Good morning. Here is the weekly detailed report on the midnight outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Sunday August 18th 2013.
The General Situation 5-7 days. The models currently show a Westerly flow across the UK carrying a mix of sunshine and showers for all today. The flow weakens over the next 24 hours as pressure rises from the South with just the North at risk of showers tomorrow while the South stays dry and bright. On Tuesday and Wednesday a small depression is shown to move NE across Scotland carrying rain at times across the North and West. This now looks it could spill further South and East on Wednesday with all areas under a lot of cloud with chiefly light rain at times. By Thursday the weather should of become warmer and drier for 24-48 hrs and although there could be quite large amounts of cloud at times across the UK some good sunny spells will develop and it will feel warm or very warm locally. Very late in the week and more likely over the weekend the weather will slide downhill again, this time from the South or SW as Low pressure develops there with thundery rain or showers edging slowly North and East across some parts of the UK in varying degrees next weekend.
GFS shows the Low complex further north to the west of the UK making the breakdown more widespread and affecting most of the UK by next Monday as it slowly moves East over the UK with many areas then becoming cooler and drier again for most of the extended range with High pressure back down to the SW with a tenuous ridge over the UK. NW winds look the most likely option with a lot of dry weather but some occasional rain in the North with temperatures close to average.
The GFS Ensembles show strong support for a warm up in this coming week with a lot of dry and bright weather. There is also now good support for a spell of potentially wet weather in the South next weekend as Low pressure pulls in from the SW or West. Thereafter there is a lot of spread between the members with an array of options ranging from warm and settled to rather cool NW winds and a little rain at times. This weeks spoiler Low to the NW on Tuesday/Wednesday appears to dilute the sunniest conditions away from UK through the middle of this week too.
The Jet Stream shows the flow across the UK splitting this week with one arm travelling North of the UK and as it does so opens the door to a Southern arm which becomes responsible for carrying next weekends unsettled spell across the UK. Beyond that the flow becomes much weaker and diffuse with one arm travelling North over Greenland and another one East over France and Europe.
UKMO closes it's midnight run with Low pressure positioned over the English Channel and Southern England next Saturday with outbreaks of showery and potentially thundery rain in warm and humid conditions while the North sees the best of drier and bright conditions.
GEM on the other hand brings developments to the NW into play next weekend with the short fine spell extended on rather longer in the South in slack winds before cooler and more changeable conditions come down from the NW at the start of Week 2 with outbreaks of rain or showers in cooler Westerly breezes and temperatures close to average by then.
NAVGEM takes the UKMO and GFS type route developing Low pressure close to SW Britain next weekend with outbreaks of rain and showers developing for the South and West following several warm, sunny snd dry days. The North and East would stay rather drier and warm inland in association with High pressure having moved off to the NE by then.
ECM today shows Low pressure too over the English channel or Northern France next weekend, close enough to the South for cloud and outbreaks of thundery rain to develop. In the North things look like staying more favourable under a slender ridge of High pressure stretched across these areas from the Atlantic. Under this pattern it does appear it would stay reasonably warm though in any brightness.
In Summary today our projected fine and very warm spell has been reduced to something more akin to a warm snap this morning. Problems arise from both the onset of the spell and the end as the spoiler Low he models have struggled with for days seems to get hung up over the UK air mass and leads to a lot of cloud and light rain for all midweek with large amounts of cloud now looking likely into the latter end of the week too for some. Nevertheless there should be a couple of reasonably summer like days late in the week before the second problem arise from developments to the South and/or SW next weekend. It looks likely that Low pressure will develop to the SW of the UK early next weekend with a spell of thundery rain or showers in these areas lasting several days. The north may be OK next weekend as a ridge from one source or another holds sway. Further out is anyone's guess this morning as a cocktail of options are shown but it does look disappointingly for many that this weeks and what was a probable longer prospect of good summer weather has been tempered somewhat on the outputs today.
Originally Posted by: GIBBY