Penellype's Weather Channel

[Penellype]

The warmer weather is on track for the bank holiday weekend, with remarkably little difference from the forecast in post #691. The jet stream is a little nearer to Scotland so the north and west may have showers at times, and there could be thunderstorms in the south by Monday, otherwise a good deal of warm and dry weather is likely. Don't be surprised if the next couple of days are rather cloudy, especially in the west, but things should brighten up for most places by Sunday, when it could reach the mid 20s in the south. No frost to worry about after tonight as far as I am aware, although things could cool down later on in the month.

After the weekend the model members are split between continuing the high pressure, warm and dry weather and returning to a more westerly, changeable routine. The operational run consistently favours the return to cooler and more changeable weather and I think this is the most likely scenario, so enjoy the next week or so. Be aware that it is not too late for cold nights even well into May, and proceed with caution with vulnerable plants.

[kobzy_garden]

Cheers Pen!

Thanks for the good news Re: Bank Holiday weekend! I'm off to Hull on a cycling trip so that is great news weather wise.

Also, wanted to just say thank you for these detailed weather reports. I really enjoy getting the thoroughly scientific meteorological analysis that you provide.

[Nicos]

Interesting you talk about Ice Maiden days 11-15 May.
In France we have this...
"Les saints de Glace sont les jours de la St Mamert (11 mai), St Pancrace (12 mai) et St Servais (13 mai).
AKA Ice Saints!

[Penellype]

As expected the warm/hot weather over the weekend has now been replaced by cooler atlantic air (nearer normal temperatures for the time of year) and we are into a more changeable regime, with bands of rain always heaviest in the north and west. This looks set to continue for a while, although ridges of high pressure between the lows will give some pleasant days.

I mentioned the ice maidens around 11 May. Interestingly the forecast temperature chart for 3am on 11 May is:



This is cold enough for a ground frost in much of the north, so be aware and ready with the fleece! (I'm not so impressed with the prediction of nothing but rain throughout May though!).

Quite a way off, and subject to change, there are also a few coldish nights in the forecast for next week, along with the potential for some quite windy weather mid week - this needs keeping in mind when thinking of planting things outside.

The driver for this appears to be development of a high over Greenland. This is never good news as low pressure systems run underneath the high, usually over the top of us, and pull the wind in from the north as they leave. It remains to be seen how this develops.

[Penellype]

Quick update to illustrate the uncertainty around the weather at the moment - these are the ensemble charts for York from the 6am run yesterday and the midnight run today:

Yesterday



Today



Just look at the difference in rainfall forecast for tonight and upper air temperature for tomorrow and Monday (both well within the "very reliable" timeframe) between the 2 runs less than 24hrs apart! I can't remember seeing such a big change at such short notice before but I may just have forgotten.

Apparently this uncertainty is due to a low pressure having detached itself from the jet stream and hovering over us (this brought yesterday's rain in the west). This is unusual and the models do not handle it well, which means pinning down the positions of the fronts and associated rain (and the warm air behind the warm front) is difficult.

So, take forecasts for the next couple of days with a pinch of salt and rely on the radar to forecast imminent rain. Its supposed to have been raining over night here and still be cloudy - we have had no rain at all, the sun is out (sort of) and the radar for much of the country is completely clear at the moment. https://www.netweather.tv/live-weather/radar

What does seem to be likely is that next week may contain a few cold nights with possible ground frost. Keep an eye on the temperature forecasts for your area and be prepared to protect plants if necessary.

[Penellype]

The forecast models now appear to have reached a consensus, and its quite nice.

A cold front will move down across the country tonight - this is already producing some rain in Scotland and Ireland, but it is expected to weaken so many places may just get cloud. This will introduce cooler air for a couple of days, and ground frost is possible particularly in vulnerable areas, so be prepared to protect your plants for the next few nights.

