Penellype's Weather Channel

[Penellype]

The more unsettled and sometimes showery theme continues for the next week or so, with the south potentially seeing quite a bit of rain on Tuesday. Details are still somewhat uncertain as the position of the low that will cause this is moving from run to run. Elsewhere expect some showery rain just about everywhere at times, but also some drier and sunny intervals in between.

[Penellype]

Today's charts are somewhat interesting in the medium to longer term (which can of course change).

The GFS has recently been keen on building high pressure over the country from the middle of next week, and today's midday run produces this for 10 days time:



This is an absolutely classic summer chart and could lead to a fairly long period of warm and dry weather with the jet stream (roughly the black line between the green and yellow areas) pushed well to the north.

The ECMWF has not been seeing this, with the changeable weather continuing right through to day 10 with the jet stream never that far from Scotland. Until the latest run. Suddenly we have this:



This looks pretty similar to the GFS, giving encouragement that summer could be back with us fairly soon.

Plenty of time for both models to change their minds, of course, but if you like "proper" summer weather things are not looking bad this evening.

We shall see.

[Penellype]

Update on the potential for a heatwave next week...

What seems to be going to happen is not quite what we were led to believe. Currently temperatures are slightly below average in a westerly flow with low pressure never far from Scotland. Over the weekend a ridge of high pressure will push into the south, although the north will remain changeable. The high then centres itself over the country on Monday, giving everywhere a nice, summery day.

On Tuesday and Wednesday the high drifts east, pulling up a plume of hot air from the south as it does so. This is a classic 3 fine days and a thunderstorm situation, and a thundery breakdown is very likely on Wednesday into Thursday as a low moves up from the south joining forces with a trough in the atlantic. This will lead to cooler, fresher conditions afterwards. Timing and positioning of all of this is uncertain, as is what happens next. The options seem to be a return to more unsettled conditions generally, or a repeat of the ridge, heat, thunder sequence.

[Penellype]

Rather wetter today than expected with most places showery. Somewhat better tomorrow, although there will still be some showers about.

Monday still looks nice, but the low that is coming up from the south may arrive earlier than expected bringing rain or storms to the south west and then moving north during Tuesday. It could still be hot and unpleasantly sticky in the south on Tuesday afternoon, and in parts of the south east on Wednesday, but in general the heat has been moderated somewhat and the general outlook looks rather more unsettled than it did.

I conclude that the models haven't really much of a clue what they are doing!

[Penellype]

Much more certainty now about what is going to happen for the remainder of July and into the first part of August, and it is not good news.

This is the situation at midday today, showing the low that has brought a lot of rain to the south west and west of the country:



This is the start of a much more unsettled spell of weather. The problem lies in the high pressure which is building over Scandinavia. This is forecast to drift north and join up with a ridge in the atlantic, and the high then settles over Greenland. This leads to a series of low pressure systems running underneath the high, straight over the top of us. This is shown well on the chart for Thursday:



At present the high is forecast to stick around Greenland for the forseeable future, leaving us in the firing line for more and more lows.

The ensemble chart for York shows that there is unlikely to be any more lengthy warm and dry spells for the whole of the run, with temperatures around average for the time of year, and plenty of rainfall spikes, with some drier or showery interludes:



At some point something will change to flip the weather out of this pattern - this is often caused by a dying hurricane in the atlantic at this time of year. We will just have to wait and see.

[Potstubsdustbins]

That settles that then.

Only this evening as we ate SWMBO said "Will you ask Penellype when summers going to return?" I can now tell her not yet a while.

[Penellype]

No significant change in the forecast - unsettled, with rain or sunshine and showers (possibly with hail and thunder at times) and remaining relatively cool for the foreseeable future. A low pressure remains stuck to the north west of Scotland as is illustrated by tomorrow's chart, which differs very little from any you care to look at between now and the end of July:



The ensemble chart (for York) shows the continuing average to cool conditions and frequent rainfall spikes:



I hope those massive blue rainfall spikes are an exaggeration or we will be under water!

Longer range models point to a possible improvement for mid-August, but that is far too far away for any sort of confidence.

[Thelma Sanders]

It should have been obvious to all the weather would worsen now - the school holidays have just started

My lot are due to go on a camping holiday next week What joy

[Penellype]

Just a hint of something warmer possibly showing now for mid August, but until then expect the cool and changeable weather to continue.

The latest ensemble chart for York shows the expected change well:



The white average prediction line is below the red 30 year average line until about 11th August, when it starts to lift above average. The little rainfall peaks will be mostly showers, with something a bit wetter likely on Monday. There is a lot of scatter, as always in the 2nd half of the ensemble, with some members going very hot and a few remaining cool and unsettled, but the general trend appears to be warmer.

The current unseasonably cool and wet weather has been caused by an unusually strong (for the time of year) and southerly tracking jet stream, which is currently over the southern half of the country:



Note that the green to yellow colours are towards the higher end of the scale. By 11th August we have:



This isn't wonderful, as the jet stream is still close to Scotland, but it has definitely weakened and moved a little north. The operational run of the model (on which these charts are based) brings the weakened jet further south again fairly quickly (the thick green line on the ensemble chart is one of the coolest). The earlier 6am run of the same model had this chart, which is much better:



So there is a possibility that summer could make an attempt at a return in about a week to 10 days time, but there is still a lot of uncertainty and the models are changing from run to run.

[Potstubsdustbins]

Oh I do hope your right Pen I am of work week beginning 14/08 so hope for some days out with SWMBO

[Penellype]

Its a long way off in forecasting terms, and things can change a lot. This is the current 2m temperature and pressure (Bodendruck) for Nottingham:



You can clearly see the forecast rise in pressure and temperature, although some of the runs are better than others. How long this lasts is anyone's guess at this point - it may stretch out into a decent spell of better weather, or the ridge may be swept away in a day or so. Too soon to tell.

To see these charts for your nearest town or city, go to Wetterzentrale.de - Diagramme and type it into the box. The charts I usually post are the 2nd from the bottom in the menu on the left - this chart is the sea lvl pressure one. The website is German, but publishes charts for all over the world - useful if you are going abroad.

[Jay22]

Well, if the warmer weather reaches here it will be just in time for the kids going back to school!

[Penellype]

Well, if the warmer weather reaches here it will be just in time for the kids going back to school!

Oh dear!

[Penellype]

The warmer, drier weather that the models were seeing for the end of next week has almost completely disappeared, at least for northern areas

This is today's latest ensemble chart for York:



It seems to be autumn.

[Jungle Jane]

Hopefully they'll change that forecast when they spot some heatwaves it's been quite sunny here but very cloudy. Bit windy for August,I had to tie my runner bean teepee to my shrub the other day,never had to do that before but it was a big worry imagining it blowing down with the force of that wind. Thanks for keeping us updated its good to know whatever's happening