Model Output Discussion

[Lewis]

The GFS at the moment is looking very good, and its started to come on board with the euro's, i'm not going to get excited because if you look at the time difference of 12 hours since yesterday's 18z, there's such a huge difference with the outputs. I'll be waiting until wednesday 00z before i jump on the bandwagon.

Edited January 24, 2010 by grab my graupel
Move on please

[snowmadchrisuk]

My guess is that they'll wait until the model-runs become more consistent, before issuing any warnings??

There Warning's only go out 5 days so I doubt they will be issuing anything yet , Anyway apart from things turning a little Colder again what would the warning be for , We would need Snow/Freezing rain for Ice to be a problem and we have no idea at this stage if any troughs would be in the flow and I have never seen them Issue a warning for Frost. I'm with you on this one mate

[bluearmy]

We won't be seeing anything like that. The GFS is synoptically highly unlikely; Low pressure would develop off S Greenland and topple the High. Many northerlies of this type over the years have seen maximas in the 7 to 9 range for coastal Southern areas particularly. I'm still favouring a quick toppling and a mild early Feb.

so ian, you are right and the entire ens suite of GEM and GEFS is wrong

http://www.meteociel.fr/modeles/naefs_cartes.php?ech=6&code=0&mode=0&map=1

it took you a long time to come round to reality in december. dont make the same mistake again by being so certain about whats around the corner. looks like a 50/50 call to me after the northerly

[john mac]

The expected pattern change from mid-week onwards is still evolving as to are the movements

of the polar vortices's. I think some are getting to hung up on this toppler scenario, I would not

be at all surprised to see a potent, very potent north northeasterly last for much longer than some

are thinking.

Great start to the day though.

Cheers Winter79 for your comments in the last model thread.

Hi CC

ATM i cant see this northerly being anymore than a toppler, it may last a couple days longer, but unless the atlantic ridges more to greenland then it will topple IMO.

[Guest North Sea Snow Convection]

Hi CC

ATM i cant see this northerly being anymore than a toppler, it may last a couple days longer, but unless the atlantic ridges more to greenland then it will topple IMO.

In the true sense it might not topple - in terms of the jet pattern that this means that airstreams are likely to alternate between arctic maritime (maybe even arctic continental?)and polar maritime air in less cold 'warm' sectors.

The pattern to me, for reasons already given, looks to inhibit any Azores ridging eastwards and flattening through europe, which is the sort of classic toppler progression that is usually assumed following a northerly, which leads to tropical maritime air, and appeared to be a greater possibility up to yesterday.

The outlook is a colder one today for sure.

Edited January 24, 2010 by North Sea Snow Convection

[grab my graupel]

Cut out the bickering please folks, it's becoming rather tiresome

Thanks

Brian

[Frosty.]

PL's are not likely in this set up IMO,

Depends on whether there are any more upgrades, I would think there will at least be troughs swinging south which will pep up the shower activity and merge the snow showers into longer periods of snow and combined with strong to gale force northerly winds there would be plenty of drifting, ice days, severe frosts and lasting a good 3-4 days hopefully. Fantastic model output but could suddenly downgrade on 12z or tomorrows 00z, if it still shows in the morning I think it will happen.

[TEITS]

How can the BBC (Or anyone else?) factor model-runs into their forecasts - before said model-runs appear?? IMO, that would be crazy. It would also leave forecasters open to all sorts of questions and accusations...Maybe expect a change in prediction once the data have all been collated and analyzed?

Morning Pete.

When I say farce im referring to the BBC taking a full 24hrs to say the same as I did wrt to the E,ly. I haven't watched the BBC forecasts this morning but again im perplexed if they are saying mild next week. The fax charts clearly show a cold front moving S on Thursday which is wny im puzzled at their forecasts.

I realise that the BBC forecasts will always be outdated due to the wealth of data at our disposal. However this still isn't an excuse for some of their poor forecasts. If the BBC employed some properly trained Meteorologists who monitored the latest models, Sat pics, Radar then these errors wouldn't occur. I will never forget the occasion when a few yrs go the BBC continued to predict heavy snow along S Counties on their 22.30 forecast and yet at 18.00 it was clear this snow would remain in the channel. A simple glance at the radar would of resulted in a more accurate forecast.

