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Thunderstorms Of 23Rd July 1984


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Posted
  • Location: Guildford, Surrey.
  • Weather Preferences: Thunderstorms & Snow
  • Location: Guildford, Surrey.

    July 1984 had been a mixed month with quite unsettled weather at times but with relatively little rain. There had been a lovely sunny spell with increasing temperatures from the 3rd onwards with a heatwave around the 5th to 8th with maximum temperatures reaching 29~30 deg.C. A thundery outbreak early on the 9th brought little rain to local areas in southern England but heavier rain and thunderstroms further North. York Minster was hit by lightning and damaged in the subsequent fire on the 10th.

    A cooler N.W.ly situation took over with weak Atlantic fronts moving S.E. with some light frontal rain but also sharp showers on the 12th~14th. This situation favours heavy shower development in East Anglia and that region enjoyed some cool N.W.ly instability thunderstorms on the afternoon of the 15th. Further west, this was the start of a dry period but with pleasant sunshine and warm temperatures. A warm front introduced muggy air around the northern periphery of an anticyclone on the afternoon of the 18th. The next few days were very warm with sunshine at times and by the 21st, it looked like settled condiitons were in order. That afternoon, a small 'heat low' developed over central England with large convective clouds but just not enough energy to kick off storms. On the Sunday 22nd 'Farmers Forecast', I was pleased to hear of an increasing thundery risk but the chances of a storm were small. However, by the evening of the 22nd, thing looked a little more exciting and with more potential. There were reports of isolated thundery showers in the west London area on the Sunday evening.

    On the morning of the 23rd, the BBC1 Breakfast Time forecast by Francis Wilson warned of afternoon thunderstorms to the west of London. A very warm and sunny morning and early afternoon with temperatures up to 27.5 deg.C brought increasing altostratus and convective cloud. I distinctly remember looking out to the west (over towards the Hook direction) at around 3 pm and seeing odd reddish orange tinged clouds. On walking home from school I jokingly said that we are going to have a BIG thunderstorm this evening. I was not serious about my forecast as I only had a few days of term left to live down any jibes about getting it wrong and I just wanted to show off a bit! My forecast however came very true and a very excting event unfolded over the next two hours. Up to the wonderful 33 cm snow enjoyed on Monday 2nd February 2009, the thunderstrom of Monday 23rd July 1984 was my best weather event. It now stands in a close second position.

    Having got home from school, I noticed the sky was darkening to the S.W. alhtough the surface wind direction was N.E.ly. There seemed to be a convergence overhead and I was becoming increasingly hopeful of an exciting event especially as 23rd July 1983 was still fresh in my mind! At 4:12 pm there was the first rumble of thunder. The next was at 4:16 pm and the lightning and thunder increased to follow and there were a scattering of rain droplets of about 1.5~2 cm on the paving slabs. At around 4:30 pm the thunder became louder with some lovely loud overhead cracks and loud enough to sound 'dangerous'. The sky was very dark to the S.E. and I started to grumble, "I bet some ******d is getting a fantastic event out of this". As it happened, areas to the S.E., such as Farnham, had moderate showers but no heavy rain. My friend at Alton reported seeing a huge cumulonimbus to the North and was frustrated that he was missing the storm and it looked like Fleet was getting it 'full on'.

    Having ventured into the garden and walkd around for a while enjoying the overhead thunder and expecting nothing more than a good electrical storm or 'dry' thunderstorm I was walking across the patio and was hit by large rain drops which made spots 3~3.5 cm on the paving slabs. I could already see rain lashing on the garage roof next door and realised that we were probably about to get a good dose. Having got back indoors, I remained rooted at the back door and started my brand new Walkman to record this part of the storm having already got some good thunder already. Having started at approximately 4:42 pm, the rain quickly became very heavy and I decide to take some pictures. I only had 5 pictures left on the 35 mm film so had to be careful what I took! The first photo was at about 4:50 pm during the ordinary very heavy rain where about 8 mm had fallen by now.

    post-7417-12482980103513_thumb.jpg

    The rain increased in intensity and became torrential and around 4:57 pm the phone rang and it was my Mum to say she would not walk home from work in this. Already excited I said something to the effect, "we're going to get over an inch out of this", and not really expecting this and just expecting the usual cessation of rain and thunder moving away, I was even more excited when I started to hear a loud cracking sound on the skylight. In my wisdom as a keen 15 year old amateur weatherman I forgot that a storm like this may produce hail - LARGE HAIL! (I remember watching David Attenborough's "Living Planet" and the severe thunderstorm with large hail and tornado earlier in the year). At about 5 pm, the severest phase was reached with incredible torrential hail, most of the hailstones being 10 mm in diameter for a few minutes. The noise on the skylight was deafening. Meanwhile the garden was getting flooded to depths I had never seen before and I was still recording all this. The second picture shows the hail during the most intense stage, probably around 5:05 pm.

