RaVeNStOrM

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.

BBC Radar for Thunderstorm BBC Radar for Thunderstorm
 


 
Mark Seltzer  www.electricsky.co.uk

 

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