Sunday’s Showers/T-Storms Should Focus On Wales, Midlands, Little Action Over Lond, E Eng & Scot!

Written by on August 11, 2012 in Rest of Europe with 0 Comments

Following a glorious week of weather and glorious second week of weather for the Olympic Games, we of course always have that breakdown looming, especially this summer when you creep into day 5 or 6 of warm sunshine.

That breakdown will come tomorrow but it has limitations as to how much the warmth breaks and the sunshine dissappears. For many from London to Inverness, tomorrow will be another warm and sunny day but from the Southwest of England, up through Wales and into the Midlands, possibly extending into the North of England, a warm and sunny start should give way to increasing cloud and eventually some showers and thunderstorms will develop through Sunday afternoon.

EARLY SUN: GFS Precip chart courtesy of MeteoGroup

Heights are falling throughout the UK as of this writing but the outer edges of the low to the SW will bring the change to Ireland, Wales and the Midlands and it’s here where we may see some lively downpours with small hail, lightning and local flooding but I feel pretty confident that eastern England, from London all the way up from Scotland (away from the Midlands, perhaps into NW England, it should stay warm and sunny.

So, today, may well be warmer than today in such places as London where we may see a 27 or 28C. East Anglia, Lincolnshire, Yorkshire may all enjoy 21-25C depending on location. High clouds could will drift over western Scotland through tomorrow afternoon, shutting down daytime cooling and holding highs in the 18-21C range but from the Central Belt north and east, where skies are sunnier and with southerly winds, we may see an odd 24 or 25C over the Central and NW Highlands.

SUNDAY PM: GFS Precip chart courtesy of MeteoGroup

The GFS CAPE (measures level of convective energy potential) forecast reiterates how the concentration of shower and thunderstorm activity tomorrow afternoon is mostly confined to Wales and the Midlands where heights drop most and there is sufficient mid and upper level cold to break the cap. The cap should stop clouds and storms from forming around the outer edge of the trough these areas include, Greater London, eastern England and Scotland and by the time the cap does break with the further advance of the front and low pressure system late tomorrow night, into Monday, the air mass will have cooled, so the dynamics are no longer supportive of heavy showers and thunderstorms.

Check out the below map showing the GFS CAPE forecast. Notice where the brightest colours are (N and W of London). The brighter the colours, the better chance for storms to pop. The simple reason showers develop here and not further east or north is that has to be the timing is right with the advance of the trough and cooling of the 850 level (5,000ft up) with daytime heating. Warmth building raises the rate of upward motion and if the upper atmosphere cools, the cape can break, cumulus clouds can start to build vertically into the much needed cold upper atmosphere and it’s these dynamics which allow showers and thunderstorms to form. IF the 850 temperature is too warm, upward moving air can only get so far before it hits a ceiling and the air sinks back to the surface. The GFS is seeing a cap over eastern and northern Britain tomorrow but where these cells do pop, they could pack quite a punch.

Soaking rains return Monday for most of the UK

By Monday, heights will be considerably lower everywhere and rain will be allowed to spread across most of the UK duyring Monday with a fresh breeze. A lot of cloud with steady and at times heavy rain will make for a very different day Monday with daytime highs likely confined to around 16-18C for many. At best 22-23C where the sun does shine for a decent duration.

Check out what the GFS has for Monday!

Potentially very wet, very windy end to next week with sub-988mb low crossing, Ireland, Scotland?

While Monday’s wet and cooler weather slaps us back to reality, the low responsible for this change won’t push across the UK despite it’s fronts doing so as ridging remains too strong over Scandinavia. According to the GFS and ECMWF, the low will meander offshore through the early part of next week and then late next week it deepens, tracking northeast, eventaully crossing Scotland Friday. This could bring heavy rains and strong winds to much of central and northern Britain. This is the next feature which will be worth watching closely. The models have this low between 986-990mb over the Irish Sea, piling driving rains and strong southwest winds across a large portion of the UK with coastal gales..

Below is what the GFS has for next Thursday.

This GFS chart interpreted by WeatherBELL Models shows 988mb low tracking NE into the UK next Friday! (Chart courtesy of WeatherBELL Models)

here’s the ECMWF for next Thursday.

ECMWF forecast for next Thursday interpreted by WeatherBELL Models. (Courtesy of WeatherBELL Models)

 

 

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