Penellype's Weather Channel

[sandspider]

Thanks P

Looks like we're in for a soggier spell. Any ideas yet on what August might look like?!

Appreciate your efforts here, generally more reliable than the various weather forecasts I look at!

[Penellype]

Thanks P

Looks like we're in for a soggier spell. Any ideas yet on what August might look like?!

Appreciate your efforts here, generally more reliable than the various weather forecasts I look at!

August is often a disappointing month and the long range models are implying that will be the case this time. The high pressure that caused last week's heatwave is forecast to move up to Greenland, which is never good news. This basically puts us back in the sort of pattern we had in June, with high pressure to the north and lows running underneath it. If this does happen, expect wetter weather than we had in June because the atmosphere in August is generally hotter and holds more water. Personally I think we have had the best of the summer, such as it has been, and we can expect more unsettled weather for at least the first half of August, possibly the whole month. If an ex-hurricane comes along it could change everything though.

The wetter pattern continues this week with the front responsible for the weekend's rain moving out of the way for Monday, to be followed by a deep low pressure system moving in from the south west. This moves north east across the country on Tuesday bringing heavy and thundery showers or longer spells of rain and some very strong winds for the south. There is already a yellow warning of thunderstorms for Tuesday for parts of the western side of the UK. Because of the showery nature of the rain, weather apps can be expected to perform poorly with regard to timing and positions of showers, so again it is more reliable to check the radar and the sky to see if it is about to rain. Some places may get quite a lot of rain in a short time, and as there is already very wet ground or flooding in places, this could cause problems.

What happens next depends on which model you look at, as some have the low sticking around, keeping it showery all week, while the GFS has a ridge of high pressure building briefly. As most weather apps use the GFS, it could turn out to be wetter than the apps are forecasting in places. The one thing that is certain (as far as anything can be with regard to the weather) is that although at times it may be warm and humid (blight alerts likely), there will be no return to last week's record breaking temperatures in the near future.

[sandspider]

Thank you.

[Penellype]

As expected we have had a very showery week with flooding in several places. Unfortunately things look like getting worse rather than better, with a stream of low pressure systems moving in off the atlantic. These will bring bands of rain and showers, some of which could be heavy and thundery. At first the south east may miss the worst of the rain, but later in the week it looks likely that a deep (for the time of year) low could move into the south giving previously drier areas a drenching too. Depending on how this low progresses it could become windy as well. The best day of the week looks likely to be Thursday when a brief ridge of high pressure may build, but even so it may not be completely dry.

Keep an eye on the Met Office warnings for the possibility of more flooding as the rain moves in over already saturated or flooded ground. Expect more blight alerts too, although it is likely to get cooler after this evening's storms pass over.

[Penellype]

The Met Office have released warnings for the next few days - thunderstorms in Scotland today and tomorrow, then rain for much of the UK on Friday and thunderstorms for the northern half and wind for the southern half of the UK on Saturday. https://www.metoffice.gov.uk/weather...ce/uk-warnings

The low arriving on Friday into Saturday looks particularly unpleasant for the time of year, so please check that garden furniture and anything else left outside is secure.

[Penellype]

The next week looks like a continuation of the same theme, although it will become noticeably cooler. Showers and bands of rain will never be far away and currently there is the possibility of another deep area of low pressure producing gales and heavy rain next weekend. Not all the models see this and it may not happen, but the generally unsettled pattern looks set in for the week. As always in an Atlantic weather pattern, west is wettest.

Keep an eye on Met Office warnings (there is one today for Scotland) as more rain on already saturated ground could well cause further flooding.

[1Bee]

I'm feeling uncharacteristically smug because for the first time ever I got the onions in before the rains.... ;-)

[sandspider]

I'm guessing that's really the end of summer weather then? Nice to have some rain, but maybe a bit too much recently! And the winds have knocked over a few of my trees...

[Penellype]

It is rather autumnal for the first half of August. However, September can be a very pleasant month with a tendency towards high pressure which can give summer-like weather in the first half of the month. There are a few tentative signs of a change towards the end of the model runs (around the bank holiday possibly), although it is far too far out for any sort of certainty. But don't give up on summer yet. It only takes an ex-hurricane to change everything, although I am not aware of any hurricanes forming at the moment.

[sandspider]

Thanks P. Fingers crossed!

I should probably stop moaning and enjoy whatever weather comes along! I do enjoy the changing of the seasons...

[Penellype]

Very interesting little video from Channel 4 weatherman @liamdutton on Twitter today https://twitter.com/liamdutton/statu...72964802908160 explaining how a typhoon currently heading for Japan may get caught up in the jet stream and change our weather pattern. Seems I was looking too close to home when thinking that an Atlantic hurricane might do the job!

