Short range model discussion - into 2018

[johnholmes]

The latest chart I linked to above is shown on the link below, the area, v roughly in the circle is where the low is developing with falls over 7 mb per 3 hours

 

[knocker]

The next low and fronts after Eleanor set to bring more rain and strong winds on Thursday with more snow in Scotland

[knocker]

As has already been well sign posted the ecm has a very wet and stormy night tonight and by 12 Wednesday the low is in the eastern North Sea and the UK in a strong north westerly with frequent showers

Meanwhile out to west a wave and associated fronts are winging their way west on a very strong jet and by 00 Thursday the low is just west of Ireland with the warm front and rain SW Ireland > Cornwall  but by 12 the front(s) have cleared south east England whilst the low has tracked north east to be 982mb south of Ailsa Craig with a belt of rain which may fall as snow on the mountains of Scotland. It is here that it phases with another shallow low that has tracked in from the north west (two energy flows)

It is also from here the complications set in. By 12 Friday the merged low has tracked south east into the North Sea and the next wave and front are pushed south into northern England as the surging high pressure to the west (initiated by the N. American east coast storm) begins to ridge north east over Iceland

This process continues and by midday Saturday the high cell is centred south of Iceland stretching east  and with the general area of low pressure now over France and Iberia the UK is now under a NE or E flow.

Edited January 2, 2018 by knocker

[johnholmes]

The latest UK chart shows an area with pressure falls of 100 or 10.0 mb in 3 hours. A typical indicator of a surface low deepening, link as shown in posts earlier above this.

 

[johnholmes]

It is on the first page, anyway, here is the chart

http://meteocentre.com/analysis/map-surface.php?map=UK&date=2018010220&size=large&lang=en&area=uk

 

[knocker]

Worth a look here as well

https://earth.nullschool.net/#current/wind/surface/level/orthographic=-1.06,52.76,3000/loc=-5.132,50.122

 

[johnholmes]

To me checking the 2200 position of the low it is tracking a bit south of east, probably to exit not that far from Newcastle?

[knocker]

10 minutes ago, johnholmes said:

To me checking the 2200 position of the low it is tracking a bit south of east, probably to exit not that far from Newcastle?

I would have thought it would have to dive fairly sharply SE to do that John. Although they seem to be putting it a tad further north than the 1800 fax.

[knocker]

You were pretty much spot on John. Here the 02 & 04 charts plus 00 fax and this morning's gfs. A pretty wild night down here with a full gale and gusting 60mph.

[knocker]

Following on from the above Eleanor is over Denmark by midnight and the twin energy flows can be clearly seen to the west with the next low west of south west Ireland with the warm front orientated from there to Cornwall

By 12 tomorrow the low is 984mb in the Irish Sea en route to the North Sea bringing a wet day to most, perhaps snow in Scotland, leaving behind to the west a quite complex surface analysis under the upper trough as can be seen. What is also evident is the surging Bermuda high pressure as the east coast storm tracks north.

As we move into the weekend the ridge moves east and continues to stretch north east which deconstructs the upper trough, trapped  as it is between the European high, resulting in low pressure to the south of the UK and initiating a north easterly wind over the UK with some very cold air poised to the north. And here we must leave it.

 

Edited January 3, 2018 by knocker

[knocker]

Sat at 0530

[johnholmes]

So onwards, after the storm, will we get a cold spell by T+72 or soon after.

Again for guidance, rather than some hot air at times in the other model thread, this link gives the idea from UK Met Fax charts

http://www.weathercharts.org/ukmomslp.htm#t72

It shows northerly, even NE winds by Saturday with the ridge moving from its original position over Greenland, then over Iceland and the 72h shows it west of the UK. What happens after that?

This link shows how the two models are dealing with it after T+72, GFS and ECMWF. As you can see the EC version holds on to the riging east of the UK more than GFS. So much discussion about this in the other model area

https://www.netweather.tv/charts-and-data/model-comparison

The UK Met model out to 144h (sorry not really for this thread) shows more like the ECMWF development on the link below

http://www.meteociel.fr/modeles/ukmo2.php?ech=6&carte=1021

From a lot of expereince of IF a high does develop in a position to slow or even block the Atlantic then the break down almost always is later than first predictions. So the probability is, to me, that the 'cold' may last well into next week. Of course will it snow will figure large in that time. So lots to keep us going in the T+72 link.

Personally I would like this area to go out to 120 hours as it is well within the reasonably 'high' expectation of the forecasts being near the mark as with the models. Watch how they vary from out at 240h with one another, just use either the 00z or 12z for comparison. Then no matter how different they are at 240h they start to converge below, it varies, from 144h down to as close as 72h, but then they are pretty similar.

 

 

Edited January 3, 2018 by johnholmes

[knocker]

17 minutes ago, johnholmes said:

Personally I would like this area to go out to 120 hours as it is well within the reasonably 'high' expectation of the forecasts being near the mark as with the models. Watch how they vary from out at 240h with one another, just use either the 00z or 12z for comparison. Then no matter how different they are at 240h they start to converge below, it varies, from 144h down to as close as 72h, but then they are pretty similar.

 

 

For what it's worth I would go along with that.

[phil nw.]

2 hours ago, knocker said:

For what it's worth I would go along with that.

...except perhaps when an easterly is on the cards-like next week?

We have seen them implode earlier than T120hrs -maybe T96hrs is a good compromise in general if we were to change this thread?

