Cold Spell Media Forecasts and Model Output (General Chat)

squigo

Sorry folks but how do you put images onto your post directly?

BEASTERLY

RAIN RAIN RAIN:( Thats all I can see on the 18z for here, FFS, i hope its just a dud run and not the start of a trend.:rolleyes:

irish1967

Pangea wrote: »

Im suprised ,I havent had any grauphel here, just a bit earlier before the real snow came.
A few showers came earlier and had real fluffy snow, like if it was coming out of a blowing machine ,didnt last too long though.

Could one of the experts explain why all the 'snow'' I am also getting is grauple ? Radar showing the precip but it's not snow. Will it change and what present condition needs to change to facilitate this change. Thanks.

Harps

irish1967 wrote: »

Could one of the experts explain why all the 'snow'' I am also getting is grauple ? Radar showing the precip but it's not snow. Will it change and what present condition needs to change to facilitate this change. Thanks.

I've always wondered that as well. Asked during the last cold spell as it seems totally random as to whether it falls as snow or graupel.

Obviously there has to be a reason behind it

ffarrell7

Even on some of my money trips to the French alps there are times when a lot of graupel falls but I do not know why.

ciaranm

ffarrell7 wrote: »

Even on some of my money trips to the French alps there are times when a lot of graupel falls but I do not know why.

Oooooooh la de dah

what the hell is a money trip?

Musicman2000

BEASTERLY wrote: »

RAIN RAIN RAIN:( Thats all I can see on the 18z for here, FFS, i hope its just a dud run and not the start of a trend.:rolleyes:

Thats not a precp type chart posted above, this would be.
There is a serious amount of toys being throwing out of the pram over on netweather, but dont panic the GFS is all over the place, take it with pinch of salt if it did come off, get the snow ploughs out

Hammy_irl

Here is what Irish weather say graupel is:
http://www.irishweatheronline.com/2010/12/grapuel-what-on-earth-is-it.html

lucernarian

The pattern for me was that showers that only started to form when the humid air reaches the coast fell more as graupel, while more mature showers that were already formed by the time they hit the coast fell more as snow. So places further inland or where the showery conditions are more established or indeed organised were possibly more likely to see snow instead of graupel?

cherryghost

I'm not trusting any GFS models beyond 24 hours at this point. Everything that it's rolled out this week has gone awry. The only event set in stone is tomorrow evenings one and even that's been given a slight downgrade

cherryghost

Right, I'm off for the night. Got a headache looking at everything change so drastically in the space of 24 hours:

To summarize:

West/Midlands, expect 10-15cm of snowfall tomorrow afternoon and evening
North, expect about 10cm of snowfall on top of what you already got
South/East, expect about 5-10cm of snowfall

Saturday should be showery again, but the damn models are showing some snowfall on the south/east, and some aren't showing anything, so hard to predict.

Sunday is showing a snowstorm with a possibility of rain along the south/east margins. Really can't see it happening. Very confused :pac:

Night all

Rosswind

https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxmap_all.cgi?type=prod&area=ngp_europe2&prod=prp&dtg=2010121618&set=Core

Thought I'd add my tuppence and see does anyone agree that Sunday seems to be showing as the day the low really develops and arcs back over Ireland (South and East). If it deepens to the 968 suggested here there could be massive fallout with potential for drifting... Supposed to be driving from Cork to Mayo on Monday....
Edit: I've used this site for years even though Explorer doesn't recommend entering it.

Pangea

Grauphel showers here now. What a waste.

@ Rosswind
It won't go to 968.
That kind of thing only usually happens over open water.Anyway thats the nogaps model,it's not consulted very much I think.

The GFS especially and all models are chopping and changing right left and centre so really all you can do is take and average and hope for the best.
That would broadly put the heaviest precip south of Dublin alright.
It should be snow except for some sleety mixes within a mile of the coast from time to time as the strong winds slosh up the 11c sea adding a bit of warmth above it.
Note though that in the previous spell,there were strong winds at times too with the streamers and here 2 miles inland,it all fell as snow and 3 weeks later it's still on the ground,some of it!

BEASTERLY

Deleted User wrote: »

@ Rosswind
It won't go to 968.
That kind of thing only usually happens over open water.Anyway thats the nogaps model,it's not consulted very much I think.

The GFS especially and all models are chopping and changing right left and centre so really all you can do is take and average and hope for the best.
That would broadly put the heaviest precip south of Dublin alright.
It should be snow except for some sleety mixes within a mile of the coast from time to time as the strong winds slosh up the 11c sea adding a bit of warmth above it.
Note though that in the previous spell,there were strong winds at times too with the streamers and here 2 miles inland,it all fell as snow and 3 weeks later it's still on the ground,some of it!