I probably should stress the word "may" - as always with the weather this is by no means a done deal.

[Penellype]

Well, the models are making a real meal of the bank holiday weather. The coming week will start showery and cool in the north, but things will slowly (and I mean slowly) dry up and warm up so that by Friday most places are likely to see a warm and dry day, although the north of Scotland will never really lose the wetter weather.

Saturday will probably be mainly dry but a trough moves in for Sunday, bringing a return to cooler and wetter weather especially in the north. How quickly this happens is up for grabs, with big differences between models.

And then we have Monday. This is the latest run of the GFS model, a chart that would not look out of place in October:



Severe gales and bands of heavy rain would be on the menu.

However the previous run of the GFS produced this for the same time:



This would be showery in the north with more rain over Scotland, and the south would be mostly dry. it would not be particularly windy.

The ECMWF has this for mid day on Monday:



This has a nice ridge of high pressure building from the south and would give a good deal of fine and pleasantly warm weather away from the north of Scotland.

The uncertainty shows in the spread of lines in the ensemble graph, and the rainfall spikes show that it never really dries up as far north as York:



So, as far as bank holiday Monday is concerned, almost anything is possible. Before that, expect more showers, a gradual warm up to a couple of days of more summer like weather (possibly restricted to southern areas, possibly bordering on hot) followed by more showers which could be thundery on Sunday and then just about anything could happen.

[Penellype]

So, it looks like the ECMWF was right and high pressure looks due to hold sway for the bank holiday, although there is still a slight trough on Sunday which could lead to more cloud and possibly showers in places. Temperatures over the holiday could be very warm with high 20s or low 30s possible in the south. Next week looks like a return to lower pressure, with cooler temperatures and return of showers or thunderstorms as the high pulls away into Europe. The timing of this is uncertain and it could begin as early as Tuesday.

[sandspider]

Is it too early Pen to have a guess as to whether it'll be a cold autumn / winter? Weather without technology chap thinks it will be, at the moment at least, but I've found his predictions to be a bit hit and miss...

[Penellype]

Any predictions for further than a few days will be hit and miss, and any long term forecasts should be viewed in terms of probability, not certainty. Think of it this way - if a forecast says there is a 75% probability of a cold winter, then you can expect 1 in 4 of those winters not to be cold. 75% would be regarded as a fairly high probability, so you can see what you are up against with this sort of thing.

Currently the models are struggling to agree on what happens on Monday/Tuesday of next week, so asking for a prediction for Autumn or Winter is clearly going to be tricky. You have to look at the wider picture and use indicators that point towards higher and lower probabilities of a particular outcome. I am not an expert in this and it is too early for some of the indicators (such as the extent of snow cover over Europe in October) to be available.

There are 3 drivers of the weather that I think I might understand enough about to make some sort of comment on their likelihood of a cold or somewhat cold winter (autumn is a tricky season, often affected by hurricane activity and I can't make head or tail of it, sorry). All 3 of these drivers point towards some possibility of cold this winter. NOTE THAT MY UNDERSTANDING AND THE SUMMARIES BELOW ARE VERY BASIC - THERE IS A LOT MORE TO ALL OF THIS THAN I UNDERSTAND. They are:
1. Solar activity - low. We are at solar minimum, and this is thought to increase the likelihood of high pressure over the arctic. We have seen a lot of this over the summer, and I see no reason why this should not continue, as once there it tends to persist for some time. Many of the long term forecasts I have seen for winter retain this "northern blocking".
2. The QBO, which is a measure of the wind direction in various layers of the atmosphere over the equator and changes in a usually predictable way over about 18 months. Currently we are coming out of a westerly QBO and it is expected to become easterly over winter. This has the effect of dampening down the jet stream, leading to less likelihood of atlantic storms (warm, wet and windy weather), and hence a greater probability of cold.
3. ENSO (El Nino) is in a neutral state at the moment and forecast to remain around neutral or possibly weak La Nina. If I understand things correctly (and I may not), weak ENSO states tend to favour colder weather in the UK as far as I can gather, although I am not sure of the strength of the connection.

There are plenty of other drivers and some of them will contradict the above. The most obvious that I can see is a large pool of warm water around the coast of Alaska. This tends to favour high pressure here, which can ramp up the jet stream and bring milder conditions to the UK. Nothing is ever certain with the weather!

My prediction for the winter is about a 60% likelihood of a colder than average winter based on the above, which will increase as we get closer to the time if the high pressure currently resident over Greenland stays where it is.