Model Output Discussion - 15th April Onwards

[shedhead]

Certainly a cool/very cool outlook as we head towards May, with lashing of rain to come at times this week across the south, real drought busting stuff by the look of things. Longer term GFS suggests something more settled, but far too early to have much confidence in that evolution, so for now the unsettled pattern goes on.

[lorenzo]

Pretty astonishing that the NWerly incursion of cold shots that was one of the themes of winter still showing itself in the Model Runs for May.

The remnants of another fixed pattern so slow to shift from the charts.. Key question being - Is it better to get this muck now and will it benefit our summer?

[J10]

Some heavy snow over the higher slopes of the Alps today as the season closes down, this time last year, many of these fields were green, after such a mild April.

[Thundery wintry showers]

I've always disliked the simplistic categorisation of the UK's weather into "settled" and "unsettled", which seems to be taking over the model output thread again as we approach summer. The images of clear blue skies, warm sunshine and evenings sat out with the BBQ are only one facet of settled weather- if the high pressure isn't close enough and/or is in the wrong place, it can end up mostly dry and cloudy with a chilly breeze. The GFS 06Z FI strongly points to the latter scenario to me- quieter, but possibly cloudier, relative to what we've been having recently, and not necessarily significantly warmer either.

The ECMWF ensemble mean this morning hinted at a similar evolution to the GFS 06Z with high pressure ridging towards us from the Azores but nothing really convincing. However the operational run went for something more changeable with a couple of attempts at northerly outbreaks. It's worth noting though that this sort of setup is far from unusual at this time of year- recent Mays (apart from 2005 and 2010) have been quite unusual for their lack of northerly winds and mid-Atlantic highs.

My summary of the longer-term outputs is that we're likely to keep winds from a mostly north-westerly quarter as we head into May, so probably remaining on the cool side, but sunshine and rainfall amounts are open to question- both probably not far from the long-term average though.

[Summer Sun]

May looks like starting more settled than it is now, with less deep low pressure systems heading our way

http://www.null/ds/gfs.htm

[ribster]

May looks like starting more settled than it is now, with less deep low pressure systems heading our way

http://www.jp2webdes...o.uk/ds/gfs.htm

Do you mean looks as in is likely, or that's what a model suggests, as I think there is a very important distinction between the two. As it is, I can only see a slight hint of that on the GFS towards the end of the run. In fact ECM has another low winding itself up towards the end of it's run. In the meantime, lots more wet weather to come this week.

[damianslaw]

Next few days will see more of an emphasis on longer spells of heavy rain as opposed to showers, so some very useful rain indeed especially for SE parts, which unusually will bear the brunt of the weather systems.

East Anglia looks like having potentially 4 days of constant rain as one low pressure system is replaced by another on Wednesday.

Models continue to suggest more rain and cooler than average temperatures as we end the month with the trough locked in situ.

[Milhouse]

I know its FI but that ridge on the ECM at 240h looks likely to give a welcome return so something drier and warmer if it was to verify. From what i can see, the low to the east moves away quick enough to allow a temporary ridge to come our way. I cant see the low to the NW coming into play for another couple of days following the previous low departing.

[bluearmy]

tonights ecm op looks to be 'off on one' re the pattern in the arctic. starting to wonder if the trough is going to reload from the nw once the initial one sinks far enough sw for us to escape its influence. next weekend could see a very active front lying between the cool trough and the plume to our east. gem 12z has this across the south of the uk.

[AWD]

I maybe wrong here but the abcense of deep lows doesn't necessarily mean less rain! Indeed, a slack flow/shallow low can provide just as much rain as a deeper LP. Deep LP systems are often accompanied with stronger winds, thus pushing rain bands through more quickly!

From what I can see from an admittedly quick glance at the models is a very wet week to come this week, followed by a slightly less wetter week next week, something similar to this week just gone in fact. It's not until the last few frames of the GFS that I would start using the word settled. The turn of the month looks just as unsettled as the week just gone IMO.

All the time, temps rarely getting above average.

[Scorcher]

Looks like there could be some very high temperatures in Central/Eastern Europe next week, with parts of Poland and Germany getting into the high 20s. GFS is even suggesting 30C could be exceeded in western Poland- exceptionally warm for late April. What a shame we're going to miss out on the plume!

[Glacier Point]

tonights ecm op looks to be 'off on one' re the pattern in the arctic. starting to wonder if the trough is going to reload from the nw once the initial one sinks far enough sw for us to escape its influence. next weekend could see a very active front lying between the cool trough and the plume to our east. gem 12z has this across the south of the uk.

.. a distinct possibility Nick.

