phil nw.

Model Output Discussions 12z 01/06/2017

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GFS is showing a couple of very warm days in the E/SE Friday/Saturday....temps up to 25-27c perhaps. Pretty localised and cool elsewhere, especially in the NW closer to the low. Your classic NW/SE split in evidence once again.

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Keeping an eye on the projected strong ridge set to develop over eastern europe, which might cause a more amplified flow to set up shop over the continent, which would suggest slow moving trough/cyclonic/frontal activity over the Uk perhaps becoming squeezed out in time and lifted or split apart in time as we come under the influence of heights to the east, another plume development perhaps as we enter August. Another scenario might though simply be low pressure just filling over the UK topped up by another one in succession - we saw such conditions in winter 13/14 dare I say it.. when low after low settled over the country and couldn't move away, no ridges were then able to develop, lets hope this latter scenario doesn't settle in - a very wet August would be on the cards. Also unlike early summer, the weather does tend to get stuck in a rut during latter part of summer, with less variation.

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10 hours ago, Scorcher said:

Honestly, is there any need for such an over the top emotive post? How on earth did you come up with mid September? It's almost 2 whole months away! 

Its not over the top at all, I'm just saying what I think based on this becoming locked pattern. Another very dull summer month likely on the way by the looks of it. GFS with non stop low pressure, low temperatures, showers or longer spells of rain and wind. The jet stream is too far south and is struggling with the door wide open for as many low pressure systems as it wants to come along and dump the atlantic on us.

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54 minutes ago, 40*C said:

Its not over the top at all, I'm just saying what I think based on this becoming locked pattern. Another very dull summer month likely on the way by the looks of it. GFS with non stop low pressure, low temperatures, showers or longer spells of rain and wind. The jet stream is too far south and is struggling with the door wide open for as many low pressure systems as it wants to come along and dump the atlantic on us.

i agree with this, because usually once established, a pattern as described is hard to shift . its perfectly feasible that a trough dominated unsettled regime could last some time - i hope it doesnt, but the reality is the odds would favour a longer pattern rather then shorter.

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1 hour ago, 40*C said:

Its not over the top at all, I'm just saying what I think based on this becoming locked pattern. Another very dull summer month likely on the way by the looks of it. GFS with non stop low pressure, low temperatures, showers or longer spells of rain and wind. The jet stream is too far south and is struggling with the door wide open for as many low pressure systems as it wants to come along and dump the atlantic on us.

You could be spot on, the short, medium and longer term signal is for changeable atlantic driven weather, gradually becoming a nw/se split with the best of any short-lived fine and warmer spells for the south & south-east but all of the uk having cool, breezy wet conditions at times, especially the north / north-west.

Edited by Frosty.
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Unfortunately as we enter the main holiday period there is no sign yet of anything other than brief settled interludes between the Atlantic systems.

The UK fax for Tuesday shows one of those as a weak ridge moves across after the current slow moving low finally exits east.

 fax84s.gif?2

We can see though how we lack any influence from the Azores high as modeling continues to show those eastern Atlantic  -ve 500 hPa height anomalies.

A look at the ECM 500hPa mean anomaly charts underlines this,these are days 5 and 10

EDH101-120.GIF?22-12EDH101-240.GIF?22-12

So it's a case of the odd fine day or 2 interspersed with more unsettled spells of rain and showers as the Atlantic jet continues to run across our latitude.Temperatures in this setup will naturally be somewhat disappointing.

 

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The idea that the models can't be trusted is often overdone imo, but this really is one of the rare times where I'd say enjoy the sun and warmth on Monday and Tuesday, and then who knows where we go from there. The difference between the GFS, UKMO and GEM are so stark tonight not just for the middle of the week, but for the whole subsequent evolution. The GEM is even pushing the Atlantic trough backwards by Thursday, suggesting that a ridge may emerge over the UK to split the west and east troughs. In contrast the UKMO conjures up a low for Wednesday that I haven't seen modelled thus far. I think it's what you get in summer when there's a lot of slack pressure around, little forcing and small disturbances milling around aimlessly. I think @damianslaw 's post above has a couple of ideas that have a chance, but I think there are even more than he mentions. FI is T96 for me right now, and long term trends hard to see.

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30 minutes ago, Man With Beard said:

The idea that the models can't be trusted is often overdone imo, but this really is one of the rare times where I'd say enjoy the sun and warmth on Monday and Tuesday, and then who knows where we go from there. The difference between the GFS, UKMO and GEM are so stark tonight not just for the middle of the week, but for the whole subsequent evolution. The GEM is even pushing the Atlantic trough backwards by Thursday, suggesting that a ridge may emerge over the UK to split the west and east troughs. In contrast the UKMO conjures up a low for Wednesday that I haven't seen modelled thus far. I think it's what you get in summer when there's a lot of slack pressure around, little forcing and small disturbances milling around aimlessly. I think @damianslaw 's post above has a couple of ideas that have a chance, but I think there are even more than he mentions. FI is T96 for me right now, and long term trends hard to see.

