May 2004; highly varied month

[LetItSnow!]

May 2004 was an unusual month with large variations in the weather including one of the strangest northerlies ever.

It has a C.E.T. of 12.1 (+0.7) and an EWP value of 47.5mm of 74%. The UK sunshine average was 110% of the norm.

The month began unsettled with the deepest May low since 1943. The pressure dipped to 971mb over northern Scotland. It was the lowest pressure anywhere in the northern hemisphere. This unsettled spell gave not just heavy rain and strong winds but also thunderstorms from the 4th to the 6th. There were thunderstorms in places such as the south-west, NI, northern England and the London area. While we were chilly and unsettled, this deep low helped very warm air surge northwards over Scandinavia. Important to note.

After generally low pressure meandered over the country for a few days it finally cleared to the east and lead to cooler northerly winds. Well, actually, no. These were not cool northerlies at all. They were very warm northerlies. How is that possible? Well, the warm air over Scandinavia hadn't really budged, so low pressure sent it back down. The far north, usually having no shelter from spring northerlies, baked (relatively) under near-record temperatures. Altnaharra reached 20.7C on the 9th with Peebles reaching 24.3C on the 10th. These northerlies weren't entirely quaint though with some severe thunderstorms breaking out. 

By late morning convective clouds were developing in many areas and these turned showery and thundery over central and southern Scotland, northern and western England and also in Wales. In Scotland, one man died after being struck by lightning on Ben Oss (1029m), near Tyndrum at about 1800GMT. Flooding was reported in Abergavenny and Looe, Cornwall, and a tornado was sighted at Brecon.

After these oddities there was a long, fine spell. Apart from a few weather fronts here and there the second half of May 2004 was high pressure dominated with lots of bright and sunny weather and temperatures frequently in the low to mid 20s. There weren't any extremes of temperature though with the highest being 25C reached in central London on the 17th and 19th.

There were some isolated storms that broke out on the 20th, for example in the late afternoon and evening there were thunderstorms from east Hampshire to Kent with reports of 15mm of rain about two hours from Shoreham - but many areas across England were dry in the second half of May. Across most of the south-west there was no rain at all from the 6th to the 27th.

A more unsettled end to the month as low pressure made inroads for the first time with some outbreaks of rain and some thunderstorms, but the south-east remained warm with temperatures in the low 20s.

The first half of June 2004 would remain anticyclonic and perhaps thoughts of another fine summer were to come, but the summer changed its tune very quickly in the second-half of June. Read about summer 2004 on my thread from last year:

 

Edited May 9 by LetItSnow!
Added some data.

[MP-R]

Remember this may quite well. Particularly the gales and volume of rain on the 04th-05th, and the thunderstorms on the 10th-11th (a common time for thunderstorms). As you mention, it was the unusual combination of warm hazy sunshine and N-S movement of storms. The sort of weather more common when they move E-W.

That was the last sizeable rainfall until the 31st/01st, then another long rainless spell until the 21st June… before that notable summer gale! The summer never quite recovered after that.

[Harry233]

I remember May 2004 being quite a pleasant month generally. I think I was maybe a bit lucky however. I don’t recall any heavy storms or strong winds at all. It was generally a warm, dry and sunny month. I didn’t have any real heat that month, the highest I recorded was 23.C. Seemed quite a similar May 2016 being generally dry and sunny and quite warm without any extreme heat. Most days seemed to stay around the high teens with the odd day in the low 20’s.

[Weather-history]

Remember the thunderstorms of 10th May 2004, north to south was strange to see.

 

Edited May 9 by Weather-history

[Summer8906]

I remember the month started unsettled but don't remember that deep low specifically - just that the start of the month was rather dull and damp.

I do remember the warm northerly arriving though, and it then turning warm and sunny with occasional thundery outbreaks for what must have been almost three weeks. I don't remember any storms locally but do recall the occasional day with distant Cbs visible.

I remember the breakdown in the weather arriving on the Friday before the bank holiday weekend (would be the 28th) and the bank holiday weekend itself was fairly unsettled though without large volumes of rain.

The first few days of June were unsettled again before it was dry and hot for about 10 days, but the second half of the month was indeed wet. In a common late spring, early summer pattern, the high retrogressed westwards to introduce a northerly which was initially dry but then became more showery with some more organised rain from troughs, and then further retrogression resulted in a trough over the country and attracted in a very deep Atlantic low on the 22nd, one of the worst June storms I can remember. Would probably be a named storm nowadays. It remained very wet for a few days and the last three days or so were drier and fairly warm.

Edited Saturday at 11:10 by Summer8906