Model Output Discussions 12z 08/03/17

[Summer Sun]

GFS still looking pleasant enough temps wise for large parts of UK with the mid 20s still possible mid week

[snowray]

2 minutes ago, northwestsnow said:

I think the SE might hit the low 20s for a couple of days but north of Birmingham it doesnt look to clever..

Probably be mainly cloudy even down here though if UKMO is right.

[knocker]

Interesting the gfs is sticking to it's high pressure remaining quite influential routine next week and even brings a trough north to the south west of the UK which is much to do with upstream energy tracking around the southern flank of the ridge. Well it's a change

Close but no cigar

Edited May 11, 2017 by knocker

[mb018538]

Yes knocker, gfs has been slowly coming round to the idea of high pressure remaining dominant....baby steps though. Looks like Wednesday will just about hold on to some warmth in the SE before all change again. A blink and you'll miss it warm shot, but not to be sniffed at in mid may.

[knocker]

23 minutes ago, mb018538 said:

Yes knocker, gfs has been slowly coming round to the idea of high pressure remaining dominant....baby steps though. Looks like Wednesday will just about hold on to some warmth in the SE before all change again. A blink and you'll miss it warm shot, but not to be sniffed at in mid may.

Oh I wouldn't bank on this mb given that the ecm wasn't on board earlier. We'll see what it says later.

[knocker]

The ecm has modified it's earlier stance vis the end of next week and takes the main low further east, So although there is a period when the wind veers NW/N and accompanied by  some unstable showery weather it is quite short lived as the high pressure nudges in from the west. This is still a long way from being resolved.

[Singularity]

If you look at the strong MJO activity currently in phase 1, allow for typical lag of 10-16 days from a few days ago when the MJO first reached this phase, and then consider the analogues for such activity first in May and then in June (as we will be moving closer to June and the transitions are not restricted by our human application of month boundaries), you can really see where the models are coming from - though the move east of HP across the UK may be too fast, particularly in the GFS 12z run. 

I'd not be surprised to see a strong ridge moving slowly but surely eastward to give another lengthy dry spell that starts on the cool side but then warms to average and, in time, above. 

Too far out to draw solid conclusions yet though. Say the MJO was to scoot over to phase 2 while retaining decent amplitude - that'd encourage the ridge to instead become centred over or a bit N/NW of Scotland (again!) with a chance of some showery activity in the south.

Edited May 11, 2017 by Singularity

[Summer Sun]

GFS, GEM & ECM all showing high pressure at d10

What could possibly go wrong

[damianslaw]

Models hinting at mid atlantic ridge/heights but too far to the west and north to deliver anything particularly warm, with the threat of slow moving frontal features moving around its flank from the NW, resulting in showery cool conditions at times. In time the ridge could easily centre itself over the country bringing much warmer conditions, but may take a bit of time..

[knocker]

The NOAA and GEFS and EPS anomalies have all been indicating ridging in the Atlantic recently and last night was no exception. Thus we have a ridge to the west and the trough to the east and as ever in this sort of pattern the key will be in the detail and precisely where the surface features reside. As indicated by damianslaw above ideally the high cell will be close to the UK which forces the track of any troughs further to the east. This would portend dry and cool conditions over the UK in a mainly NW/N airflow. The outlook could be worse, albeit little sign of above average temps until, perhaps, later in the period. The EPS is similar.

Meanwhile back on the farm. The main depression in the Atlantic and subsidiary perturbations dominate proceedings over the weekend into Monday, albeit with a slight respite on Sunday, so that by early Monday the next depression that has tracked rapidly north east and is NW of Ireland with the UK in a moist, warm, south westerly airstream

From here the evolution continues with what has been indicated for a while with the main Atlantic low drifting east north of Scotland, weak fronts traversing the UK as the wind veers westerly and the temps are briefly above average, until we have this position by 00z Thursday.

As can be seen from that chart the high pressure is beginning to surge north in the Atlantic and north east into the UK and this continues and becomes more influential over the UK with the surface wind veering northerly for a time dropping the temps a tad. What now follows is quite complicated but a perfect illustration of why the precise orientation and configuration of the ridge and troughs are so important. The next low tracking east is duly well north of Scotland

But the upper trough to the east has made a connection with the ever present low pressure to the south west and this suddenly becomes a different ball game as the surface  low to  the north nips south east to southern Scandinavia, phases with the low pressure in the Bay of Biscay and the UK is back in a northerly, albeit nothing drastic. And this is really where we came  in

Edited May 12, 2017 by knocker

[knocker]

Just to confuse matters again the ecm has reverted back to the previous 00z run and at T156 has already started to track the low south east over the UK and Thursday sees showery, cool, and unsettled weather over most regions. The ridging to the west then follows but the orientation of this north east introduces an NE/E component over the UK with the possibility of some inclement weather affecting the south from the S/SE. Needless to say given the continuing differences between the gfs and ecm, and even the latters inconsistency, confidence in the evolution post T144 is low.

