Hi everyone. Here is the evening version of the midday outputs from the big 5 weather forecast modules for today Tuesday August 20th 2013.
All models show a depression moving NE close to NW Scotland with rain spilling NE across Northern and Western parts of Scotland and Northern Ireland through the night and tomorrow before dying out steadily by Thursday. England and Wales lie under a ridge of high pressure with quiet and benign conditions over the coming few days though with an increasing risk of showers. A push of warm air on a Southerly breeze moves up across principally the SE on Friday at the same time as a weakening frontal zone moves East across the UK with outbreaks of rain or showers, some heavy in places. This showery pattern looks like continuing on into the first half of the weekend too.
GFS then shows the second half of the weekend on an improving note especially in the North as a ridge spreads slowly SE across the UK over the first half of the week with fine and dry weather for most. Through a large part of the extended run the weather maintains this pattern with High pressure lying across the UK with fine, dry, sunny and reasonably warm weather continuing for most until a change looks possible right at the end.
The GFS Ensembles show a spell of average temperatures both at 850 levels and on the surface as a period of West or NW winds look likely from early next week as High pressure remains dominant to the SW and rain bearing Lows cross east to the north of Scotland.
The Jet Stream does indicate a shift in the flow to the North of the UK for much of the period although it's axis ridged over the Atlantic means a flow from the NW moves down over the UK at times.
UKMO shows a weak area of pressure across the UK in almost'col' type conditions indicative of a sunshine and shower scenario with light winds and average temperatures.
GEM tonight holds High pressure down to the SW with successive ridges interrupting spells of showery weather in a rather cool NW flow for most of the time.
NAVGEM shows an area of slack pressure across Southern Britain with sunny spells and the odd shower. A more direct Westerly flow blowing across the North is shown which could bring fronts across at times with a little rain. Temperatures indicate near to average levels are the most likely.
ECM tonight shows a showery weekend in a NW flow behind the exiting weekend trough. then through next week the weather stays changeable but with a lot of dry weather as well with occasional bursts of rain or showers in near to average temperatures for late August.
In Summary the pattern remains somewhat confused with the favourite option being one of NW winds with High pressure down to the SW from next week on. The uncertainty falls on how big a role High pressure down to the SW is going to play on the UK weather with varying degrees of this shown tonight ranging from a continuing feed of showers from Low pressure close to the East or a full blown ridge across the UK from the SW.
Originally Posted by: GIBBY