THUNDERSTORM T0036 Date: Saturday 26th August 2000 Time:
19:15 BST (19:50 BST until the cell developed overhead) Location:
Macclesfield, Cheshire UK Path: Overhead
Atlantic cold front running into back of Spanish Plume Duration: 1 hour Type: Possibly Supercell (very localised with very high shear
environment) Average lightning type: C-G Average discharge rate: 26 seconds (early development), 47
seconds (whole storm)
Hi-8 / VHS
was the “Storm of the Year”, an absolute corker, and ironically one of the
An Atlantic surface cold front was on approach running into the elevated Spanish plume
day/night before (T0035). This front was disassociated from the plume itself
(not the west edge of the plume). However, upper-level winds were still likely in the jet trajectory
so the wind shear at this point was likely quite large with steering flow
(~850hpa) going east. So some good wind shear here. Also, in satellite data it looked like it coincided with an upper
trough/PV anomaly which came up from the south. Furthermore, the low level flow
was chaotic. It was overcast and low-level stratus was actually moving from
north to south, so something else was going on...
Preceding this, it was apparent there were two
cells, also likely thundery, positioned both north and south of Macclesfield
over Manchester and Staffordshire, which could be heard through
distant thunders. Radar sequences showed these two cells married and merged.
The observed low-level northerly was against the pressure pattern, so my
hunch was this was outflow from the northern storm.
a lot going on! This storm was probably the product of double, or even
triple surface outflow convergence (cold front included), good upper
vertical wind shear, upper trough forcing, and plume feeding. With this
amount of wind shear and compactness, doubled with the intensity of the
storm, and the storm favouring CG, I'm thinking along the lines of Supercell.
minutes into the show an aggressive CG barrage suddenly started overhead
with 2 very close (off camera) strikes 14 seconds apart. This was then
quickly followed by a monsoon-style torrential white-out, some of the
heaviest rain I've seen here, then
further CGs thereafter.
Unfortunately most of the CGs were out of the camera’s view, although the thunders
were IMMENSE. On a personal note, I remember my mum had just a couple of minutes ago left the
house to walk to work in the rain, I feared for her life! Luckily I think
she grabbed a lift half way...
The discharge rates with
the lightning that followed (further CGs) were
short and consistent, showing persistent and aggressive development of the
cell. Nearly 100 discharges were recorded all-in from this event.
The storm showed
sustainability and changes in its characteristics as it rolled over the
Pennines. The CGs eventually turned into C-C and
I-C as the cell grew more mature and the charge spread itself up
and outwards, and then the discharge rates dropped as it rumbled off into
Unfortunately, apart from
the sound and lightshow, the footage wasn’t as good as I was hoping for
three reasons; 1) it was right overhead and difficult to chose which
direction to point in (kept missing CGs), 2) I was aiming for CGs that were
no longer happening (so lots of C-C missed), and 3) the visibility was very
low due to the intense downpour.
However, the icing on the
cake was the ambience of the storm itself. It’s not often we get
thunderstorms in the fading evening light, and those which do occur are
great as the lightning shows up brilliantly against the cloud formations,
and the senses you get from the natural ambience of a quietening busy Earth is much stronger. This is the type of storm I
hope to see more of. This was the last storm for 2000, and
what a way to go out!