Model Output Discussion

[johnholmes]

A slightly colder GFS 06z run, but this low is going to have a mind of its own this week, the models are going to struggle with this one, as Dave the Eye mentions earlier, a nightmare to forecast detail this week, rain could very easily turn to snow and cause al kinds of problems, then again if snow is forecast, many thousands of tons of salt and grit could be wasted as it all gets washed away by just rain.

The overall pattern though from the models does suggest a mostly rather cold and unsettled week, wintry outbreaks could occur just about anywhere, with high ground being more likely to receive snowfall. Frost and fog overnight looks to become widespread.

A band of slow moving precipitation, nightmare for forecasters, rain or snow?

projected temperatures during same time period.

Slack low pressure, frost and fog at night.

Widespread low temperatures at night

thanks Paul-a nice presentation for everyone

[cooling climate]

Yep much further S as yesterdays GFS runs had this around N England!

Looks a good call from CC because he said this would happen i.e blocking to our N pushing everything further S.

Lets not forget CC & Tamara also said the mild SW,lys wouldn't occur last week. These are the type of members I like as they don't depend on the model output and use experience and instinct.

It is looking more promising this morning with the MMW starting to show up in the nwp models or at

least the effects of the MMW over Svalbard and Scandinavia which look to me to be very conducive

for a change to a more suppressed and much colder last week of February.

This suppression (southerly track ) perhaps showing up as we go through this week.

The warming at the 30hpa level over Svalbard and Scandinavia is set to continue and this

should lead to blocking in this area.

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=town&alert=1

This should help to pull the -NAO back to a more east based one.

[johnholmes]

Although it cant be ruled out, a return of the very cold weather to our north is a long shot at present but thats not to say things wont change in a week or 2.

For those looking for further snow, we have been spoilt of late and now its a run of bad luck from a snow perspective and cold, but as ive said before with the cold continuing to hold strongly over Scandinaviathe chances are in favour of another cold out break perhaps as we go into march and disruptive snow is still a possibility

true enough D.K I would not rule it out after a rather milder start to March.

[kold weather]

The key looking at the ensembles for snow risk is keeping the main LP/upper vortex either voer the UK or to our east, once it goes to our west if its too strong the circulation will drag milder air up across the UK, still fairly cold BUT the wrong side of marginal.

Still things seem like they are dominated by low pressure, hopefully we can stay on the right side of marginal at least further north...

I'm still happy with the call for attacks from the SW, though still early days and could be more rain then snow if things don't work out.

[Frosty.]

true enough D.K I would not rule it out after a rather milder start to March.

Well according to the GFS 06z it will become milder by around 4th March, I must say that the 6z run is a stunner for those north of the border with little or no mild weather for the next 384 hours and several blizzards thrown in for good measure. The latest meto update is actually suggesting what the 6z is showing with the north getting the lions share of the frost and snow potential but cold and wintry at times in southern britain as well.

[MR EXTREMES]

Well according to the GFS 06z it will become milder by around 4th March, I must say that the 6z run is a stunner for those north of the border with little or no mild weather for the next 384 hours and several blizzards thrown in for good measure. The latest meto update is actually suggesting what the 6z is showing with the north getting the lions share of the frost and snow potential but cold and wintry at times in southern britain as well.

i cant see where any of the models suggest cold for southern england the meto advisory shows the outcome for the southern half of the uk.

there is not one model and the ens dont support this either,

so it would be a good idear if some would not miss inform others about cold for the south,

but north and east is different story the models very much support cold with snow a plenty m4 north looks good.

Edited February 15, 2010 by badboy657

[kold weather]

Depends on what you mean by the south though BB, afterall for people in Scotland I dare say anything south of B'ham would be classed as the south probably...

Still as Forsty said this could well be a very impressive period of weather coming up for those further north, still this is a very fluid set-up, esp as any secondary depressions could alter the picture yet again...

I'd guess there will probably be a good 2-3 sanow events at least for various parts of the country, mainly north of the midlands but some ensemble members have the threat almost to the south coast...it all depends on the exacts of the flow and how the LP develops...