    post-7417-12482980339807_thumb.jpg

    Returning to the rear of the house, after about 5:05 pm the hail became smaller and dissappeared, but the torrential rain continued. A make shift raingauge put outside recorded 24 mm after the hail had knocked it over. The flooding in the garden was impressive, as seen in the next two pictures.

    post-7417-12482980624503_thumb.jpg

    post-7417-12482980768149_thumb.jpg

    After 5:10 pm, the rain became lighter and then had died out by 5:15 pm. There were rumbles of thunder to the N.E. until about 5:30 pm. Little thunder was heard during the torrential rain and hail which was thought to be the storm 'spending' itself but a better explanation was that the intensity of the precipitation was masking it!

    I ventured out and measured 35 mm rainfall on my basic gardeners raingauge as seen in the next picture.

    post-7417-12482981026726_thumb.jpg

    The flooding subsided and the paths were coated in silt and mud which had washed down from flower beds and the slight slope from N.W. to S.E. in the garden. My mother, finally walking home from work reported her offices had flooded, many cars in the neighbouring road had broken down and that the small 50 cm wide stream at the bottom of the road, which is normally no deeper than 3 cm was an overflowing torrent. A few hailstones remained on ground that had not flooded and were dutifully collected and stored in the freezer.

    My 35 mm compared well with the official wettest of 43 m at Beaufort Park in Berkshire. However, I have always wondered if my total would have been much higher as some of the hail could have bounced out of the gauge and my mini-raingauge measured 24 mm after the hail. Winds were light during the storm but I remember a few lines of lashing rain racing N.E. along the patio towards the end of the storm. The wind was not sufficent to disturb the trees during the event and all tree debris downed was due to the large hail.

    I was a temporary celebrity at school the next day, proving that interesting weather events generate conversation with people who don't normally want to chat, and I found out form a friend in Hartley Wintney (about 7 km to the N.W.) that it remained sunny with no rain and just distant thunder. Apparently, the edge of the storm was here as there were reports of 10 mm diameter hail on the outskirts of this village. The school playground and roads looked like a building site with mud, sand and silt washed everywhere. I was also told that the main River Hart feeder stream which runs through the Calthorpe Park Estate burst its banks. The water level increased from 5 cm to just under a metre in less than half an hour - a true flash flood.

    The 23rd July 1984 will be long remembered but since then there have been similarly good thunderstorms but none quite as intense or prolonged. Interestingly, the next occasion that I saw large hail was on the 23rd July 1996 when at Guildford, but that's a different story.

    I hope readers enjoy this report and can add any memories of their own regarding this event, the summer of 1984 and other home grown convectional rainfall events.

    Edited by Severe Blizzard
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    Posted
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)
  • Weather Preferences: Sunshine and 15-25c
  • Location: Edmonton Alberta(via Chelmsford, Exeter & Calgary)

    i remember summer 1984 as being very warm and at times thundery..but nothing remarkable in terms of storms. The story you share dosnt seem anything unusual and a short lived affair.

    June 1982 was very thundery..i remember one saturday in june 82 where there was a constant stream of storms one after another that lasted most of the day!..also as a child i remember one huge overnight storm i think it was april 1973..that caused chaos with severe flooding and trees being stripped of their branches etc so much so that all the local schools were closed.

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    Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

    Lovely well-constructed account SB...Thanks fo all the effort. :)

    I don't recall much from 1984 myself; but I do remember the whopper that moved through Milton Keynes and Northampton in July 1983.

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    Posted
  • Location: Derbyshire Peak District 290 mts. Wind speed 340 mts
  • Weather Preferences: Rain/snow, fog, gales and cold in every season
  • Location: Derbyshire Peak District 290 mts. Wind speed 340 mts

    An interesting summary there, S.B. With regard to the amount of rain falling during the storm I think, had you had a standard rain gauge. the amount would have been somewhere around 50mm. Not only did you miss the hail but the gauge you had, mounted on a pole, would undoubtedly have under-recorded. The under recording could possibly have been as much as 30% if there was any wind associated with the storm but more likely in the region of 15-20%.

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