Penellype's Weather Channel 2

[Nicos]

Thanks for the heads up Pen…I thought we were forecast 8-11C this week but I just checked on a couple of french sites and it looks like 5C is a potential for our area…and given we’re in a small frost pocket
Really appreciate this heads up as I probably would have missed having the potential for frost.
Will get the fleeces out for the outdoor tomatoes and cucs.

[Bren In Pots]

Thanks Pen, I'm down to have overnight lows of 7 to 8c.

[Penellype]

Some chillier nights coming up as the remains of hurricane Lee move away, bringing in air from a more northerly origin. Expect single figure temperatures from tonight until Sunday, with Friday night looking the coldest at present - these are the forecast minimum temperatures at 6am on Saturday from the high resolution Met Office UKV model:



Worth keeping an eye on.

[Penellype]

Thanks Pen, appreciate the thoughts as ever! I now hear tell there may be a warm spell in early October, but we shall see...

Too far ahead to forecast that sort of thing, especially at this time of year when an ex-hurricane can change the pattern very suddenly, as happened with Franklin, and is happening now with Lee and Margot - Lee in particular is fuelling a stronger jet stream. The current pattern looks unsettled for the next couple of weeks, which is as far as the short term models go, but even that is subject to sudden change.

[sandspider]

Thanks Pen, appreciate the thoughts as ever! I now hear tell there may be a warm spell in early October, but we shall see...

[Bren In Pots]

Thanks for the weather update Pen.

[Snoop Puss]

Thanks, Penellype. Always good to read your views despite the long-term uncertainties you point to.

[Nicos]

Interesting info there Pen - thanks for that.

[Penellype]

Well, Autumn is here now it seems. Expectations seems to be for a fairly cold winter. What do you think, Penellype? A quick summary is fine if you like, I trust your reasoning!
Thank you.

It is far too early to make any firm predictions about winter, although a few of the basic drivers are known. We know that the QBO, which is an important part of the mix, is going to be in its easterly phase, which works to dampen the prevailing westerly winds which hold the polar vortex over the arctic, which in turn can allow colder air to escape south. If that cold air comes in our direction it can give us a cold winter, but it can equally go south elsewhere. We know that this winter will be an El Nino winter, but we don't yet know how strong the El Nino will be or where the focus of the heat will be. As I understand it if the heat is focussed in the central Pacific this can lead to a cold winter here, but I'm not sure how strong this influence is, and at the moment the hotter water is to the eastern side, near Peru.

Unusually in an El Nino year we appear to be having a big hurricane season in the Atlantic, and this is already showing signs of increasing higher pressure over the north pole. If this tendency continues this could lead to a colder winter, again depending on where the cold air goes. There is time for this pattern to change before winter.

All of the above could be why you have heard that a colder winter is expected, and certainly some of the few model runs I have seen do hint at this possibility. However, they are little more than a guess at this time of year and there are other factors that point more towards a warmer winter. The sun is approaching solar maximum, while solar minimum is linked more to colder winters. The Atlantic is very warm indeed and this tends to increase the power of the low pressure systems, both fuelling their energy (lower pressure, stronger winds) and increasing their water content, which seems likely to lead to a wet and stormy remainder of autumn and this may well continue into winter. Stormy winters are usually mild or very mild. We are also having a very warm (possibly record breaking) September and there is considerable evidence that warm Septembers do not lead to cold winters.

In addition to this we have very warm global temperatures, with the year as a whole more likely than not to break the 1.5C above pre-industrial temperatures mark for the first time. How this will affect our winter is unknown. My instinctive feeling is that winter is likely to be wet and stormy at times, but this may be interspersed with colder periods, if high pressure in the arctic sets up in the right place, where it could be strong enough to block the storms from reaching us. There are plenty of factors that are not yet known, such as how the pressure patterns behave during the remainder of Autumn, and how much energy from the tropics is transported to the arctic via hurricanes. The development of the El Nino may be important and I have no idea how the MJO is expected to behave or even if it can be forecasted this far ahead or what its effects will be.

Sorry for all the uncertainties, but weather forecasting beyond about 5 days is always full of uncertainties.

[sandspider]

Well, Autumn is here now it seems. Expectations seems to be for a fairly cold winter. What do you think, Penellype? A quick summary is fine if you like, I trust your reasoning!
Thank you.

[Nicos]

Thanks for the heads up Pen.
I had noted that for the next 3 nights we are due 10,9 and then 8C and had thought about throwing fleece at least over the peppers and chillies.

[Penellype]

A couple of potentially quite chilly nights (mid single figures) tonight and tomorrow, particularly in the west, but cool for the time of year everywhere. While protecting outdoor plants is probably not possible, it might be a thought to consider closing greenhouse and poytunnel doors in the evenings to keep the daytime heat in as much as possible.

[Bren In Pots]

Thanks Pen.

[Penellype]

Head up for some strong winds over the weekend, accompanied by heavy rain. Yellow wind warnings have been issued for much of the southern half of the country in the west on Friday and the east on Saturday.

Check garden furniture etc is secure, and be prepared to shut greenhouse doors if they face the wind direction.

[Nicos]

Wow - very interesting, thanks Pen.