Penellype's Weather Channel

[Jungle Jane]

I was driving this morning between 10-11am & we had a tiny bit of snow,it was only two wipes of the windscreen worth didn’t last long,very fine & small pieces it wasn’t rain & it was 6 degrees,only lasted about thirty seconds. The wind here is freezing cold,lovely sunshine though

[Gillykat]

I clocked the weather warning and immediately logged in to the vine to check this thread...

Me too!

[Chippy Minton]

The good lady wife has been promised snow. Now they're back-tracking. There will be heck to pay is SWMBO doesn't get snow........

[Penellype]

Snow is always very tricky to forecast as about 5 things have to be just right in order for it to happen. This really is a very finely balanced situation, and I think the met office are playing it safe by warning of the worst case scenario, which could be really quite nasty - blizzards, particularly on hills as well as possible freezing rain, which is very dangerous indeed. It also needs to be remembered that the warnings take into account the likely severity not just of the weather but of the impacts, and this weekend is one of the busiest shopping times of the year.

The latest run of the high resolution Arpege model is still showing quite a bit of snow for Saturday afternoon/evening:





Charts from https://www.theweatheroutlook.com/tw...=Precip%20type

There is still plenty of time for this to change though.

[Penellype]

Most of the country is now covered with warnings, yellow for snow, ice, wind and rain and amber for snow (Scotland) and ice (much of southern Scotland and northern England). The ice warning is significant - freezing rain is forecast.

Freezing rain occurs when rain from upper temperatures that are above freezing falls onto surfaces which are below freezing, and freezes on contact. The result looks like wet ground, but is extremely slippery black ice, hard to stand up on and impossible to drive on. Please take extreme care if you have to go out tomorrow or Sunday and the ground appears to be wet.

[Penellype]

The Met Office have named today's storm Dierdre, which is probably no surprise because of all the warnings. In amongst all the talk of snow and freezing rain the prospect of strong winds has been somewhat ignored. Some of the models are forecasting a sting jet developing off the coast of south Wales this afternoon, moving rapidly north east overnight, weakening as it does so. This is a small area of intense wind which occurs in rapidly developing low pressure systems where there is a disconnect between the warm and cold fronts which seems to allow the air to plummet downwards in huge gusts. If you live in the area between south Wales and Newcastle, be prepared for some very strong and sudden gusts of wind later today, particularly along the coasts of Wales.

The Arpege model forecast, with the sting jet outlined in black:

[bikermike]

we didn't have snow, but were at the Epping&Ongar railway for a santa special and it was freeeezing. some slightly lumpy rain.

we had a cracking pub lunch too, but that's not really weather-related...

[Gillykat]

Very brief few flakes of sleety-snow at 7pm on Saturday night but otherwise just very very windy and wet.

Same today - wet & windy

[Penellype]

A very wet day for much of England and Wales today. After this, with a bit of luck, the rain should move away (this may take some time to clear the south) and high pressure should build to give a mainly dry week. Upper air temperatures are warm, but high pressure doesn't always mean warm on the surface at this time of year. There are 2 possibilities (or a mixture of both) - clear skies with frosty nights (and a possibility of fog) or cloudy skies but milder temperatures. Forecasts predicting bright sunshine may in fact denote foggy days, and forecasts predicting cloudy but dry may result in drizzle.

This morning's GFS ensemble shows today's rain and the transition to drier weather, and the warm upper air temperatures. Towards the end of the ensemble some members show a change to colder conditions, but this is a long way off for now.



You may have heard talk of a "sudden stratospheric warming" (SSW) which is currently taking place. This is similar to what happened in January last year leading to the beast from the east cold spell. There is a tendency for these warmings to lead to high pressure over the polar region a few weeks later, but they do not always result in cold weather for us. As is always the case with the weather, the exact positioning of high and low pressure systems will determine the source of the air that we get, and this will determine the weather. It is far, far too early to be making predictions about cold weather resulting from the SSW just yet, but the probability of a very cold spell later in the winter has to be greater now than it would have been without the SSW. We shall see.

[lottie dolly]

Thankyou Pen for our forecasts,much apreciated

[Penellype]

Yellow warning of fog tonight and tomorrow for much of England https://www.metoffice.gov.uk/public/weather/warnings.

Please take care if you are travelling and stay safe.

[Penellype]

Happy New Year all!

A cold front is moving south today with colder, clearer air behind it but very little rain. Nights will be colder with frost much more likely and fog a possibility too.

High pressure is going to stick around for at least the next week, possibly rather longer. This means little or no rain:



The colder upper air temperatures are clear to see, but don't be fooled by the rise over the weekend, as this won't be reflected on the surface. The warm upper air will move over the top of the colder surface air, resulting in an inversion, which will probably simply trap cloud and chilly air underneath it.

