Good morning folks. Here is my version on the course of events over the next 14 days or so using the midnight computer outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Friday July 19th 2013.
All models seem to handle the synoptics very similar for the next 5-6 days taking us up until the middle of next week. High pressure rmeains the dominant force positioned over Northern parts of the UK with a gentle but subtle feed of ENE winds across Southern parts. These winds will advance low cloud across from the East tonight to greet most Central and eastern parts with a grey and cooler start to the day tomorrow. The highest temperatures will then be felt over more western and NW areas where skies stay clear and sunny with these conditions spreading back to the East during the daytime's tomorrow and Sunday. Early next week winds are shown by all models to fall slack and light and with more humidity being fed into the UK the temperatures will soar again for a while early in the week and with the injection of humidity the risk of isolated showers and thunderstorms increase across the South and West by Tuesday as a trough edges in from the SW.
GFS then develops this feature more later in the week though less dramatically than last night. There would be a zone of thundery weather trundling North over the UK followed by brighter and fresher weather with sunny spells and dry conditions again most likely for a time over the weekend. Then through the second week Low pressure takes more overall control feeding in cooler atlantic air and setting the UK up for a heady mix of breezy conditions, average temperatures and rain at times with Low pressure in close attendance near the UK.
The GFS Ensembles show Low pressure developing to the West of the UK later next week as the favoured option with still a fair amount of dry weather to be found, especially towards the East where it would likely stay warm for a time before a Westerly flow is favoured by the end of the run. The 26th still looks the preferred date of change from GFS.
The Jet Stream today shows the flow to the NW breaking up over the next few days in response to High pressure migrating further North. Then as Low pressure meanders up from the SW the flow out of the States is engaged and eventually carries the flow across the UK through Week 2.
UKMO today shows a shallow and showery trough across the UK on Thursday of next week, moving slowly North. There would most likely be a band of showers and thunderstorms moving slowly NE over the UK, more likely over the North by Thursday while the South becomes brighter and slightly fresher but still warm with just scattered showers in winds turning to the SW.
GEM today is slower to bring the thundery zone North. It reaches the South on Thursday and becomes a slow moving and complex thundery Low feature with a lot of warm and humid air entrained. Slightly fresher air then movesacross from the SW across Southern areas over next weekend.
NAVGEM is also trending towards a thundery breakdown later next week as Low pressure moves slowly North from Biscay late next week. There would be some fine and sunny weather about still, especially in the North but most Southern areas would be likely to see at least some thundery rain or storms by the weekend.
ECM today shows a thundery trend too later next week though it's hard to gauge the Northwards extent and how widespread such an event is likely to be with no definitive movements to the features bringing this change. As a result the UK is left in a humid pool of very warm air which looks like becoming slowly displaced from the West over next weekend as Low pressure and cooler air to the West exerts some influence towards and over the UK then.
In Summary though a basic slow trend towards something more thundery next week is emerging where it leaves the UK by the end of the week and next weekend is unclear. GFS has ditched it's deeply unsettled phase next weekend with a much more gentle approach this morning while the other output all show a zone of thundery weather moving slowly North later in the week. I am less then convinced that a major thundery outbreak is likely from these type of synoptics as the features moving up from the SW are shallow and ill defined. Yes, I'm sure there will be some nasty storms scattered about next week but 'scattered' is likely to be the key word as I think some places may miss them and stay largely dry and still very warm at least until the weekend when a gentle cooling trend might edge in from off the Atlantic.
Originally Posted by: GIBBY