Posted 21 April 2012 - 12:24
Some thoughts from Wales.
So far, this has been a non-photogenic convective spell here. In April and May, and often the first half of June, sea temperatures are playing catch-up, which means they do not aid and abet convection over the Irish sea, at least in its wider northern parts, as they increasingly do late summer into the autumn and early winter. Instead, the best possible scenario here involves a slack low centered over E England, which results in a gentle N airflow across Wales. Clear mornings followed by initiation and sea-breeze interaction then make for some interesting conditions. A southerly will do too, but is particularly good later in the year when cells that form inland over SW Wales are able to continue developing as they track N-wards across Cardigan Bay: such conditions associated with good deep-layer and low-level shear accounted for the two best wall-clouds I've seen, in summer 2010 and autumn 2011.
These rather moist SW to W airflows, on the other hand, generate a scattergun pattern of cells in these parts, heavy and thundery yes but often partly to wholly obscured by other low and midlevel cloud: with a marked lack of clustering along convergence lines, targeting is difficult and the cells are always heading away eastwards (C/S/E England always best in such scenarios as the better storms are obvious by the time they are heading into these areas). Hence I've not been out on the case with anything so far during this past few days. Here's hoping for a few slacker days in the coming weeks!
Cheers - John