Penellype's Weather Channel

[Jimmy]

but lock your doors they can't get you

Aliens can walk through doors, apparently !

[Jungle Jane]

No aliens about luckily It was still foggy last night in Braintree but it cleared as I got to stansted & London,much clearer there. It might be good to top up your screen wash if you haven't already,I had to squirt mine loads yesterday. The temperature here was 11 degrees at about 4pm or 5pm it seemed strange,bit warm for winter

[Penellype]

After several days of this sort of pattern:



with warm air, often a lot of cloud and sometimes rain coming from the atlantic, the forecast is that by next weekend the high pressure will build again to give something like this:



At first glance there is not a great deal of difference, but the centre of the high has moved north. The upper air is still warm, but if you trace the isobars back they are now coming from the south east instead of the south west.

This is one of the situations in which the upper air temperature graph is totally misleading - look where the thick green line is for 18th December!



There is still uncertainty at this point, but this signal keeps popping up for next weekend, and the result would be a return to much colder temperatures and some hard overnight frosts. It could all change - this is outside the 5 day more reliable timeframe, but it is worth keeping an eye on, as the logical continuation of this process, with the high drifting further north COULD (and it is only a possibility at this stage) lead to a significant cold spell.

[Penellype]

Oh what a difference 3 hours makes to the forecast for next weekend. From the midnight run (above) the temperature range for next Sunday here was -2 to +3. The 6am run gives the following chart for the same time as the one in the previous post:



The high is slightly further south here, and the corresponding temperatures for Sunday now come out at +5 to +10. So much uncertainty from so small a difference.

[Penellype]

Here we go again... Weather: Wall of SNOW to smash UK as SNOWBOMB hits in COLDEST freeze for 53 years | Weather | News | Daily Express.

There are so many errors in this article (published on 14th December 2016) that it is completely laughable. However, my favourite bit is this:

"Colder conditions will be accompanied by potentially countrywide snow events particularly around the periods of the 12th to the 17th and the 21st to the 29th of December."

Um... what's the date today? 14th December. I thought so. Where's the snow? Its 9 degrees out there at 10am. There is no possibility of countrywide snow before 17th December. Zero, zilch, none. They can't even get it right when talking about the previous 2 days (12th and 13th)! Maybe these people are based in Iceland or something, that must be it.

This is the current chart for Christmas day from the GFS:



Admittedly the charts for Christmas from various models have been very inconsistent, and still are, but the models are slowly converging on a more unsettled outlook for the Christmas period. This particular scenario is mild - trace the isobars back to near the azores. As Matt Hugo tweeted this morning:
"Trend now for any block to decline middle next wk. Pot luck now as to whether Xmas is timed so we get a SW'ly or post-low colder W or NW'ly."

None of the sensible weather forecasters would care to give anything like a firm prediction of what will happen over Christmas at this stage - it is still much too far ahead, but I would be confident that they would all rule out a "wall of snow" and "temperatures of -20C".

Don't believe what you read in the papers, particularly when the forecasters concerned are named as Piers Morgan and James Madden. These guys are always behind the weather scare stories. I suppose one day they will be right, but its not going to snow between now and 17th December unless you live on a mountain top or somewhere outside the UK.

[Penellype]

So, after the "wall of snow" disappears over the horizon, this is how the week upto Christmas is looking:



The high pressure which is giving mainly dry weather today along with some fog especially in the south looks like retreating slowly east towards mid week. This is tomorrow's chart with high pressure over the whole country giving a repeat of today, with a possibly frosty start if skies clear:



There are already signs of a change coming - note the blue colours changing towards purple over Greenland. By Wednesday we have this:



Whenever the purple colours intensify like this expect a change to wet and windy weather. This is the polar vortex strengthening (which reflects a strengthening jet stream) and it is never good news. Wednesday night and Thursday are potentially quite wet as fronts associated with the deep low pressure run up against the high pressure to the east and stall. It is too far ahead for exact details, but it needs watching as there could be a lot of rain.

This particular run of the GFS has calmed down the storminess somewhat, with Christmas Eve looking like this:



This would be quite chilly and wet, with snow possible over high ground in the north. Most of the purple has gone, and after a couple more low pressures the high builds again in a very similar way as it has done over the last couple of days, to take us back to square one around new year. 12 hours earlier the same model came up with this for Christmas day:



Here the isobars are very close together and with likely fronts in the mix that would produce an absolutely foul wet day with gale force winds - this is still a possibility. That particular run also continued the westerly "atlantic" conditions into new year - there is still plenty of uncertainty about if/when the high pressure will return.

[Penellype]

Looks like the charts hadn't quite finished updating when I posted the last lot of screenshots, and the Christmas eve and later charts were from yesterday's run - sorry about that. The correct chart for Saturday is this one:



which doesn't look all that different, but while yesterday's run led to a fairly benign if chilly Christmas day and high pressure building for New Year, today's run produces a horrific chart for Christmas which is even worse than the one posted above:



The high pressure doesn't return for New Year on this run, with another nasty looking storm and the purple colours returning on 2nd January (far too far off to be anything other than speculation):

[Penellype]

Some scare stories about "storm Barbara" and more snow predictions from some of yesterday's papers. While it is looking increasingly likely that the Christmas period will be wet and windy, possibly disruptively stormy and with some wintery weather possible in the north and on hills, as usual the papers are going way over the top.

