Model Output Discussion

[Snowyowl9]

A cold N-ly with snow showers and air frosts of -5c around april 20th use to be rather expected.

Even on rarer occasions into the middle of may -3c on this date.

Quite a blocked run from ECM showing up.

[SP1986]

Perhaps but where? on hills, frost hollows, cities, the coast? Its quite important to detail where of course.

I very much accept frost hollows can hold onto frost later, and hills can still get snow showers into May. The difference between inland and coast at this time of year is very impressive.

[reef]

With sub -5C 850hPa aloft and high pressure influencing the UK as shown in the T+144 range on the GFS 12z, -4C temperatures would be quite widely attainable at this time of the year. SSTs are still at the same temperature now as early January and the nights are sufficiently long to allow plenty of radiative cooling.

Even here close to the coast we managed -2.4C on 14th April 1999 and even managed -1.8C on 26th April 1989.

Not to say the GFS will be right (at that range its too flaky to be looking at such detail), but what its showing is certainly possible.

[Thundery wintry showers]

No I am not suggesting -4C cannot be reached in April, but with the conditions the GFS suggests, -4C is unlikely. You really need deep seated cold with a powerful northerly to reach such temperatures widespread as the GFS shows.

I don't think that's true- a sluggish northerly with cold upper air can deliver similar minima, the difference is more that the daytime maxima tend to be higher in that case. There were widespread air frosts in the north from a similar sluggish northerly around 17th May 2005. It was a similar story during September 1986, a dry sunny month dominated by a slack northerly regime and unusually cold nights.

Regarding coasts, it probably depends on which coast- for example Cleadon near the Tyne & Wear coast got down to -3.8C on the 14th April 1999, but I imagine it would be far harder to get temperatures that low around the Wirral.

[Frosty.]

I'm really happy with the GFS 00z, a return to colder weather is on the way with a chance of wintry showers, especially down the eastern side of the uk and overnight frosts returning, high pressure looks like being generally out to the west and ridging northwards with troughs dropping into scandinavia once we get through to the end of this week onwards and as lows develop near iceland and dive south east, we could have repeated N'ly outbreaks or at least some incursions of Pm air. The rest of this week should see cloud amounts increasing by wednesday with a few light showers but sunnier for thurs/fri although rain will be spreading into northern scotland by friday with a cold & showery weekend to come up there and a lot of snow for the scottish mountains seems a fair bet if the gfs 00z op run was to verify..no sign of spanish plums on this run.

[mushymanrob]

The mean would still be quite a bit below average based on the 06z charts, with temperatures in the CET zonr averaging about 2-3C minimum and probably 9-10C maximum (if we can trust the GFS temperature predictions ahem), this is as much as 1-1.5C below average is it not for approaching May?

so what? does it matter if the mean is slightly below average? tbh id expect that after a cold winter as the overall synoptics are pretty similar with blocking to our north and no sign of the jet.

id rather have it there and get an artic winter than an roasting summer.. after a while summer gets really boring in fact after a month it will get boring.. as its just blue skies..

and weeks of endless cold arnt boring?..... tbh i think this is the first time ive ever seen anyone moaning at blue skies!!!!

-4c? i pretty sure ive never seen -4c in the second half of april here in derby. is it possible? possibly, yes but its highly unlikely!

fi is suggesting a below average theme for late april, nothing to worry about though assuming the current trend becomes reality. plenty of sunshine on offer once these pesky northeasterlies subside and even in cooler fresher air itll feel nice in the sun.

[Frosty.]

BIG differences between the gfs and ecm 00z in FI (whats new) Ecm brings in a warm SE'ly later and the earlier N'ly only just makes it into scotland with pressure remaining fairly high to the southeast, will be interesting as always to see which model has to back down, I would prefer the gfs outcome as it would prolong the risk of snow for northern hills, theres plenty of time for warm SE'lies in may,june,july and august.