Hi BB, the 18Z shows pure rain not even a hint of sleet for the south east(netweather precip-type charts). Do you think this wrong?

M.T. Cranium

I've been basing my forecast on the assumption of greater development around 19th-20th so the 18z GFS isn't going to cause a forecast amendment, as to the actual strength of the storm as shown, would prefer to see this confirmed by model consensus at 00z ... agree that it shows potential for very heavy precip that could be mixed near southeast coast, but would likely be all snow inland. My hunch is that the eventual solution will be similar but a bit further south and angled somewhat less to the northeast, perhaps a track across the south coast of England as far north as London. This would allow some of the toys back into the pram over on the other forum, without robbing Ireland of its snow.

Not wanting to wishcast either but I have to keep the larger picture in mind and with the PV dropping southwest then apparently circling around to ESE, the more likely track evolution would be west to east along the 528 dam thickness. Just looks a bit too easy a rebound on the 18z GFS.

BEASTERLY

M.T. Cranium wrote: »

I've been basing my forecast on the assumption of greater development around 19th-20th so the 18z GFS isn't going to cause a forecast amendment, as to the actual strength of the storm as shown, would prefer to see this confirmed by model consensus at 00z ... agree that it shows potential for very heavy precip that could be mixed near southeast coast, but would likely be all snow inland. My hunch is that the eventual solution will be similar but a bit further south and angled somewhat less to the northeast, perhaps a track across the south coast of England as far north as London. This would allow some of the toys back into the pram over on the other forum, without robbing Ireland of its snow.

Not wanting to wishcast either but I have to keep the larger picture in mind and with the PV dropping southwest then apparently circling around to ESE, the more likely track evolution would be west to east along the 528 dam thickness. Just looks a bit too easy a rebound on the 18z GFS.

Hi M.T,

How from the coast would you consider inland. I presume if the low shifts south there will be less chance of the precipitation to be mixed? Mild air not getting as far north?

Eastcoastryan

Deleted User wrote: »

@ Rosswind
It won't go to 968.
That kind of thing only usually happens over open water.Anyway thats the nogaps model,it's not consulted very much I think.

The GFS especially and all models are chopping and changing right left and centre so really all you can do is take and average and hope for the best.
That would broadly put the heaviest precip south of Dublin alright.
It should be snow except for some sleety mixes within a mile of the coast from time to time as the strong winds slosh up the 11c sea adding a bit of warmth above it.
Note though that in the previous spell,there were strong winds at times too with the streamers and here 2 miles inland,it all fell as snow and 3 weeks later it's still on the ground,some of it!

Hey BB, thanks for the updates today. Just a quick question if you dont mind. I noticed on the weather earlier that Evelyn mentioned a Low Pressure coming down from Scandanavia tomorrow and positioning itself over Ireland for the weekend, would this mean continuous snowfall or would it fizzle out? I have noticed over the past few years that we seem to do much better from streamers from the Irish sea rather that weather fronts, the latter seem to raise temps and generally mean rain for here. I also noticed that even though winds were easterly, that trogdors site was saying NW winds for here, I am assuming that dropped the temp as the air wasn't coming off the warm sea, when it did switch Easterly, the temps went up!!!

Sorry if I am waffling but I am wondering (based on models) which set up is most likely for this weekend?

Eastcoastryan

M.T. Cranium wrote: »

I've been basing my forecast on the assumption of greater development around 19th-20th so the 18z GFS isn't going to cause a forecast amendment, as to the actual strength of the storm as shown, would prefer to see this confirmed by model consensus at 00z ... agree that it shows potential for very heavy precip that could be mixed near southeast coast, but would likely be all snow inland. My hunch is that the eventual solution will be similar but a bit further south and angled somewhat less to the northeast, perhaps a track across the south coast of England as far north as London. This would allow some of the toys back into the pram over on the other forum, without robbing Ireland of its snow.

Not wanting to wishcast either but I have to keep the larger picture in mind and with the PV dropping southwest then apparently circling around to ESE, the more likely track evolution would be west to east along the 528 dam thickness. Just looks a bit too easy a rebound on the 18z GFS.