[Frosty.]

i cant see where any of the models suggest cold for southern england the meto advisory shows the outcome for the southern half of the uk.

there is not one model and the ens dont support this either,

so it would be a good idear if some would not miss inform others about cold for the south,

but north and east is different story the models very much support cold with snow a plenty m4 north looks good.

You are being a bit nit picky IMO, the 6z run shows a good chance of snow and frost in all areas, a much better run than the 00z and more in line with the earlier gem which is a stunning run. The meto update covers all bases and includes the risk of snow in the south although temps look like being up and down a bit in southern britain it has to be said.

Edited February 15, 2010 by Frosty039

[D KARLSON]

Just had another look at the charts in detail and i think perhaps some snow potential has been overlooked !!!!

As the associated fronts clear most of the uk ,apart from the south east and scotland a rather cold polar maritime airmass comes in this could well bring in some heavy showers that as they cross the pennines and push east are likely to turn to snow and sleet especially as they encounter those colder nightime temperatures to the east even lower ground is a possibility ,certainly one to keep an eye on

[Ben_Cambs]

I agree with the previous 2 posts that GFS 06z showed a good chance for snow for the whole country, as by next weekend colder uppers filter southwards. But all in all the models are very messy just because of the LP. Im very sure that especially Northern and Eastern Scotland will do very well with snow this week, this is the time of winter when I hope for the snow event and Im not looking for any prologned cold spell anymore as we near the meterological end of winter.

In the shorter term Tuesday night into Wednesday still looks marginal to me, as the risk of snow is put further north westwards, IMO the Chilterns could do well out of this though. We will see how much evaporative cooling there may be, how intense this front will be as it stalls is still unknown. I think this could throw up a few suprises though

[full_frontal_occlusion]

It is looking more promising this morning with the MMW starting to show up in the nwp models or at

least the effects of the MMW over Svalbard and Scandinavia which look to me to be very conducive

for a change to a more suppressed and much colder last week of February.

This suppression (southerly track ) perhaps showing up as we go through this week.

The warming at the 30hpa level over Svalbard and Scandinavia is set to continue and this

should lead to blocking in this area.

http://strat-www.met.fu-berlin.de/cgi-bin/times?plot=town&alert=1

This should help to pull the -NAO back to a more east based one.

CC. All of the signals appear to back up your assertion, but like last year and the MMW that never was or this years Siberian high in need of Ritilin, it's a good trend if but only if it verifies.

I'm constantly pleasantly surprised in the wealth of knowledge displayed by posters (whatever method of forecasting used) on this forum and not just from the acknowledged experts. To all of you: Don't ever stop!

Just like the NWP ensembles, the spread of those posters interpretation bounds the extremes between which the true synoptic outcome lays. For me, the question of weighting any given forecasters interpretation is a matter of credibiity based on the frequency of displayed skill at hitting the correct outcome - again by whatever method is used provided its not random luck. In that respect one could get a skewed result also from how many posts a given individual makes.

Old school experience is hard to substitute especially when unusual (read unrecognised) synoptic patterns are thrown up. But even some of these interpretations can be swayed if emotion is allowed to bias judgement.

Everyone (on this forum knows that all NWP - which includes the emerging science of Teleconnections - is based on the solid laws of old school physics heavily statistically extrapolated.

Return to mild is not a question of 'if' but definitely 'when'. Spring and summer cannot be stopped any more than the earths' orbit around the sun. The teleconns for me in no way suggest an abrupt Atlantic dominated change. A gradual pattern change with a cool late winter into spring and then an unsettled period as insolation melts the continental snow fields. El Nino induced bbq summer must still be the odds-on favourite.

Pattern recognition and pulling a signal from the noise should be a skill at which humans excel. NWP indicators are merely a tool no matter how complex the equations or computer software becomes lest the servant becomes the master.

ffO.

PS. I, Robot.

[kold weather]

Just had another look at the charts in detail and i think perhaps some snow potential has been overlooked !!!!

As the associated fronts clear most of the uk ,apart from the south east and scotland a rather cold polar maritime airmass comes in this could well bring in some heavy showers that as they cross the pennines and push east are likely to turn to snow and sleet especially as they encounter those colder nightime temperatures to the east even lower ground is a possibility ,certainly one to keep an eye on

Yep it sure is one to keep an eye on, esp as the colder air digs down.

