Well we have at last enjoyed a bit of sunshine recently, giving us a bit of a break from the relentless wet weather. With clearer skies we also get colder nights of course, providing the opportunity for some interesting frost formations. These pictures of “hair ice” were recently sent in to me from Ashley in Throwleigh. The photos were taken last Saturday 18th January at the National Trust car park in Postbridge. I must say that I am unsure as to why ice formed on this particular branch, so if anyone has any ideas then please e-mail me!
Well it’s been a while since my last blog, so time to update on the latest weather over Dartmoor.
Last December was my second wettest month at Haytor since I started recording in 2003. I collected 408 mm which was only surpassed in Nov 2009 with 418 mm. The rain has certainly been extremely heavy. Our local river Lemon flooded 3 times in two weeks and on 23rd Dec Postbridge collected 156 mm of rain in 24 hours. Every path coming down from Haytor Rocks that day was a fast flowing stream. Last Sunday I was walking near Hexworthy and just made it over the stepping stones at Week Ford. I was astonished to see a watermark at 8 feet high from when the Dart was in flood!
So, has this stormy wet weather finally come to an end? Well the polar vortex has now split, one half has drifted south into the States giving them severe cold and the other half is making its way down into northern Russia. Incidentally Siberia, Russia and Scandinavia have had an unprecedented mild December. The jetstream is weakening and we have seen the last of the rapidly deepening Atlantic storms. However, we have not seen the end of the rain. In fact later in the weekend, especially on Sunday into Monday, rain systems could well end up over the UK as slow moving features exacerbating the flooding risk. During next week there are now clear signs that the weather is set to turn colder for the second half of January with strengthening easterly winds possible.
So on that potentially snowy note all that remains is for me to say Happy New year!
I have been looking with some interest at the numerical weather prediction models during the past few days. All of them have consistently been showing a cold front marching steadily eastwards across the Atlantic during 1st to 4th December. Nothing unusual in that except that the cold air behind the front originated from some very cold (for time of year) air over Arctic Canada. The effect of this will be to collapse our high pressure around 4th December and introduce a progressively cold Arctic airmass into the UK with the risk of widespread snow by the 6th. But that is not the whole story … as the cold air comes across the Atlantic, some model runs are indicating that tropical air moving north may interact with this (see previous blog on climate change) in such a way as to explosively develop a deep Atlantic depression bringing in severe gales as well as rain and snow. I’m not saying that this is definitely how it will all pan out, but I am pretty confident now that big changes are on the way next week with very cold conditions set to come down from the NW with a real risk of widespread snow. I’ll be issuing my regular forecast for Dartmoor tomorrow, so more details then.
This is not a blog about Climate Change per se as I do not get into such debates. I accept that the world has undoubtedly warmed in the past 100 years. However, have you all noticed the weird weather which is occurring more frequently in the past 5 years? As a meteorologist I remain amazed at some of the weird weather charts that keep cropping up, the clincher for me was the recent tornado outbreak in the States. Although not unprecedented, it was a Spring situation occurring in November with terrible consequences. The Phillipine typhoon was unfortunate in that it made landfall at its strongest, but they don’t normally do that? Was that just unlucky – maybe, but in the context of other world weather events, maybe not. Now, over the Atlantic the weather chart to me looks “weird” and some forecast charts even weirder with tropical systems moving north meeting unusually widespread (for the time of year) very cold air in the Arctic. It is my view that Climate Change is happening right here, right now, not in the future. What does this mean for our weather on Dartmoor? To be honest I don’t really know! However, it could mean that we will have a benign winter, possibly even record breaking dryness, but more likely we will have to remain alert to the real possibility of some extreme weather which may be in the form of floods, violent storms or heavy disruptive snowfalls. We could be in for a rough ride. Stay tuned.
The cold spell that I talked about in my last blog is now looking more certain as very cold air moves across Dartmoor on Monday night. The bitter N to NW wind is likely to bring a mix of hail and snow showers on Monday night and during Tuesday. Difficult to say how much snow there is likely to be, but going on past experience about an inch above 300 metres asl would be a reasonable stab. After Tuesday snow showers are likely to die out when winds swing NE’ly and it becomes mainly dry and frosty with some ice. I will be updating my weekly forecast tomorrow at http://www.lyneside.demon.co.uk/weeklydiscussions.htm .
There are indications now in NWP model outputs of a plunge of very cold air from the Arctic bringing snow to Scotland next Monday 18th with wintry conditions on Dartmoor by Wednesday 20th. Far too earlier to talk about severity, but after a benign autumn so far, it will come as a shock and at the very least we will see some frost on Dartmoor with perhaps a few snow showers. Stay tuned, probability of cold weather is increasing and is now rated at 70%.