Penellype's Weather Channel

[Penellype]

A weak cold front moves down across the country today, introducing a really quite cold air mass. The wind will turn into the north and tonight could be really cold especially in the north, with a widespread ground frost and an air frost in places. Tomorrow will be a really chilly day for the time of year before milder air moves in from the west on Monday night.

There doesn't seem to be much change to the pattern of alternating temperatures and some cold nights through next week, as low pressure areas continue to move to the north and the centre of the high which is keeping most of us dry moves about a bit, changing the wind direction. There is a possibility of things becoming more unsettled from next weekend, but there is a lot of variation between the models and runs. Again the cause of the uncertainty is probably the track of tropical storm Leslie, which is currently meandering about in the middle of the atlantic and appears to be going nowhere fast. This may develop into a hurricane briefly next week. Eventually it will either fill and disappear or move, and the uncertainty is probably linked to when and where it will go.

[sandspider]

I see we're in for a cold weekend, but then there's a forecast for 24C next Wednesday!

[Penellype]

I see we're in for a cold weekend, but then there's a forecast for 24C next Wednesday!

Yes, a cold front is moving south through the country, giving central and southern areas a very cool and wet day on Saturday and potentially a cold and frosty start to Sunday especially in the north.

What happens next week is critically dependent on the behaviour of hurricane Leslie, which has been meandering about in the central atlantic for some time. Some model runs have this coming in our direction towards the end of next week, which will have the effect of inflating the high over the continent and drawing up some very warm south or south easterly winds ahead of the storm. Currently the storm itself is forecast to move north to the west of Ireland and therefore miss us, but things can change and not all models agree on the warm temperatures. Also, as the air is from the tropics it will contain a lot of moisture and could therefore produce very cloudy skies, which would curb the temperatures somewhat.

Next week's weather is not a done deal by any means, and needs watching, as fairly minor changes to the path of Leslie could mean what is currently forecast to be warm and dry becomes wet and windy or even stormy.

[Penellype]

A potentially frosty night tonight, and a very, very wet start to the week for north western Scotland - there is a yellow warning for heavy rain, which is likely to continue on and off until Tuesday.

The rest of the country will have a mostly dry and increasingly warm week, although there is a possibility of some rain in the west on Friday. How warm it gets will depend on how much cloud there is, and there is always a risk of fog with high pressure at this time of year.

[Penellype]

Models changing their minds again, as often happens when we are on the edge of a high pressure system. Thursday and Friday looking rather wetter than previously on the latest runs, but things could still change. Whatever happens, with the wind from the southerly quarter it will be mild/warm.

[Penellype]

Models are firming up on a rather more unsettled picture than was forecast earlier in the week, although it will remain warm for now. Friday will be windy, probably stormy in the west, with the possibility that the storm may be named Callum. This is not the same storm as Leslie, which is still wandering about in the middle of the atlantic, although the persistent rain which is causing problems in the west of Scotland is linked to Leslie by a long trailing front. Leslie is now expected to become a hurricane again and move east towards Africa, possibly ending up as a decaying sub tropical storm in Portugal, but it is most unlikely to come this way.

Hurricane Michael, due to hit the south coast of America shortly, may well come this way later next week. As always with these ex-hurricanes, there is a huge amount of uncertainty, and all will depend on whether or not it moves into a position where it gets caught in the jet stream. Treat any forecasts for next week with extreme caution for now as they are likely to change as the track of Michael unfolds.

[1Bee]

The yellow warnings for wind and rain for Fri/Sat (NW, SW Scotland, W Wales etc) are starting to stack up.

Doing the mental checklist already...

[Penellype]

Very heavy rain in the west today and tomorrow with warnings in some places including an amber one for south Wales, as well as a yellow warning of wind for the western side of the UK today. https://www.metoffice.gov.uk/public/...ate=2018-10-12.

Much more rain to come for western areas, so if you are in one of the warning areas keep an eye on flood warnings.
England https://flood-warning-information.se...ov.uk/warnings
Wales https://naturalresources.wales/flood...nings/?lang=en
Scotland http://www.floodlinescotland.org.uk/flood-updates/

[Penellype]

Update on the storm/hurricane situation.

Storm Callum continues to bring rain to the west with risk of flooding as a front has become stuck across the western side of the UK, extending into the north east. A frontal wave is developing into a small low along this front, bringing more wind and rain today. The front extends a long way south and connects to hurricane Leslie.

Hurricane Leslie (currently category 1) has been meandering about in the atlantic for nearly 2 weeks, strengthening and weakening intermittently. It has now started to move east and is due to hit Portugal in the vicinity of Lisbon tonight. The NOAA hurricane centre has Leslie as a sub tropical hurricane at the time it makes landfall https://www.nhc.noaa.gov/graphics_at...?cone#contents. Once it moves over land Leslie will quickly weaken to a sub tropical storm and then a low pressure system as it moves across Spain and into the south of France.

