Penellype's Weather Channel

[Penellype]

Couple of things to update this morning.

The 2nd low due to arrive on Christmas Day has been named storm Conor and an amber warning of wind has been issued for northern Scotland.

This morning winds are already gusting at around 70mph on the west coasts of Scotland and Ireland:



Note that the figure of 112 is over Cairngorm and the 80s and 90s are also mountain readings - but it is this sort of thing that will be quoted on news bulletins and in the papers. You can find these maps at Weather Online UK - current weather and weather forecast worldwide > Current Weather > United Kingdom > Peak Gusts.

Also of interest is the trailing cold front, currently over Ireland. This is showing signs of developing squall lines:



These narrow areas of intense rain and gusty winds come and go and can form much bigger lines than these. They can also harbour funnel clouds, which become tornadoes if they touch the ground. Some of the weathermen are saying funnel clouds are likely in association with today's cold front.

If you are going out today, keep an eye on the radar and pay attention to any narrow lines of heavy rain. If they are coming your way, take cover!

The edited picture hasn't come out very big. Here is a close-up of the southernmost of the 2 squall lines circled above:

[BUFFS]

we have the wind and rain now and the gales are getting stronger as the day goes on so it will get interesting about late evening/bedtime til dawn....

[Penellype]

Good luck Buffs - hope everything stays put!

[Penellype]

Squall line looking much more developed now:



Image from Will it Rain Today? | Rain radar for the UK | Going to rain? | MeteoGroup

Update - just hit us here at 16.05 - like a jet washer against the window!

[Penellype]

So, the stormy forecasts for Christmas were correct in that northern Scotland had gales and the rest of us had varying degrees of gusty winds, not at all bad further south. Everywhere started very warm - the maximum temperature of 15.1C made it the joint 2nd warmest Christmas Day on record. One of the places that saw 15.1 degrees was Dyce on the east coast of Scotland. Bizarrely it was also a white Christmas in Scotland with a cold front moving south during the day, introducing much colder, showery weather, the showers falling as snow over the highlands by the end of the day. I wonder if a near record high and a white Christmas have both ever happened on the same day in Scotland before - I have no idea, but it certainly seems strange.

Today is another windy day with gales in the far north as storm Conor moves away east. Scotland is again seeing wintery showers, but further south it is mostly sunny and much colder than yesterday as a ridge of high pressure builds towards Iceland. This will move over the top of us for the next few days, giving lighter winds and a return to probable frost and fog. This is the same situation as we had before Christmas with relatively warm upper air temperatures but colder conditions at the surface due to lack of wind to mix the layers of air:



As we move towards new year agreement between the models is good that the high pressure flattens off and another ridge builds further west towards Greenland, bringing in colder winds from the north. We are likely to feel somewhat warmer as the ridge flattens out, then colder again by New Year:



As always confidence in the models drops the further away you go, and it is not clear what will happen next. The current run has the high collapsing over the top of us bringing us back to "square 1":



However by this point there is a lot of scatter on the ensemble graph, with some of the runs going really quite cold while others bring back the rainfall implying a more westerly pattern:



So far this winter is panning out much as expected with alternating periods of warmer and colder weather as we remain in the "battleground" between the warmer atlantic air and the colder continental air. The real cold is not that far away and it would not take a huge shift to plunge us into something much colder. The models keep playing with this idea, which is probably where the papers get their scare stories from, but so far the position of the jet stream has mostly kept us relatively mild overall. My untrained and amateurish interpretation of what I see at the moment is a continuation of a similar pattern. There is no real indication of a sustained flip to stormy atlantic weather, with the high pressure seeming to want to return and block it off after a few days. The setup also doesn't seem to be quite right for a change to prolonged very cold weather, although there is still plenty of time for that to happen. As always it is a case of wait and see.

[Penellype]

Snowmageddon scare stories likely to be around again today after an extraordinary GFS run at 6am this morning. This puts us firmly into the freezer in the 2nd week of January:



This would give blizzard conditions, and the model follows this with the high pressure moving north to bring in exceptionally cold air from the east. By 6am on Fri 13th January the MAX temperatures look like this:



Looking at the ensemble chart you can see that the thick green line that these charts represent is a cold "outlier":



The midday run is quite different:



This gives a chart for 8th January that looks like this:



Still cold, but no blizzard, and the high is collapsing down over us rather than moving north to put us into the freezer.

