ELEMENTS: HEAVY RAIN. LOCALISED FLOODING. THUNDERSTORMS.
A complex area of low pressure developing to the south and south-west of the UK is set to bring some inclement conditions to parts of England and Wales during Wednesday and overnight into Thursday. The low pressure is an amalgamation of the remnants of tropical storm Henri and also a more text-book North Atlantic depression. However, the entrainment of the remnants of Henri will aid to boost rainfall totals along the weather fronts associated with the low pressure system, but also bring a risk of thunderstorms to some areas.
The complex nature of this amalgamation of two weather systems continues to lead to some uncertainties in the forecast.
CENTRAL-SOUTHERN ENGLAND, E WALES, MIDLANDS and E ENGLAND
Weather fronts associated with the low pressure system are forecast to move northwards across parts of England and Wales during the course of Wednesday and overnight into Thursday. The northern and western extent of the heaviest rain is of primary uncertainty, but at the moment Central-Southern England, E Wales, Midlands and across into parts of E England look to be at greatest risk of some persistent and often heavy rain as Wednesday develops. A general 20mm to 30mm of rain is possible within the highlighted region (A) but there is the possibility of rainfall totals exceeding 40mm or more within 24 hours.
Clearly any additional rain that falls across parts of E and NE England will only compound matters after some significant rainfall there within the last 24 hours or so. Some strong and gusty winds will accompany the rain, but at the moment any severe weather is likely to be due to surface water and spray on many road networks and also a risk of some localised flooding as Wednesday progresses.
E ANGLIA and SE ENGLAND
As the weather fronts clear to the north and west of SE England and E Anglia during Wednesday afternoon, quite a warm and humid air mass will then be in place. When this combines with some cloud breaks and surface heating during the course of Wednesday afternoon then a scattering of locally heavy and thundery downpours are possible. The ingredients are there for these storms to drop up to 20mm to 30mm of rainfall within quite a short space of time, produce some frequent lightning and perhaps hail as well. As is often the case though these storms will be ‘hit and miss’ and not everywhere within the highlighted region (B) will be affected. However, where these do develop on Wednesday afternoon then some severe weather and travel disruption is possible.
Valid From: 0600 Wed 16th September Valid Until: 1200 Thu 17th September