Penellype's Weather Channel

[Penellype]

Most places are likely to have a pleasant, sunny day today, although there are some showers about in western Scotland. Enjoy it while you can as we are in for a cool and changeable week next week, with low pressure systems bringing wet weather in from the west tomorrow into Tuesday and Thursday into Friday. This is clearly visible on the latest ensemble chart for York:



Things start to get interesting next weekend, which is not yet in the reliable timeframe. There is a clear trend on the GFS ensembles for warmer and drier weather, although not all of the runs agree and there is a fair bit of scatter. This morning's run shows the operational (thick green line) as one of the warmest, so this should be treated with caution. The ECMWF is not in agreement with this and keeps low pressure dominant for the next 10 days, giving a much more changeable longer term outlook.

GFS 23 August:



With the high pressure just to our east this would be warm or even hot and probably sunny (I'm not very good at predicting the positions of miscellaneous fronts on these charts).

ECMWF 23 August:



This is completely different and much more like what we have at the moment with low pressure to the north and the main Azores high well to the south and west of us. This would be changeable and much cooler.

GFS 28 August:



Low pressure is moving back in and this would be cooler and more changeable again.

On the 23rd August GFS chart, just under the (c) bottom left, there is a small circular low pressure. By 28th August this has developed into a full blown hurricane which is lurking off the American coast. This is most unlikely to trouble us, but it will be interesting to see if it develops and if so, where it goes.

[Penellype]

You may have heard that we are going to be hit by hurricane Gert (nicknamed Gertie McGertface on Twitter) at the weekend. As usual the press are making a mountain out of a molehill - yes the remains of what is currently a category 2 hurricane are coming this way, but by the time it has crossed the cool north Atlantic it will be a fairly standard low pressure, currently forecast to pass to the north of Scotland.

As you were...

[Chippy Minton]

You may have heard that we are going to be hit by hurricane Gert (nicknamed Gertie McGertface on Twitter) at the weekend. As usual the press are making a mountain out of a molehill - yes the remains of what is currently a category 2 hurricane are coming this way, but by the time it has crossed the cool north Atlantic it will be a fairly standard low pressure, currently forecast to pass to the north of Scotland.

As you were...

"Earlier on today, apparently, a woman rung the BBC and said she heard there was a hurricane on the way... well, if you're watching, don't worry, there isn't!"

I trust we won't be refering to you as Penellype Fish come next week

[Penellype]

Ahh, but there IS a hurricane on the way - an ex-hurricane. The exact path of it is not completely certain and the models are delaying it a bit.

This is where it is at the moment:



Gert is circled in black.

The GFS wants to bring the remains of the hurricane across Scotland on Monday:



This is an active low pressure with quite a lot of tropical moisture still caught up in it, so it will be warm and quite wet, and breezy. But at 1000mb it is hardly a hurricane.

The ECM wants to delay it until Wednesday, when it is really quite a weak feature:



This would still be quite wet, but not notably windy. It is a week away so outside the "reliable" timeframe.

This uncertainty with the fate of ex-hurricanes is quite normal - they are hard to predict. There are also currently 3 more potential tropical storms/hurricanes forming in the atlantic in what is looking to be developing into a very active hurricane season, so we probably need to get used to this sort of speculation in the coming weeks.

More details of the current positions of Gert and the 3 disturbances here https://www.accuweather.com/en/hurricane/atlantic

[Penellype]

The latest runs of the models are delaying the appearance of ex-hurricane Gert even further, leaving it stuck to our west until possibly Friday. The result of this is that western areas will be quite wet at times, but southern and eastern areas should have a relatively dry week. It won't be completely dry as there will be showers about at times. The first half of the week will become warm and humid, especially in the south, courtesy of the tropical air caught up in Gert.

The bank holiday is proving a nightmare to forecast because of the uncertainties surrounding Gert, but the general trend is towards low pressure rather than the high that was forecast earlier this week.

The latest ensemble forecast for York looks like this:



This shows the rise in temperatures early next week, followed by a fall towards the end of the week as Gert passes to the north of Scotland. There is then a lot of uncertainty and a big spread of temperatures, but if you follow the individual coloured lines they are mainly up and down, indicating the warm and cold sectors of low pressure systems, and this is backed up by the rainfall spikes along the bottom. So it looks like the weather has finally realized that next weekend is a bank holiday and reverted to type, although things could still change.

