Convective/Thunderstorm Discussion - Spring 2023

Meteorite58 · 07-05-2023 11:51pm

From Convective weather, link to site below.

http://www.convectiveweather.co.uk/

Day 2 Convective Outlook

VALID 06:00 UTC Mon 08 May 2023 - 05:59 UTC Tue 09 May 2023

ISSUED 22:00 UTC Sun 07 May 2023

ISSUED BY: Dan

Upper ridge over western Europe will slowly topple southeastwards on Monday, as an upper trough advances from the Atlantic (the trough axis not crossing Ireland until Tuesday morning). A series of fronts will cross the British Isles, bringing extensive cloud and outbreaks of rain across Britain for a time, but leaving Ireland/Northern Ireland with increasing amounts of insolation through the day as convective overturning breaks up the cloud. As such, heating of the moist low-level airmass (dewpoints 13-15C) coupled with cooling aloft as the upper trough approaches, is likely to yield an increasingly unstable environment with scope for locally in excess of 1,000 J/kg SBCAPE. Forecast soundings suggest a cap will initially be present at ~800hPa, but this should erode by around noon as cooling aloft occurs. As such, heavy showers and thunderstorms should develop fairly readily once surface temperatures reach the mid-high teens Celsius - this appears most likely to first occur over Ulster from around 13-14z onwards, and then perhaps an hour or two later further south into the Irish Midlands vicinity and points east, where surface troughing is expected during the afternoon aiding low-level convergence. Thunderstorms will mature in size and intensity as they drift gradually to the east/northeast at 20-30mph, therefore the most widespread coverage of lightning is anticipated in eastern areas where a MDT was introduced.

Forecast soundings suggest convective cloud tops could reach -50C / 30,000ft. Shear is somewhat limited due to the main jet activity remaining to the south of Ireland, but that said 20-30kts should be sufficient, especially in central and southern Leinster, to help separate updrafts/downdrafts and aid some organisation of cells, perhaps with some transient supercellular characteristics. Some very active and long-lived thunderstorm clusters are possible, perhaps back-building such that some areas receive multiple thunderstorms and therefore increasing the risk of local surface water flooding. Hail and gusty winds will likely accompany the strongest cells, although both aspects probably below severe limits (1.0-1.5cm and 35-45mph respectively) - however, the strongest cells in central/southern Leinster may be capable of producing hail closer to 2cm or so in diameter, and a SVR may be introduced in subsequent updates. Cloud bases during the first half of the afternoon will typically be around 1,000ft, but should lower to 500ft (or less) towards evening as dewpoint depressions reduce. This, coupled with modestly increasing low-level shear/vorticity as storms approach the east coast, may provide a brief window of opportunity for an isolated tornado, but the risk is deemed rather low overall. Thunderstorms may well persist until mid-late evening in eastern areas, but a gradual decay is anticipated through the evening hours as they drift across the Irish Sea towards the Isle of Man, W/NW Wales and NW England.

Elsewhere, thunderstorms emanating from Northern Ireland may spread into S/SW Scotland, especially during the late afternoon and evening hours, although how long they continue to produce lightning is questionable given only modest instability here. In addition, surface heating in north and northeast Scotland coupled with orographic forcing and some low-level convergence may encourage a few heavy showers/weak thunderstorms to develop here during the late afternoon and early evening hours. A few lightning strikes may also be possible in the morning/midday period near/over SW England and Wales on the rear of the frontal rain, but forecast profiles do not appear to be fairly conducive to sustain deep convection and so have refrained from introducing a SLGT here. Towards the end of Monday night (and this forecast period), a shortwave trough approaching SW Ireland may produce a few sporadic lightning strikes, but much (if any) activity may hold off until 06z Tuesday before making landfall.

Dazler97 · 07-05-2023 11:53pm

Dublin will be added I'd say by morning as well as louth, wexford and westmeath

esposito · 07-05-2023 11:56pm

Great post Meteorite 58, love your explanations. As ever with thunderstorms in Ireland nothing is guaranteed but certainly looks interesting tomorrow.

pauldry · 08-05-2023 12:23am

Tomorrow looks the most exciting day in quite a while for thunder and lightning. Will be a lot of plusses on the map at 1500 tomorrow.

Meteorite58 · 08-05-2023 9:46am

Updated warnings

Screenshot_20230508_094518_Met ireann.jpg

pauldry · 08-05-2023 1:37pm

Interesting hours ahead

Robwindstorm · 08-05-2023 2:16pm

This will be very interesting to see how this unfolds. Murky damp morning with plenty of drizzle, now humid sunshine in North Meath. Not much development on the radar yet compared to the same time the last few days. Let's see what happens?

Dazler97 · 08-05-2023 2:20pm

https://www.boards.ie/discussion/comment/120569811#Comment_120569811

Aw sweet carrick is in a high risk too

Supercell · 08-05-2023 2:28pm

Lovely morning and afternoon so far after the overnight rain went. Have to say I thought we would have seen some showers by now here. Hoping for something later.