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April 2004

The averaging period used for the following assessment was 1961-1990.

UK overview

A wet month across the majority of the UK, with the exception being parts of N Wales and NW England, which experienced less than average rainfall. Another month of well above average temperatures across the whole of the UK. However, many northern and western areas experienced well below average sunshine.

Sennybridge recorded a low of -4.0 °C on 9th, whilst central London reached 23.4 °C on 24th. Sheffield recorded 33 mm of rainfall in an hour on 26th, and near Worcester, 43 mm fell in 2 hours overnight 26/27th.

England and Wales diary of highlights

Rather warm and wet overall. Some warm dry spells falling between thundery outbreaks at start, middle and end of month.

1st to 7th Low pressure to the west slowly moved east and north, driving bands of rain and showers across the region. The 4th onwards saw showers, often heavy and thundery, with hail in many places. Warm at first, colder later as winds veered from the S to the NW. The south-east saw most sunshine.

8th to 14th The Azores high extended a weak ridge across southern parts of the UK. It was chilly at first with some overnight frost, -4.0 °C being registered at Sennybridge/Wales on the 9th. After a few showers on the 8th, and a little light rain on the 9th and 10th, mainly dry warm weather with good sunny periods prevailed. Northern areas were cloudy at times, and some light rain spread in later on the 14th to the north-west.

15th to 21st Active depressions resided close to or over the UK bringing a second spell of unsettled weather, however, it was dry and warm at first, particularly in the south-east. Fronts made erratic progress eastwards during the 17th and 18th bringing lower temperatures and copious amounts of rain to many places. Some local flooding was reported in the Midlands. Further bands of rain and showers affected most areas from the 19th to the 21st, with hail and thunder mixed in, however, the sun shone in between. Reigate in Surrey experienced a violent thunderstorm later on the 19th, with heavy hail sleet and wet snow, children were seen making snowmen!

22nd to 25th After scattered light showers on the 22nd, very warm sunny weather arrived with 23.4 °C reached in central London on the 24th. There was patchy hill and coastal fog in places, and thunder later in the north on the 25th.

26th to 30th Low pressure developing off southern England caused bands of thundery rain to affect many areas with numerous reports of local flooding and lightning strikes. On the 26th one band stretched from north-east England to the Severn estuary. There was 33 mm in one hour during a storm at Sheffield which caused local flooding; a shop was also struck in Selby. Overnight on 26/27th, Worcestershire was hit by storms with many homes or businesses struck by lightning with some local flooding. Near Worcester, 43 mm fell in two hours. The south-east and East Anglia were also affected later on the 27th with outbreaks in south-east London causing much disruption to rail services during evening rush hour. Heavy hail and local flooding were reported from a number of localities. The 28th saw more outbreaks over the south-east and East Anglia, and a particularly violent storm broke out around the South Downs/Sussex area during the late afternoon. It was warm at first but became colder on the 28th as NNE winds picked up. The 29th saw more rain heavy at times and again early on the 30th in the south.

Scotland diary of highlights

Warm, dull and wet.

A strong south-easterly airstream on the 1st gave bright and warm conditions in the north-west However, fronts crossed Scotland on the 2nd and 3rd as low pressure in the Atlantic moved north towards Iceland, bringing rain to most parts.

From the 4th to the 7th the low pressure transferred from Iceland to the Norwegian Sea and winds over Scotland veered into the north-west and then the north. The weather was rather cold with sunny periods and showers that fell as snow over the hills.

On the 8th high pressure developed in the mid Atlantic and milder air spread south-east across Scotland, accompanied by cloud and overnight rain. The next day was rather cloudy but sunny spells to the lee of the hills enabled the temperature at Leuchars to reach 17 °C.

From the 10th to the 12th an anticyclone near the Azores extended a ridge to England with light westerly winds across Scotland. The weather was mainly cloudy but mostly dry and mild with some sunny intervals.

A marked deterioration in the weather set in on the 13th as low pressure became established near Iceland and mild south-westerly winds covered Scotland. There was much rain as fronts moved north across Scotland on the 13th, returned from the west on the 14th and did not clear eastward until the 15th. Clearer and colder conditions with light winds arrived on the 16th, allowing the overnight temperature to fall to -4 °C at Aboyne.

More wet weather followed from the 17th to the 19th as another major depression approached Scotland from the west and became slow moving before retreating towards Iceland. On the 17th there was 32 mm of rain at Eskdalemuir and the wind gusted to 62 m.p.h. at Barra.

A brief respite followed on the 20th with southerly winds giving mainly fair weather in the north and the temperature reached 16 °C at Altnaharra. Another depression moved north to the west of Scotland over the next two days, bringing a return to unsettled weather. This time the emphasis was on the wind, with gusts reaching 69 m.p.h. at South Uist on the 21st. The warmth was maintained with the temperature rising to 17 °C at Lossiemouth.

On the 24th high pressure developed over the British Isles and the North Sea with sunny periods developing. The temperature rose to 19 °C at some eastern locations on the 25th and 26th.

On the 27th the anticyclone transferred west into the Atlantic, low pressure developed over Europe and north-easterly winds blew across Scotland. In the east it was cloudy with periods of rain and the temperature reached only 8 °C at Charterhall on the 29th. In the west there were sunny periods with showers in the north-west on the 28th and 29th.

Northern Ireland diary of highlights

Warm and wet.

Temperatures were again above normal - especially at night with positive anomalies of 1 to 3 degrees. Rainfall was above average, though by varying degrees due to the often showery nature of the weather. Sunshine values were generally near or a little below average.

The first three weeks were unsettled with showers or some longer spells of rain at times. Some of the showers were heavy with hail and isolated thunderstorms were reported locally on the 3rd and 6th.

The Easter holiday period was relatively quiet with a lot of cloudy, dry weather and any rain was mostly insignificant. Clearer spells at night, however, did allow some ground frosts.

Like March, the most unsettled period occurred around mid-month and active fronts brought 10-15 mm of rain to many areas overnight on the 14th. This was followed by a couple of brighter days with good sunny spells but some heavy showers with hail and thunder. Another very active front brought a further 15-20 mm of rain on the 17th and this was driven along by strong and gusty winds. It was cold too with some sleet/wet snow reported in the Omagh area as afternoon temperatures struggled between 4 and 6 °C.

By the evening of the 20th, more rain was arriving as a deep depression tracked northwards along the western coast of Ireland. 5-10 mm occurred in many areas and southerly winds increased to gale force in many areas on the morning of the 21st with inland gusts reaching or locally exceeding 50 m.p.h., causing some minor damage to trees.

By the 22nd pressure was rising and a spell of warmer, sunnier weather arrived for the last weekend of the month with temperatures on the 24th and 25th reaching 17 or 18 °C inland, the highest of the month.

The remainder of the month had a good deal of dry and sunny weather though it felt quite cool as northerly winds strengthened.



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