Penellype's Weather Channel 2

[Plot70]

The ground began to thaw on the surface on my plot. It was very slippery to walk on.
It has now dropped below freezing again. It may be a bit awkward for a few hours before turning fully to mud.

[Bren In Pots]

Thanks Pen, yesterday evening it rained so the last of our snow disappeared, this morning its very frosty and icy out.

[Nicos]

Spot on as usual Pen. We hit -11.7C last night and now we have fine drizzle.
Everywhere has gone from crisp and white to green and crusty slush

[Bren In Pots]

We’ve got black ice here it’s not very good out on the roads so I’m happy to be home.

[sandspider]

Endless rain here, but not too cold. Looks like the forecast remains changeable, but leaning towards mild for the time of year... Unless Penellype thinks differently!

[Penellype]

Endless rain here, but not too cold. Looks like the forecast remains changeable, but leaning towards mild for the time of year... Unless Penellype thinks differently!

Mild for the moment but signs of a possible change next week to somewhat colder conditions, although not a "big freeze". I think it likely that we will see a continuation of the unsettled and rather wet pattern, with intermittent colder snaps as the jet stream moves a little further south and the wind turns into the north as lows move away to the east.

[sandspider]

Thank you. Time to top up the heating oil, perhaps!

[Penellype]

The models are now firming up on a 4-5 day cold snap starting on Sunday night, with the possibility of snow in places.

[Nicos]

Thanks for that Pen. I was planning to do my big food shop on Monday, so I’ll shift it to Friday.
I’ll grab my chances now too for a bit more weeding before it’s ‘frost bite’ time again

[Nicos]

Hey Pen,..any updates? or is it just just more of in and out of cold snaps for now?

[Penellype]

The current situation is that we have high pressure through the country with the wind coming from the west in the north and from the east in the south, producing the bizarre situation where Scotland has been rather a lot warmer than southern England. A cold front is currently moving south bringing with it patchy rain and milder temperatures for a while before clearer, colder air moves in behind it. This appears to be clearing southern Scotland at lunchtime today. The chilly air sticks around for the weekend as the high pressure continues to give mostly dry weather with light winds. There is the potential for frost, fog and cloud, although some places could see plenty of sunshine (I find the difference very hard to forecast). On Monday some colder air plunges down from the north, and some models have us included while others keep the cold to our east. Even if we do go cold, it doesn't look like it will last very long as the atlantic is becoming more active and looks very likely to start bringing in more changeable and at times wet and windy weather from the west. Depending on how far south the lows go this will either be typically mild, or possibly quite cold with some wintery potential. The models can't make up their minds.

Further ahead is even more uncertain. At present there is an ongoing warming in the stratosphere over the arctic, but this is not a straightforward sudden stratospheric warming (SSW) as for some reason the cold polar vortex does not seem to be going to completely collapse. The affects of these things on the weather are extremely hard to predict at the best of times although an SSW can lead to cold weather a few weeks later (think of March 2013 or the 2018 beast from the east), but this does not always happen. I don't remember seeing anything quite like what is happening at the moment before so it isn't particularly surprising that the models are finding it hard to forecast. I'm going to file this in the "too difficult" tray for the moment!

[Nicos]

Ha!…thanks for that Pen. Your time spent explaining is always appreciated x

[sandspider]

Are you able to forecast / hazard an informed guess when things may warm up permanently, and the frosts go away, Pen?

Thanks!

[Penellype]

Are you able to forecast / hazard an informed guess when things may warm up permanently, and the frosts go away, Pen?

Thanks!

Not really. It is still winter, and you need to remember that spring is much more likely to be cold and frosty than autumn. The current mid range forecasts (into early March) are very uncertain due to ongoing events in the stratosphere. At this time of year strong waves in the upper atmosphere can cause the temperature over the north pole to rise quickly, in what is known as a sudden stratospheric warming (SSW). This displaces the cold polar vortex, disrupting and reversing the normally westerly winds up there. Sometimes when this happens the disruption propagates down into the troposphere (where weather happens) and this can cause high pressure to develop or migrate towards the arctic. This can happen a few weeks after the SSW. Depending on the position of the high, if it does this, the result can sometimes be cold weather into spring. This is what happened in 2018 with the "beast from the east".

It is important to notice the presence of the words sometimes, can, depending on and if in the above explanation of a SSW and its possible effects. It is often the case that a SSW does not result in cold weather here, but it does increase the chances of it happening.

All current weather models are indicating that after a couple of "failed" attempts, there is going to be a SSW around 16th February. There is therefore a huge amount of uncertainty from around the beginning of March onwards, with some of the models apparently picking up on the SSW and showing high pressure migrating north. It is much too soon to tell what effect, if any, this will have on the weather here.

In general, if you want to be safe and avoid frosts in the vast majority of years, unless you live on the coast or in a built up area (which is warmer) it is safest to leave planting out tender plants until May. That is far too far ahead for anything other than a guess from the position in mid February.

[sandspider]

Thank you, interesting and informative. I don't plan any planting out yet, but would like to prune my orchard...