Good morning everyone. Here is the report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Saturday Julu 20th 2013.
All models now support a change of sorts as we progress through the course of next week. After another surge of heat and humidity in the first half of the week following a cooler weekend a Low pressure looks likely to move slowly North to the West of the UK carrying a zone of thundery rain or storms NE across the UK midweek before potentially cooler and fresher conditions arrive thereafter.
GFS shows the end of the week and weekend as a mix of sunshine and showers, these chiefly in the West. While cooler and fresher it will hold quite warm, especially in the East and SE in a light Southerly flow overall. Through the following week conditions deteriorate further with Low pressure and cooler Atlantic Westerly winds playing a much more dominant role with rain at times and temperatures close to normal. Some drier and brighter periods are still possible though.
The GFS Ensemble data today continue to show the wind of change of previous runs bringing it forward to the 24th and 25th with rainfall scattered about across the UK from then on quite copiously so at times. The general pattern indicated to start August is a broad westerly flow with Low pressure to the North and High near the Azores with fronts crossing East giving all areas occasional rain and temperatures close to average.
The Jet Stream shows the flow to the North collapsing over the next few days with the flow realigning towards the South of the UK as early as the middle and end of the coming week where it remains flowing East over the Atlantic towards Southern Britain thereafter.
UKMO today shows a front moving slowly NE across the UK midweek with a small Low close to western Britain. Behind a band of thundery rain moving East midweek the weather would become steadily fresher though still warm locally with a mix of sunny spells and scattered showers, still potentially thundery in places.
GEM this morning shows a less thundery breakdown with the SE likely to see the greatest risk from this toward midweek before Low pressure moving slowly North and East over the North and West ushers in cooler and fresher weather with rain or showers at times to all areas by the end of the week and over next weekend.
NAVGEM shows thundery conditions moving slowly North over the UK midweek before a slow decline in temperatures result in fresher air being fed into the cyclonic flow over the UK at the end of the week with further showers at times, some heavy especially in the South.
ECM today shows a weak thundery phase midweek more likely for the SE while the majority of the UK would fall under a cooling and fresher regime later in the week following a band of thundery rain moving NE. Behind this brighter skies would most likely lead to sunny spells and continuing warm conditions in the SE while the North and West continue to be prone to showers and outbreaks of rain then in a SW flow and this gradually pushes any remaining warmth away from the SE towards the end of next weekend with rain and showers for all in average temperatures by then.
In Summary today there seems less chance of a flash, bang, wallop end to this hot spell as there looks to be less chance shown of a direct Continental feed promoting thermal Lows usually required for such an event although the SE does look most likely to be at risk of this should it develop. The more cross model support today is given towards a band of thundery rain on a trough associated with a Low just to the West of the UK to trundle NE midweek and in it's wake introduce cooler and fresher conditions from the West slowly across the UK. By the end of the week this process is more or less complete though very warm air remains close to the SE for a time before the Atlantic winds and occasional rain extend through all of Britain on a Westerly flow to commence August. It's hard to say at this range how influential or long lasting this change will be but it does appear odds on now that the end of this memorable hot spell is on the way and we will have to start looking for the green shoots for the start of the next one over the coming days outputs.
Martin G
Kilmersdon Radstock Bath Somerset