There is a more down to earth summary of the possibilities here Stormy Christmas Weather On The Cards? - Blog by Nick Finnis - Netweather.tv. Christmas day needs keeping an eye on as the models are often coming up with a very nasty looking storm, but it is far too early for details yet.

[Penellype]

Ok folks, time to batten down the hatches for Christmas as a strong jet stream pays us a visit.

Wet and very windy weather is due to move in from the west on Friday - this has now been named storm Barbara as an amber warning for wind has been issued for Scotland. A yellow warning extends south as far as the north midlands Severe weather warnings - Met Office.

Gusts upto 90mph are expected over parts of northern and western Scotland as the storm deepens rapidly:



This then moves away for Friday night, but another storm is waiting in the wings for Christmas Day. This has been well forecast for some time, although its evolution is somewhat different from Barbara. Whether it will be named Conor depends on whether the Met Office issue an amber warning, which they might because of the possibility of disruption on a day when a lot of people are travelling about.

The Christmas storm can be seen as an innocuous looking circle at 1010mb straddling the black line of the jet stream just off Newfoundland on the above chart. Unlike Barbara, and somewhat unusually, this system does not wind itself up into a "dartboard" low. Instead, it elongates north and east to join up with Barbara to the west of Scandinavia by the early hours of Christmas morning:



The high pressure is being sucked northwards and the result is that the isobars are getting squashed closer together. Although this does not look as vicious as Barbara, it would be quite enough to bring strong and gusty winds over the whole country from the early hours of Christmas day, lasting much of the day before moving away in the evening. On this run the winds are slightly lighter and arrive earlier than on previous runs, and things could still change either way before Sunday.

The stormy period, which looked due to last about a week, now looks likely to end on Boxing Day as the high continues to be sucked north. Initially it will become colder as the winds turn into the north, but it looks likely that the high will soon move over the top of us, returning us to light winds with the possibility of fog and frost, depending on the exact position of the high. How long the high remains is anyone's guess as there are various possibilities. It could stay put as the last one did, it could be flattened by the jet stream to return us to wet and windy weather, or it could move north, allowing the wind to turn into the east or north east, which would be much colder. Last night it was moving north by the end of the run, this morning it is being flattened off by the jet stream, so as always it is very much a case of wait and see.

[BUFFS]

we had the strong winds and powerful rainstorms last night, loud enough hitting the windows that we had to turn the volume up on the telly to hear it, a lovely but bit cloudy morning now , so I am off to lift my Christmas parsnips before the weather changes again....
just had a telly weather forecast for our area.....70-90mph winds for Christmas eve onwards, so lots of power failures forecast for that period, don't you just love this season of good will !!!!!!!

[Penellype]

Latest on the stormy weather and beyond...

Storm Barbara is now starting to move into western areas with strong winds and heavy rain associated with a cold front. As mentioned before, there are yellow and amber warnings of gales - the areas for these have changed with the amber area further north as the centre of the low passes closer to Iceland than previously forecast, but the yellow area extending much further south over the western side of the country. Away from the north the worst of the winds are likely to be associated with the cold front and could be very gusty and squally for a fairly short time as this passes over.

Christmas Day now looks less windy as the low (which looks far more "normal" than the last chart I posted) goes rather further north. The result of this is lighter winds than previously forecast away from northern Scotland, although there are still yellow warnings at present.



Christmas Eve and Boxing Day are now likely to be rather windier than previously forecast, with gusts likely to be the feature rather than sustained high winds.

As before, high pressure is forecast to build again after Christmas, but this is lasting less long with every run. The latest idea is that around New Year high pressure builds towards Greenland with the winds turning into the north and something very much colder may arrive.



The low pressure near Scandinavia then moves south, bringing in some very cold air from the continent:



This is a very long way off, but needs watching as it would certainly be much more wintery than anything that we have had so far. These charts are from the GFS model, the ECMWF is similar. On the latest GFS run this does not last long with the high collapsing to allow the westerlies back in around the end of the first week in January (the ECMWF does not go that far ahead), but remember that anything more than a few days away cannot be relied upon (this time yesterday all the models were seeing high pressure over us well past New Year).

[Jay22]

A big thank you to our very own weather girl Penellype!

[Bigmallly]

I nominate we have a thread entitled "Penellype's Weather Channel".............

[Penellype]

I nominate we have a thread entitled "Penellype's Weather Channel".............

I'm happy to do weather updates as long as everyone realizes that this is only a hobby of mine - I have no training whatsoever in meteorology. The aim of this thread was to alert people to upcoming weather events which might have an effect on gardening or plants and to try to cut through the excitable hype that the papers have a tendency to produce in favour of a more balanced and realistic view. I hope I am managing to do that - I don't expect to always be right!

[Bigmallly]

I'm sure it would be informative & accurate than we see on't Telly.