Hi, I know this thread is for model discussion only but can I just say that it's great to see somebody thats so dedicated to weather and so detailed in their analysis, it helps so many people over here, I dont like bashing Met Eireann as I know sometimes they are in a no-win situation but if they gave an accurate forecast like you do, then I think they would be appreciated much more! I look forward to reading your forecasts and want to wish you a Happy Christmas!

maquiladora

BEASTERLY wrote: »

Hi BB, the 18Z shows pure rain not even a hint of sleet for the south east(netweather precip-type charts). Do you think this wrong?

Huh? Might be sleet right on the coast at times but away from the sea at all and you would have serious snow inland for the southeast of the GFS.

mickger844posts

BEASTERLY wrote: »

Hi BB, the 18Z shows pure rain not even a hint of sleet for the south east(netweather precip-type charts). Do you think this wrong?

Just took a look at GFS and UKMO and your right, -4 850s :eek: We are screwed in the south east if that happens.

M.T. Cranium

I would consider "coastal" when applied to snow discussions to be land within 5 kms of the shore that is also lower in elevation than 50 metres asl. But I should get a handle on what readers think coastal means, because if I use it, I would like the readers to get the right message from the use.

Around here, we also get a lot of mixed winter precip by shoreline exposure and elevation. I live about 120 metres above sea level and probably 10-15 kms from the shore depending on the operating wind direction. In general, this is just about the 50-50 point for rain and snow in marginal situations. There's a hill nearby here (with a university on it) that rises to 300 metres and it quite often has snow when we have rain and 3 degrees or less.

Whether it would work around Dublin and the southeast, I'm not sure, but I've learned to recognize maybe three rain-snow boundaries at approximately 25m, 100m and 200m that seem to occur more frequently than other possible elevation dividers. Perhaps this has something to do with the way arctic air flows out of the interior from perhaps three different routes with varying intensity to almost reach the shore.

In a normal winter, we get a bit more snow even in the lower elevations around here, than most of Ireland, but this winter, we have had only two days with snow lying at my location, and maybe five days on "the mountain" but the local real mountains have remained snow covered throughout the past two months. Our local mean temperature so far this month stands at about 4.5 C. The "IMT" that we use in the forecast contest is below zero C.

isle of man

isle of man wrote: »

they do, but there going that hard that it passers before it gets chance to do anything worth talking about.

its all hail so far

i would like to thank my negative comments that brought the snow, 10mm so far dropped in about an hour between showers,

BEASTERLY

maquiladora wrote: »

Huh? Might be sleet right on the coast at times but away from the sea at all and you would have serious snow inland for the southeast of the GFS.

This shows rain for me anyway(15km inland):


M.T's post has reassured me a bit though:)

BEASTERLY

M.T. Cranium wrote: »

I would consider "coastal" when applied to snow discussions to be land within 5 kms of the shore that is also lower in elevation than 50 metres asl. But I should get a handle on what readers think coastal means, because if I use it, I would like the readers to get the right message from the use.

Around here, we also get a lot of mixed winter precip by shoreline exposure and elevation. I live about 120 metres above sea level and probably 10-15 kms from the shore depending on the operating wind direction. In general, this is just about the 50-50 point for rain and snow in marginal situations. There's a hill nearby here (with a university on it) that rises to 300 metres and it quite often has snow when we have rain and 3 degrees or less.

Whether it would work around Dublin and the southeast, I'm not sure, but I've learned to recognize maybe three rain-snow boundaries at approximately 25m, 100m and 200m that seem to occur more frequently than other possible elevation dividers. Perhaps this has something to do with the way arctic air flows out of the interior from perhaps three different routes with varying intensity to almost reach the shore.

In a normal winter, we get a bit more snow even in the lower elevations around here, than most of Ireland, but this winter, we have had only two days with snow lying at my location, and maybe five days on "the mountain" but the local real mountains have remained snow covered throughout the past two months. Our local mean temperature so far this month stands at about 4.5 C. The "IMT" that we use in the forecast contest is below zero C.

Thanks M.T, im glad to hear im not coastal:D
Cheers

Musicman2000

mickger844posts wrote: »

Just took a look at GFS and UKMO and your right, -4 850s :eek: We are screwed in the south east if that happens.

Dont worry it wont, That low could push further south, and MT also said this

Musicman2000

BEASTERLY wrote: »

This shows rain for me anyway(15km inland):


M.T's post has reassured me a bit though:)

wouldnt worry to much about that chart:)

maquiladora

BEASTERLY wrote: »

This shows rain for me anyway(15km inland):


M.T's post has reassured me a bit though:)

I wouldn't put those kind of charts too much attention. You'll notice that all areas of snow, everywhere are surround by bands of rain/sleet at the edges regardless of what the conditions are.