[john mac]

In the true sense it might not topple - in terms of the jet pattern that this means that airstreams are likely to alternate between arctic maritime (maybe even arctic continental?)and polar maritime air in less cold 'warm' sectors.

The pattern to me, for reasons already given, looks to inhibit any Azores ridging eastwards and flattening through europe, which is the sort of classic toppler progression that is usually assumed following a northerly, which leads to tropical maritime air, and appeared to be a greater possibility up to yesterday.

The outlook is a colder one today for sure.

Hi Tamara, i agree with you that the outlook is definately colder today, which is good news.

What is your opinion on the possibility of a polar low in this set up?

[weather eater]

Well I have to admit to being amazed at the model output this morning. I have no problem in admitting that I could of got this entirely wrong, although that wouldn't be a first.

What im amazed at isn't so much the strength of the N,ly but the length of this and what follows after. As you know i've been saying what the models have been progging never happens and this always results in a 48hr N,ly followed by a toppler. However the sinking HP with LP tracking to the N of the UK isn't being suggested by the GFS.

As an example look at the SLP mean for Iceland. Now if we we're to see a sinking HP with deep LP systems tracking to the N you would expect the SLP mean for Iceland to be around 990-1000mb. However as you can see the mean is 1020mb!

http://charts.netweather.tv/ensimages/ens.20100124/00/prmslReyjavic.png

We can also see this in how cold the ensembles are for Cambs with the mean never rising above -5C.

http://charts.netweather.tv/ensimages/ens.20100124/00/t850Cambridgeshire.png

So beyond the N,ly there is the chance of N,ly reloads.

Morning Dave I wouldn’t berate yourself to much, we've got so used to looking at the models in a certain way and this winter has taken many by surprise. In fairness you've long preached the wisdom of looking for trends in FI, trouble is when faced with more than one it can be difficult to know which is the right one. What is certain is that the GFS picked up this trend a week ago, here’s two posts I made on the 18th

Its a mid Atlantic ridge that keeps appearing, that's now shown its hand about four times over the last five or six runs worth watching if the ECM also starts to pick this idea up.

I can't see us being influenced by the Siberian high at least not in the way that many on here think, in other words an easterly. Our next meaningful cold outbreak will come from the N/NW west initially, this then may tap into the cold to our east. I think there is a fair degree of operational support for something of this kind, least wise there are more pointers towards this than anything else is, unfortunately all very FI at this stage.

Not exactly right but not far of, I think only BFTP supported this view at the time, my posts were effectively ignored and his were rather shot down. Although I don’t rate his climate theory stuff he’s as good as anyone at reading the models, however I’m sure he will claim it for his LRF. All in all what an interesting winter we are having, a learning curve for all of us.

[Guest North Sea Snow Convection]

Hi Tamara, i agree with you that the outlook is definately colder today, which is good news.

What is your opinion on the possibility of a polar low in this set up?

Hello John

Pass - to be honest! I'm no expert at all on these features. People like Nick F for eg etc on the team are the one's in the know for the ingredients needed here. All I know is that they can crop up in unstable northerly flows, especially when they are sustained for long enough. But then most of us know that anyway already I guess!

I think that 'sustained' might need clarifying. Upwards of 3 - 5 days maybe. The upcoming pattern might well give us at least a cold start to Feb before high pressure becomes close by. But that is an improvement on how things looked yesterday for sure

Edited January 24, 2010 by North Sea Snow Convection

[stratty]

I wouldn't worry about the BBC forecasts after the recent farce. If the models continue with the trend then a cold front will be sweeping S during Thurs and by Friday we shall all be under a bitterly cold Arctic airmass.

Back to the models and I can't help but wonder whether a Polar Low may develop in this N,ly. My mother always tells me about the infamous blizzard that hit Peterborough during Feb 7th 1969. This was a Polar Low that hit the E Midlands and remains one of the greatest snowstorms to ever hit Peterborough. Apparently over a foot of snow fell within the space of a few hrs!

