Model Output Discussion

[frostyjoe]

It would be quite a shock to the system if the charts at T+240 were too come off after the warmth of this weekend. Very unlikely at this stage I must say, but the ECM and GFS 6z are carbon-copies of each other at that range today.

It would bring some quite exciting weather. Pleasant sunshine with temperatures of 5-8C, falling close to freezing in heavy snow showers and the possibility of thunder. It would then be very cold with some hard frosts overnight and quite late ones at that compared to recent years (Its 12 years since we had a frost in the second half of April here). Its definitely not what most on here want, but it would be a welcome change from what is turning out to be another fairly boring spring again in regards to extremes (so far).

In the mean time theres a bit of disagreement between the models and what the MetOffice/BBC are forecasting with regards to cloud amounts. As usual with this setup its next to impossible to predict and could be a case of sticking your head out of the window to see.

we had that last week and i must admit it was great!

The set up isn't rare, but 5c is very hard to get in April, let alone late April in London..

From the nearest station to me (not including this year)

April 2009 recorded 0 days with a max below 10C

April 2008 recorded 3 days with a max below 10C - 2 of those days in the snow event at the start of the month, the other one was 9C in mid month, lowest was 6C

April 2007 recorded 1 day with a max below 10C - 9C on the 3rd

April 2006 recorded 4 days - the lowest 8C, all before midmonth

April 2005 recorded 0 days below 10C

April 2004 recorded 0 days below 10C

So in the last 5 years at least it would be very rare

how is it i had a max of 3c last week and 2c the day before...

[Derp Patrol]

we had that last week and i must admit it was great!

how is it i had a max of 3c last week and 2c the day before...

I was talking about this region..

[Bottesford]

Did sommeone mention northerly? I do love a good northerly in April. Wonderfully sunny skies punctuated only with heavy wintry showers when the wind veers NWly. If I can't have proper warmth then throw a good northerly in! (but just keep them away late May to September otherwise bring 'em on!).

[Cheese Rice]

If we look at past record for Leeds-

Single figure maxes in April-

2009

28th- 9.c

2008

5th- 9.c

6th- 7.c

7th- 8.c

11th- 9.c

12th- 9.c

13th- 8.c

16th- 7.c

18th- 7.c

19th- 7.c

20th- 8.c

2007

3rd- 7.c

5.c maxes look quite possible if the northerly is strong enough with enough cold air, in-fact 5.c maxes in the south are likely if we can get -10 850's. Even in late April single figure maxes were achieved on several occasions, notably a max of just 7.c on the 19th (2008). The northerly shown by the GFS probably wouldn't bring maxes of 5.c (for the south at least), probably higher unless there is a constant feed of showers across much of the country. Ideally we want -10 850s, but anything below -5 will probably be enough for 5.c maxes or a little above.

Off topic but I find it quite interesting than maxes of single figures were achieved ten times in 2008, yet in 09/07 this was achieved only once. Goes to show there is no correlation between a cold winter and a cold spring as shown by 2008.

how is it i had a max of 3c last week and 2c the day before...

Because you were under very heavy rain/sleet, with cold air undercutting.

[damianslaw]

A very nice weekend beckons for western parts, Saturday being the better day for most of the country but by Sunday good chance of some low level cloud in the south and east as we begin to pull in a light easterly drift.

Into next week, models all in agreement that the central part of the high will transfer to scandanvia with potential for quite a long easterly draw with a northerly component which would bring fairly chilly winds to the south and lots of cloud, though the north west could hold on to some milder conditions with plenty of sunshine.

Beyond, the models keen on retrogression as we see lower heights over Norway and the development of a scandi trough, but more importantly we see low pressure over Spain and the Bay of Biscay - a classic evolution to a northerly further down the line. Still beyond the reliable timeframe but I do feel the evolution is not to a south easterly or to a return of the atlantic more likely one of the following:

A northerly and a potent one

Anticyclonic with high just to the NW keeping a cool northerly/north easterly flow

Cyclonic cold conditions with lows over the country courtesy of strong west based NAO and high advecting from Greenland to Canada - synoptics we saw in late feb and late march.

This is the time of year when switcharounds often occur from spring warmth to winter cold and when northerlies and easterlies reach their yearly maxim. If a northerly does develop as shown by GFS and ECM it would be a cold one, and those who say northerlies by late April can't deliver snow and cold, look back at 1981..