[mb018538]

Lots of chopping and changing - and a definite move away from last nights 12z solutions. The GFS is one of the cooler options in the ensembles this morning:

http://www.theweatheroutlook.com/twodata/gefs.aspx?modelrun=na&lg=850&lglocation=london

But that said, there aren't any really warm runs in there at all now. Looking around average, with drier and brief wetter interludes possible.

[Summer Sun]

If NMM is right the bulk of tomorrow's rain/showers will be in the north

Most areas see a band of rain crossing Saturday night this clears in the early hours to leave a day of showers most of these stay in the west

[knocker]

The EPS mean 850mb is in the same ball park as the det. run although i expect the orientation of the HP of the latter will be subject to change.

[mb018538]

The models also seem to be slowly edging away from the very warm 850s, the 10c barely makes an appearance on the 6z.....could just be it doesn't warm up at all now, with a continuation of what we've had.

[Scorcher]

37 minutes ago, mb018538 said:

The models also seem to be slowly edging away from the very warm 850s, the 10c barely makes an appearance on the 6z.....could just be it doesn't warm up at all now, with a continuation of what we've had.

To be honest quite a few places reached 21C yesterday anyway- I doubt it will get warmer than that in these parts next week.

In all honesty if we had a continuation of the recent weather in these parts it wouldn't be bad at all.

Sometimes as weather watchers we can get caught up thinking about what's coming when actually what's happening now is pretty decent for May (although we have had our first rain for some time this morning).

[mb018538]

Yes we are above average - but the models (and the BBC extended outlook 2 nights ago) both suggested a 25c early/mid next week. That has certainly been downgraded by the looks of things, but 21c is still above the May average and warm enough  Much more uncertain after, with plenty of solutions, though not with big heat.

[Summer Sun]

UKMO 850's show a clear north-south split early next week with 25c still possible in the SE according to the lunchtime news

[Eugene]

GFS 12Z only showing highs of 16C/17C for tuesday in the midlands with a band of heavy rain moving in, this tropical air is just bringing in lots of damp cloudy weather, roll on the fresher clearer conditions later next week.

 

 

[knocker]

The differences between the gfs and ecm continues to be massive the gfs is still tracking the main Atlantic depression east to be away NE of Scotland at T144 whilst the ecm has it WNW, and quite close, to Stornoway  Thus by Saturday the gfs has the UK under the influence of the large anticyclone to the west whilst the ecm has the UK in a general area of low pressure with a fair bit of rain about. Any further comment is superfluous.

 

[mb018538]

7 hours ago, Summer Sun said:

UKMO 850's show a clear north-south split early next week with 25c still possible in the SE according to the lunchtime news

Looks quite wet on the evening update, trailing weather front will probably scupper things again. Looked so promising earlier in the week, but as In winter, the closer we get to the time, it's gets watered down to nothing. In all honesty the next 10-14 days is looking very uninspiring.

[knocker]

The gfs this morning.

Sunday/Monday it has fast moving depressions tracking NE in the southern flank of the main Atlantic trough and by Monday midday one, center 994mb, is NW of the Hebrides with the UK in a moist south west airstream.

From this point the main Atlantic trough moves quite quickly NE and it is around here that the gfs began to differ quite a lot from the ecm last night. This morning it has moved somewhat towards the ecm as, although it still tracks the trough NE as mentioned, the amplification now taking place, with the High pressure surging north in mid Atlantic, it simultaneously has the upper trough doing the same in the opposite direction just to the west of the UK. On the surface this translates to a slack low pressure area over the UK bringing with it some unsettled, showery, conditions with temps varying around the average.

All of this does somewhat delay any influence from the high pressure to the west despite a valiant effort on Saturday, and the next trough nips around it to be southern Norway early Sunday and thus initiating a cool northerly over the UK, From here the high pressure does gain more of a foothold but this very dodgy territory so best not go there.

All in all we are looking at quite a mixed bag next week with at least some rain for most areas

Edited May 13, 2017 by knocker

[knocker]

The gfs and ecm continue to differ next week. By 12z Thursday the latter has the Atlantic low filling NW of Scotland and has the UK in a slack low pressure area, In this respect only it is not at odds with the gfs. This low pressure over the UK becomes more concentrated over the next few days initiating a lot of instability, showers and temps around average for just about all regions. And whilst this going on the high pressure ridges strongly north in mid Atlantic and then east into Scandinavia! I'll believe all of this when I see it.

Edited May 13, 2017 by knocker

[johnholmes]

All 3 anomaly charts are back, not totally in detailed agreement to an upper flow from N of W in the 6-14 day time period. So no marked heat of any length is likely if at all?

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

[mb018538]

Looking like probably the worst kind of set up - and quite unusual. high pressure surrounding the uk, with a small low sat over us with nowhere to go. Net result will be cool and unsettled for the middle third of the month.