Model Output Discussions 12z 08/03/17

[Summer Sun]

UKMO begins to cut off the cooler flow of air as the weekend progresses

Some rain at times this easter weekend yes but not a washout by any means certainly not a right off

[Summer Sun]

If ECM is right Easter day should be settled for many temps around average and feeling quite pleasant in any sunshine

It could be far worse than what ECM shows

[Singularity]

The HLB seems less solid on the evening runs, particularly ECM, with more of a mid-lat block and lows trying to drop down on the east side, though with HP keen to stay close by as has been the trend of the year so far.

GFS continues to insist that a trough by Iceland will cut through a building bridge of high pressure over the top of low heights S of the UK, turning the would-be foundation of the bridge into a secondary feature that dances with the one from the NW with a focal point across the UK. Things almost take on plume characteristics in the SE as some warm air makes it close by, but for most the interaction of cool and warm airmasses just leads to a heavy spell of rain - which for a fair few in the south would be the first appreciable rainfall amounts (i.e. more than just a splash from a shower) seen in a fortnight or more.

Really though, I reckon the ECM day 10 is a good summary of the overall tendency to be expected until further notice;

Pressure highest to the west and lowest to the NE and on occasion E, often on the cool side but with some warmer interludes possible especially for many western parts of England and Wales, and notably dry for many unless a cold airmass can make enough inroads from the N/NE without anticyclonic subsidence preventing this from giving rise to decent instability with heavy, at times thundery showers breaking out.

[Frosty.]

I think more runs are needed the ecm is so different from the gfs / gem it's laughable. 

[Methuselah]

Just now, Frosty. said:

I think more runs are needed the ecm is so different from the gfs / gem it's laughable. 

More runs needed? Holy sheet Frosty, I am shocked! I thought it was all 'nailed on'????

[NorthYorksWeather]

8 minutes ago, Ed Stone said:

More runs needed? Holy sheet Frosty, I am shocked! I thought it was all 'nailed on'????

Good job its not winter or all hell would be breaking loose in here, it does seem like models have had a cold bias for a good few months now.

I was quite looking forward to a good period of below ave temps but its gradually becoming very average!

[knocker]

The anomalies this evening are all in pretty good agreement as the pattern change gets underway in the 5-10 day period. Upstream we have the Alaskan ridge pushing into the Pole and a quite intense vortex lobe over northern Canada with associated trough orientated south east and a gateway to the Scandinavian trough. Downstream the amplification is well under way with the Azores surging in the Atlantic and the aforementioned trough. As mentioned in previous missives the intensification and alignment is fairly crucial when it comes the UK weather and something the det runs will need to sort. Suffice it to say at the moment the percentage play is for the upper flow to veer NW/N and thus temps will trend below average but the weather will depend on the aforementioned caveat as to how any systems tracking around the high pressure impact the UK  At this very general stage it could indicate a SW/NE split.

,

moving into the 10-15 period there are no indications of any significant change, perhaps a slight move east of the downstream pattern that would consolidate a dry cooler regime continuing for a few days.

Edited April 11, 2017 by knocker

[knocker]

Trying to avoid wittering on about the weekend as it's been covered every which way but need to start there in order to approach the gfs take on next week which will no doubt be of interest. Or not of course.

Sunday sees the shallow low track south east across Scotland and the North Sea to be N. Germany by midnight bringing some showery rain to the north during the journey.

From this point the main players are the Azores starting to ridge north and in particular the jet driven trough and the energy being emitted from the vortex lobe tracking east around the top of the high pressure and by 12z Tuesday this is delicately poised

Then comes the amplification with the Azores surging in the Atlantic and the trough shooting south east to southern Scandinavia with the wind veering northerly over the UK

This opens the door for the HP to take center stage for a few days and as mentioned when briefly discussing the anomalies where this aligns will control what any systems will have as they sneak around the top and drop south east. The detail of all this will obviously change over the next couple of days but I would think the general picture to be quite likely. Just a quick word vis rainfall. Model rainfall figures need to be treated with a great deal of caution but keeping that in mind it's still looking pretty dry in many areas for the next ten days, and probably longer.