Longer term there is huge uncertainty with the GFS wanting to keep high pressure in almost the same place by day 10:



while the ECMWF moves the high to Scandinavia by day 10, pulling in colder air from the east:



This is not a "beast from the east" scenario (yet) as the air is coming from a south easterly source, but it could easily evolve into a much colder pattern without much adjustment.

This is only one run and one solution, and simply serves to illustrate the differences between the models and consequently the uncertainty in the forecasts. Yesterday's ECMWF run had the high moving closer to Greenland (also a cold solution), while the GFS was keener to let the atlantic lows bring milder, wet and windy weather this way shortly after day 10.

The message is to take any forecasts beyond about 5-7 days with a pinch of salt, and any attention-grabbing newspaper headlines as pure speculation, but expect it to feel rather colder than recently for at least a week.

[Chippy Minton]

Just been watching the racing from Cheltenham (as I am still struck down with the Lurgy). One of the owners made a very interesting observation. She mentioned that the drought had lasted well into November and interrupted her racing season . However she also made a throw away comment about there being no (substantial) rain in the forecast for 2 months (unless I heard wrong). I thought it interesting that we tend not to talk about dry winters, cold yes, windy yes, wet even, but dry no. Looking at the ensembles there is limited precipitation, which if it persists, could be interesting on the back of a very dry summer.

Living in the north west though I do find it difficult to comprehend of "dry" It's all relative I guess

[Penellype]

Sorry Chippy Minton, only just seen your post.

As with most weather-related things, "dry" is a relative term. Measurements are compared with the average and amounts of rain can vary tremendously over short distances. In general it has been a drier than average year with much of the rain falling in the spring and most of the summer rain being from showers and storms that were localized and sometimes torrential. Therefore, where I am we have had around average rainfall total for the year, fields are standing in water in places (although this is slowly disappearing) and yet the Met Office anomaly maps for 2018 show that for Yorkshire every single month this year has been drier than average, many notably so. Yorkshire Water are worried about the reservoir levels. This is difficult to understand when the allotment was under 4 inches of water at the end of July and the soil surface has not dried out since. Torrential local downpours do nothing to fill reservoirs unless they are upstream of them.

Currently we are under a strong ridge of high pressure, which means basically dry. For York that often means not quite dry as we tend to get showers coming in off the North Sea with some orientations of the high pressure. The next week or so looks pretty dry away from Scotland and the north west, where there will be more in the way of rain as low pressure systems skirt round the top of the high. There may be a little light rain elsewhere from associated fronts, but for the time of year it is very dry.

The models want to bring low pressure back at some point around or after next weekend, although they keep pushing this back. Everything is very uncertain because nobody really knows the effect of the sudden stratospheric warming yet, so virtually anything could happen after this. The general consensus is that things are likely to get colder but whether we get a prolonged cold spell or just short cold snaps with milder interludes is up for grabs at present. Cold air holds less moisture than mild air, so the likelihood is that we will continue with the drier than average theme for a while yet.

[Penellype]

I haven't done a weather post for a bit because I've been waiting for some sort of agreement between the models. That does not seem to be forthcoming, but I thought I'd better post something!

Currently it is fairly mild for January, and that will continue for the next couple of days with the wind coming from a westerly direction. Around Wednesday the high pressure that has been around since Christmas will start to slip away to the south. As it does so a cold front moves south through the country introducing a colder, northerly wind. Nothing drastic, just a colder feel, with rain and potentially snow over hills in the northern half of the country. It's after this that the fun starts.

A brief ridge of high pressure builds on Thursday, within cold air, making Thursday a colder day. The high is under attack from low pressure to the west, but the models differ significantly as to how this plays out.

The GFS wants to bring the low in fairly quickly on Friday, with rain preceded by a little snow on the leading edge. After a chilly weekend, milder air essentially wins the battle and we are off into a series of lows and highs, with rain bands interspersed with brighter and showery weather, sometimes windy or possibly stormy later.

The ECMWF is not having that at all. The high pressure from Thursday sticks stubbornly over us, giving colder days and nights with frost, but probably mainly dry. Eventually the atlantic breaks through in the middle of next week (on this morning's run), with what looks like a very strong storm which could well start with a real dumping of snow.

Neither of these is a "beast from the east" scenario, contrary to what the papers would have us believe. However there are signs in the unreliable extended timeframe of the shorter term models that high pressure may be starting to build to the north, which would bring colder weather this way. This agrees with the longer term models such as the CFS, which have consistently been predicting "northern blocking" for February (and March and April) for some time now. This is not unexpected after a sudden stratospheric warming, and we will just have to wait and see how things pan out. I am working on the assumption that a possibly fairly lengthy cold spell is more likely than not, as this seems the safest policy this year.