Hardly call it a farce, Old Boy! - with this amount of scatter in only a few days - in other words still nothing is certain with regards how cold and if there will be the odd snow shower/flurry around for just a few days time! Poor BBC

With regards to the northerly - we are in one of the better places for this at present! Fingers crossed for some PLs if we get to that stage!!!

[TEITS]

All in all what an interesting winter we are having, a learning curve for all of us.

Morning WE.

I fully agree mate this winter has been a learning curve and in my opinion the GFS has been an excellent trend setter.

Based on this winter I would use these models for these timeframes.

0/+48 NMM/NAE

+48/+72 Fax charts

+72/+120 ECM/Fax charts

+120/+192 ECM/ECM ensembles

+192/+240 GFS/GEFS/GEM ensemble mean.

I didn't include the ECM +240 because in my opinion I find the ECM at this timeframe rather inconsistent and prefer to just look at the ensemble means of GEFS/GEM.

What I find interesting this morning is I thought all models would show a toppler as yesterdays output seemed inplausible. However im learning this winter that what wasn't achieveable is becoming achieveable this winter!

[Duane S.]

The expected pattern change from mid-week onwards is still evolving as to are the movements

of the polar vortices's. I think some are getting to hung up on this toppler scenario, I would not

be at all surprised to see a potent, very potent north northeasterly last for much longer than some

are thinking.

Great start to the day though.

Cheers Winter79 for your comments in the last model thread.

Absolutely agree there CC. This Northerly blast has been coming for the past two weeks and often looking at the Reyjavic SLP ensembles, the Operational has been an outlier (in terms of showing low pressure) VERY frequently of late (I posted yesterday's outlier) indicating that height rises over Greenland have been under estimated.

What is a toppler? A 24 hour event, A 48 hour event?? Depends on your interpretation I suppose, but whilst I don't see a full-on retrogression occuring, this Northerly blast will likely last longer than that. The MJO is looking very strong at the moment as well & this will very likely work further in our favour!

Afterwards? Well the almost instant downwelling from the recent warming is certain not going to hinder our chances for sure and ATM I will keep an open mind but the first week of Feb is looking increasingly interesting!

Also, look at the difference in ensembles for my area between those from just three days ago and today's...

[cold snap]

And there was me wanting some time off from model watching.was not expecting that ouptut this morning.

But do Northerlys ever last more than what being shown this morning?

48 hours is the usual time or less.but this morning models want it progged for longer,will take that.

Also to note this seams to refuel the cold pool to the east,they must be having some serious harsh cold in eastern europe right now.which seams to be going on since the early stages of December with the cold air path coming into Germany each and everytime.they do so well on this current setup.

GFS and ECM and UKMO all go hand in hand with a Northerly outbreak.however if you just saw the BBC forecast.you would think nothing was going on .

If the Northerly does come off towards the end of this coming week it will be intresting to see what happens there after.I would not be suprised if we might be looking east again.as we have some often this winter.

A really amazing output this morning.the sleepless nights continues.waiting and wondering.im going to sleep all summer at this rate.

[snowmadchrisuk]

In the true sense it might not topple - in terms of the jet pattern that this means that airstreams are likely to alternate between arctic maritime (maybe even arctic continental?)and polar maritime air in less cold 'warm' sectors.

The pattern to me, for reasons already given, looks to inhibit any Azores ridging eastwards and flattening through europe, which is the sort of classic toppler progression that is usually assumed following a northerly, which leads to tropical maritime air, and appeared to be a greater possibility up to yesterday.

The outlook is a colder one today for sure.

It looks on latest output that instead of the usual topple SE , It may just slowly Sink South which would block the Atlantic for longer . Everything after that remains very uncertain .

[TEITS]

What is a toppler? A 24 hour event, A 48 hour event?? Depends on your interpretation I suppose, but whilst I don't see a full-on retrogression occuring, this Northerly blast will likely last longer than that. The MJO is looking very strong at the moment as well & this will very likely work further in our favour!

Interesting question RE toppler.

