Good morning everyone. Here's my take on how the models are shaping up for the impending cold spell for this morning Monday November 18th 2013.
All models do indeed show an impending and probably prolonged cold period beginning today in the North and West and tonight elsewhere. The current cloudy and dull conditions across the South with some light rain will be pushed away SE this evening and tonight then all areas will be covered by a NW flow with wintry showers affecting all Northern and Western areas with settling snow on the hills and frost and icy roads elsewhere. This lasts until Wednesday when a new Low moves down the North Sea with a spell of strong winds and rain preceded and followed by the risk of snow over the hills as it pulls away South on Thursday. High pressure builds in across Northern areas particularly by the end of the week with frost and fog widespread by night with cold crisp days where fog clears. In the South more of a NE or East wind looks likely to persist removing the risk of wide scale fog but keeping some cloud and the possibility of wintry showers instead, especially near the SE coast.
GFS shows the South cold and breezy through the weekend while northern areas stay brighter and cold with frost and fog patches. It should stay largely dry though. The status-quo persists through much of the remainder of the run though the Easterly flow in the South is shown to veer SE and decrease as renewed High pressure then settles the whole of the UK into fine and cold weather at the end with further frost and more widespread fog problems.
UKMO this morning ends it's run with High pressure positioned over Northern Scotland with ridges to Iceland, Scandinavia and the Azores. A cold NE flow is maintained across the South with largely dry conditions apart from the odd wintry shower near the Coast. Elsewhere would be dry, bright and sunny by day with frost and freezing fog patches overnight, likely to be slow to clear in places.
GEM today has a more UK based High pressure area over the weekend and the start of next week with frost and fog widespread in light winds. Towards the end of the run the High is shown to pull slowly NW introducing a cold NE feed across Southern and Eastern England with a few showers by midweek next week.
NAVGEM keeps High pressure much further NW, near Iceland which keeps all of the UK under a cold and wintry North then NE flow with wintry showers all down Eastern coasts throughout and spreading well inland at times towards Central areas. The West would stay largely dry with clear or sunny spells but it would be cold for all with widespread night frosts though little fog from this set-up.
ECM builds High pressure in temporarily from the West and NW to affect all but the far SE towards the weekend with a cold, dry period with frost and patchy fog for all Western and Northern areas in particular. Eastern and SE coastal areas will continue with an onshore NE wind bringing the risk of the odd wintry shower. Then as the High retracts North towards Northern Scandnavia an unstable, fairly light but cold Easterly flow will increase the threat of wintry precipitation late in the run, more especially for Southern and Eastern areas.
The GFS Ensembles show that any mild weather is fairly unlikely through the forecast period. It is therefore more likely to trend rather colder than average overall with not much in the way of rain indicating the proximity of High pressure to the UK. The High's position is mandatory for cold weather over the UK and most do trend for it to be towards the North giving the UK a good chance of seeing some early winter chill.
The Jet Stream today shows the flow buckling South across the UK to feed a Southern arm of the flow over Southern Europe. A split flow is shown later in the week before the pattern become diffuse and unclear next week.
In Summary today the models have taken a step forward towards a more cold prospect being maintained over the UK for the majority of the period at least. With a much increased trend to show High pressure to the North of the UK it leaves the gates open for Northerly or Easterly incursions to envelope the UK aided by Low pressure over Southern Europe. There is a rather unsettled period to get through during the middle of this week before the pattern will clarify further but as it stands cold weather looks set to stay for quite a while and though mostly High pressure based ECM and NAVGEM show the possibility of a much more unstable NE flow setting up with the chance of some wintriness scattered about towards the end of the outputs. Frosts look like becoming widespread but with the prospect of High pressure staying just offshore to the North of the UK the slightly stronger breeze may limit this somewhat from what was being shown recently.
Transcript taken from:-http://www.norton-radstockweather.co.uk/Model-Analysis(2859336).htm
Martin G
Kilmersdon Radstock Bath Somerset