[Potstubsdustbins]

Thanks Pen guess I'll be taking my brolly to the bank holiday barbi, much as usual then.

[Potstubsdustbins]

Just received a long range forecast. Its going to be a bad winter this year! Forecaster SWMBO, why because we are due one.

God help me if it comes to pass after the comments I made.

[Penellype]

Just received a long range forecast. Its going to be a bad winter this year! Forecaster SWMBO, why because we are due one.

God help me if it comes to pass after the comments I made.

There are good reasons why warmer and colder winters come in cycles, and why we are "due" a cold one soon. Various long term natural variations tend to have regular or fairly regular osscillations, and when they combine together in particular phases they do affect our weather quite a lot. The absolute extreme, when everything is exactly right, gives you an ice age. We are not (yet) heading into one of those.

This year we are heading towards solar minimum, in which the number of sun spots decreases down to near zero. This is an 11 year cycle and the theory is that low solar activity (and hence low numbers of sun spots) can lead to an increase in the risk of northern blocking, which if it is in the right place, can lead to a cold winter here. Cold winters tend to coincide with the phase where we are coming out of solar minimum (as in 2008, 2009, 2010) and we haven't quite got there yet. Give this one another couple of years.

Another supposedly "reliable" osscillation which can affect our winters is the QBO. This one is to do with the upper level winds over the equator or thereabouts, which tend to flip every 16-18 months from west to east and then back again 16-18 months later. You therefore get a year and a bit of westerly, then an easterly phase and so on. When the QBO is westerly it tends to strengthen the jet stream, which in turn tends to give us milder and wetter winters. Easterly QBO tends to weaken the jet stream making northern blocking more likely. Again, if it is in the right place, this can give us a colder winter. The QBO was supposed to go easterly for last winter, but did an about turn, giving us another westerly winter (this has never happened before in the records of the QBO which go back to the 1950s I think). It is now firmly heading for an easterly phase.

There are other cycles and drivers which are too complex for me to begin to understand. The sea surface temperatures have a lot to do with how easily storms form both in the summer (hurricane season) and in the north atlantic in the winter. I'm no expert, but the weather forecasters mention something called a tripole, where the atlantic is warm in the north, cold in the middle and warm around the equator as favouring a colder winter. To my eyes it looks to me as though the atlantic (which has been cold in the north and warm around the equator for some time) is starting to line itself up into a tripole, with noticable warming around Greenland. However last time I remember the forecasters getting excited about a tripole was 2014, and that was a warm winter. Of course the pacific also has an effect on the weather, but I'm not at all sure what it is.

The current long range forecast models that I have seen are favouring a warm, wet and windy winter, but at this range that is in the realms of a complete guess. My complete guess, at present, is a mixed bag, with some warm, wet and windy periods and some colder interludes, with the possibility of something a bit colder than we managed last year at some point. I don't think we are heading for a repeat of the sort of conditions we had in December 2010 (famous last words).

[Jay22]

So just weather then Penellype?

[Penellype]

So just weather then Penellype?

That's all you can really forecast at this range. I do think though that after a run of 4 really very mild winters, this time we are likely to get something colder at least for a time, even if the winter as a whole comes out on the milder side.

[Jay22]

Sorry I wasn't being facetious there Penellype, I just meant that in this country it just seems to be weather we get now rather than four distinct seasons! Always love a cold winter but as you say it's been a few years since the last one in 2010!
I always look to the Rowan trees, probably a load of rubbish but I think if they have loads, and I mean loads, of berries on it's going to be a harsh winter.

[Jimmy]

Whew temperature in Preston shot up.
Jimmy

[Penellype]

Yes, we are currently in the warm and humid air sucked up from the tropics by hurricane Gert. Expect the temperature to fall back just as suddenly some time tonight or tomorrow depending on where you are, probably with accompanying rain and possibly thunder.

[vixylix]

^^^ We have had all of the above today, and a blight warning too for good measure!

[Deano's "Diggin It"]

But they are forecasting a good weekend, which will be a novelty it being a "Bank Holiday"