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8th May 1993: 1030mb+ pressure but heavy thundery rain.


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Posted
  • Location: Irlam
  • Location: Irlam

Something "odd" happened on the 8th May 1993. Pressure was highest over Scotland but during the early hours, heavy thundery rain broke out across central Lowlands and slowly moved southwards before dying out.

Rrea00119930508.gif

So what caused this? Upper level trough?

Michael Fish forecast

The forecast for the previous day suggested maybe a few showers but did not expect the extent of the rain nor thundery nature.

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  • 10 years later...
Posted
  • Location: Coventry, 96m asl
  • Weather Preferences: Snow in winter, thunderstorms, warmth, sun any time!
  • Location: Coventry, 96m asl

Something similar happened early March 2021, on the 3rd, with a similar setup to the May 1993 case. A very weak low within a high moved slowly northward and brought some patches of quite heavy rain which I remember fairly well. The rain fell through low level cloud as well as shown on the satellite:

CFSR_1_2021030312_1.thumb.png.23b682d107532c2fc47f898a362cf78d.pngimage.thumb.png.5de27397ea695d7e872ee3976dad3939.pngsatvisuk-14-45.thumb.jpg.7b58a00e5ce8ee775c6416b0f3df4560.jpg

Edited by Metwatch
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  • 2 weeks later...
Posted
  • Location: Hampshire
  • Weather Preferences: Warm-by-day sunny thundery summers , short cold snowy winters.
  • Location: Hampshire

I remember the general sequence of events in early May 1993, and it being very interesting and unusual - but they relate to a different weather system, the warm front showing as moving in from the SE on the weather forecast above.

May 1 had been warm and a little humid (the last day of a warm, humid spell at the end of April with low pressure to the south) before it turned cooler the following day behind a dry cold front and an anticyclone built from the Atlantic. The next few days were perfect early May weather: clear blue skies, small fair-weather Cu, and very low humidity with temps around average.

What happened then was the unusual thing, however. Towards the end of the week it was forecast for a warm front to move in from the SE producing thundery rain and showers on Fri 7th, and later introducing warm and thundery weather. This is alluded to on the BBC forecast above, though a day or two earlier it was suggested it would turn thundery during the 7th; the forecast above has already watered it down quite a bit though the front is shown on the map.

At this stage (with a weather memory stretching back only 10-15 years at the time) the whole sequence seemed very, very unusual. I'd never heard of a thundery front moving from the SE into low-humidity air, so it seemed absolutely incredible to me at the time. When Fri 7th dawned with the same weather of clear blue skies and low humidity, I could not believe that thundery rain would move in later...

.... and in fact it didn't. The front was considerably weaker than anticipated and was not evident during that day at all. However it did pass over perhaps on the 8th as it did then turn more humid and hazy with some rather thundery skies that day, and the next few days were indeed warm and thundery.

Yet, after this unusual sequence of events, a repeat happened just 4 years later when a thundery warm front from the SE moved into fine, low-humidity weather on the evening of Sun June 1 1997, following a beautiful week of clear blue skies. This time however it was more active, there were thundery showers after dark, so it did literally turn thundery directly within low-humidity air. This was, like the 1993 occasion, then followed by humid, hazy air.

Maybe I'll start a thread on these kind of events because there were one or two others later still.

(As an aside, just look at those min temps in early May, and even the max temps are moderate considering the sunshine. A reminder of what normal times were like, I guess...)

Edited by Summer8906
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Posted
  • Location: Islington, C. London.
  • Weather Preferences: Cold, snowy winters and mixed summers.
  • Location: Islington, C. London.
On 05/04/2024 at 18:08, Summer8906 said:

(As an aside, just look at those min temps in early May, and even the max temps are moderate considering the sunshine. A reminder of what normal times were like, I guess...)

To be fair there does look to be a nagging easterly breeze. The nights, definitely, though recent Mays have had chilly nights at times. 2020 definitely did. 2018 also had some, as late as the 20th locally (I wasn't in London at the time, but NW Kent). 2021, 2019, 2016 definitely did. Infact I recorded an air frost on the 1st of May, 2016.

May 1993 was a hot one on the continent

image.thumb.png.b676c266cdc4985aec0cdc2df21041b7.png

Very easterly  month by the looks of it (SLP anomaly)

image.thumb.png.17c45ce4cd168713199ab24e072382da.png

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Posted
  • Location: Hampshire
  • Weather Preferences: Warm-by-day sunny thundery summers , short cold snowy winters.
  • Location: Hampshire

 LetItSnow! I remember May 1993 was a very interesting month synoptically. Very blocked, but with variable wind direction and conditions.

IIRC it played out as follows in my area of the south.

1st-8th already described above.

9th-11th featured warm, thundery weather (max temp perhaps 21 or 22C). Sunday 9th had large Cbs developing inland though it was sunny on the Hampshire coast, while Tues 11th had much Ac Cast develop and some dark looking, thundery skies in the evening (I think there was lightning visible, though it stayed dry locally).

The following few days then featured a battleground as really cold air tried to move down from the north and produced some wet and very cold weather further north (I was in Glasgow and Edinburgh some time that week, so I remember experiencing it directly). The south I believe remained warmish and showery with temps in the high teens with rather slack, lowish pressure.

Early the following week, around the 16th-18th the weather became less blocked as an Atlantic system moved across, but following this was a return to blocked conditions with, IIRC, high pressure out in the Atlantic and low pressure in the North Sea. It became sunny and relatively cool but the forecasts were always threatening further bouts of thundery rain from the east from frontal waves. Towards the end of this week one of them did reach the London area (where I was) though it was just rain, no thunder. Perhaps this was the western edge of the hot area over the continent?

Another change then occurred as the 21st was sunny with average temps in a ridge (with the North Sea low moving east or weakening) but then a plume developed with low pressure out in the Atlantic becoming more dominant than the former North Sea low. The 22nd/23rd was warm again (low 20s) and the 24th warm and rather thundery with some patchy thundery rain later after a sunny start. But later that week, the 25th and 26th I think, some really heavy thundery rain and thunderstorms affected the south with the Atlantic low and its fronts becoming slow-moving.

Eventually the low moved northeastwards leaving a dull, breezy and somewhat damp southwesterly for the final days of the month (not unlike the last few days)  - but the pattern of thundery plumes and slow-moving lows to the west was repeated at least twice in early June.

Edited by Summer8906
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