[Cheese Rice]

So far a stunning GFS run so far, maxes of single figures across the whole of the UK by Tuesday. The easterly will definitely bring a big change, if it comes of maxes of 16.c widely on Monday, by Tuesday maxes of just 8-9.c.

Edited April 8, 2010 by 10123

[mushymanrob]

"its only cloud"?... true, but its boring and most of us would prefer a more animated skyscape, and those of you :cough cough: tamara:cough: that see no problem with days of cool grey stratus, would you be so nonchalant about acg in winter when you want snow?

fi again has a worrying northerly.... yep its nice enough, sunny, fresh, cool weather type which isnt a problem for a few days, im still haunted by the spectre of spring 1975.

So far a stunning GFS run so far, maxes of single figures across the whole of the UK by Tuesday. The easterly will definitely bring a big change, if it comes of maxes of 16.c widely on Monday, by Tuesday maxes of just 8-9.c.

i wouldnt get too excited about the prospects of that happening, the 00z has a much better prospect of plenty of spring warmth with a southerly slant of the easterlies, and with a southern origin.

[johnholmes]

Once again though GFS is not consistent, it showed the cold northerly at T+240 along with ECMWF yesterday on its 00z run. Today its 24-48 hours later and not as 'full on'. EC still shows it from T+240 'abouts but again not full on.

Next week will be a time to watch the first visual sat picc each morning to try and assess how long cloud will last inland, along with the other guides I suggested yesterday.

[Tom D]

I'm hoping for a bright, dry and mild week from the 19th... which the ECM is not showing. It won't be too fun walking around Dartmoor with a northerly going.

[frostyjoe]

I'm hoping for a bright, dry and mild week from the 19th... which the ECM is not showing. It won't be too fun walking around Dartmoor with a northerly going.

its not that bad we had this last week... its not as if we have been in double figures for like 3 months... seriously though yesterday was the first double figure this month so i don't know what everyones going on about!

[Frosty.]

fi again has a worrying northerly

Made me laugh, yes a northerly in late april is so worrying

A quieter phase is upon us with plenty of sunshine and winds becoming lighter but still a chance of overnight ground frost or just very dewy, prospects are for the settled spell to continue for several days.

[Guest North Sea Snow Convection]

"its only cloud"?... true, but its boring and most of us would prefer a more animated skyscape, and those of you :cough cough: tamara:cough: that see no problem with days of cool grey stratus, would you be so nonchalant about acg in winter when you want snow?

fi again has a worrying northerly.... yep its nice enough, sunny, fresh, cool weather type which isnt a problem for a few days, im still haunted by the spectre of spring 1975.

i wouldnt get too excited about the prospects of that happening, the 00z has a much better prospect of plenty of spring warmth with a southerly slant of the easterlies, and with a southern origin.

Hi If there wasn't snow, then yes I would be quite happy with acg in winter. Much better than wind and rain.

The northerly does look quite likely. All the computer models agree on our high moving westwards into the atlantic as we go through later next week. The only question is what sort of northerly it is?

In the meantime, a glorious day today, a very nice weekend with an easterly developing in the south especially early next week (for me to look forward to ). Bring it all on, including the potential northerly. Nice variety there I think .

[frostyjoe]

Hi If there wasn't snow, then yes I would be quite happy with acg in winter. Much better than wind and rain.

The northerly does look quite likely. All the computer models agree on our high moving westwards into the atlantic as we go through later next week. The only question is what sort of northerly it is?

In the meantime, a glorious day today, a very nice weekend with an easterly developing in the south especially early next week (for me to look forward to ). Bring it all on, including the potential northerly. Nice variety there I think .

yea but it wont be a cold northernly it wont snow.

[Frosty.]

Probably best to make the most of the weekend sunshine because the ecm 00z and gfs 06z show the high drifting into the atlantic by early next week with a cooler and cloudier NE'ly flow spreading down around the top of the high which is unfortunate and FI looks like becoming more unsettled and rather cool.

Edited April 9, 2010 by Frosty039

[Thundery wintry showers]

The "it's only cloud" syndrome reminds me of many frustrating experiences on the Tyneside coast that I referred to in the North Sea low cloud thread. The typical scenario would feature warm/hot sunshine mixed with thundery showers except on North Sea coasts where a sea breeze kept the storms away, suppressed temperatures by several degrees and pulled in plenty of stratus. I'd then get informed, usually by older relatives, of how fortunate I'd been to escape the storms and only suffer cloud. That should give some perspective on why I see it as a matter of preference!