I agree. I was really taken a back with the 12z runs thus far as like you say, there is much divergence even at 4 days out which is quite unusual. Even today has gone against the forecasts. We were meant to have quite frequent heavy showers up here but we haven't had one and it has turned out to be a half decent day. Something tells me there may be a few surprises this coming week. 

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GLAAM has stepped up a bit and looks to stay there, and good support for eastward MJO propagation from the Indian Ocean has emerged over the past few days.

This should help mitigate the influence of the strong C Pac trades but by just how much is clearly very uncertain given recent model flailing.

There is a discernable net trend toward more ridge influence from Europe which is encouraging, as is the fact that more complications to the Atlantic jet are more likely to help rather than hinder us next week (typically more complications emerge nearer the time), but these trends and tendencies are still fairly slight or tenuous so for now I'm remaining cautious with respect to getting my hopes up for later next week. A good shift toward more settled from ECM, which has the strongest C Pac trades and has - likely as a result - been most reluctant to settle things down, would be the best sign so far and start to raise the possibility toward a notable level. Fingers crossed!

Edited by Singularity
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gefsens850London0.png?cb=481

12z GEFS ensembles look more encouraging with a fair few hotter runs breaking out from the pack when compared with the last couple of days. Much to be resolved and altered of course, but there's a real chance something hot could sneak up on us again :)

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Hmmm ... ECM sticking to its general plan of getting the low in its favourite position between Iceland and Scotland, and then sticking it there. GFS is similar so that would have to be the preferred solution for now. Which means, for next weekend, incrementally better weather the further south and east one goes. - as usual. Could turn out rather good in the SE. With a bit of luck, some decent spells further north too but unlikely to avoid some sort of frontal activity.

But, as mentioned earlier, still options for more settled throughout and less settled for all. We, the UK, ride the dividing line between summer and non-summer

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216_mslp850.png?cb=631 240_mslp850.png?cb=631

ECM's eventually like, 'alright fair enough, I'll edge that plume close enough to tease/torment UK residents (delete as appropriate) :rolleyes::laugh:. It is amazing how readily and far Europe keeps on heating back up at every opportunity this summer.

I must express my disapproval of it's decision to produce the flattest jet stream configuration on days 4-5 with the least ridging across the UK. Probably those anomalous easterly trades at work given how this model usually tends toward the other side of the coin. 

ALL_emean_phase_full.gif

It has the least enthusiastic eastward MJO propagation so there's little working to try and weaken the trades. That the 12z gets anywhere at all (days 8-10) having been so resolutely flat in the earlier stages does I suppose offer a little further encouragement.

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hmmm, makes you wonder, 240 ECM but could end up a 'heat spike' after all it is Mardi

ECM1-240.GIF?22-0

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Not going to bother with too much analysis so just a quick take on the ecm for next weekend.

At 12z saturday it it has quite an elongated positively tilted trough just the west of Ireland, running away to the south west, centred between Scotland and Iceland.

The front(s) Scotland Scotland associated with the surface feature are orientated Scotland/Ireland/and points south west with rain into the north Midlands upwards.

The front(s) and rain swing quickly NE into the North Sea leaving the north in a showery, blustery, westerly by 06z Sunday but a wave has formed on the front to the south west which nips north east and brings rain to the south on Sunday just to even things up.

ecm_z500_anom_natl_8.thumb.png.574be5fbd952eff677dee495256157b3.pngecm_mslp_uv850_natl_8.thumb.png.10336aa1cf80809117e4c374a0a40b9e.pngecm_mslp_uv850_natl_9.thumb.png.62e609442ba1bd3feec1e30115ec9efb.png

ecm_t850a_5d_natl_11.thumb.png.c11aab03f11c8eca5494d60d96977acc.png

Edited by knocker

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4 minutes ago, I remember Atlantic 252 said:

hmmm, makes you wonder, 240 ECM but could end up a 'heat spike' after all it is Mardi

ECM1-240.GIF?22-0

Yes Tuesday is the day!!! Probably the peak of any heat in the coming week, and looks the same on this chart too!!

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There's also less ppn on the ensembles going forward....so not a complete washout, just fairly average. Our best hope at present is a plume resulting from a stalled low I feel, still doesn't look like a settled spell is anywhere closer tonight.

