Penellype's Weather Channel

[Penellype]

Yellow warnings of wind and rain for northern and western areas tomorrow.

[chillithyme]

It has been very windy, my pots have fallen and broken. It is not as windy here as it is for for others in the north and west, hope that its not too bad for every body else.

[Penellype]

Sorry to hear about your pots, chillithyme. A slight lull in the wind today, but breezy again tomorrow and potentially very windy again on Saturday. More rain and some cold nights likely too for the next week or so at least. Snow can't be ruled out on higher ground in the north.

[chillithyme]

Thanks Penellype. There was a bitterly cold wind late morning, but it warmed up by the time I went back out again. I don't mind the cold, its the wind that hurts

[Penellype]

Plenty of warnings over the next few days for fog, ice, wind and rain. Keep an eye on them here: https://www.metoffice.gov.uk/weather...ate=2019-12-17

[Penellype]

Still plenty of rain around, particularly in the south with associated warnings until Sunday.

The picture at and after Christmas is still very confused with uncertainties about the position of high pressure resulting in huge differences in forecast temperatures. Christmas itself looks likely to be cool, and probably mainly dry, but what happens next is anyone's guess:



One thing that is becoming clear is that there are fewer rainfall spikes, so some relief from the deluge is hopefully on the way.

Notice the difference in rain amounts forecast for York between individual ensemble members even for today - this is because York is right on the edge of a rain band to the east and very small differences in the position of this would make big differences to the amount of rain.

[Penellype]

Yellow warning of thunderstorms for parts of the south west tomorrow. Yes, you did read that right, thunderstorms.

[Penellype]

After what has seemed like almost incessant rain since mid summer, things should get a chance to dry out a bit in the next week or so as there is little rain forecast away from north and west Scotland, and perhaps parts of the south around New Years Eve. High pressure is moving in and looks like hanging around for a while.

Don't expect bags of warm sunshine. The upper air is mild, almost warm, but at this time of year high pressure often brings one of two things - a lot of cloud or frosty nights and possibly fog. The upper air temperature is often masked by an "inversion" where it is colder at the surface causing water to condense out of moist air. The current high is likely to be mostly cloudy, with the air coming over a long sea track from the Azores, meaning it will pick up plenty of moisture. It will be mild though, with temperatures reaching double figures at times. If skies do clear overnight frosts are possible as the heat can radiate away very quickly during long clear nights.

[Penellype]

Perfect example of a temperature inversion today. The upper air temperature is around 5 degrees:



But at ground level it is much colder:



There is almost no wind to mix up the air and it is taking the weak winter sun a long time to lift the temperatures above freezing.

A cold front moves in by the weekend, hence the sudden drop in upper air temperatures. This will mean it will get colder at the surface, but because the rise in upper air temperatures next week is associated with high pressure and light winds, it is likely to stay cold with night frosts under another inversion.

[sandspider]

Thanks for your efforts Pen, and happy new year! (And to all ��)

Just wondering, is it too early to predict (or have a guess!) what the rest of winter will be like? The weather without technology chap predicted a long, cold winter, but so far, for us in South Wales at least, it's been wet but pretty mild. Just wondering if there might be a serious cold spell to come? I appreciate it's not easy to forecast, especially a long time in advance...

[Penellype]

Long range forecasting is (at present at least) the next best thing to impossible. All you can really do is look at the overall situation and basic "drivers" - the sun, oceans and regular cycles such as the QBO and try to predict what is most likely to happen. Sometimes one particular factor overrides all else, such as a very strong el nino (which we don't have at the moment).

Most of the drivers for this winter favour cold, and many of the professional forecasters went for a cold or cold at times winter. All the long range models have stuck fast to warm, wet and windy. So far the models are more right than the apparent influence of the drivers, which I attribute (possibly wrongly) to 2 factors - a warm pool of water to the south of Alaska, which tends to fire up the jet stream, and a very strong Indian ocean dipole (differences in pressure between the east and west of the Indian Ocean, I think). This has been mentioned several times by people who know much more than I do as a reason for the mild and up to now wet weather and has also been blamed for the incredibly hot conditions in Australia.

The warm pool of water south of Alaska does not appear to be going anywhere fast and is therefore likely to keep influencing the jet stream. However I think the Indian ocean dipole is now weakening. What effect this has remains to be seen, but we do recently seem to have moved into a different pattern of high pressure and likely colder and drier weather. Even the short term models are not agreeing on where we go from here - some have the westerly driven low pressure (warm wet and windy) regime coming back, others put the high over the top of us (cold and dry), or to the east (warmer and dry) or to the north east (very cold and dry). There is also the possibility of a sudden stratospheric warming which might happen later in the winter and could lead to colder conditions later on. Currently there is little sign of anything strong enough to break the hold of the strong polar vortex that we have at the moment.

My take on it, for what its worth, is that January will at least start drier than we have had in the last few months, and fairly cold under high pressure (Scotland is likely to be warmer). I suspect the low pressure will try to break through at times, but may have problems shifting the high. I would be surprised if we go the whole winter without a cold spell, although the longer range models seem to imply that we could. If this sounds like hedging my bets, its because everything is up for grabs. Winter may be 1/3 of the way through, but where it goes from here is far from clear.

[sandspider]

Thanks P, makes sense. I'll batten down the hatches to be on the safe side!

[Penellype]

The models have changed their tune a bit about the cold air behind the front, which is moving through the country today. It is much less cold than previously predicted and frosts (away from high ground in the north) are now less likely.

It is also looking wetter and windier next week, which means that it will be warmer - in fact it could be very warm for the time of year at times, with much more influence from low pressure than was expected last time I posted. it doesn't at this stage look like a return of the deluge, but bands of rain will move across the country at times, especially in the north. There is currently no sign of any significant cold in the first half of January.

This illustrates well how difficult longer term forecasting is. Just 2 days ago I predicted the first half of January (the supposedly easiest bit) to be fairly cold, and now it looks mild to very mild!

[Thelma Sanders]

I've given up with the forecasts for more than a day or 2 ahead - it all looks nailed on, and then whoops everything has changed, and often to the complete opposite
I really don't know how they can pretend to know much at all about it tbh

[Chippy Minton]

I predict a mild winter. Based on having 3.5 bags of grit salt for the drive. Whenever I have a surplus it's a mild winter, the year we didn't replenish stocks - Beast from the East. We were snowed in for a good 18 hours.

I personally find it fascinating that we should even anticipate being able to predict the weather beyond what we can see coming and how that may play out. The atmosphere is such a complex system, interacting with land and sea masses and taking and losing energy from and to space and air and land and sea. All sitting on a spinning globe in 3 dimensions. Chaos ensues, we can predict the chaos at a large level but the chances of predicting what will happen in any one tiny spec of land is highly unlikely.

Or to put it another way:
Just, remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour
That's orbiting at nineteen miles a second, so it's reckoned
A sun that is the source of all our power

Keep up the good work Pen, it's really useful to see the forecasts and make some assumptions about what needs opening up, closing down, protecting, watering, etc!