TWO Buzz

Weather news and views from Brian Gaze.

Change on the way

Thundery showers this weekend?

Posted Wed 15th May 17:54

Temperatures this afternoon reached 24C (75F) in Scotland and much of the UK had more fine weather. However things will change during the next few days as more showery conditions develop. In much of the country temperatures take a dip. How's it looking for the weekend and next week? 

Thunderstorms this weekend?

The weekend weather looking mixed and showers could be quite widespread. One thing to of note is the possibility of thunderstorms in the south east.

The GFS chart below shows forecast 850hPa temperatures for 15:00 GMT on Sunday 19th May. Values are quite high in East Anglia and the south east. 

GFS 850hPa temperatures

At the same time the GFS precipitation forecast shows showers in much of the UK and in the south they are quite heavy. I wouldn't place too much stock in the details and subsequent runs could still adjust things markedly. Nonetheless if it is on the right track for now the next thing to consider is the CAPE and Lifted Index forecast. (More about CAPE and LI) .    

GFS precipitation

The CAPE and LI chart below is for the same time. The negative values and yellow shading highlight the areas where the greatest risk of thunderstorms is.



Basically East Anglia, the south east and central southern England. The values don't suggest huge amounts of instability but there could be enough to trigger some thunder and lighting.  

GFS CAPE and Lifted Index

Warmth not far away next week?

Next week the changeable conditions probably continue. The London GEFS 06z plot below shows forecast 850hPa temperatures and precipitation for the next 16 days. Things to note are:

1) 850hPa temperatures are above the 30 year average for much of the next 10 days 

2)  After a dry start the risk of rain increases but it isn't looking very wet

London GEFS 850hPa temperatures and precipitation

At this time of year temperatures at the 850hPa level don't tell the whole story. Even if they are above average cloud and rain can keep it cool at the surface level. In other words they aren't necessarily a guarantee of warm weather.

On balance I think the likelihood is temperatures next week at the surface level to be a little over the average in most of the UK. Therefore despite the mixed theme we could end-up with a week at the better end of the changeable spectrum! In other words dry and warmish conditions may have the upper hand over wet and cool ones.   

TL;DR

The current settled period will be replaced by changeable weather in the next few days. Showers perhaps become widespread this weekend and they may be thundery in the south east and East Anglia. Next week the prospects are mixed but at times it could be quite warm and mainly dry.

Latest model charts

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