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UKMO extended shows a fairly deep low to the north west of Scotland wet and fairly windy in the north and west drier further south and east

ukm2.2017072912_168_lant.troplant_prp_fcst.gentracker.thumb.png.bea29e6bb72962994dbf21f54c26b197.png

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16 hours ago, Matthew. said:

Maybe a weeksworth of 30c he meant. Even the much coveted Dover couldn't claim that this summer even if they have stolen all the sunshine.

My post indeed said "a weeks" worth of 30c+ but looks like weve used them all up already. It felt a bit northern today I actually have had to put trakkie bottoms on this evening instead of shorts for once! Unusual for this summer so far down here where it's been so muggy and warm!

Edited by Kentspur
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18z showing some interesting signs that hotter weather is around the corner and that Summer could well make a return in the first week of August... 3/4 days heat = thundery breakdown by the looks of it

AUGUST.png

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16 minutes ago, TJS1998Tom said:

18z showing some interesting signs that hotter weather is around the corner and that Summer could well make a return in the first week of August... 3/4 days heat = thundery breakdown by the looks of it

AUGUST.png

This is 11 days away.... Summer is always 'around the corner' if you look that far out on any op run. Give me jam, today.... not tomorrow. 

Edited by draztik
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Last night's anomalies were very uninspiring so just the EPS will suffice to indicate a not dissimilar upper pattern to a couple of days ago. Strong ridging N. Pacific, low pressure over the Arctic with a conduit to the upper low north west of the UK via a trough northern Canada and ridging to the east extending into Greenland. The latter feature inhibits eastward movement of the Atlantic trough but with still quite a strong jet emanating from the eastern seaboard there is a danger of it being 'topped' up from time to time which would increase it's longevity and thus an unsettled weather regime.

ecm_eps_z500a_5d_nh_11.thumb.png.4c8e7ada3c0181e084136929c6ccafb3.png

Meanwhile back on the farm this morning. The low pressure perched over us finally departs east late tomorrow but not before quite a cool day on Monday in the east with temps perhaps not rising much above 15C in the Cambridgeshire area. But Tuesday most of the UK is in a col and a generally a much warmer  and tranquil day with temps in the 23-25C region in England and not too shabby elsewhere.

So on the Wednesday By 12z the upper low is west of the Hebrides as is the surface feature, the fronts from which are busy traversing the country bringing wet weather to most and quite windy in the north and west.

gfs_ptype_slp_eur3_15.thumb.png.b9734bbaa6c1f7094c7dc6d512bc1251.pngPPVM89.thumb.gif.ff8dbddbec4ad2627337e933e65f9825.gif

For the next couple of days the surface low wanders around between Iceland and Scotland with much of the Britain in a showery westerly with just the south hanging on the any influence from the Azores and thus drier and less windy here although the temps no great shakes.anywhere. But at the same time another system is tracking in from the south west (topping up the main low) and by Saturday a more general area of rain affects the UK.

gfs_ptype_slp_eur3_23.thumb.png.d8344695d11228449151b81e2b133141.pnggfs_z500a_natl_23.thumb.png.5d40062110154e1f59b58ef00a8f1c04.pnggfs_ptype_slp_eur3_28.thumb.png.302660bb3bd835189f5e05c9b21663a8.png

At the beginning of next week the main low does fill and move away NE and thus some transient ridging from the Azores but this starts to give way to the next Atlantic low Tuesday evening. The detail of these last few days will obviously change, and probably be treated differently by the ecm anyway, so merely to be noted. All in all not a lot different to earlier outlooks. changeable but certainly not a worse case scenario but that does rather depend on where you are given the usual NW/SE bias.

gfs_ptype_slp_eur3_40.thumb.png.a979537f80af7cdfa13c5c9ac08e3626.png

I was wondering why eastward movement seemed to be underway later on and this would appear to be because the GEFS anomaly is dropping (at the moment anyway) the idea of sustained pressure rises to the east.

 

Edited by knocker
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The ecm pretty much in the same ball park as the gfs this week with fronts affecting the country Weds and the weekend but it differs at the beginning of next week which is not altogether a surprise as the details in this area await verification.

It fills the main low in situ rather than tracking it NE but it does get reinforced by systems tracking from the south west. and then the whole caboodle moves to the north east leaving the UK in a light NW flow. But what awaits? What adjustments will be made in the interim? In the meantime it could be worse

ecm_mslp_uv850_natl_10.thumb.png.68e589499462575e1368eb1c04d95e34.pngecm_mslp_uv850_natl_11.thumb.png.cb58b5264744a3d472a2eafa9357f096.pngecm_t850a_5d_natl_11.thumb.png.e42518b4c39b8da0ba5c7ed664c018d1.png

 

Edited by knocker
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