I've always classed a N,ly toppler via an Atlantic HP as a weak N,ly flow with the airmass riding over the top of the HP for 48hrs before this flow is cut off and we see milder W,lys. However this mornings output is showing a N,ly via a direct Arctic source that could last upto 3-4 days.

So I personally wouldn't class this mornings output as a classic toppler. Infact im even beginning to get rather excited.

[cold snap]

Interesting question RE toppler.

I've always classed a N,ly toppler via an Atlantic HP as a weak N,ly flow with the airmass riding over the top of the HP for 48hrs before this flow is cut off and we see milder W,lys. However this mornings output is showing a N,ly via a direct Arctic source that could last upto 3-4 days.

So I personally wouldn't class this mornings output as a classic toppler. Infact im even beginning to get rather excited.

Dave is this not the biggest change in the models in some time?

Because i remember you saying you were taking a break from model watching.what a overnight break,lol

In all jokes aside i just looked GFS and ECM again and cant believe what im seing.time for some caution me thinks

[yamkin]

Interesting question RE toppler.

I've always classed a N,ly toppler via an Atlantic HP as a weak N,ly flow with the airmass riding over the top of the HP for 48hrs before this flow is cut off and we see milder W,lys. However this mornings output is showing a N,ly via a direct Arctic source that could last upto 3-4 days.

So I personally wouldn't class this mornings output as a classic toppler. Infact im even beginning to get rather excited.

Very exciting Ensembles http://www.null/two/ensembles/ :) :cold: By the way, 'TWO Forum' are also getting excited with the latest models & Ensembles

Edited January 24, 2010 by yamkin

[Guest North Sea Snow Convection]

It looks on latest output that instead of the usual topple SE , It may just slowly Sink South which would block the Atlantic for longer . Everything after that remains very uncertain .

There is now a signal for high pressure in the atlantic along with a Scandi/euro trough to last, perhaps, for much of the first week of Feb. Assuming that verifies, then we have an extension of the cold pattern window, at the least, that didn't seem as possible previously. Beyond that, as you say, it is very uncertain. But quiet high pressure close by is a favourite (which would still give overnight frost) but with still the small chance of a cold pattern continuing with renewed northern blocking.

Anything can happen of course, but anything definitively mild keeps being put back further.

Edited January 24, 2010 by North Sea Snow Convection

[Cloud 10]

06z ensembles showing a 4 day cold snap with more support for the high being toppled after this than was evident on the 00z ensembles.

I now declare that a 48hr toppler is a thing of the past,and that the new "modern toppler" will last a minimum of 72hrs.

[bluearmy]

http://www.meteogroup.co.uk/uk/home/weather/services/ensemble_forecast.html

the extended ecm ens look cold and settled to me. no sign of any zonality. the clumping is definitley in the cold camp.

[snowmadchrisuk]

06z ensembles showing a 4 day cold snap with more support for the high being toppled after this than was evident on the 00z ensembles.

I now declare that a 48hr toppler is a thing of the past,and that the new "modern toppler" will last a minimum of 72hrs.

It is possible the new Modern could be for things to last longer and be colder , the milder winters lasted roughly 20 years with the odd cold winter thrown in for good measure. If this cycle reverses then I would say the next 15 years or so will get colder and colder with the odd mild winter thrown in here and there .

Support is growing for a longer Northerly that is for sure and if nothing else at least it will feel like Winter. Even if trough's don't develop and there isn't a wide spread snow event it looks like the sort of setup that would lead to clear blue sky's and Sunshine shining on the crisp Frost.

[Frosty.]

Very exciting Ensembles http://www.null/two/ensembles/ :) :cold: By the way, 'TWO Forum' are also getting excited with the latest models & Ensembles

Can we thank the seagulls for this sudden change?

Well the 6z gives us a 72 hour Northerly blast and perhaps more cold in FI, there is a chance the N'ly could be more prolonged than that though, amazing upgrade really.

[bluearmy]

given how cool/cold its been for the last month or so, a period under the influence of warm sector is going to feel quite different. once the warm front comes thru, it will feel mild for a couple of days. the cold front is also not immediately followed by really cold air so until friday, probably wont feel too cold, especially the further south you are.