Regarding possible northerlies it certainly can snow from a northerly at this time of year, the typical scenario is along the lines of what Reef described with maxima slightly short of 10C, temps falling close to freezing in showers, and low dewpoints resulting in showers falling predominantly as hail, sleet and snow with chances of thunder despite temperatures mostly well above freezing. However that setup does rely upon a "clean" northerly flow from near the pole, so significant shortwave development, or the northerly flow being displaced to the west and having to return a long distance over the Atlantic, would result in cool wet cyclonic weather. Or the anticyclonic weather could continue with the northerly being shunted out eastwards.

Regarding the situation on low cloud next week, GFS humidity profiles suggest a fair amount of low cloud coming into eastern Scotland by Monday, and possibly featuring near the coast on Sunday, but eastern England should stay in the clear on both days. There are then strong indications of low cloud becoming much more widespread from Tuesday onwards.

[Optimus Prime]

Frostyjoes our new Messiah n weather forecasting and climatology. Perhaps he could tell us what the weather from May to September will be like? See whether he could do a better job than Harry Redknap in taking Tottenham over.

Edited April 9, 2010 by Optimus Prime

[Archie_Lewis]

Hi If there wasn't snow, then yes I would be quite happy with acg in winter. Much better than wind and rain.

The northerly does look quite likely. All the computer models agree on our high moving westwards into the atlantic as we go through later next week. The only question is what sort of northerly it is?

In the meantime, a glorious day today, a very nice weekend with an easterly developing in the south especially early next week (for me to look forward to ). Bring it all on, including the potential northerly. Nice variety there I think .

Variety? No thanks..... I know everyone has there own take on what weather they want to see and I appreciate that everyone is different.

The last thing I would want to see is a cold northerly break out now... What is the point? It would only bring snow to hills and mountains.

We have had 6 months of cold grey cloudy dark dreary days..... You say you are looking forward to a grey cloudy easterly... Wow... You obviously dont get affected by the SAD effect then....

BRING ON THE WARM SUNNY DAYS.......Thats what Im looking forward to.

The models are showing an increasingly cloudy set up and cloud piling in from Sunday, things could still be bright for my area tomorrow but id expect it to be cloudy Sunday and feeling cooler.

Cant wait till those plumes are showing on the models. Not too long now hopefully

[Thundery wintry showers]

Falling snow is still possible even at low levels from a northerly at this time of year, it's only lasting snow cover that is invariably restricted to hills and mountains. Some enjoy the bright showery type described earlier that you get from a relatively "clean" northerly flow, though if we add mixing, fronts and shortwaves then the result tends to be cloudier with snow restricted to northern hills and that wins fewer supporters. The "what's the point in a northerly if it doesn't snow" is a bit like saying "what's the point in sport X"- we all have things we enjoy which seem pointless to others.

Regarding the upcoming easterly I think it will take until Tuesday for the cloud to start spilling in over eastern England, especially somewhere like Hertfordshire which is quite far inland. There is also a fair amount of uncertainty still- I think cloud would be quite restricted if the UKMO verified, but ECM and more especially GFS point to a cool cloudy week away from the west.

[Derp Patrol]

Variety? No thanks..... I know everyone has there own take on what weather they want to see and I appreciate that everyone is different.

The last thing I would want to see is a cold northerly break out now... What is the point? It would only bring snow to hills and mountains.

We have had 6 months of cold grey cloudy dark dreary days..... You say you are looking forward to a grey cloudy easterly... Wow... You obviously dont get affected by the SAD effect then....

BRING ON THE WARM SUNNY DAYS.......Thats what Im looking forward to.

The models are showing an increasingly cloudy set up and cloud piling in from Sunday, things could still be bright for my area tomorrow but id expect it to be cloudy Sunday and feeling cooler.

Cant wait till those plumes are showing on the models. Not too long now hopefully

I'm also looking forward to the warmth.. today has been great! Models have shown the first real plumes in FI in recent runs, one the other day suggesting temps of 22-24C, but we'll probably have to wait a few weeks for some real warmth.

[Eugene]

Variety? No thanks..... I know everyone has there own take on what weather they want to see and I appreciate that everyone is different.

