Penellype's Weather Channel

[Penellype]

Yellow warning of rain for the southern half of Scotland and the eastern side of England on Sunday. A front will grind to a halt over the country resulting in hours of potentially heavy rain falling on already saturated ground. Flooding is likely.
https://www.metoffice.gov.uk/weather...ate=2019-10-06

Thankfully after tomorrow it is looking slightly less wet for a while - still unsettled but with more sensible amounts of rain rather than deluges.

[Penellype]

The yellow warning of rain for East Anglia has been updated to amber for this afternoon, with flooding likely.

[Penellype]

More yellow warnings of rain appearing for Friday, Wales and parts of the north west in the firing line this time. More warnings may appear later as the weekend is looking rather wet.

[Penellype]

Another yellow warning of rain today for a large chunk of England south of the Humber. https://www.metoffice.gov.uk/weather...ate=2019-10-14. All this wet weather is a result of the jet stream being nearby or over us with associated low pressure systems. There is no real sign of an end to this pattern, with changeable conditions and more wet weather throughout this week. Some of the ensemble runs are forecasting drier weather to end October, but this is very uncertain at present, partly because of the as yet unknown impacts of typhoon Hagibis, which recently hit Japan. This could later affect the jet stream with consequences for our weather, so as usual treat any forecasts beyond the next few days with caution.

[Penellype]

Yellow warning has now been upgraded to amber warning of thunderstorms for the south east corner of England. Heavy showers with hail and thunder are likely but not everyone will get one.

[Penellype]

I've been waiting for some clarity in the forecasts before posting, but it isn't happening. This is today's forecast for York today:



So its currently tipping it down.

This is the ensemble forecast from the latest run of the GFS model:



As you can see, the next few days are forecast to be "dry", which probably means damp. By the weekend there are enormous differences in forecast upper air temperatures, with the ensemble members roughly equally split between warm and cold. The only thing that seems highly unlikely is that we will get something in between, which is where the white average line is.

So, expect some sort of let up in the rain in the first part of this week, but not necessarily completely dry. Expect anything (including the possibility of snow over Scottish mountains) later in the week, although it looks likely to get wetter again by the weekend.

[Penellype]

Just to throw a little more uncertainty into the mix, the midday run of the GFS has 8cm (3 inches) of snow arriving on York on Friday evening:





I very much hope this is wrong, but everything is so uncertain at the moment that nothing would surprise me.

[Chippy Minton]

That's a hefty dip in temperatures 25th (Friday) with a spike in precipitation straight afterwards. Presumably that results in your snow forecast? Either way I'm glad I bought that roll of fleece. The xmas spuds (outdoors) will need a blanky, and the pots will need hefting into the greenhouse.

And the dog will be expecting the fire lit

[Penellype]

Snow is one of the hardest weather types to forecast.

I think the snow is unlikely to happen at low levels although there could be some over hills. The cold is due to us being on the eastern side of a ridge of high pressure, bringing the wind down from the north or possibly north east. Exactly where the ridge is centred is crucial - a little further east would put us on the warm side of it, hence the huge disagreement within the ensemble.

The snow issue is due to a front between 2 air masses, cold to the north and warm to the south. This front trails from a low pressure to the north, across the country to low pressure near the Azores, and the temperature contrast helps to build a low pressure system as can be seen on the chart corresponding to the precipitation image in the previous post (arrow pointing to forming low):



This would result in very heavy rain with cold air to the north of it, and evaporative cooling may well cause the rain to turn to snow on the northern edge - hence the forecast.

This is only one model run. The 6pm run had the low a little further south, with some heavy snow over Wales and the west midlands and lighter snow over high ground further north, and this theme is continued in the latest midnight run, with rather more heavy snow this time:



It is somewhat worrying that the GFS sees this so consistently, but it is worth pointing out that the higher resolution (and therefore in theory more accurate) Arpege model is seeing very little snow indeed, confined to the very highest ground mainly in Scotland:



Whatever happens regarding snow, some frosty nights are distinctly possible next week as the forecast high pressure is building into cold air. Even if the upper air temperatures are reasonably high, light winds mean that colder air can remain undisturbed at the surface (an inversion) leading to cold nights if skies are clear.

[Penellype]

The GFS ensembles have now finally (mostly) come to an agreement on the colder side of the high:



The low pressure forming tomorrow is slightly further north which pushes the snow risk north - I still think this is likely to be confined to higher ground. What is very clear from this morning's run is that much of England, Wales and Ireland are due for a very, very wet couple of days. It will also be rather windy in the south, and next week nights will be cold with frost likely.

[Penellype]

Enjoy the drier (if colder) weather as it is unlikely to last beyond Thursday. A low pressure near the Azores has unexpectedly turned into tropical storm Pablo, and as it dies down this is forecast to interact with the jet stream, powering it up and bringing more wet weather by next weekend. Unfortunately this looks as though it could turn into a prolonged wet spell with more flooding probable into November.

[Penellype]

Yellow warnings of wind for the south tomorrow and rain for the south west tomorrow and parts of eastern Scotland for tomorrow and Sunday as low pressure moves back in.
https://www.metoffice.gov.uk/weather...ce/uk-warnings

[Penellype]

More yellow warnings of rain, this time for north east England and north Wales tomorrow as yet another deluge arrives. Flooding expected. https://www.metoffice.gov.uk/weather...e/uk-warnings?

[Gillykat]

Looks like I won't be going to the allotment after work then I'd planned to start doing even just a tiny bit of digging on every visit in an attempt to regain control but I think, instead, I shall sort out my umpteen boxes of seeds and see what I've got for next year

[Penellype]

The area between Leeds/Sheffield/Manchester now has an amber warning of rain.

Watch out also for frosty nights when skies clear as the air mass is currently rather cold. Tomorrow night looks a likely candidate for quite a sharp frost.