Heavy rain with embedded thunderstorms & flash flood risk - South, East - Aug 1-3

M.T. Cranium wrote: »

The areas that have dried out past 2-3 hours just to northwest of Dublin are close to the upper-level low which is drifting northeast and will be over county Down by about midnight, taking this drier zone along in that direction. At the same time, the occlusion running into the secondary surface centre under the upper low (the primary is over the north Irish Sea) will plod north and resume at least moderate rainfall for areas that it covers from Dublin north. On the east coast you can expect to see winds going from east to south, then southwest and west but inland the sequence will be from east to north and northwest then westerly.

The intense looking return flow from west across portions of Laois, Carlow, south Kildare will be dragged northwards and upslope against the Wicklow-Dublin Mountains could create locally heavier rains around the western portions of Dublin but then later this feature will be returning to the east coast without running into that upslope. There may be a slight rainshadow effect east of the hills that will fade out from Bray northwards later. So would expect a further 20-40 mm rain in most of Leinster as the dry centre of the system moves more into east Ulster. This wrap around could then become thundery with some hail embedded. Be alert for thunderstorm development about 4-7 p.m. in the Dublin region then this will slowly shift north during the evening.

The section of the storm now over west Ulster will be held in place for the rest of the day and through most of tonight, and I suspect it may be under-modelled so expect some locally torrential downpours in parts of Donegal, Sligo, Leitrim, Roscommon and eastern Mayo-Galway with 20-40 mm further rainfall there, also in Derry, Tyrone and Fermanagh.

This storm will likely continue for a significant portion of Sunday in most of Ulster and the parts of Leinster and Connacht within about forty miles of Ulster, and the current sharp boundaries may degrade as areas of showers begin to rotate around the more persistent rain bands.