Risk of disruption from rain/wind tonight/tomorrow morning
Afternoon Update: Some clarification on the latest severe weather warnings;
The Yellow Alert for wind has now been pulled altogether whilst the Yellow Alert for rain has been withdrawn southwards across Cumbria so that it now includes just the far SE of Cumbria, along with the remainder of the region. Within this warning there is reference to the possibility of strong winds on Monday morning but, as the earlier briefing suggested, this looks unlikely to come about, based on present predictions.
There is now increasing confidence that, for the Northwest at least, tonight’s/tomorrow morning’s much-heralded weather system will prove be much more of a rainfall-based event with the risk of disruption from strong winds having receded southwards. The reason for the change of emphasis is that the low pressure centre responsible is now expected to take a slightly more southerly track than was predicted yesterday. This effectively reduces the likelihood of any strong winds affecting the Northwest but also introduces more uncertainty as to exactly how far north the main area of heavy rain will extend. Hence the remainder of this morning’s briefing will focus on the rainfall aspect.
- Latest forecast sequence: Rain spreads northwards into the region late this evening with some persistent and possibly heavy outbreaks affecting the more southern parts of the region through the early hours of Monday. During tomorrow morning the more persistent rain pulls away eastwards to replaced by a showery regime which then holds sway for the rest of the day. The winds throughout remain below disruption thresholds although later tomorrow afternoon and evening may become strong, especially along the coasts and near to showers.
- Main uncertainties regarding rainfall: The two key issues are i) how far north the more persistent and heavy rain will extend across the Northwest and ii) how much rain will fall in the wettest areas and what the associated impacts will be. A consistent signal is for the largest rainfall totals to be recorded across the more southern parts of the region (Lancashire southwards).
- Severe Weather Warnings/Flood Guidance Statement status: There are currently Yellow severe weather Alerts in force for wind (Lancashire/Merseyside/Greater Manchester/Cheshire) and rain (all areas bar the far N of Cumbria). These will be updated in the next hour or so but, after internal discussions this morning, I anticipate the northern limit of both these Alerts being pulled a little way southwards to reflect the latest ideas – exactly how far south the Chief Forecaster will decide. I also understand that the Yellow Alert for rain will not be upgraded to Amber, this being to avoid adding too confusing look to the severe weather warning’s board. This morning’s Flood Guidance Statement shows Lancashire, Merseyside, Greater Manchester and Cheshire on Amber (Medium) flood risk for tomorrow before reverting to green from Tuesday onwards. The Amber shading reflects a medium likelihood of significant impacts resulting from surface water excess with a low likelihood of significant impacts from river overspill.
This is the picture as it currently stands but it is worth bearing in mind that the scenario may yet require further revision, depending upon what this afternoon’s update forecast produces.
With kind regards,
Alan Goodman; Met Office Advisor (Civil Contingencies)