Also I still feel this could well be a very snowy period coming up for some parts, I said on Saturday its not a cold spell we have to look for but a snow spell, further north looks best at the moment but things can still change.

[Duane S.]

Not withstanding some very interesting snow potential this week, are we beginning to see tentitive signs of a trend that will end up showing LP's tracking more southerly on W-E path? I can certainly see the potential is there if that blocking above starts moving things south, which is very plausable.

However, I thought this last week though and had been expecting the models to relfect it by yesterday at the latest. Still time yet for the charts to change though I suppose but SW'erlies (not the v. mild variety) for the south are still a very viable possibility though IMO.

[Drew]

For those of you wondering whether this current set up could bring snow to the south.. I have just stepped outside to get some lunch and it is trying to snow in Westminster.....

[Archie_Lewis]

For those of you wondering whether this current set up could bring snow to the south.. I have just stepped outside to get some lunch and it is trying to snow in Westminster.....

Same here. Im can confirm its snowing in South Herts.

Back to the models the front does seem to stall further NW then thought this time yesterday.

I really wouldnt read in to it to much though, I would of thought that tomorrow afternoon into the evening will definately be a nowcasting event and it could very well happen that the counties in the SE that have had their advisories will be suprised tomorrow.

Its happened so many times, unexpected snowfall. As ever the radar shall have the final say.

[TEITS]

Well according to the GFS 06z it will become milder by around 4th March,

I can't see any signs of a mild start to March. For me a continuation our our current pattern with blocking to our N with a jet further S than normal.

We have to remember that F.I model output will always be uncertain and this is where you need to have some forecasting instinct. Some got caught out (not mentioning any names) last time by congratulating GP for his mild Feb forecast when the models were predicting mild S,lys. As we know this didn't occur although the likes of CC & Tamara didn't because they knew exactly how the models were incorrect in what they were suggesting.

[bluearmy]

I can't see any signs of a mild start to March. For me a continuation our our current pattern with blocking to our N with a jet further S than normal.

We have to remember that F.I model output will always be uncertain and this is where you need to have some forecasting instinct. Some got caught out (not mentioning any names) last time by congratulating GP for his mild Feb forecast when the models were predicting mild S,lys. As we know this didn't occur although the likes of CC & Tamara didn't because they knew exactly how the models were incorrect in what they were suggesting.

i guess we ended closer to an easterly than a souwester. the 'mild feb' outlook was made in the third week jan when teleconnections indicated this was a stronger possibility than a cold one. i recall this didnt last for more than a few days when the nwp began to point to the siberian high heading our way and holding the atlantic at bay.

i agree that the return of the atlantic is 'overdone' in some posters minds. the trough looks to be continuing to be centered over the southern half of the UK/northern europe, retreating west from time to time. still think snow events for northern england/scotland are going to be the main news over the next 2 weeks or so.

[Harsh Climate]

Models looking great at the moment!

http://www.wetterzentrale.de/pics/Rtavn1082.png

[Coast]

OK folks, yet another request to keep things on-topic and to keep views about other peoples success (or lack of success) in interpreting the models and their outcome, polite, succinct and relevant.

[Frosty.]

I can't see any signs of a mild start to March. For me a continuation our our current pattern with blocking to our N with a jet further S than normal.

We have to remember that F.I model output will always be uncertain and this is where you need to have some forecasting instinct. Some got caught out (not mentioning any names) last time by congratulating GP for his mild Feb forecast when the models were predicting mild S,lys. As we know this didn't occur although the likes of CC & Tamara didn't because they knew exactly how the models were incorrect in what they were suggesting.

To be fair TEITS, even JH thinks march will start milder and the gfs 00z showed milder air sweeping northeast across all areas well before the end of feb, feb 23-24th I think it was. These wild model fluctuations will continue every six hours until the gfs becomes set on a pattern whether it be for NE'ly cold or SW'ly mild, the jury is still out.

[grab my graupel]

If you'll bear with me folks, I'll just quickly open a new Model thread before this one gets too long

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