We are reconcilling a global wind oscillation (atmospheric base state) which is transitioning but still reflective of a La Nina phase (signal for mid Atlantic ridge / Euro trough) and developing mean easterly zonal wind across the Arctic and tropical signal which is very keen to recirculate an MJO phase 7-8 (interestingly this spring looks like giving us the most number of days in MJO phase 6-7-8 quadrant since records began in 1974 (for interest other years were 1993, 1994, 2004, 2009)).

From this I think we can conclude a general trend for mean trough, punctuated by phases of higher pressure from the north and west, and general patterns becoming slow moving and evolutionary. Not much to signal spring warmth until perhaps mid May at the earliest if and when we get the MJO triggering another nudge towards a weak summer El Nino.

Edited April 22, 2012 by Glacier Point

[SP1986]

tonights ecm op looks to be 'off on one' re the pattern in the arctic. starting to wonder if the trough is going to reload from the nw once the initial one sinks far enough sw for us to escape its influence. next weekend could see a very active front lying between the cool trough and the plume to our east. gem 12z has this across the south of the uk.

I suspect this has a rather high chance of occurring.. judging by the movement of depressions from the northwest, it does look like one of those slider 're-load' patterns you get, ensuring the jet is kept south. It will eventually migrate back north or introduce easterlies; I've never come across a situation when it hasn't, but it might take a while. My guess is that this pattern will hang around for a long long time, but eventually it has no choice but to let warm air in. Whether that's in May, June, July or August though is still up for debate.

As for the European temperatures; I suspect if the GFS has trouble modelling UK temperatures, it might also have trouble with European temperatures; although no denying it's going to be exceptionally warm over in central-eastern Europe - a total opposite to ours.

Worth noting even at the end of the 18z the low slides down to pin the jetstream southwards of the UK, so the signals are suggesting this pattern is rooted for the long term, so I guess cool, below-well below average temperatures and heavy rain is something we'll all have to get very used to!

For gardeners this is catastrophic, as if this pattern continues, certainly as a gardener, I will not plant bedding, as it simply won't grow well in the temperatures predicted; and I'm pretty sure if the synoptics continue, I will have to shelf any bedding displays for this year - and so will councils perhaps. For weather fans of the cold loving variety - It's definitely your turn to enjoy the weather!

[Cheshire Freeze]

For weather fans of the cold loving variety - It's definitely your turn to enjoy the weather!

I am definitely one of those people....sorry to say it

[johnholmes]

.. a distinct possibility Nick.

We are reconcilling a global wind oscillation (atmospheric base state) which is transitioning but still reflective of a La Nina phase (signal for mid Atlantic ridge / Euro trough) and developing mean easterly zonal wind across the Arctic and tropical signal which is very keen to recirculate an MJO phase 7-8 (interestingly this spring looks like giving us the most number of days in MJO phase 6-7-8 quadrant since records began in 1974 (for interest other years were 1993, 1994, 2004, 2009)).

From this I think we can conclude a general trend for mean trough, punctuated by phases of higher pressure from the north and west, and general patterns becoming slow moving and evolutionary. Not much to signal spring warmth until perhaps mid May at the earliest if and when we get the MJO triggering another nudge towards a weak summer El Nino.

I have to agree with that overall assessment Stewart-there does seem little to break the present overall upper wave length going into May, and possibly well into May. Just an occasional 'blip' you might call it as a high gives some semblance of warmth between generally unsettled spells of cool weather.

[Bottesford]

For gardeners this is catastrophic, as if this pattern continues, certainly as a gardener, I will not plant bedding, as it simply won't grow well in the temperatures predicted; and I'm pretty sure if the synoptics continue, I will have to shelf any bedding displays for this year - and so will councils perhaps. For weather fans of the cold loving variety - It's definitely your turn to enjoy the weather!

Yes it really isn't good for gardeners. As my first year doing gardening 'properly' (well almost) it is most depressing to see how growth has slowed to a crawl and everything is getting water logged. Also found my entire crop of rocket seedlings have been eaten by slugs this morning. Flaming things - need some hot sun to get rid of them!

Although we can't see any improvement now in the models remember it was only 4 or so weeks ago we were locked into an unending drought with no sign of much change. I don't subscribe to the springs over camp and certainly not the summers over one!

[Scorcher]

For gardeners this is catastrophic, as if this pattern continues, certainly as a gardener, I will not plant bedding, as it simply won't grow well in the temperatures predicted; and I'm pretty sure if the synoptics continue, I will have to shelf any bedding displays for this year - and so will councils perhaps. For weather fans of the cold loving variety - It's definitely your turn to enjoy the weather!

Can anyone remember what happened with this in 1996? The plants and trees must have struggled growth-wise with that very cold May.

I think those of us who are not of the cold loving variety are going to have to remain as there is little hope of anything settled and warm in the next couple of weeks.

