Severe Weather Forecast
TORRO CONVECTIVE DISCUSSION 2016/007
A TORRO CONVECTIVE DISCUSSION has been issued at 11:10GMT on Thursday 15th September 2016
Valid from/until: 12:00-22:00GMT on Thursday 15th September 2016 for the following regions of the United Kingdom & Ireland:
Parts of southern and central England
Isolated tornadoes; gusty winds; heavy rain/flash flooding; CG lightning
A warm/moist airmass across much of England/Wales and eastern Scotland will remain in place this afternoon. Overnight, a cold front will move in slowly from the west. In the upper levels, a trough will approach western Ireland this afternoon, and an upper low will be fairly slow-moving over southern Biscay. Overnight, this upper low will start to lift north-east and fill, whilst the trough to the west will move across the UK, sharpening somewhat in southern areas as it interacts with the upper low to the south.
Surface heating this afternoon along with low-level convergence should allow scattered showers and thunderstorms to form across parts of central southern England. Other cells may form further north, e.g. over the Pennines. Any of these will have the capability to produce torrential downpours, given a very moist profile. The highest chance of a brief tornado will be where low-level convergence is maximised - this appears to be in the risk areas shown, although cannot be ruled out further north too. The moist profile and lack of shear may limit hail potential, but at least marginally severe hail seems possible too.
Storms in the south may drift slowly westwards with the mid-level flow this afternoon - overnight, the upper flow will become slack and then south-westerly, but shear will never be supportive of organised severe storms. However, storms this afternoon may form into a small cluster as they drift westwards, perhaps with gusty winds on the leading edge of a developing cold pool.
Overnight, as the upper trough and cold front move in from the west, thunderstorms and showers may become more widespread, and the risk of isolated tornadoes will decrease - a cluster of storms may then spread eastwards.
This is quite a complex and rather tricky situation - the overall risk of severe weather is low, but the risk of local flooding is high where storms develop.
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