Towards the weekend things are expected to warm up again, and with high pressure in control there should be plenty of dry weather. It even looks possible that we may get another warm and sunny Bank Holiday weekend, as there is little change forecast into the beginning of June.

Details will vary from day to day - there is always the possibility of little low pressure systems developing, particularly towards the south, which may spark off thundery showers at times. But in general from this weekend on, expect plenty of dry, warm and sunny weather for probably the remainder of May!

[sandspider]

Interesting Penellype, thank you.

Do you know when we might get any rain in South Wales?! Looking fairly dry here already and I have lots of new plants in, and am going away for a week next week!

[1Bee]

*fistpump* Excellent news.

Mind you, like sandspider, it's surprisingly dry here...

[Penellype]

Interesting Penellype, thank you.

Do you know when we might get any rain in South Wales?! Looking fairly dry here already and I have lots of new plants in, and am going away for a week next week!

There is no rain in the forecast for South Wales until after the weekend at the earliest. There is a possibility of some probably showery rain on Monday, but nothing definite, and the next forecast rain is for Wed 30th May, which is way too far ahead for any certainty. Things can change, but if I were you I would plan for it to be dry throughout and try to enlist someone to water the most important plants for you if possible.

[Penellype]

The warm weather looks set to continue for the whole of next week and into the bank holiday, although it may not be quite as dry and sunny as looked likely earlier this week.

Tomorrow a front will continue to bother western Scotland and much of Ireland, and some showers may develop, particularly in the south and west. The front should move away by Tuesday, but the risk of showers remains and these may become heavy and thundery. The models do not handle showers well, so it is hard to say where these will be, although the south looks likely to see the most of them, as it will be warmer there than further north. The air is particularly hot over France, and this may push into the south for a while, sparking off storms. It will generally be a bit cooler in the east in the easterly wind, and this could drag in some cloud over eastern areas at times.

There is the possibility of some more general rain for a time on Friday, although not all models are seeing this. The uncertainty is due to a low pressure over Biscay, which may or may not move north to affect us. If it does, high pressure looks likely (at the moment) to become re-established for the bank holiday.

[Chippy Minton]

Our sandy soil could do with a drop of rain (overnight obviously )

[Penellype]

I think there will be a lot of gardeners looking for a drop of rain soon - its looking very dry (thundery showers apart) for the rest of the month. This is the ensemble chart for York:



As well as the solidly above average temperatures, there is almost zero rain forecast for the next week.

[bikermike]

Is this likely to be the start of a blocking high for the summer, or just part of the ebb and flow?

[Penellype]

Its hard to say as long range forecasting is always tricky. However, this high pressure is in a very similar position to the one that brought the "Beast from the East" earlier in the year, the difference being that by May the continent is warm, not freezing cold. The atmosphere does tend to get stuck into a repeating pattern at times, and it could be that this blocking high will either stay put or keep reappearing with brief more unsettled interludes.

The main question that affects us, is if this high pressure does continue over the summer, where will it be centred. This is crucial - at the moment we have the centre over Scandinavia, which is bringing in warm easterly winds. If the high drifts south the wind will turn into the south east (very warm) or south (hot) - the hot air is not very far away now in any case (France is forecast to become very hot over the bank holiday). However, if the high drifts west into the atlantic, we will be in a north westerly flow which is much cooler. Its still dry, but nowhere near a heatwave.

There is a good explanation of this in a video posted here https://www.gavsweathervids.com/ecmw...-forecasts.php yesterday - the 2 models covered show these 2 options nicely, with ECMWF going for a high to centre itself over the top of us with plenty of warm weather, while Meteo France goes for the atlantic high and a cooler summer. Remember that these models are experimental and it may be that neither scenario happens.

[Chippy Minton]

Well it's been intermittently chucking it down (technical term) here. Short, sharp showers. Hopefully that's enough until the weekend. It's been so wet through Spring that the established stuff is OK, just concerned about the seedlings.

Asking the great weather guru Penellype for some rain worked a treat