 

[johnholmes]

I would go along with that phil, although I still suggest 120h as that is, an about average, with reasonable certainty through the year that the models 'begin' to converge.Obviously there are exceptions but more cases of converging around that time. Maybe leave it until after the easterly either sets up or disappears then extend it to 120h if we can get Paul to agree with this?

 

Edited January 3, 2018 by johnholmes

[Ukwoody]

Firstly, this is a so much better thread!  I personally think T96 is better.  My reasoning is by extending it to T120 you are really verging on the main model thread, and more worryingly is that by extending the time, leads to more uncertainty in understanding the models which leads the possibility of more arguments!

T96 is a good compromise for sensible friendly discussion and respectful disagreement

woody

[starstream]

This thread has clarity, and I do understand , by the longer term nature of the Mad/Mod thread, that is why this one is clearer .

but there are , so far, no Nostradamus quatrains being spouted, nor requests for snow depth in  Droitwich south, at No 27 brewers drive!

Thankyou Gents, and Sydney of course.

[knocker]

A quick look at this evening's gfs.

Storm Eleanor finally clears but the next system is on it's way and the rain from the warm front has already arrived here and by 06 tomorrow is tracking north east whilst the associated low is 984mb just west of Ireland. As can be seen from the 06 chart there are two energy flows with waves also approaching from the north west and they merge during tomorrow and track into the North Sea.

By 06 on Friday more little lows are forming in the southern Quadrant of the main trough to the west and tracking east and one such is over the Midlands at 12 on Friday. But simultaneously major changes are afoot to the west where the east coast storm has initiated a surge of the Bermuda high pressure that impacts the jet.

The ridge continues to move E/NE and thus relegating the main trough south and which also initiates a north easterly flow over the UK by 12 Saturday with the very cold air trapped to the north  Where will it go next I ask myself and Sidney.

 

 

Edited January 3, 2018 by knocker

[knocker]

Nothing significantly different that I can see with the ecm so I'll just post the surface analysis for 12 over the next three days and the NH temp anomaly and contours.

[knocker]

Just to note on the gfs 1800 the pattern and energy flow with cold/warm air boundaries highlighted.

[knocker]

Today sees a belt of moderate rain moving north east (just cleared here) with the low over NW Scotland at 12. This moves quickly east to Denmark leaving quite a complex surface analysis before another low and more rain brings more rain to the south overnight with snow in Scotland.

By 00 Saturday the expected amplification of the high pressure is taking place in the Atlantic as it ridges north then north east pushing the upper trough over the UK south. It is worth noting here the low that has formed between Greenland and Iceland as it is the movement east of this low that delineates the boundary between the warmer air to the south and the much colder airmass to the north. This is illustrated very well as the ridge sinks south and the north easterly flow introduces a modified form of the colder air into the UK over the weekend.

Edited January 4, 2018 by knocker

[knocker]

Further to the above the METO have issued a strong wind warning. I should have mentioned the wind in my earlier post as it's blowing a bit again down here.

Quote

Chief Forecaster's assessment

The strongest winds will affect southwest England and Wales during the morning, moving east to reach eastern parts of England later in the afternoon. Gusts of 50-60 mph are likely fairly widely with some gusts reaching 65-75 mph along exposed coasts and over high ground in the west.

https://www.metoffice.gov.uk/public/weather/warnings

[knocker]

The ecm surface analysis for T48, 72. Quite a strong easterly on Saturday in the south with max temps in the plus 6C range but markedly colder on Scotland and struggling to get above freezing.

 

[johnholmes]

Not time to post just now but this thread is getting into a similar area to the other one at T+72h. Hopefully it can remain polite and constructive which the other one certainly is not.

[johnholmes]

Well shall we try and make some sense of how the models are treating things out to 72h and perhaps peeking out to 120h?

Below is the UK Met model output on Net Wx

https://www.netweather.tv/charts-and-data/met-office

We can use this and others I'll show to see how their model is dealing with the development/movement of the surface high and also at 500 mb, which is where the real work of forecasting occurs. Get that right and there is a good chance the surface will be near to what happens. Get it wrong then forget any prediction.

It does show the surface feature moving east, perhaps a shade NE comparing 00z with 12z yesterday. The upper trough, watch the 558 black line, has moved east and extended/sharpened somewhat, causing the surface ridge to be moved NE compared to the previous 12z issue. But remember this is partly sequential anyway, 12 hours further on, and to me it looks a reasonable prediction.

Now let us compare the GFS and ECMWF models over the past 24 hours, just out to 120h, as we can then see direct comparisons with UK Met.

https://www.netweather.tv/charts-and-data/model-comparison

For all the hot air being put out in the main model thread, admittedly much directed beyond 120h, I would not be believing that there is that much major differences in the 3 main models. Not sure what you reading this may think?

Overall then we look to be set for colder weather setting in, and also less windy and wet than currently, over the weekend. How long this 'block' will last is still far from clear. Nothing new in that, if any read my comment in the main thread about cold blocks and how they are often difficult to shift. Hence leading to errors on the models as they show the Atlantic pushing the cold air away. Fascinating to see just how long the cold weather over the UK may last. I still feel that this time next week we will still be watching the Atlantic trying to make inroads to the cold air with the ridge being reluctant to give way.

Turning to events now, the link below shows the weather system triggering Met Office warnings as it tracks across the country. It, at 1000, is WSW of the Isle of Man and tracking about east looking at the isollabars (pressure falls), probably cross the east coast in the Bridlington area.

http://meteocentre.com/analysis/map-surface.php?map=UK&date=2018010409&size=standard&lang=en&area=uk

Edited January 4, 2018 by johnholmes