[SP1986]

so what? does it matter if the mean is slightly below average? tbh id expect that after a cold winter as the overall synoptics are pretty similar with blocking to our north and no sign of the jet.

It matters, it really does!

Of course it doesnt matter, well not to us but it must matter to someone. Besides look at all those who seems to be desperate for a below average year, it matters to them

I actually would not expect continual cold after a cold winter, the opposite in fact in most cases. I cant say I'm a fan of stubborn patterns, except maybe thundery ones.

[Frosty.]

The GFS 06z shows a more full on N'ly for the coming weekend followed by a brief respite and then further chilly weather into the first half of next week with a possible N'ly reload, so the 6z has not backed off yet unlike the ecm 00z, still very uncertain what will happen as a lot depends how the trigger low near iceland develops at the end of the week, will make all the difference between a fairly potent cold blast and a more atlantic NW'ly flow.

[johnholmes]

BIG differences between the gfs and ecm 00z in FI (whats new) .... will be interesting as always to see which model has to back down,

its very very early days yet but I've started another jh check. This time once a week on the T+240 output. Only on the 3rd one and, to my surprise, I have to admit, the first 2 GFS was a better guide than ECMWF. The 3rd one ending this Friday and GFS, at the moment, looks the more likely option.

After 3 or 4 months it may show some kind of pattern. NOAA checks at 6 days, more so than at 5, and ECMWF is rarely not the better of the major weather models but we shall see how the 'big' 2 deliver for this small part of the northern hemisphere.

[mushymanrob]

It matters, it really does!

Of course it doesnt matter, well not to us but it must matter to someone. Besides look at all those who seems to be desperate for a below average year, it matters to them

I actually would not expect continual cold after a cold winter, the opposite in fact in most cases. I cant say I'm a fan of stubborn patterns, except maybe thundery ones.

below average doesnt bother me, its still nice, prolonged cold however wouldnt be pleasant.

i do believe that patterns can continue for lengthy periods, it took spring 1979 ages to get going (with a hiccup over easter when it was great!), and 85, i think that cold patterns take ages to really go... but that might be just perspective and not reality. im not sure, but i dont think i can remember a cold winter being followed by a 'good' spring with the exception of 1982, imho cold winters tend to lead to poorer springs but i might be totally wrong.

either way, the 06z promises below average temps, but without much precipitation and sunshine levels hopefully quite high then it shouldnt be bad at all.

[Optimus Prime]

Yeah cold winters usually lead to cool springs with the exception as you say above but also 1947 which had a very cold first half but very mild second. As a result the mean spring temperature was almost exactly average.

Cold winters usually lead to mild Mays and Junes and October and sometimes November. December can also be mild. 1963 was one of the only exceptions to have a very cold December after an exceptionally cold winter.

Summers are usually very cool.

[Eugene]

Dont agree at all there are big differences between ECM 00Z and GFS 00Z/06Z looks the same pattern to me that of a HP block to northwest, only differences is ecm has a break away ridge which settles over us while GFS keeps us it to our west, GFS 06Z is very poor for warm weather fans.

-5C likely next sunday/monday night, very cold for parts of cornwall and dorset.

http://www.wetterzentrale.de/pics/Rtavn16817.png

[Derp Patrol]

FI is changing so much right now that I'm not going to believe anything. Recently it's been showing the possibility of plumes on one run and then northerlies on the next. Last week it was suggesting a cool and cloudy week for down here in the south east, but as it turns out there hasn't been too much cloud, and the rest of the week looks set to have some sunny intervals and pretty average temperatures from 13-15C

[londonsnow]

can't help feeling that we are about to skip from a noneventful spring into another wet summer. is the damn jet going to do what it did last year? 6z certainly chilly in the short and long term, but mostly dry with occasional frost. that chart eugene flagged up is the stuff of misery for those with fruit trees/orchards, but it's a way off so hopefully it wont be as cold as that

[Stormyking]

There is still 2 months or so before summer so anything can change before then so just trying to stay positive and hope we get a hot summer unless the people who prefer a cooler summer that's their opinion.

