Good morning. Here is this morning's offerings from the midnight outputs of GFS, UKMO, GEM, NAVGEM and ECM for today Tuesday September 11th 2013.
All models show an occlusion close to the SE moving away East. A new set of fronts over the NW are shown to move South and SE through the day bringing outbreaks of rain and drizzle, heaviest in the West through the latter half of today. The cold front then gets hung up over the South as it loops back and returns East over the North tomorrow as a warm front with rain and drizzle for the North and cloudy but less damp weather in the South. As the cold front slips South on Friday and Saturday it develops waves which enhance rainfall over Southern Britain for Friday and Saturday clearing late in the day. The North will be brighter and fresher on Friday and Saturday. By Sunday all models show freshening Westerly winds and fronts approaching from the West with rain following later in the day moving East.
GFS then shows the deep Low bringing Sundays rain further North than last evening's midday run and consequently brings less dramatic changes to the South at least. Nevertheless, all areas will see a spell of rain and fresh to strong winds with gales in the North and NE followed by brighter and cooler weather with NW winds, the showers most prolific in the North. Later in the run the weather warms up somewhat for a time, especially across the South as High pressure ridge up into Southern England. This is then pulled east in response to the remains of an ex-tropical storm heading NE towards Iceland and giving the UK a spell of rain as it's cold front clears through and followed by Low pressure to the North delivering further showers or outbreaks of rain in temperatures close to average to end the run.
The Fax Charts show a complex array of fronts mostly affecting the South and West with rain and drizzle over the coming days before the large depression forming on Sunday brings a warm and cold front East across the UK at the end of the weekend with wind and rain for all.
The GFS Ensembles show very little cohesion following the weekend Low pressure with a wide spread between members showing many different options again this morning. The only general theme I can pick up is that following the weekend rainfall the trend shows rather less rainfall for the South the deeper we move into the run. The temperature profile is hard to quantify today as the average shown by the mean line for the run is skewed by equal warm or chilly options with the operational a warmer outlier in it's latter stages.
The Jet Stream shows the off shoot from the flow moving South or SW today in association with today's complex front structure dissolving away later tonight as the main arm rides NE to the North of the UK for tomorrow until the weekend. The flow strengthens early next week innitially across the UK from the NW before lifting slowly North towards Northern Scotland or even further North deeper into next week.
UKMO today holds the deep Low to the North of the UK early next week with the brunt of the cold and showery weather held to these areas while Southern areas become at risk of further Atlantic disturbances running East in the flow with spells of rain but less cool conditions than in the North.
GEM develops the Low as the other models and maintains Low pressure close to the North and NE of Britain well into next week with unstable, cool and showery conditions for all with the added ingredient of rather more prolonged rainfall at times as troughs running East in the West or NW winds continues until later in the week. Then High pressure builds from the South with a quieter Autumnal spell of dry anticyclonic weather likely for a time towards next weekend.
NAVGEM brings the Low pressure towards Northern Scotland at the beginning of next week and holds it there while filling slowly for several days, all the while continuing to spiral areas of cloud, rain and showers East across Britain in a cool West to NW flow.
ECM today shows the deep Low to the North and NE of britain at the start of next week with a band of rain followed by showers for all. It then draws a secondary depression into it's flow towards midweek which would bring heavy rain across england and wales followed by very cool Northerly winds and showers to all for a while later in the week before a ridge of High pressure in the wake of the Low topples East over the UK with further low pressure, this time well to the NW delivers cloud and rain on milder SW winds towards the end of the run.
In Summary today it's a very mish mash selection of charts which while showing some interesting synoptics offer no cohesion in patterns making next weeks weather extremely difficult to decipher today. It looks odds on that some sort of wet and windy spell early next week is likely, most effective in the North while the South may see no more than a strong breeze and a band of rain. Where that depression goes in the longer term is open for debate this morning as options of High pressure rebuilding or continuing unsettled weather with Low pressure to the North are all shown to some degree or another with anything possible. To use the much used phrase on this forum it's a case of many more runs needed before things become any clearer and commonplace between the models.
Originally Posted by: GIBBY