The last thing I would want to see is a cold northerly break out now... What is the point? It would only bring snow to hills and mountains.

We have had 6 months of cold grey cloudy dark dreary days..... You say you are looking forward to a grey cloudy easterly... Wow... You obviously dont get affected by the SAD effect then....

BRING ON THE WARM SUNNY DAYS.......Thats what Im looking forward to.

The models are showing an increasingly cloudy set up and cloud piling in from Sunday, things could still be bright for my area tomorrow but id expect it to be cloudy Sunday and feeling cooler.

Cant wait till those plumes are showing on the models. Not too long now hopefully

Yes spot on post, today has been the first proper spring day here and people want it gone already, they must be mad a few more weeks of 17C and light winds please not the easterlies of early next week bringing a chilly wind.

[Eugene]

Models have shown the first real plumes in FI in recent runs

Not so sure about that, The last two GFS FI runs and other ones on recent days have shown cold northerlies.

[Rollo]

Yes spot on post, today has been the first proper spring day here and people want it gone already, they must be mad a few more weeks of 17C and light winds please not the easterlies of early next week bringing a chilly wind.

I think you are of the same opinion as I am,snow is great in winter but come mid-March it is time to think (and hope) of a pleasant spring and a nice warm dry summer,we do not often get what we want but I think many on the site do not want next weeks promised cold easterlies and something from the South would suit me fine.

[Cheese Rice]

A tasty looking GFS with the northerly slowly but surely coming into the reliable time frame. I for one would like a northerly, there would be plenty of sunshine on offer for the whole country, I suppose the only downside is the low temps but I'm sure we can allow it for sunshine.

Hopefully convection will be ripe with the stronger sun but it remains to be seen, I would of thought so but we will have to wait and see.

Blast from the past?

[RichardR]

A tasty looking GFS with the northerly slowly but surely coming into the reliable time frame. I for one would like a northerly, there would be plenty of sunshine on offer for the whole country, I suppose the only downside is the low temps but I'm sure we can allow it for sunshine.

Hopefully convection will be ripe with the stronger sun but it remains to be seen, I would of thought so but we will have to wait and see.

Blast from the past?

One thing I would love to see in Model Chat on this forum is an absence of this descriptive bias applied to the charts because of what YOU like. So what that you think the chart is "tasty" looking, we would prefer a professional objective look at charts and the POSSIBILITIES they indicate please. Not everyone loves freezing cold all year round (though that's not the point).

Nothing tasty about numb hands, lashing cold winds and a runny nose, unless you like the taste of your own snot dribbling into your mouth.

Edited April 9, 2010 by RichardR

[Cheese Rice]

Variety? No thanks, I know everyone has there own take on what weather they want to see and I appreciate that everyone is different.

The last thing I would want to see is a cold northerly break out now. What is the point? It would only bring snow to hills and mountains.

We have had 6 months of cold grey cloudy dark dreary days. You say you are looking forward to a grey cloudy easterly? Wow, you obviously dont get affected by the SAD effect then.

Bring on the warm sunny days, thats what Im looking forward to.

The models are showing an increasingly cloudy set up and cloud piling in from Sunday, things could still be bright for my area tomorrow but id expect it to be cloudy by Sunday and feeling cooler.

Cant wait till those plumes are showing on the models, not too long now hopefully

I guess its a matter of opinion, no-one is looking forward to grey skies but at the same time most aren't dreading it either, if you don't like variety get out of the UK as the weather is as varied as you could possibly get.

Also a northerly doesn't just bring snow it brings an abundance of Sunshine across the whole of the UK, I'm quite sure wall to wall sunshine beats Atlantic driven weather of rain after rain.

One thing I would love to see in Model Chat on this forum is an absence of this descriptive bias applied to the charts because of what YOU like. So what that you think the chart is "tasty" looking, we would prefer a professional objective look at charts and the POSSIBILITIES they indicate please. Not everyone loves freezing cold all year round (though that's not the point).

If you bothered to read my post properly you would see I gave my own opinion on the chart and also what would occur ie. "plenty of sunshine", "low temperatures" and "convection".

Also how am I been biased, again if you read my post properly I said "I for one", this is my opinion. If you care to elaborate on how I am been biased I will happily listen but until then don't post until you read what I actually said.

Edited April 9, 2010 by 10123