The EOTS team had not long returned from their successful storm chasing trip to Florida, when some powerful UK thunderstorms decided they was going to compete for our appreciation! In fact, such was the power and ferocity of the thunderstorm which struck Weybridge, Surrey, during the evening of 27th July 2006 that it would easily rival anything we'd seen in the Sunshine State!

Warm and very unstable conditions continued across the UK during the 27th, continuing the sort of setup which saw immense thunderstorms across East Anglia a day earlier (see "Cambridgeshire Destroyer"). Through the day, thunderstorms had developed throughout the Midlands and northern England and were gradually homing in on south-east England as evening approached. The following synoptic chart (provided by http://www.wetterzentrale.de and copyright UK Met Office) shows the pressure patterns and frontal analysis for midnight on 28th July, just hours after the storm struck Weybridge:

At around 3pm, a fairly harmless line of cumulus moved gradually eastwards across central-southern England, connected northwards to lines of thunderstorms over the north Midlands. The following high resolution satellite images are copyright Eumetsat and MeteoGroup UK, and show the evolution of the thunderstorms as they developed.

At 3pm, a long line of cumulus clouds stretches back from storms over the Midlands, towards the Isle of Wight.

An hour later at 16:00, the line of cumulus suddenly erupts into several discrete cumulonimbus cells, producing heavy showers. Note the simultaneous development of thunderstorms across northern France too.

The initial cell development produces some short-lived thunderstorms to the north and west of London although these quickly die off. As their streaming anvils decay as they move northwards, the storms had left behind a pool of moisture in north-east Surrey, just as the line of cumulus, stretching back towards the Isle of Wight, moved in from the west.

Just 30 minutes later at 17:30, the cumulus ingests this moisture and a titanic thunderstorm erupts over northern Surrey. The updraft was to the west of Weybridge at this time, and can be seen here on the southernmost edge of the storm. The thunderstorm's huge and solid anvil can be seen streaming northwards into the east Midlands. Note the outflow boundary line of cumulus already heading south-eastwards away from this monster of a storm.

The thunderstorm upraft reached Weybridge here at 18:00, and began to regenerate on its southern flank in a spectacular back-building manner. As each updraft erupted and moved north, a new one would develop over the village. This process repeated itself between 5 and 7 times, with each new cell reinforcing the thunderstorm. The 'V' shape of the thunderstorm is almost text-book in appearance, with the sharp updraft on the southern edge complete with the feeding flanking line to the south-west, and the raging anvil spreading out northwards. In an identical manner, note the lines of cells erupting into giant mushrooms over France.

This image from 18:15 shows beautifully how the new cells were developing on the southern side of the storm. This particular updraft would provide the finale over Weybridge, with rainfall like the EOTS team had not seen in this country, and lightning every 5-10 seconds.

The EOTS team arrived into Weybridge train station just as the thunderstorm began unloading its contents over the village and surrounding area. The following account shows photographs from this event.

This is the scene that greeted us as we drove back through Weybridge; daytime darkness, torrential rain and flooded roads. The only daylight was provided by the lightning!

No enhancements have been carried out on this image, except to increase the brightness! Conditions really were like the dead of night as the thunderstorm sat overhead.

We had never seen rain like this in the UK before. It came down in
torrents, overpowering guttering and causing rapid flooding.

As the first cell moved away, and in the short break before the next developed overhead, we took a quick walk around and were greeted with this scene on the local cricket green!

Here is a panoramic view of the flooded cricket green. Click on the image for a larger version.

A video capture showing a CG lightning strike, both in the air and on the water!

More flooded roads, with water pouring into shop fronts and buildings.

With closed roads and flooded buildings, the emergency services were out in force.

Many roads were close to being impassable due to flood water.

You know you're in trouble when the water is deep enough to cover the front lights!


This was the radar frame at 1700z, where black shows the most intense rainfall. The red flag marks the position of Weybridge.Radar copyright MeteoGroup UK

Nearly an hour later, and the intense echo remains right over Weybridge, corresponding
to where the updrafts were back-building, developing and collapsing.

The EOTS team collected each 5km resolution radar image between 16:00z and 19:00z, and used a technique to estimate the rainfall totals, based on the radar pixels alone. During the three hour period, we calculated that 48mm of rain had fallen, 42mm of this in one hour. However, we managed to obtain the 1km resolution, 5 minute radar sequence from the UK Met Office (we do not have permission to reproduce this) and the rainfall estimation over the same period is 82mm, 71mm of this falling in one hour. Unfortunately, we did not have an accurate rainfall gauge and thus this is purely an estimate. However, we feel it is a fairly good estimate based on the intensity of the rain and the resultant flooding.

The best footage we obtained from this monsterous back-building thunderstorm was in the form of video, some of which was taken on our digital camera, and some on our camcorder. The following links are to several of these videos which give a good indication of the rainfall intensity and lightning proximity.

Extremely close CG lightning discharge:
Format: Windows Media Video (wmv)
Video: 2.36mb, 0:12

A wander around between storm cells
Format: Windows Media Video (wmv)
Video: 18.2mb, 1:41

Rainfall footage from digital camera
Format: Windows Media Video (wmv)
Video: 8.06mb, 0:44

It is extremely difficult to put across the shear intensity of this thunderstorm in photographs and videos. It was without doubt the most intense thunderstorm we'd ever seen, all taking place right over the top of Weybridge and lasting for a considerable length of time. Narrow lines of back-building thunderstorms can deliver a huge amount of rainfall to very localised areas, and due to the nature of their regeneration over the same spot, they can last for quite some time.

This was a spectacular storm which had the effect of making us behave rather wrecklessly. It's extremely dangerous to wander around outside with frequent lightning in the area and we do not condone such activities in any way, shape or form.