As usual 8th January is far too far ahead for predictions, but this situation certainly needs keeping an eye on.

In the more sensible time range the current frosty and foggy conditions that many places are having are likely to give way to breezier, warmer and cloudier weather by Saturday, followed by a change to colder weather behind rain from a cold front on Sunday. There is a possibility that the cold front may grind to a halt over the south, with the rain turning to snow for a while. There may also be snow showers on northern and eastern coasts on Sunday and Monday (note the rainfall spikes on the ensemble charts above, which as usual are for York).

[Penellype]

If only the weather was as predictable as the papers!
January 2017 weather: Heavy SNOW to hit in days as UK faces four-week -15C ARCTIC FREEZE | Weather | News | Daily Express

Ok, its going to get colder on Sunday, and shock, horror, it may even snow. It is winter after all. The wind will turn into the north behind a cold front, snow is likely over high ground and it is possible that it may snow for a while in the south if the cold front stalls. Snow showers are likely into Monday in Scotland and on north sea facing coasts and some may make their way inland.

By Tuesday any showers should turn to rain and fade as high pressure topples over the country and we revert to the familiar frost and fog routine before another cold front brings a repeat performance towards next weekend.

Beyond that it is not possible to say what will happen at the moment. Most of the forecasters seem to agree that some sort of cold spell is possible. Cold seems more likely than warm, and some of the models have occasionally gone for very cold, but there is a lot of disagreement at present, and some of the runs even go for milder and stormy conditions. To forecast freezing rain at this distance is impossible (its hard enough at a few hours notice). To call it a crisis and compare it to 2010 is totally irresponsible. So is crying "wolf" every time the models hint that the temperature might drop below freezing. What happens when (not if) we do eventually get some very cold weather, as does happen occasionally in the UK? Will anyone take any notice then? Grrrrr.

A sensible and interesting look at the current model outputs here:
http://www.theweatheroutlook.com/two...r+-+HEADS+UP+2

[Thelma Sanders]

I've been following it on Netweather - looks interesting specially to all the 'coldies'.
The GFS does look very cold for Europe, whether (lol) it will come our way or not, we just don't know yet!

[Penellype]

Models having a major wobble today regarding the cold later next week. Far too soon to write anything off, but the recent trend is to develop more of a westerly pattern rather than a cold northerly or easterly one. Big disagreements between individual members of the ensemble with some still going very cold and others fairly mild.



Note that the average of all the members (white line) is now above the 30 year average (red line). This is the GFS model, but the ECMWF ensemble is having similar problems finding a solution. The longer range CFS model is still showing a cold pattern for much of January.

All very interesting, but we will have to wait and see what happens in reality.

Meanwhile it will still turn colder over the next few days, with snow still a possibility in places as outlined in my previous post.

[Penellype]

Well, the models have now pretty much thrown the idea of a serious cold spell at the end of this week out of the window.



The northerly winds that are responsible for the current colder conditions turn more westerly through tomorrow, before turning back to the north briefly through Thursday. The high then collapses over us again on Friday along with some fronts associated with a low further north (hence the rainfall spikes). The cold air is well to the east, being sucked down into Italy and Greece as the upper air temperatures for Saturday show:



After this there is a lot of scatter highlighting the uncertainty about what happens next. Several forecasts that I have seen have gone for a colder 2nd half to January, and certainly the cold runs do seem to come back towards the end of the ensemble graph. However I'm not convinced.

In the first post on this thread I mentioned that several factors were set up very differently from last year, and one of these was the polar vortex, which was split and very weak. This is no longer the case - the temperature over the pole has fallen rapidly over the last week or so and the polar vortex is now quite strong:



These are the temperatures at 10hpa, high in the upper atmosphere. The purple colours indicating -80 or -85 are now comparable with those at this height last winter. This favours a stronger, less wavy jet stream and a more westerly, stormy weather pattern, although it can take 2-4 weeks for the effects of this to propagate down through the atmosphere, so the current regime of high pressure, frost and fog with occasional colder northerly blasts will probably continue for a while yet. I am only an amateur, and there may be things I don't understand or have missed, but I am confused that the models and forecasters are not picking this up and forecasting a warmer, wetter, windier 2nd half of January. It does not look like a cold setup to me (famous last words!).

