

Does anyone remember the bad snow of 1982? I think, (January). The reason I ask this is because I wondered if such a snow had been predicted by the Met Service. I particularly remember going to bed on the previous night and myself and my Dad looking out the front door and it was lashing rain, we both commented on it. Then lo and behold the next morning when Dad opened the front door it was to a wall of snow, where it had drifted in to our front porch. Dad says it was totally unexpected (to him anyway) and I wondered if this was a general concensus (or just him).

I ask because I wondered if this could happen again? as in unexpectedly large deposits of snow over night?

red_bairn

Missymoohaa wrote: »

Does anyone remember the bad snow of 1982? I think, (January). The reason I ask this is because I wondered if such a snow had been predicted by the Met Service. I particularly remember going to bed on the previous night and myself and my Dad looking out the front door and it was lashing rain, we both commented on it. Then lo and behold the next morning when Dad opened the front door it was to a wall of snow, where it had drifted in to our front porch. Dad says it was totally unexpected (to him anyway) and I wondered if this was a general concensus (or just him).

I ask because I wondered if this could happen again? as in unexpectedly large deposits of snow over night?

I wouldn't be surprised, unless the professionals here can tell us.

Capillatus

Missymoohaa wrote: »

I ask because I wondered if this could happen again? as in unexpectedly large deposits of snow over night?

Well, in my humble opinion, I wouldn't bet on it. With the numerical predictions being advanced as they are (in the 0h-24h range), and with all the satellite and radar observations, it would be hard to "under-forecast" the snowfall in a way that you would be really surprised. There is always a certain tolerance in +/-, but I don't think a chance of 50mm of rain ending up in 40in of snow would go by unnoticed.

But hey, there is always great variance in nature and many things can go "wrong"

Rougies

Capillatus wrote: »

Well, in my humble opinion, I wouldn't bet on it. With the numerical predictions being advanced as they are (in the 0h-24h range), and with all the satellite and radar observations, it would be hard to "under-forecast" the snowfall in a way that you would be really surprised. There is always a certain tolerance in +/-, but I don't think a chance of 50mm of rain ending up in 40in of snow would go by unnoticed.

But hey, there is always great variance in nature and many things can go "wrong"

You're right in general, for most places in the world the models have things pretty nailed on in the 0-24hr range. But in Ireland things have a great tendency to go "wrong" in both directions when it comes to snow.

It's almost always a marginal situation temperature wise when we're guaranteed the precip. and then when we're guaranteed the low temps it's usually a roll of the dice when it comes to precip. Then lots of other factors like local topography, Isle of Man (lake effect) shadow, Cork snow shields etc. come in to play. It's very difficult to get snow (especially at sea level) in Ireland. We're really up against it but we fight hard.

But anyway my point is, because it's usually so marginal and difficult to predict when and where it snows in this country, surprise snow is actually probably more common than predicted/forecast snow here. "scattered snow showers" can lead to a foot of snow ... and "heavy rain with strong winds" can lead to a foot of snow with 8 foot drifts.

In living memory I can't recall heavy snow been forecast and it actually happened. (not met bashing, this is model related as it;s model questioning ) Most recently in 2010 heavy snow was forecast and the government on a Friday ordered all schools to closed on Monday. It rained.

Mr Bumble

If I remember correctly, in 1982 a big low came up from the Bay of Biscay and collided with an easterly to produce the dump we got. My best memory was of Evening Press vans snowed in at the back of the EP's Burgh Quay offices while trying to load up the early edition which had a huge banner headline reading "Snow to Miss Us".........given the very damp squib event this week, it goes to show that uncertainty has always been the key player in Irish weather

Sponge Bob

Capitallatus summed it up.

Such an event would be predicted days in advance nowadays with all the extra sensing Sats and online synop data feeding our many modern weather models with all sorts of inputs for a run every 6 hours usually.

We also have infinitely more computing power with which to run these models. My phone is more powerful than a 1982 Supercomputer was.

So a January 1982 event catching us unawares nowadays is impossible..although there was that Day after tomorrow movie.

SEPT 23 1989

1982

The Naas Road ground to a halt and cars,vans and trucks were abandoned ,during the night some residents of one village cleaned out all the vans and trucks of their cargo

the headline in one newspaper read

"WOLVES IN THE SNOW":pac:

whitebriar

A Jan 82 style storm or any storm can be easily mid modeled even with today's technology.
Suggesting otherwise is nonsense.

The last fortnights uncertainty should teach us that.