I can also tell you as a fact that during the last cold spell I had snow falling at close to sea level where that GFS precip type chart was showing rain/sleet.

The situation would be more complex than those type of 'black or white' charts can display.

Anyway, this is far from nailed yet so no point looking at it in much detail yet, things will change before then.

isle of man

If things stay as they are.

then the isle of man is right in the fireing line of all that prep going round in circles,

o the joys:D

Calibos

BEASTERLY wrote: »

Thanks M.T, im glad to hear im not coastal:D
Cheers

150m from my house...



F**K

:rolleyes:

th3 s1aught3r

Calibos wrote: »

150m from my house...



F**K

:rolleyes:

Seriously, does it ever snow at the beach ?

delw

isle of man wrote: »

If things stay as they are.

then the isle of man is right in the fireing line of all that prep going round in circles,

o the joys:D

hope it doesnt make the IOM sink with all that snow,what will we do without the IOM shadow in the future

Calibos

th3 s1aught3r wrote: »

Seriously, does it ever snow at the beach ?

Yes, but I'm disgusted it only lasted for two days on the promenade and till the next high tide on the beach proper:D



I am trying to remember whether MT said coastal fringes were marginal for the last snowy spell a few weeks ago. Brays problem last time wasn't marginality, it was gap in streamerality and IOM snow shadowality

fizzycyst

it definately snows on the coast......sometimes this is tramore on December 1st


2010 btw

smellslikeshoes

th3 s1aught3r wrote: »

Seriously, does it ever snow at the beach ?

It did here in north Wexford during the last spell. I'm 50 meters from the sea and we had 6 inches here, it even stuck on the sand right down to the water line.

megatron989

Calibos wrote: »

Yes, but I'm disgusted it only lasted for two days on the promenade and till the next high tide on the beach proper:D



I am trying to remember whether MT said coastal fringes were marginal for the last snowy spell a few weeks ago. Brays problem last time wasn't marginality, it was gap in streamerality and IOM snow shadowality

True that, the IOM shadow was totally killing the buzz in bray.
Could have been epic! (Heres a second chance so bring on the
snowmonster!)

lucy2010

Calibos wrote: »

Yes, but I'm disgusted it only lasted for two days on the promenade and till the next high tide on the beach proper:D



I am trying to remember whether MT said coastal fringes were marginal for the last snowy spell a few weeks ago. Brays problem last time wasn't marginality, it was gap in streamerality and IOM snow shadowality

Whats your views on it for this one Calibos? As its coming from the west this time could the mountains take it all ????

Calibos

lucy2010 wrote: »

Whats your views on it for this one Calibos? As its coming from the west this time could the mountains take it all ????

Hard to say. On the last big day of snowfall during the last period with the organised band of precipitation coming from the west we saw the band split in the middle as it crossed the midlands with the gap opening up crossing South Dublin and North Wicklow. However then the southern portion of the band which was trailing about 2 hours behind the Northern portion started to turn NE towards us in Bray. This was the last hope for a topup for Bray. Alas it petered out over the Wicklow Mountains.

I'd say any precipitation coming from the W or SW if its no more intense than that last organised band I mentioned woulc probably indeed be soaked up by the Wicklow Mountains. However if the Snow forecast for the weekend is more intense and/or its coming from the NW (ie. only has to cross the low dublin foothills to get to us) then we should get something out of it.

Musicman2000

GFS OOZ run just on the way out, that low sunday night is still on the same route not much change from the 18z run

M.T. Cranium

True but cold air remains a bit firmer in place while the low crosses south-central England, and there is less chance of mixing rain with the snow in southeast Ireland. It looks like a good start, awaiting some other model output for comparison. Then the system for the 23rd is held further south without the warming trend on the 18z, looking now at 25th, the usual GFS lurch back to default warming is apparent but even on these suspect charts the temperatures would stay around freezing to mid-day 25th or longer.

By now, I think we've all gotten used to the day 8 GFS warming trend that has failed about 70% of the time since mid-November and resulted in a mean error of about 15 dam (equivalent to 3-5 deg of latitude in track errors).

Will comment further in a while on the other models. But this GFS run is nearly perfect from my point of view, if you want prolonged cold and a major snowfall over the weekend. It's the old risk-reward problem, move the low too far away to eliminate all chance of mixing, and there can't be as much snow. Move the low closer for even more precip, and there's too much risk of mixing. The perfect track for this thermal gradient is just about what's shown on 00z GFS, and quite an intense low given the synoptics.

