Tornadoes, hail, thunderstorms and heavy rain possible in Derry and Donegal today storm research group predicts

The Tornado and Storm Research Organisation (TORRO) has suggested much of the north and a small part of the north and west of the south of Ireland could be affected.

It forecasts a range of possible hazards including isolated brief tornadoes, heavy rain, hail up to 10 to 15mm in diameter and cloud-to-ground (CG) lightning.

TORRO scientists say their forecast is valid until 8 p.m. on Friday and outline the technical reasons why tornadoes could occur.

"An upper shortwave trough will move north-north-east across the area today. Daytime heating will allow for 500/700 joules per kilogram of convective available potential energy (CAPE) air to develop.

"Low-level convergence zones and fairly low cloud bases brisk the risk of one or two brief tornadoes. Slow-moving storms will bring locally torrential rain, and heavy hail is also possible. CG lightning could become briefly and locally frequent," they state.

TORRO defines a severe thunderstorm as producing one or more of the following: one or more tornadoes and/or waterspouts; hail intensity of at least H3 [when hail breaks glass and dents vehicles] at ground level; non-tornadic winds gusting to 55 mph or more at surface (but which are not part of synoptic-scale straight-line winds of such velocities).

Thunder/lightning does not necessarily need to be present for any of the conditions listed above to occur.

TORRO carries out research on many aspects of severe weather including hailstorms, lightning impacts, tornadoes and thunderstorms.

State meteorologists have warned of heavy showers on Friday.

Met Éireann state that 'showers will be heaviest in Leinster, Ulster and east Connacht, with a risk of thunderstorms in Ulster this afternoon'.

The Met Office forecasts, 'some brightness at times along with a few showers, some of these heavy and thundery in the afternoon across central and western areas. Light winds. Maximum temperature 15 °C'.