Hi everyone. Here is my report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Friday September 20th 2013.
All models show a very confused and mixed pattern beyond the start of next week with a variety of different outcomes on offer this morning. In the short term the weather will be straightforward enough with a fine day today with sunny spells under a ridge of High pressure. A weak warm front tracks NE across the UK tomorrow injecting milder Atlantic air across the UK with more cloud, hill fog and light rain and drizzle to the north and West before the weather brightens again from Sunday with some warm or very warm sunny periods developing in the South. Then things begin to diversify between the models as we progress through next week.
GFS shows lowering temperatures creeping down from the North later next week along with falling pressure with an eventual Low pressure belt developing from the Azores, across Southern England all the way to a deep centre over Russia. The result would be to increase the risk of rain over the UK with potentially rather cold conditions developing over the North as a NE flow develops. This Autumnal feel continues as pressure patterns reset to Low pressure developing over the UK vigorously and meaning rain and gales in rather cold conditions for all at the end of the run.
UKMO today has Low pressure slipping South towards Norway with another centre well to the SW while Southern Britain clings on to High pressure with fine and dry weather maintained for most at this stage with mist and fog issues at night a probability while the days stay bright and warm but less so in the North.
GEM shows colder air gradually sinking South across the UK next week as high pressure leaks away to the SE. Some rain or showers could well affect the North later next week in a cool NW flow while Southern areas come under attack from the SW later as Low pressure troughs edge in from the SW as part of a deep parent Low well out in the Atlantic Ocean.
NAVGEM is very much more relaxed in it's output today offering some influence from the Low to the SW early next week when some rain may occur in the far SW for a time as High pressure declines SE. However, later in the week the Low fills and High pressure is shown to build back up over the UK maintaining fine and dry conditions for all of the UK once residual cloud and any rain leaves the SW in relatively mild conditions.
ECM shows a period of slack winds and pressure for a time next week as our weekend High declines. Thereafter a new High forms close to the NW in much colder air which infiltrates down over the UK beyond midweek. Towards the end of the run milder Atlantic winds battle the cooler Autumnal air lying over much of Northern Europe with the North and East staying largely cool and bright while the SW become at risk from some heavy rainfall from slow moving troughs in a cool ESE wind.
The GFS Ensembles paint a strongly cooling trend this morning with uppers falling below average for a while following the warm interlude of the next few days. After a settled start the weather is shown to turn more changeable from most members with considerable spread at a quite an early stage of the output so much indecision is still likely with some stark changes run to run over the next few days likely.
The Jet Stream shows the flow being pushed north of the UK over the next few days before high pressure over the Arctic pushes it slowly back South over the UK and potentially to the South later next week, a pattern that we have seen so often over recent Autumn and Winter seasons, a trend that looks like it could be replicated again at the start of this season.
In Summary today there is a real cocktail of options on offer between the models and the ensemble members within each model. The next 4-5 days should be OK with benign and settled weather likely with some warm sunshine to be found, especially over the South. However, from early next week things become very complex as the surge of cold air over Northern Europe is shown to be considerable on some output. It is the interaction of this along with warm Atlantic air added to the fact that pressure is high over the Arctic that could set up some interesting synoptics over the next couple of days and I wouldn't be surprised to see a major and intense depression shown somewhere soon if these two opposing air masses are allowed to interact. As it is currently a gently cooling trend is shown with the risk of rain increasing from later next week as Low pressure gradually squeezes the life out of any UK High pressure later next week but will the rain come from the cold air to the North or warm air to the SW is anyone's guess this morning. Very interesting synoptics nonetheless.
Edited by user
20 September 2013 08:31:41
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Reason: Not specified
Martin G
Kilmersdon Radstock Bath Somerset