Good morning. Here is the report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Wednesday November 20th 2013.
All models show a deep Low pressure moving South down the North Sea on it's journey towards Southern Europe and the Mediteranean tomorrow. As a result today will be an unsettled and rather cold day with showers and outbreaks of rain, wintry on hills affecting many parts, some of it heavy and squally with hail a possibility. Later today, tonight and tomorrow improvements will sequentially move down from the NW as pressure builds strongly. By Friday the improvements to dry, cold and settled conditions look complete with a fine but chilly weekend with frost and freezing fog patches night and morning looking likely but with pleasant daytime weather where fog clears.
GFS keeps High pressure over the UK for much of next week with the continuing likelihood of overnight frost and freezing fog to keep temperatures rather lower than they otherwise would be. Some bright or sunny spells are expected though. Later in the period pressure falls as the Atlantic breaks through with wind and rain for a time before things become more settled again at the end of the run with Northerly winds and strong High pressure over the Eastern Atlantic.
UKMO closes it's run with High pressure over Ireland with fine and settled weather for all but with a lot of night frost and freezing fog in the very light winds. This would become hard to shift through the daytime's making it feel very cold where that occurs.
GEM keeps High pressure locked in over the UK with varying positions determining the amount of cloud gets carried within the flow. As a result frost and fog amounts would be tricky to predict but there most certainly would be some perhaps biased more towards the South without the Atlantic drift.
NAVGEM today has played catch up at last joining the other models in a Southern UK based High with cloud cover spilling across Northern areas and down over the South too later restricting the amounts of fog and frost late in the run with benign conditions developing and temperatures slowly recovering somewhat towards near average.
ECM shows High pressure in control over the UK but the position has slipped further west and SW this morning allowing the Atlantic to pull cloud cover around the top of the High and down over the UK gradually replacing the overnight fog and frosts with cloudy skies and lifting temperatures slowly towards the average. A little rain could move SE on a weak trough towards the end of the run followed by a pressure rebuild across the South.
The GFS Ensembles are not exciting for anyone with a long period of normality with regard to uppers and with little rain shown High pressure will remain close by. Frost and fog will be the main issues and this can make fundamental differences to temperatures experienced at the surface with the likelihood of conditions ending up rather cold especially at first before Atlantic cloud cover gradually erodes the risk of both of these perils to help aid temperatures back to average at the surface too.
The Jet Stream is forced to High latitudes after this week and beyond as a UK or East Atlantic based high pressure area develops soon.
In Summary there is little to be said about the prospects from the models that hasn't been said on previous runs. In essence all areas look like becoming dry and settled soon with light winds. With clear skies frost and fog will make for difficult driving conditions at times and this may prove stubborn to shift through the mornings. However, as time progresses it looks like our High will infill with cloud cover from off the Atlantic to allow temperatures at the surface to modify to nearer the average with less in the way of frost and fog. As usual the further out one goes into the output the chances of a breakdown look feasible and on this morning's evidence it looks like any such breakdown would look to be likely from the NW as the High declines.
Martin G
Kilmersdon Radstock Bath Somerset