 

 

Edited April 12, 2017 by knocker

[knocker]

The ecm is currently dropping the trough next week further west which brings it straight down over the UK

[Summer Sun]

If the ECM weeklies issued on Monday are correct we're going to see a cooler end to April with temps widely a bit below average

A tad milder to start May?

[snowray]

UKMO looking pretty decent there with high pressure taking control.

[snowray]

GFS continues on the same vein. No sign of any significant rainfall for the southern half of the country in particular and temps picking up nicely after a slightly colder blip over Eater.

[snowray]

Snow in eastern Europe, including the Balkans, and of some late season snowfall for our Greek friends. 

[Singularity]

Compared to previous runs such as the 06z shown on the left, the 12z GFS brings a big change in the angle of the jet stream for early next week:

 

 

Flatter, with more of a 'bridge' effect achieved by the ridge. It seems the cutting off of a low by Iberia and the effects of this on the ridge are giving the models a hard time.

UKMO still looks more inclined to try and bring that low SE from Iceland, but it's less convincing than it's previous runs (slower for a start).

So at this rate it could be decent across many parts for a few days or more starting Sunday, though there is a chance of chilly air feeding in from the east:

The 12z ECM of yesterday explored this idea before today's 00z was a curious jump toward what GFS had been running with up until a day or so beforehand. 

GFS is really keeping the cold air away on this run. Should ECM at least trend toward this, it will start to appear likely that 2017 will prevent yet another potential unusually cold spell from becoming a reality. Whatever's going on, it's giving us some impressively persistent anomalous warmth.

 

[snowray]

GEM

[ANYWEATHER]

Evening all. What does stand out from the model output is how dry most of the country will be in the days ahead. With little if no rainfall for much of the country so far this month and after a dry winter it may become somewhat a concern for farmers and growers As for the chart below, just a few hundred mile shift in wind direction can make all the difference

[NorthYorksWeather]

Quite a chilly ECM this evening, especially for southern areas later in the run as we pick up a chilly easterly.

A small adjustment south of that high could quite easily give much more pleasant weather as per GFS.

Generally its looking mostly dry, and temps around average to slightly below for the next few days.

 

[damianslaw]

A fairly quiet outlook as others have stated, the most notable aspect is the continued dry theme, very little rain for the south and east for the foreseeable, and nothing especially heavy or long lasting further north and west as we see weak frontal features and weak convection take hold in the days ahead, courtesy of a cool predominantly NW airstream. The SW could see quite a decent easter period, coming under the influence of ridging centred just to the west. The models are playing around with the orientation of such ridging, which is crucial, if it holds its current position, less chance of showery outbreaks coming down on a chilly northerly flow, it it begins to migrate towards Greenland as GFS in particular keeps showing, then a cooler more unsettled interlude for the north and east at least will verify. Either way, not a very memorable easter coming up weatherwise, temps mainly around average in the south, a bit cooler than normal in the north but with much cloud I don't foresee much in the way of frost away from sheltered notorious hollows.

Longer term, the ensembles are suggesting a ridge to the west and a deep long wave trough to the east, consequently we would maintain the generally fair conditions, but quite cool. All very normal synoptics for mid-late April, when the atlantic typically settles into its annual slumber and we see the last of the deep cold air over the arctic bleed southwards.

[knocker]

The interesting aspect of the ecm run, IMO of course, is once again the influence of the cutoff upper low to the south west.

At T120 it has spawned another little fella that is west of Portugal and impacting the ridging.

At T144 it is closer to Portugal but note the other trough winging in from the north west into N. Ireland which is just about to track south.

Which by T168 it does and phases in with Portuguese low and creating a low pressure area to the south west with a conduit to the trough to the east and at the same time allowing the HP to ridge north east. Whether this will be repeated on the next run is highly debatable

,

Edited April 12, 2017 by knocker

[Singularity]

A more pronounced Sun-Mon sliding low and then a second one Tue-Wed make for more of a draw of cold air from the NE while also setting up the longwave pattern further west in the 7-10 day range. 