It is very rare for hurricanes to hit Iberia. There was one in 1842 which destroyed homes in Seville and caused damage throughout Spain with hurricane force winds as far inland as Madrid. Hurricane Vince, which hit southern Spain as a tropical storm in 2005 followed a similar track, but I can't find any other references to this happening, and both of these previous hurricanes/storms made landfall south of Lisbon.

If you live in Portugal or Spain, keep a close eye on this and follow any instructions from the authorities. This may not be of the intensity of hurricane Michael that recently hit Florida, but it is more than a usual low pressure storm.

Stay safe everyone.

[sandfields]

Sounds like this has battered Portugal. Anyone out there with news?

[Penellype]

After a very wet and unusually warm weekend in places, yet another change in the weather is now being forecast. Once today's remnants of the rain are out of the way in the south eastern half of the country, high pressure is forecast to build leading to a mainly dry week (although possibly somewhat wetter in the north west). Temperatures won't be anything special as cool air moves around the top of the high and there could be some night frosts in places as well as mist and fog or quite large amounts of cloud.

The ensemble chart for York shows an exceptionally dry forecast for the time of year, with very few rainfall spikes:



850mb temperatures are up and down as the centre of the high moves around. Towards the end of the ensemble (very unreliable, but consistently appearing at the moment) the 850mb temperatures on many of the individual lines drop below the -5 line. This coincides with this chart for 28th October:



The high pressure has moved to the west of us, opening the door to an arctic northerly flow, which would certainly be cold enough for snow in Scotland and possibly further south too. Temperatures below freezing at night would be widespread if this forecast was correct. However this is a long way off, in the unreliable timeframe, and there is plenty of time for it to change. It would not last long at this time of year, but it serves as a reminder that winter is not far off.

[Chippy Minton]

Thanks Pen, will hunt out some fleece for the late season potatoes that I'm once again trying to grow for that time we aren't allowed to speak of yet......

[sandspider]

I'd like to plant out some small trees in a place it's hard to water. Accordingly, there is no rain forecast for the next 10 days or so! Hopefully this will change...

[Penellype]

I'd like to plant out some small trees in a place it's hard to water. Accordingly, there is no rain forecast for the next 10 days or so! Hopefully this will change...

Rain is unlikely in the next 10 days as high pressure is sitting over the country. Things can always change, but with little hurricane activity to give the atmosphere a nudge, I think it is unlikely. We are entering a period known as St Luke's little summer, often dry and fairly warm, which starts around 18th October and is said to end on St Jude's day (28th October), which is often stormy and wet.

The weather patterns continue to be odd at present (they have been since the beast from the east back at the end of February), and therefore forecasting what happens next is tricky.

[Penellype]

Plenty of hysterical headlines around about cold weather about to engulf us. The current position is as follows.

At the moment we are under a ridge of high pressure which extends over the country from the south west:



The flow is coming up from the central atlantic and is relatively mild, although clear skies at this time of year can lead to chilly nights, especially with light winds.

The centre of the high moves around a bit during the week, and by next Saturday it has moved out into the atlantic and is ridging towards Greenland. With low pressure to our east, this brings the flow straight down from the arctic:



All of the models are now seeing this, although upto last night the GFS (above) had the high slightly further east, protecting us from a direct northerly flow.

This is NOT snowmageddon. While the -5 isotherm (one of the requirements for snow) is over most of the country by this point, we are still under high pressure (1025mb). There is not going to be a lot of snow about, although a few wintery showers around north facing coasts and hills are possible with this setup. It will be cold, with frost very likely at night, and with a fairly strong northerly wind it will feel very cold indeed compared to what we have been used to.

It doesn't last long. Within 48 hours the high has collapsed over the top of us:



This allows the flow to come over the top of the high from a more westerly direction, returning us to something a bit milder and with lighter winds.

These details are a week away and things can easily change, but at this time of year brief periods of northerly winds are not uncommon and if they occur they are cold. The jet stream is currently running in large amplified loops rather than straight across the atlantic, and this is bringing the air down from further north than would normally happen in October, hence the hysteria in the press. As long as the jet stream is doing this we could be in the firing line for both warm and cold spells depending on the position of the high pressure.

Right at the end of the GFS runs there are hints of a change to lower pressure which would bring some rain, but I would treat this will caution as the models tend to revert to normal and the basic setup for the whole of the summer and autumn so far has been a long way from normal. My guess is that the mostly dry weather is likely to continue for some time yet, with spells of warmer and colder weather as the high continues to drift about. I could be wrong, and there is still time for a hurricane to form which later gets caught in the jet stream and changes everything.