I also find the Friday night situation less subject to mixing or downgrade potential, just a straightforward intensification of surface cold feeding in from what's likely to be a frigid southwest Scotland.

Perhaps Ireland and the U.K. are the new Svalbard and the PV will settle in.

M.T. Cranium

UKMO and GME models appear quite favourable to cold and snowfall dominant outcomes.

ECM (Euro) has a rather suppressed look, maintains cold and is somewhat less snow-friendly due to less development.

Forecast will be based on blend with research model parameters guiding intensity. Could be quite the four day period for snow.

ninebeanrows

Morning runs have totally diminished the risk of widespread snow today and tonight.

The low is barely a feature on the runs.

A terrible downgrade.

GFS and UKM actually totally have got rid of it, not even a drop due in the east and not much anywhere barring the west and north.

Musicman2000

Weathercheck wrote: »

Morning runs have totally diminished the risk of widespread snow today and tonight.

The low is barely a feature on the runs.

A terrible downgrade.

GFS and UKM actually totally have got rid of it, not even a drop due in the east and not much anywhere barring the west and north.

Not according to MT'S update

ninebeanrows

Musicman2000 wrote: »

Not according to MT'S update

Well with all due respect to MT i have looked at every single model run and they have no more than 1-2mm of precipitation in Leinster from today through until Saturday afternoon/ evening.

So i would love to know where he is getting his data from or whether it is just guesswork and his estimation of how things will play out in the nowcast. Hope he is right.

The they throw up that small low feature that in yesterdays runs was intense but less intense today and going by the downgrade of todays low could be even less intense if the trend follows.

Weathercheck

Weathercheck wrote: »

Morning runs have totally diminished the risk of widespread snow today and tonight.

The low is barely a feature on the runs.

A terrible downgrade.

GFS and UKM actually totally have got rid of it, not even a drop due in the east and not much anywhere barring the west and north.

This link explains mt's thinking and the reason for this mornings optimistic forecast by him.
It seems logical to me given the woefull performance of models at the moment in what is usually the reliable sub 96hr time frame.

http://forum.netweather.tv/topic/66823-model-thread-discussion-thursdays-output/page__view__findpost__p__1975427I'm surprised you're getting into the act of getting depressed based on one run,you know better than that given their current confusion

ninebeanrows

Deleted User wrote: »

This link explains mt's thinking and the reason for this mornings optimistic forecast by him.
It seems logical to me given the woefull performance of models at the moment in what is usually the reliable sub 96hr time frame.

http://forum.netweather.tv/topic/66823-model-thread-discussion-thursdays-output/page__view__findpost__p__1975427I'm surprised you're getting into the act of getting depressed based on one run,you know better than that given their current confusion

What ya mean though? I am talking about tonights and tomorrow snow that has totally disappeared from Model Outputs?

That discusses the risk on Sunday.

MT is still forecasting 15cm of snow for Dublin up until the end of Saturday.

DOCARCH

ME are on MTs side at present:

Bitterly cold today, with.....showers mainly in Ulster, Connacht and west Munster during the day, but becoming more widespread this evening, with a risk of prolonged falls in many areas.

We'll see. This was reiterated in ME forecast just before 8 on Radio 1.

Weathercheck

Weathercheck wrote: »

What ya mean though? I am talking about tonights and tomorrow snow that has totally disappeared from Model Outputs?

That discusses the risk on Sunday.

MT is still forecasting 15cm of snow for Dublin up until the end of Saturday.

what I mean is all output is suspect and for the first time ever since you and I have been posting on this forum,we're relying on forecaster intuition -so lets think laterally and apply some of our own,we need to now

ninebeanrows

DOCARCH wrote: »

ME are on MTs side at present:

Bitterly cold today, with.....showers mainly in Ulster, Connacht and west Munster during the day, but becoming more widespread this evening, with a risk of prolonged falls in many areas.

We'll see. This was reiterated in ME forecast just before 8 on Radio 1.

How do you mean side?

I wish for snow more than the next man but i am going by what output has been put in front of me! And it spells no snow upto 2cm for the Leinster region.

Obviously this will be an interesting nowcast situation and hopefully the satellite explodes with life later but it doesn't get away from the fact that the models have shown an absolute downgrade in last 12 hours and don't really show this low getting to much.

Monkaa

Upgrade, downgrade, upgrade, downgrade!!!!! Who do you listen to! So annoying...Think ill just wait and hope the for best/worst :rolleyes: