THUNDERSTORM T0026
Date: Friday 2nd July 1999 (into 3rd)
Time:
Cell 1: 23:30, Cell 2: 00:40, Cell 3: 01:34 (BST)
Location:
Macclesfield, Cheshire UK
Path: Cell 1: ~21 miles, Cell 2: ~2 Miles, Cell 3: ~3 Miles
Synoptics:
Spanish plume
Duration: 3 hours 40 minutes
Type: Elevated Multicells
Average lightning type: I-C
Average discharge rate: Cell 1: 117s, Cell 2: 162s, Cell 3: 58s, Over
Pennines: 7s
Footage Quality: VHS
An active
Atlantic depression scooped up a continental plume and threw it across the
UK on this day, with a widespread outbreak of thunderstorms overnight,
locally severe with constant lightning. Macclesfield grazed three separate
pulses near the wave-tip of the plume, destabilised by a rapidly advancing
upper trough from the Atlantic. Very little thunder was experienced north of
the area. The day was hot and humid with 29C recorded in London, and with
the first significant destabilisation of the atmosphere was experienced over
southern Wales during the evening excluding non-thundery afternoon showers
in the west (Altocumulus Cast). These cells upscaled through the evening and
overnight into large elevated MCSs (Mesoscale Convective Systems), one over the northern
Midlands and the other towards the
Cambridge area. The northern-most
MCS (Cell 3 for Macclesfield) just clipped the area to the south-east and showed
off its 7 second
discharge rates over the Pennines.
CELL 1: 23:30BST
First sight of any lightning activity was way out to the west, with some
distant flickers on the horizon including a CG, presumably a cell which rode
up west Cheshire and into the Merseyside area.
CELL 2: 00:40BST
A
couple of fairly weak cells then approached Macclesfield, which flickered in
the southern skies and gave a few C-Cs on approach. Unfortunately this cell
died out as it got close, assumingly as more southerly-positioned MCS took
all the inflow of the plume.
CELL 2: 01:34BST
It
wasn't until half an hour later the this MCS passed within a few miles of
Macclesfield, creating the bulk of the footage. Discharge rates were seen to
be little more than 10 seconds at this point, mostly with faint upper-level
I-Cs and lightning shielded by distance and rain-curtains.
Amongst the constant
flickering there were a few close C-Cs and a fantastic I-C multi-discharge
with tens of return strokes lasting a couple of seconds. The rest of the
action was
distant I-Cs over the Pennines.
The southern part of the
storm by this time was over Derbyshire where a friend of mine was camping in
a trailer as it passed over. His eye-witness account was that C-Gs were
striking the ground viciously around them and a few trees were hit and car
alarms were going off all around them. Pretty intense.
Meanwhile the southern
MCS over towards Cambridge was now causing havoc in East Anglia as it
moved towards the North Sea at about 4-5am. This cell appeared on the radar
to be even more intense with a very defined 70 mile long squall line, generating huge quantities of lightning and intense
rainfall with 14mm of rain falling between 3 and 4am at Wattisham.
SATELLITE IMAGES (Credits)
VISIBLE 02.07.1999 17:00
VISIBLE 02.07.1999 17:00 Grid
INFRARED 02.07.1999 17:00
INFRARED 02.07.1999 17:00 Grid
COLOUR 02.07.1999 17:00
COLOUR 02.07.1999 17:00 Grid
VISIBLE 03.07.1999 04:20
VISIBLE 03.07.1999 04:20 Grid
INFRARED 03.07.1999 04:20
INFRARED 03.07.1999 04:20 Grid
COLOUR 03.07.1999 04:20
COLOUR 03.07.1999 04:20 Grid
CHARTS
(Credits)
SFERICS (Credits)
BBC Weather Grabs
featuring Isobel Lang (Credits)
First Image: 0200 Radar showing two distinct MCSs, northern-most one was
ours.
Second image: 0400 Radar showing 70-mile squall line on southern MCS.
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