Model Discussion - 27th July

[Paul]

A new thread for the model discussion.

As ever, for the sake of all users who want to read/discuss the models please keep this topic to that subject only - there's a whole host of other weather discussion ongoing in other parts of the forum, particularly the general discussion area for anything which isn't model related:

http://forum.netweat...ssion-and-chat/

Thanks

Paul

[shedhead]

12GFS throws a real spanner in the works by bringing the LP to the NW into play as early as Sunday in the west, then making it the dominant feature through the first half of next week, with a SW flow predominating. It might be easy to dismiss this new evolution as a wobble if it were not for the fact UKMO have been plugging it for 2 to 3 days now, so I don't think it can be ignored, especially as their 12 run sticks with the plan. Those looking for a very warm/hot thundery breakdown will do doubt the rather disappointed with this evenings offerings so far, but perhaps ECM will show something different again.... I wouldn't bet against it to be honest.!

Edited July 27, 2011 by shedhead

[Summer Sun]

A relatively warm to very warm weekend coming up before low pressure moves close to Scotland,

http://www.wetterzen...s/Rtavn1501.png

http://www.wetterzen...s/Rtavn1741.png

http://www.wetterzen...s/Rtavn2401.png (Just in time for the start of the football league season)

So after a settled period GFS takes us back to normal with low pressure winning out in the end, wonder what ECM comes us with.

The pressure decline doesn't seem to be an outliner either,

Edited July 27, 2011 by Gavin D

[mushymanrob]

..... and its gone! ok, its one run but relying on a 'heatwave around the corner' progged for 6 days time in such a messy synoptical pattern was reckless. is the 12z going to be proven correct or will the mini heatwave return? ok, southern areas look to be ok, but the thundery breakdown progged by other runs is gone.

tbh if it doesnt happen this time, it wont, and the chances realistically of a nice hot spell this summer are looking very bleak.

on the plus side, it wont be too wet either and will probably continue to offer us a nice enough pleasant summer.

[95 Degrees]

GFS has been up and down with it's predictions, changing from possible heatwave before the Azores High was downgraded gradully, it looks better today but the warmth isn't nailed on yet and ECM/MO aren't convinced about HP becoming important. better tonight though.

[anvilhead]

not quite sure what to make of the 12z gfs! Seems to be some strange synoptics going on with that cut off lowthat moves down near iberai, and then back up to rejoin the jetstream - I would think the ensembles when they come out will have quite a bit of scatter - ecm seems to be a wildly different evolution too in the mdeium term from what I've seen -

Cheers, Sam

[Gibby]

GFS shows high pressure close by for the next two or three days as it trundles in from off the Atlantic. A weak front also crosses east ahead of it with a band of cloud and light rain crossing the North tomorrow and a few showers across the SE on Friday. Otherwise there would be dry and bright weather with some warm sunshine but also large areas of cloud floating about too. Through next week we see weak low pressure cross NE north of Scotland with some fronts crossing east over the UK. These would likely be fairly weak with most of the rain falling in the North and West with little if any for the SE in the continuing warm conditions. Further on through the latter stages of the run the status quo persists with Low pressure closer to the North and East with the south continuing fairly dry while the North continues to see rain at times. Pressure then rises from the west with the run ending with high pressure sat over the UK with fine settled conditions for all.

UKMO also shows a weak frontal band crossing east in the next 48hrs with a lot of cloud and patchy rain in the north and west tomorrow crossing overnight tomorrow and the SE on Friday. Weak high pressure then covers the UK on Saturday giving a fine, warm day for all followed by steadily falling pressure late in the weekend and through the early days of next week. Winds stay light and variable with increasing instability allowing showers to develop by Monday/Tuesday. Things would stay on the warm side generally in the sunnier interludes.

ECM shows the same pattern up to the weekend with warm interludes and some sunshine mixed in with cloudier spells as the remains of a weak trough moving east tomorrow and Friday perhaps giving the odd spot of rain here and there. From the latter part of the weekend on pressure falls with Low pressure moving into Western Britain by Monday. With the parent depression centred to the NW on Tuesday and a slack Low pressure area over the UK heavy showers or longer spells of rain will develop widely from Monday as temperatures fall somewhat. This trend continues in the remainder of the run with scattered slow moving thundery showers almost anywhere with some bright, warm, sunny spells inbetween.

