Good morning folks. Here is the report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Thursday 5th September 2013.
All models continue to show a cold front moving in from the West today gradually replacing the hot and humid conditions in the SE today with very much fresher air reaching the north and west today and other areas tonight. As the cool air engages the warmth over the East the cold front will develop strongly with Low pressure forming near SE England and moving NW over the weekend with all areas experiencing rain or showers and cool winds. By Monday the low will of filled near the NW and it will clear East as a showery trough through Monday. In its wake pressure is shown to rise from the SW again as a High pressure ridge develops over the UK by midweek though with a few exceptions between the models by this point noted below.
The Fax Charts illustrate an unsettled weekend for all leading into a showery start to the new week as the Low forming near the SE tonight trundles NW and then back east by the weekend to be in the north sea by Monday. A complex array of troughs is shown in association with this feature with nowhere immune to rain on all of the covered days.
GFS is a little slower rising pressure from the West next week with Low pressure to the East still giving Eastern areas a cool and showery feed as late as Thursday before a much more slender ridge collapses over the UK on Friday followed by a trough giving the weekend a cloudier and more unsettled look about it again with some rain at times for all. It's not until we get into Week 2 that pressure rises strongly over the UK with fine and sunny weather with warm conditions by day but with cool and misty nights.
The GFS Ensembles show a sharp drop in uppers over the coming 36 hours as a cold front introduces Autumn to the UK. Thereafter conditions slowly improve again with less rainfall the deeper into the run we go, especially across the South. The strong anticyclonic theme of the operational later in the run makes this run a warm outlier in Week 2 but there is scope for improvements shown by other members to be sufficient to make for some pleasant and fine weather to be found at times almost anywhere.
The Jet Stream today is currently troughing South over the Uk as the Low over SE England forms. The cut off circulation in the Jet flow around this depression weakens over the weekend as it migrates North to join the main Northern Jet which then settles on a traditional and undulating West to East flow later close to Northern Britain.
UKMO today shows high pressure close to SW Britain next Wednesday with fine and dry weather for most having replaced the showers from early in the week. With a NW feed over the UK the weather will not be as warm as currently in the South with average temperatures, broken cloud and sunny spells the most likely.
GEM today shows Low pressure closer to the SE still by early next week which has the net result of allowing extensions of Atlantic depressions to sink SE across the UK very much diluting the effects of the ridge that other outputs show. in fact much of the week is shown to be rather cool with troughs delivering rain or showers at times especially but not exclusively to more northern and Eastern locations in average temperatures at best.
NAVGEM continues to maintain it's theory which has stuck too for days now in holding Low pressure close to Southern Britain well into the middle of next week with showers or rain at times continuing in the South whereas any High pressure ridge is only shown to affect the North.
ECM looks OK next week once the early week showers have cleared away East. With high pressure transferring East across Southern Britain midweek some fine and warm conditions would develop for a time away from the cloudier north though by the weekend things are looking a little bit more tentative as High pressure begins to seep away somewhat.
In Summary there is still the trend for High pressure to build into the UK again next week. However, there are many different guises in how the models show this likely to happen both in speed of developments as well as extent. It does appear almost guaranteed that the weekend Low will move NW over Britain and fill which allows Westerly winds developing to its South to usher in a showery trough and subsequent ridge by midweek. NAVGEM is the exception to this rule maintaining Low pressure close to the South well into next week while GEM and GFS are reluctant to bring High pressure in quite as quickly today. Instead it's down to the Euro models today who both show fine prospects under high pressure from midweek next week. Even given the charts don't show conditions being as warm or as sunny as conditions in the South and East of Britain have seen recently some very useable and benign weather is not to be sniffed at for what will be mid September.
Originally Posted by: GIBBY