The 6z does look chilly but its one run and anything can change, I may only be 16 but I have started to understand more about weather charts etc.

Everyone knows that April is a funny month and the fact that its right between Winter and Summer so it will chop and change.

So keep positive everyone

[Ben_Cambs]

Welcome Stormyking

I agree with Rob that there is nothing clear in FI at the moment, if you look at the ensembles the GFS Op run is always a outlier of warm or cold in the low resolution output. I think near the reliable timeframe though, a Northerly of sorts looks likely now, with the possibility of accumilations in the Scottish highlands and possibly for a time on low ground in Northern Scotland. Overnight frosts look possible anywhere next week. I do think IMO that HP will build in from the West/South West after the Northerly. With the jet continuing to be supressed southwards due to the -ve NAO, who knows what this summer will bring?

[Thundery wintry showers]

If the GFS 06Z came off then we'd be looking at sunshine and snow/hail showers from the Midlands northwards for Sunday, and the UKMO might just manage it as well. The longer-term outlook in FI looks rather unusual- the outputs suggest sunshine and cold nights despite generally easterly winds (I think the Arctic source must be the reason). But as others have said ECM looks rather different.

[Stormyking]

Welcome Stormyking

I agree with Rob that there is nothing clear in FI at the moment, if you look at the ensembles the GFS Op run is always a outlier of warm or cold in the low resolution output. I think near the reliable timeframe though, a Northerly of sorts looks likely now, with the possibility of accumilations in the Scottish highlands and possibly for a time on low ground in Northern Scotland. Overnight frosts look possible anywhere next week. I do think IMO that HP will build in from the West/South West after the Northerly. With the jet continuing to be supressed southwards due to the -ve NAO, who knows what this summer will bring?

Thankyou for the welcome

The Northerly does look like at the moment, to be honest I have always had trouble understanding ensembles as there is loads of different lines and I don't really know what I am supposed to be looking at on ensembles, Im still learning alot

It will be Interesting to see what the 12z comes up with as it is bound to change again in FI.

[mushymanrob]

northern blocking has been around for many months now, it gave us last summers poor weather, it gave us last winters freeze, as soon as it go's it isnt long before it returns, it might go tommorow but i doubt it. tbh its not looking good for summer (no im not writing summer off!!! lol) because until pressure drops to our northwest and rises to our southeast itll be more of the same .

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

Less than 45 days till summer!

[summer blizzard]

I personally don't see what everybody is getting hyped up about in regards to cold weather in the near future.

Fact 1) CET is currently above average, and will likely still be above average for at least the next 180 hours (reliableish timeframe)

Fact 2) Yes, we look to get a few cold nights, however in regards to any potent cold spell the next 180 hours see high pressure domination resulting in fairly high maxima, aside from sunday which is our one genuinely cold day, and won't produce snow further south than the Highlands, before high pressure reaserts itself for monday.

That people is my take on things upto the 20th April, though i am personally enjoying the sunny weather with a refreshing breeze, so i say long may it continue.

[johnholmes]

Thankyou for the welcome

The Northerly does look like at the moment, to be honest I have always had trouble understanding ensembles as there is loads of different lines and I don't really know what I am supposed to be looking at on ensembles, Im still learning alot

It will be Interesting to see what the 12z comes up with as it is bound to change again in FI.

yes welcome to NW

re ensembles this may help

http://forum.netweather.tv/topic/25663-guide-to-ensembles/

or this for a more detailed look

http://www.metoffice.gov.uk/science/creating/daysahead/

[Stormyking]

I know its in FI but to me it looks warmer and much different to 6z but of coarse it will probably change again.

[johnholmes]

At the risk of boring long time users of NW, stormy, following models in what some call FI range is not very productive comparing run to run. Its better, down to T+144 maybe T+168 to compare 12z with 12z or 00z with 00z etc!