The Euros's tonight agree on reasonable weather to see us through the remainder of this week and through the weekend before pressure falls over and around the UK allowing the development of heavy slow moving showers nationwide from then on. GFS on the other hand swings the axis of Low pressure north of Britain keeping its rain and showers more on course for the north while the south sees more dry but not overly warm weather.

[snowlover2009]

the charts look fairly messy around midweek next week, so I doubt we will be experiencing any heat waves any time soon. With low pressure being shown to pep up here and there and blocking playing a big feature over Greenland and much of the north, I think it is only matter of time before we revert back to our July pattern.

It looks likely we see some relatively nice few days of warm, July weather, the odd 'meh' days like we had here today, before lower pressure moves in. If you are looking for warmth and dry weather, the ecm would be pretty terrible for future weeks IMO, with all that strong blocking and messy atlantic lows etc.

[valledym]

OMG are we really back to doom and gloom. It seems like only yesterday we were all convinced the summer was about to re-introduce itself to these shores. It has, and probably will continue to be a summer of blandness. Nothing hideous (2007) or nothing scorching 2003/6) just very bland. Typified by the fact our air conditioner has been on only twice all summer. Even the last few years has seen it on a LOT more than that. Frustrating? Yes. Doom & gloom? Most certainly not. Just got to enjoy what we can, when we can.

[anvilhead]

VERY nice 18z for trough disruption and thundery weather next week! Sure its one run, but it's one run 6 hours on from the last.. No doom and gloom here, just eternal hope!

[William of Walworth]

What price on something of a halfway house between what the GFS suggests and what the Euros are suggesting?

Not had time to fuly update mysef yet but don't rule it out, I say! Low Prssure looks pretty certain to continue to play a significant role, but as valledym suggests, perhaps with less overall dominance everywhere than the more LP dominated operationals might at present suggest.

North/South split perhaps? Of several possible outcomes, that one is far from impossible -- as ever, we await further output.

Edited July 28, 2011 by William of Walworth

[mushymanrob]

well this morning its looking like a pretty warm, muggy, humid, showery, overcast (bright/milky skies) are set for most of next week as a complex area of low pressure sets up residence near/over us. thankfully the current suggestion is that itll be just to our southwest which will draw warmer air off the continent. the 10c isotherm 'upper' in residence for alot of the southern/eastern/central areas for several days (gfs 00z).

so no sunny heatwave, but a warm feeling, outdoor drinking in the evening, humid, warm, theme looks likely from sunday onwards.

fi is pretty horrendous, but tbh is possibly not worth worrying about!

[Radiating Dendrite]

The middle of next week is looking warm with hazy sunshine. Looking at the predicted temps we should be looking at around 28c for some spots by next Wednesday depending on cloud cover.

[Gibby]

Good morning.

A look at this morning's output shows GFS bringing high pressure in over the UK following a weak trough, centred over Britain by Saturday. Apart from a band of cloud sinking slowly south over the UK with a little light rain or a shower the weather would stay dry and warm with some sunshine at times. From later in the weekend on High pressure weakens somewhat as a Low south of Iceland becomes the driving force to the weather. However, there will still be enough high pressure around to the south and east to prevent too much rain here for several more days before Low pressure becomes more dominant for all towards the end of next week with some rain or showers for all by then. Into the latter stages of the run and Low pressure becomes complex and slow moving over the UK bringing some spells of rain and heavy showers for all each day with temperatures falling back somewhat too.

UKMO also shows Low pressure dominating to the NW in the longer term. However, for today and on through to the end of the weekend dry weather would predominate with some cloudier spells and the odd light shower possible today and tomorrow with a fine and warm Saturday for all with sunny spells. By Sunday the aforementioned Low will be close enough to the NW to bring some rain and it looks possible for this to extend to other areas through the early and middle part of next week.

ECM follows the same route for the next three or four days. Thereafter it shows rather less influence from the Low pressure to the NW with many places staying dry with reasonable temperatures much as we've seen recently. However, with some weak Low pressure areas floating about there could be scattered showers on some days with the extent and areas that these affect changing from day to day but certainly not a washout from ECM this morning. ECM also notably shows High pressure nudging back in from the SW by day 9 and 10 settling things down again.

