The storms of the 26th and 27th July 2006 were confined to the south eastern
quarter of the UK and were generated by a high Theta-W plume which returned west after previously moving east across
the area and the approach east of a slow moving long wave disrupting upper trough located over Ireland and down to the west
of Brittany.
On the afternoon and evening of the 26th a large MesoCyclone System (MCS) developed
over Nrothern France and gave large hourly totals of rain and impressive wind gusts (over 50knts in the Inner Paris area). Surface
based storms also developed over Cambridgeshire and Eastern England. Satellite images showed substantial evidence of "back-building"
storms (where storms continually keep developing over the same area) and in fact over 40mm in one hour was reported at Bassingbourn,
south west of Cambridge, whilst large hail broke glass in greenhouses in Lincolnshire.
During the evening elevated but very electrically active storms moved north east over Hampshire and the Isle of Wight,
with reports of houses being struck in the Southampton area.
Storms developed in similar areas on the 27th, with severe surface based storms
erupting from an unstable atmosphere over Eastern and SE England. The 06Z Larkhill Ascent (not shown) indicated well over
1100j/kg of CAPE could be released across these areas on the afternoon of the 27th given temperatures above 27C, which looked
likely to be quite readily obtainable. There were reports of hail and serious flooding from Milton Keynes, Weybridge,
Woking and West London. In addition air travel was severely affected at London's Heathrow and Stansted airport with long delays
developing. In the 15Z Surface analysis (shown in Fig 1 opposite), note the convergence over Lincolnshire and the well marked confluence zone from East Anglia
to W London (moving slowly SE). Regional radar for the south east (Fig 2), shows the intense storms
which formed across SW London which remained slow moving for nearly two hours.
However by late on the 27th, a change was already visible over the Atlantic
with a more mobile and cooler westerly airflow poised to move east and push the more volatile thundery weather east again,
into the near continent.
All Satellite Images are kindly reproduced courtesy of Eumetsat (C) 2006
Rainfall Figures are courtesy of the Met Office and Philip Eden
Text (C) Paul Blight 2006 Assoc Fellow Royal Met Society
E mail: pblightuk@yahoo.co.uk