A large Scandi trough sits too close for comfort by day 10, but it seems to me that many of these have been modelled in recent times only for them not to come together; the 'seed' disturbances fail to interact effectively enough and go their separate ways, leaving a slack area of lower heights with a flatter jet pattern both there and in the vicinity of the UK.

GFS really does make a mockery of any outlooks that followed the model consensus of two days ago with respect to Mon-Fri next week 

[knocker]

The gfs thias morning is nodding somewhat in the direction of last night's ecm. at the beginning of next week. Monday 00z sees the upper trough beginning to slide down the North Sea, a little closer to the UK than previously, and with our little ubiquitous low to the south west the high pressure is forced to ridge north west  Thus the UK in a light northerly with showers in the north. But things are about to change and this a completely different evolution to 24 hours ago.

The trough continues it's journey down the North Sea, phases in with the low to the south west, allowing the high pressure to build north east. Thus by 00z Wednesday we have a broad area of low pressure to the south stretching from the south west to south east with high cell over the UK centred over Ireland

From this point the high pressure consolidates

So what does all of this mean weather wise Well once the influence of the trough at the beginning of the week is out of the way, taking the showers with it, high pressure is in charge, So predominately dry, apart maybe some showers around the periphery (northern Scotland, east coast) with usual caveats vis alignment of the HP regarding cloud and temp. The latter probably around average but quite large diurnal and geographical swings on the cards.

Edited April 13, 2017 by knocker

[knocker]

The ecm is broadly similar to last evening vis the evolution next week and ends the week with the high pressure centred in the Atlantic. The models appear to be struggling with the handling of the position and orientation of the HP due, I suspect, in no little way to the energy tracking east from the NW and a pincer movement from the south west. If my memory serves me correctly which is extremely unlikely these days, not the first time we have seen this scenario over the last few months.

Edited April 13, 2017 by knocker

[johnholmes]

The anomaly charts are not in agreement once more, see below

EC-GFS show the upper ridge as the dominant feature. NOAA last evening had the 'classic' ridge-trough with the flow north of west into the UK.

Time to fence sit for a few days for any clear idea of what the upper air pattern will be in the 6-14 day time scale?

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

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

[carinthian]

11 minutes ago, johnholmes said:

The anomaly charts are not in agreement once more, see below

EC-GFS show the upper ridge as the dominant feature. NOAA last evening had the 'classic' ridge-trough with the flow north of west into the UK.

Time to fence sit for a few days for any clear idea of what the upper air pattern will be in the 6-14 day time scale?

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

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

One thing for sure John, the upper pattern not favourable for our Swedish friends. My daughter who lives in Stockholm reports a horrible cold and wet April so far and even snow in the wind this morning. Whether the upper ridge becomes the dominant feature  near to the British Isles or not , it looks like Southern Scandinavia in the extended outlook to remain on the cold side of the flow. Meanwhile back in Skipton, the river levels in the Dales look very low at the moment, but have to admit I am frozen living back up here. Warm sunshine would be very welcome!

 C

[johnholmes]

1 hour ago, carinthian said:

One thing for sure John, the upper pattern not favourable for our Swedish friends. My daughter who lives in Stockholm reports a horrible cold and wet April so far and even snow in the wind this morning. Whether the upper ridge becomes the dominant feature  near to the British Isles or not , it looks like Southern Scandinavia in the extended outlook to remain on the cold side of the flow. Meanwhile back in Skipton, the river levels in the Dales look very low at the moment, but have to admit I am frozen living back up here. Warm sunshine would be very welcome!

 C

Give over you softie, two good weekends here in the past 4, better than normal, Easter is traditional for cold more than Christmas some say.

Still mostly dry so more work in the garden, it could do with some rain but none of any major consequence on the horizon for here?