All models seem to have firmed up now on a depression of sorts settling South of Iceland early next week. What effect it has on the UK weather is yet to be decided with fairly flat pressure patterns continuing one could expect some showers though there distribution seems to look far from widespread at this stage. GFS takes things on a decidedly unsettled run through the latter stages of its output with plentiful rain or showers and cooling conditions there while ECM paints an altogether less pessimistic look on things with pressure remaining no lower than 1015mbs for many throughout and no distinct Low or High pressure near the UK modelled.

[casparjack]

Good morning.

A look at this morning's output shows GFS bringing high pressure in over the UK following a weak trough, centred over Britain by Saturday. Apart from a band of cloud sinking slowly south over the UK with a little light rain or a shower the weather would stay dry and warm with some sunshine at times. From later in the weekend on High pressure weakens somewhat as a Low south of Iceland becomes the driving force to the weather. However, there will still be enough high pressure around to the south and east to prevent too much rain here for several more days before Low pressure becomes more dominant for all towards the end of next week with some rain or showers for all by then. Into the latter stages of the run and Low pressure becomes complex and slow moving over the UK bringing some spells of rain and heavy showers for all each day with temperatures falling back somewhat too.

UKMO also shows Low pressure dominating to the NW in the longer term. However, for today and on through to the end of the weekend dry weather would predominate with some cloudier spells and the odd light shower possible today and tomorrow with a fine and warm Saturday for all with sunny spells. By Sunday the aforementioned Low will be close enough to the NW to bring some rain and it looks possible for this to extend to other areas through the early and middle part of next week.

ECM follows the same route for the next three or four days. Thereafter it shows rather less influence from the Low pressure to the NW with many places staying dry with reasonable temperatures much as we've seen recently. However, with some weak Low pressure areas floating about there could be scattered showers on some days with the extent and areas that these affect changing from day to day but certainly not a washout from ECM this morning. ECM also notably shows High pressure nudging back in from the SW by day 9 and 10 settling things down again.

All models seem to have firmed up now on a depression of sorts settling South of Iceland early next week. What effect it has on the UK weather is yet to be decided with fairly flat pressure patterns continuing one could expect some showers though there distribution seems to look far from widespread at this stage. GFS takes things on a decidedly unsettled run through the latter stages of its output with plentiful rain or showers and cooling conditions there while ECM paints an altogether less pessimistic look on things with pressure remaining no lower than 1015mbs for many throughout and no distinct Low or High pressure near the UK modelled.

To avoid the extreme mood swings that some posters endure on a daily basis, I have tried for the past month or so to just view the ECM (and FAX charts), two runs per day is more stable in my view than four.

What I've noticed this morning and Gibby has referred to it in his post here, is that the ECM has reverted to the more high pressure influenced, rather than dominated, regime next week that it was indicating 72 hours ago; it introduced the low right over the top of the UK on Tuesday I think, then started to inch away from the idea and now reverts this morning to something akin to its original suggestion.

We'll see over the weekend if it continues to evolve, but I feel it might be pretty close to correct...

[shedhead]

The 06GFS continues on the same theme out to 144hrs, only fidlding with the position of the LP to our NW. However, given the extent of the blocking to our north/northeast on the chart below, it's hard to envisage anything other than

a fall of pressure across the UK thereafter, with more unsettled weather predominating.

[Thundery wintry showers]

It does look as if the models have shifted towards a greater cyclonic influence for next week, but I still see no sign of a resurgent Atlantic (except well out in FI on the latest GFS run) and with lowest pressure centred to the west and generally southerly winds, temperatures should generally rise a little above average in most regions. The GFS is suggesting highs in the low 20s in most parts of the country, and UKMO looks similar, perhaps we might get temperatures a bit higher than that if ECM verifies.

It looks like a setup conducive mainly to heavy convective rainfall (probably thundery in places) with sunshine in between, though we can't rule out the possibility of weak fronts occasionally bringing longer outbreaks of rain. The relative proximity of low pressure will determine how widespread the shower activity is, and as Gibby mentioned the ECM has the low pressure rather less prominent than UKMO/GFS, perhaps suggesting more sunshine, more well-scattered thundery showers, and higher maximum temperatures.

