After a rather
disappointing month for "April Showers",
finally the combination of warm moist air and instability
allowed for a couple of good days for weather
photography. On both of these days several activists were
stationed around the UK, some experiencing strong
thunderstorms while others were less lucky!
Small Cumulonimbus and precipitation moving SSW-NNE out in the bay....
Inland the cumulus towers were building nicely, promising good things for later....
Then the Cbs out to sea started to disintegrate, their anvils pulled apart this way and that...
High-level clouds with virga were observed on and off - the remnants of the dissipated Cbs. Then, at about lunchtime, a high-level haze outto the SW signalled the approach of an expected trough feature, perhaps carrying something more organised...
Packed in fishing (no fish!) and moved inland as the trough came over. Here an embedded Cb is partly visible. Shortly afterwards, rapidly-forming stratus at several levels quickly obscured everything. I drove around a bit, but got very few glimpses of what was going on above, so gave up on this one!
It was a relaxing few hours though, watching the sea and the ever-changing clouds. The following day the fishing rods stayed strictly in the car!
|So, on the 30th,
I got up early to check the data and good CAPE, LI etc
values were still valid for large areas of the UK
including Mid-Wales. By 9am convection was already taking
off in earnest. I had to go to Aberystwyth first so set
off at about 10am. At 10.20am, halfway from
Machynlleth to Aberystwyth, I watched towering cumulus
rapidly develop into a Cb. During the cumulus stage I
noted it was leaning to the N while its movement was
SW-NE - promising because it is indicative of different
wind directions at different altitudes, which in turn can
promote vigorous convective development.
By the time I'd done my shopping another larger Cb had arrived so I set off under a darkening sky, taking the back-road towards Borth via Clarach (good for views & stopping places). However there was very little to see. In fact the precipitation (hail & rain) was so intense it sometimes lowered visibility to 50m and the road was awash with water and little white ball-bearings. Nasty. I got to Borth, under clearing skies, at about 12.30 and set up in one of my usual vantage points. Out to the SW the sky was darkening again...
As the feature approached I concentrated on photographing the chaotic cloud-structures on its underside (or as it was now becoming obvious, a great big clump of Cbs!). Here is one of many scud-pseudofunnels that I saw (R of centre). These can sometimes look very much like funnel-clouds and you need to look for the ragged appearance and lack of rotation to identify them as scud. The main "clump" was still way off to the SW at this point but it was starting to look substantial. The radio was crackling like mad due to lightning activity although most of this later proved to be inland...
1.40pm. Here it comes!
There is a major area of heavy precipitation to the R and extending well out of the field of view. All sorts of turbulence, scud going all over the place and odd lowerings to the L...
Pan round: this is immediately L of the above pic. ie - more inland...
The shape & smoothness of this feature, just to the side of the heavy precipitation, suggests that it may have been an updraught into the storm-cloud in which some rotation was present. Rain started to fall, with some hail, and I tried to get inland a bit for another look....
Shortly after that I was engulfed in rain, so retreated to the local cafe for a cuppa & some nosh. After the feature started to clear (about 2.30pm) I drove round to Borth again, hoping for something photogenic on the back edge - all that was visible was decaying precipitation above a now distant, inky-black core, with blue sky and a bit of altostratus visible out to sea...
There was a little more activity inland during the afternoon but it wasn't worth chasing after. Fog and low cloud decked the hills most of the afternoon, but in the evening it cleared, which was when I photographed this dissipating Cb anvil towering over Machynlleth.
There were some significant thunderstorms from East Wales through the Midlands into NE England on the same afternoon. So far as Mid-Wales goes it was not a bad day for cloud structure and for driving through downpours (if you like that kind of thing)!!