Another day of developing thundery downpours and attendant hazards. The blanket of low cloud that developed overnight has not stopped some early showers getting going across Lancashire and Greater Manchester and as the low cloud gradually thins/breaks and the sun quickly raises temperatures to ‘trigger’ levels, so some heavy/torrential and often thundery downpours are expected to develop quite widely across our region through the afternoon, continuing well on in to the evening before eventually easing in intensity overnight.
Just like we saw yesterday across Greater Manchester and Lancashire in particular, the impact of the intense rainfall could be rapid on the road networks and more generally within urban areas with frequent lightning and hail additional hazards to factor in. One problem facing us today is that the storms, once formed, will have only a very gentle steering wind behind them, thus running the risk of slow-moving downpours and larger localised rainfall accumulations, increasing the risk of surface water flooding. Today’s warning, attached above, reflects this concern as we have moved in to the low likelihood/medium impacts position on the risk matrix. The warning is valid from 1330 today to 0600 tomorrow morning, reflecting the possibility that areas of rainfall associated with slowly decaying storm activity may well continue into the early hours of Wednesday, extending the time for possible disruption. The warning text contains a full listing of potential impacts that might result from a ‘direct hit’.
Local knowledge of surface water hot spots and rapidly responding urban water courses could prove very useful today, as well as regular recourse to the rainfall radar on Hazard Manager, the web or the App to check on the development, distribution and track of the shower/storm activity. A reminder too that lightning distribution is available on Hazard Manager and on http://en.blitzortung.org/live_lightning_maps.php?map=12 for those without Hazard Manager. This morning’s Flood Guidance Statement mirrors the Met Office warning for today with all of the Northwest on Yellow (low flood risk) with a low likelihood of significant impacts derived largely from surface water effects.
In essence a similar type of day. Remnants of today’s activity could still be around first thing. Thereafter further scattered heavy shower/thunderstorm development will ensue from around late morning/lunchtime as temperatures reach ‘trigger’ levels with again potential for surface water flooding on the roads/urban areas, as well as lightning/hail in the hazard mix. An additional severe weather warning has been issued for tomorrow’s developments which, like today’s covers the entire Northwest but which has a validity period from midday to 2100 (see above) and a risk assessment of a very low likelihood of medium impacts. Shower/storm activity tomorrow will likely fade more definitely through the evening rather than lingering on in to the night as may well be the case today. That will then prove to be the last in the current series of the ‘downpour days’ that began on Saturday with a low pressure system that had its origins, believe it or not, up towards the Iceland/Greenland area last week !!
Thursday and beyond:
Still a rather unsettled picture beyond tomorrow though less dramatic/impactful. Thursday is likely to see a spell of more steady and non-disruptive rain edge N’wards across the region. Thereafter we will finally see a gradual return to a more Atlantic-based weather pattern for a few days with more breeze and some rain, potentially settling down more as we pass the summer solstice and head into next week.