I have reservations about calling it a "poor" outlook, because while the majority in MOD are after sustained high pressure, there are plenty of members of the forum who would welcome a convective outlook with potential for a fair amount of warm sunshine in between.

[TonyH]

Yes, could be something for everyone next week, some heavy, and perhaps in places, thundery showers at times, but also interspersed with warm, dry weather with sunny spells. As usual in such set ups, some areas should escape with mostly dry conditions and perceive the week as Summery.

Edited July 28, 2011 by Tonyh

[shedhead]

Very true, but unfortunately some places, particularly I feel across N Ireland, W England and Wales will get under some spells of very wet weather and where this occurs it'll feel far from summery. As I said yesterday, we are a relatively small island and therefore the weather is rarely the same in all areas, let's just hope those sat in warm sunshine don't again feel the need to come on here and goad those sat under cool, wet weather.

[TonyH]

Can't see it being a very wet week, only very locally where significant downpours occur. Pressure is high enough to prevent true washout days for most of us, and even if a washout day does occur (unlikely), the next day in any given location could well be drier and brighter.

This example from GFS for next Wednesday does not suggest very wet weather, rather scattered showers with plentiful dry weather around:

Neither does this ECM chart for next Tuesday:

Edited July 28, 2011 by Tonyh

[johnholmes]

To avoid the extreme mood swings that some posters endure on a daily basis, I have tried for the past month or so to just view the ECM (and FAX charts), two runs per day is more stable in my view than four.

excellent to read that, perhaps even cutting that down to 1x ECMWF run per day and comparing to 1x GFS for the same time beyond T+120 Met Fax charts?

Some disagree but I firmly believe picking 1xrun daily, comparing them with other models each day for the same time will give you a higher correct forecast score and a lot less aggro.

I'll update later today with my ideas from a week of 500mb anomaly chart viewing-what they seem to be predicting and how accurate they have or have not been recently.

[Summer Sun]

ECM doesn't look too bad comapared to GFS at present,

Yes they'll be rain and cloud at times but also some warm to locally hot conditions at times in the south where some locally heavy showers could develop, some of these perhaps thundery.

The met offices 16 to 30 day update isn't bad at all certainly for those in the south.

Edited July 28, 2011 by Gavin D

[mushymanrob]

excellent to read that, perhaps even cutting that down to 1x ECMWF run per day and comparing to 1x GFS for the same time beyond T+120 Met Fax charts?

Some disagree but I firmly believe picking 1xrun daily, comparing them with other models each day for the same time will give you a higher correct forecast score and a lot less aggro.

I'll update later today with my ideas from a week of 500mb anomaly chart viewing-what they seem to be predicting and how accurate they have or have not been recently.

.... thats fine as long as the chart run you chose doesnt happen to be an outlier! :lol:

im not so sure though, its ok if youre not bothered about what the weather may do, but if you are hoping for something be it sun, heat, frost or snow, its only natural to view as much data as you can to pick up any sign...

[NUT]

ECM doesn't look too bad comapared to GFS at present,

Yes they'll be rain and cloud at times but also some warm to locally hot conditions at times in the south where some locally heavy showers could develop, some of these perhaps thundery.

The met offices 16 to 30 day update isn't bad at all certainly for those in the south.

That doesn't even look too shabby up here either. Maybe next week might not be so bad after all................

[casparjack]

excellent to read that, perhaps even cutting that down to 1x ECMWF run per day and comparing to 1x GFS for the same time beyond T+120 Met Fax charts?

Some disagree but I firmly believe picking 1xrun daily, comparing them with other models each day for the same time will give you a higher correct forecast score and a lot less aggro.

I'll update later today with my ideas from a week of 500mb anomaly chart viewing-what they seem to be predicting and how accurate they have or have not been recently.

I tried just one, but that brought on the shakes!!

Seriously though, I cut out the GFS as it introduces too much variation with four runs every day. I plan to start looking at the 12z from ECM and GFS together in August, just to see how it compares - I'll let you know...