We shall see.

You can untangle the individual "spaghetti" members in the ensemble charts on this page Wetterzentrale.de - diagrams - hover over a line and it will be shown in bold. Click on the line and it will show you the upper air temperature graph for that member at that time.

[Penellype]

Britain on HEAVY SNOW ALERT: Polar vortex to plunge UK into WORST January FREEZE in years | Weather | News | Daily Express

"Weakening polar vortex"? Really? (see previous post).

There is no real agreement in the models at the moment beyond about 8th January. There is a tendency for the models to be forecasting colder weather after about 11th, but they were doing that around 7th this time last week and now its going to be mild this weekend. I'm not saying it won't get colder - it might, but as usual this article is way OTT. And the forecasters are? Yes, you've guessed it - our old "friends" Piers Corbyn and James Madden.

Enough said.

[Penellype]

A bit warmer over the weekend after a damp day today, with high pressure building over the country in a position which allows the flow to come up from the south west. It is likely to be fairly cloudy. There is good agreement for a low pressure to pass to the north during Monday with some wind and rain, followed by a transient ridge of high pressure, typical of a westerly pattern.



The next low may arrive on a more southerly track on Thursday:



This would pull the winds round to the north as it passed, and most of the models see this happening so it looks very likely that there will be some sort of colder spell towards next weekend. This is the current chart for Friday:



A cold front has moved south through the country and this could turn to snow as the colder air behind it arrives. This would be likely to be followed by at least a risk of wintery showers, particularly on north and west facing coasts. High pressure then starts to build again into the weekend:



Next weekend would be cold if this chart proves accurate as skies would clear but the upper air temperatures are still low.

What happens next depends crucially on where the ridge of high pressure goes. If it builds further north and then collapses over Scandinavia this would turn the winds into the east, bringing in very cold and potentially snowy weather. A couple of days ago the GFS model was showing this, but recent runs have had the high collapsing down further south returning us to a cool but not very cold north westerly flow. It is far too early to tell which of these options will happen, as can be seen from the very varying tracks of the lines on the ensemble graph.

[Penellype]

A brilliant demonstration of the uncertainty about what happens after next weekend from this morning's model runs.

Next week will become more unsettled and windier as outlined in the previous post, ending up with a cold northerly wind on Friday. Over next weekend disturbances in this flow could bring snow to some places and this needs watching as details are not possible at this range, but it looks likely that the weekend will be cold with hard frosts at night and daytime temperatures near freezing.

The huge uncertainty is what happens next. At 240 hours (midnight on Wednesday 18th), which is the furthest extent of 2 of the 3 models, this is what happens:

GFS model



A warm south westerly flow would give temperatures in double figures,

ECMWF model



The high pressure has ridged into Scandinavia putting us in a bitterly cold easterly wind. This would lead to a potentially lengthy period of very cold and possibly snowy weather.

GEM model



The country is in a flat westerly flow. This would be wet and windy at times with temperatures around the monthly average of mid single figures, depending on where you live.

Anyone got a pin?

[KevinM67]

I'm loving these updates Penellype.

Especially when you kibosh the 'WE'RE ALL DOOMED' tripe peddled by that hate-inducing, anti-immigrant rag owned by the tax-dodging pornographer.

[Penellype]

The onset of the colder northerly wind has been edging earlier with each model run (as has the end of it on those models predicting that it won't last long). The met office has just issued warnings for wind and snow from Wednesday evening in the north and west, with these extending down eastern coastal regions on Thursday and Friday - see Severe weather warnings - Met Office. Exact details are likely to change as snow is notoriously difficult to forecast.

Interesting and informative article by Simon Keeling about what you can expect from a weather forecast here: Managing weather forecast expectations. The last line is particularly important (and very difficult to put into practise) - there is a tendency for people to believe things that show what they want to see and not to believe things that don't. This is called confirmation bias, and invades absolutely everything that you do, affecting the choices that you make and what information you dismiss as either irrelevant or wrong. Given this, if for example you are convinced it is going to snow and you are shown 20 possible weather charts of which 5 predict snow, you may well have a tendency to say "I told you, its going to snow".