Mr Bumble

I think there is still potential for surprise in terms of the scale of an event as opposed to the event itself.
1982 was mainly forecast as a rain and sleet event and that's what it was on the Thursday evening but temperatures dropped sharply over night and trousers were firmly down around ankles by the morning time for ME, RTE, many media outlets and local county councils.
I agree that it is hard to imagine that happening these days with so much computing power available and so many different forecasters working the beat but there is always the possibility that the scale of an event can be underestimated. Correct me if I'm wrong but the UK Met office was absolutely hammered at least twice this year after underselling the scale of big flooding events and have been overcompensating ever since.
See below for a bellylaugh
http://www.thedailymash.co.uk/?p=2655&print=1

icesnowfrost

My god are the charts that bad that no one is talking about them as we are reminiscing on past winters.. Not much hope for snow then any time soon ?

davidsr20

icesnowfrost wrote: »

My god are the charts that bad that no one is talking about them as we are reminiscing on past winters.. Not much hope for snow then any time soon ?

I agree , let's just hope mt is rite about jan/feb cold spell in fairness he has always said December will be average temp.

Sponge Bob

Some very nice numbers in the current model runs ( see below) .

We can go back to Modelling advances now.

red_bairn

davidsr20 wrote: »

I agree , let's just hope mt is rite about jan/feb cold spell in fairness he has always said December will be average temp.

He just said today that he hasn't ruled out a white Christmas.

DOCARCH

red_bairn wrote: »

He just said today that he hasn't ruled out a white Christmas.

Going by current models the only white we will see is peoples skin (in their shorts and T-shirts)!

Speak Now

davidsr20 wrote: »

I agree , let's just hope mt is rite about jan/feb cold spell in fairness he has always said December will be average temp.

Actually temps are well below average this month

wexie

Is this Volcanic eruption likely to affect our weather at all?

Is something like that possible to model / forecast for?

maquiladora

wexie wrote: »

Is this Volcanic eruption likely to affect our weather at all?

Not at all. Far too small to have any impact. That only happens with very large eruptions.

Weathering

This guys is usually spot on with his forecasts. He doesn't sensationalise
Here's his forecast for the next week,he's hints at a possible colder turn at the end of the week
When the chips are down,spirits can only go up
http://www.weatheronline.co.uk/cgi-app/reports?LANG=en&MENU=weekahead&DAY=20121214

zidewayz

Weathering wrote: »

This guys is usually spot on with his forecasts. He doesn't sensationalise
Here's his forecast for the next week,he's hints at a possible colder turn at the end of the week
When the chips are down,spirits can only go up
http://www.weatheronline.co.uk/cgi-app/reports?LANG=en&MENU=weekahead&DAY=20121214

I don't think I am even going to look at forecasts or believe forecasts for snow in Ireland for over three days for my own well being untill I am competent in forcasting it for myself. It was too much over the last 2-3 weeks.

Nabber

The charts are terribly normal. Nothing interesting on them. Even the wind dies out before it hits us.

We have HP in the wrong places.

Birdnuts

Nabber wrote: »

We have HP in the wrong places.

That just about sums up the Irish climate - most painfull in winter and summer, with the the past 2 years being a prime example:(

Willie Stroker 1976

last week i missed a day or two here and missed out on ten pages or more as the charts were looking good.. Now with the charts looking s**t theres nothing happening here, lol cant say i disagree though, not much to be said!!

snaps

looking at this morning chats, nothing but low pressure coming in one after the other from the atlantic. The weather has really taken a depressing turn. Nothing even in FI!

derekon

snaps wrote: »

looking at this morning chats, nothing but low pressure coming in one after the other from the atlantic. The weather has really taken a depressing turn. Nothing even in FI!

Dare I even suggest that we could be in for one of those mild mucky winters that we experienced year on year from 2002 to 2008 ? :mad:

Or should we have a wee bit of hope for 2013?

D

Spindle

derekon wrote: »

Dare I even suggest that we could be in for one of those mild mucky winters that we experienced year on year from 2002 to 2008 ? :mad:

Or should we have a wee bit of hope for 2013?

D

It has hardly been a mild start to winter with all the frost we had and below normal temps, and the temps are still in single figures just nudged up to 10c in the South.

January and February are always the colder months in our climate, I think people are forgetting that because recent cold snaps have been early in winter.

Don't give up hope yet anyway as the models seem have lost the plot recently, ninja snow is the best snow

People always like to remember weather in Ireland different than the facts and seemingly dismiss the general climate record as a whole.