No, it’s not my attempt to recreate the intro to “Dad’s Army”, it’s the approximate movement northwestward of a sheet of stratus across southern areas of the country this morning (fig 1). Yesterday’s clear skies are fast disappearing as the bank of cloud moves relentlessly northward, and a return to a dull and dreary January day that we know so well.
It’s a great shame that the anticyclone of yesterday didn’t stick around longer. I’ve got a feeling that we’ll be as sick and tired of January by the end of this month as Pilot where back in 1975.
There is a sharp inversion and associated sub-zero layer on this mornings 11 UTC ascent from the Herstmonceux ascent in Sussex (fig 2), at around 3,000 feet. In fact the ‘proper’ freezing level above is at almost 8,000 feet (fig 2). Low level winds are north of east, so maybe the stratus is forming as the result of moister air feeding in from the E’NE, rather than following the flow that I’ve indicated on the satellite image (fig 1).
The low stratus across central England has been very reluctant to clear today, and I notice this afternoon that it’s now spilling down the north coast of Devon in the easterly flow (fig 1). I also notice that there’s still some sea ice visible in the northern Baltic (fig 2).
Today the 15th of March is the Ides of March in the Roman calendar, and it’s on this day in 44 BC that Julius Caesar was assassinated. On the 15th March 2017 though, the stratus that has plagued the coastal areas around the south and west has been very reluctant to shift today. Its cleared though in mid-Devon this afternoon, but it’s still clinging to the south coast from Cornwall through to Dorset (fig 1). It’s not often that it’s warmer at Dunkeswell and Liscombe than it is at Exeter airport, but it is this afternoon. St Athan is in fog and cold, with a temperature of only 7.6°C at 14 UTC, whilst on the other side of the Bristol Channel in North Devon, temperatures are close to 15°C (fig 2) with blue skies and sunshine.
It looked like the cloud would continue to thin and break, as it had done for most of this morning down here in mid-Devon, and then around 1 PM the sea breeze set in, and low stratus quickly followed to spoil it all. I just wonder if the drier air that’s advecting N’NW from France will clear the low stratus and sea fog in the Channel overnight? The streamlines seem to suggest that it might, as long as the gradient is maintained (fig 2).
Meanwhile on the north coast of Devon, Chivenor at 15 UTC is the warmest place in the country (fig 3).
Another great visible satellite image again this morning (img 1), which clearly shows the extent of the low stratus cloud sheet across the south and east of the country. The Pennines and Snowdonia are acting as a natural barrier to it, so many places in the North Wales and the Northwest of England are clear of it, and I notice that in the lee of Dartmoor there are some strung out gaps as well. Drier air is now starting to stream off France, and it won’t be long, I should imagine, before this clearance makes it across the Channel to southern counties of England.
Today’s windchill across the country is pretty high, or should that be pretty low? Whatever it’s pretty raw out there today, and typically the JAG values on lower ground are coming in at between -3°C and -7°C, but as low as -12°C on any higher ground (figs 1 & 2).
It’s took it all morning, but we’ve finally started to clear the low stratus that invaded southern parts of Devon overnight, and the sun has burst through. It’s kept temperatures at around 8°C at places like nearby Dunkeswell, I was beginning to feel how someone who lives in the east of England has been feeling in the last week. Apologies for the small animation, but my programmer chappie is having problems with the scaling of animated GIF’s, but it’s interesting to see how the edge of the stratus is running ENE/WSW across central Devon with very little movement, all I can think is the low-level flow must have backed a little and there is slightly more of a northerly component to the flow than there was earlier.