[Thundery wintry showers]

A rather wet and changeable week is in store- mainly sunshine and showers in the north, but some more persistent rain at times in the south, including today and more especially Wednesday. Wednesday in particular looks like it could be a washout for most of us, and then it is unclear exactly where the rain belt will track. Today's GFS and ECMWF runs suggest a track up into eastern Scotland and NE England with sunshine and showers re-establishing elsewhere, covering the whole country by Friday.

Thunderstorm potential looks generally lower than it has been recently, except across Ireland where today and tomorrow look set to produce some heavy and, in places, thundery showers.

Indeed, the models don't hold out much hope for those after settled warm weather. There are some who are more after warm thundery (rather than settled) weather, particularly prominent at the Convective Discussion threads, and the model outputs don't hold out much hope from that perspective either, despite the emergence of such conditions on the near-continent towards the end of this coming week. The clash between our chilly polar maritime air and the increasingly warm, thundery airmass over the continent may well give at least some of us a wet weekend., but the trough stubbornly remains too far east to allow the continental air to make it across to our shores. Definitely one for fans of cool wet weather it would seem!

[shedhead]

Gotta laff at the massive variance in the predicted maxima this weekend on the 00GFS (otherwise you might cry!), 26-28c for parts of Germany and Poland, 6-8c for parts of England and Wales. Clearly the result of being on the wrong side of the cold trough and it looks to me as if we might well stay there for some time to come, so unlike Botts I am at least writing Spring off regarding fine, warm and sunny weather.

[Alex]

I have to agree with that overall assessment Stewart-there does seem little to break the present overall upper wave length going into May, and possibly well into May. Just an occasional 'blip' you might call it as a high gives some semblance of warmth between generally unsettled spells of cool weather.

Weak el ninos during summer are best aren't they? Summer 76 definitely started neutral turning towards el niño!

Edited April 23, 2012 by Alex

[Terminal Moraine]

Can anyone remember what happened with this in 1996? The plants and trees must have struggled growth-wise with that very cold May.

I think those of us who are not of the cold loving variety are going to have to remain as there is little hope of anything settled and warm in the next couple of weeks.

I was working as a gardener for a local authority in 1996. The bedding went out at the usual time and just sat there until the weather warmed up, it then grew as normal.

Assuming it's been hardened off outdoors the majority of bedding will take no harm in a May like 1996, provided there is no air frost. More detrimental is a prolonged period of wet, cool and cloudy weather in mid summer which inhibits flowering and promotes attack by mildew on flowers and leaves due to their sitting in constantly damp conditions; plants with dense hairs and closely spaced flowers, such as Geraniums, are particularly susceptible, as are plants with flowers which do not dry out quickly, such as French and African Marigolds.

Edit; Mod's fee free to move or delete this, I hadn't even realised we were in the model discusssion when I replied

Edited April 23, 2012 by Terminal Moraine

[Alex]

The latest GFS run 06z is showing some warmer weather for a couple of days next week for southeastern areas possibly 20c if it came off.

[Robbie Garrett]

Actually having a really good feeling of the positioning of the trough, I suspect the high will sink into Europe allowing a warmer continental feed into the UK. The idea of a mid Atlantic bazores high sounds to much for me. Personally the trough will likely setup over the mid atlantic, allowing a southwesterly/southerly theme for Mid-may onwards. So not particularly settled but pretty warm.

However... there's Scenario 2...and that's the trough setting up shop pretty much where it is now.

[Scorcher]

The latest GFS run 06z is showing some warmer weather for a couple of days next week for southeastern areas possibly 20c if it came off.

Yes it's much better in terms of warmth. Not settled of course but it looks like it could be a bit warmer by this time next week.

Also GFS now showing mid teens quite widely for the weekend- perhaps 17 or 18C somewhere? Nothing amazing but I'd certainly take that given the recent conditions.

Edited April 23, 2012 by Scorcher

[Iceni]

Yes it really isn't good for gardeners. As my first year doing gardening 'properly' (well almost) it is most depressing to see how growth has slowed to a crawl and everything is getting water logged. Also found my entire crop of rocket seedlings have been eaten by slugs this morning. Flaming things - need some hot sun to get rid of them!

Although we can't see any improvement now in the models remember it was only 4 or so weeks ago we were locked into an unending drought with no sign of much change. I don't subscribe to the springs over camp and certainly not the summers over one!

Slugs are responding to the moisture — OT but always rear seedlings in the greenhouse and then plant out after the last frost for your area. And never sow seeds earlier than it says on the packet as light levels will be poor, later sowings always catch up in the end. Personally, I can't believe my luck — no watering necessary unlike last year.

I think we can settle in for another reassuringly normal British summer. Possibly a heatwave (or two) but nothing to write home about.

PS Netweather's got not one but two name checks in the Daily Telegraph… http://www.telegraph...generation.html Fame at last eh Paul?

Edited April 23, 2012 by Iceni