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Convective Outlook - Sunday 19th May 2024

Updated: May 26

Discussion:

Scattered showers will develop in the early afternoon across southern parts of Ireland and Scotland, turning thundery. CAPE will reaches 700-1200J/kg during the afternoon, perhaps allowing some well scattered thunderstorms to develop in places. These thunderstorms might bring some localised flooding especailly over the convergence zones. High PWAT (30mm) can also boost the risk of flooding. Hail showers are also possible within the heaviest showers as well. Funnel clouds are also possible in places.


Wrote: @Handry_Outlook

Technical Discussion: Falling surface pressure amid surface heating during the afternoon will lead to a few areas where thunderstorms with semi-frequent lightning can form. Mainly in parts of southern England, southern Ireland and far northwestern England into southern Scotland. Moisture convergence and surface heating will trigger 1000+ J/KG of CAPE possible with more than enough 3CAPE (150+ J/KG) for significant low-level energy. So, despite mediocre buoyancy (though strong low-level lapse-rates) and the shearing profiling being okay, some half inch hail appears possible. The strongest storms appear to be in Ireland with 9+km storm heights with the popcorn type convection allowed to last slightly longer due to kinematics. These main areas should form a few thunderstorms, perhaps more coverage in southern Ireland, in the afternoon and those should last perhaps an hour before collapsing and new ones forming. This process going on into the evening until eventually the lapse-rates become higher and the energy begins to weaken between about 8pm to midnight. Perhaps a bit earlier. Saturation appears unlikely to be an issue, but the popcorn type convection likely means that storms won't be able to punch into freezing conditions for long enough to have sustained semi-frequent lightning periods. Instead, lightning coverage is likely to be over centred over small areas with the combination of slow moving storms and short time before they collapse on themselves. Flooding is an issue. With the moisture potential and amount of storms potentially over one area. Therefore a severe for flooding has been added.

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