By Philip Eden
The easterly winds of March continued until the 12th of the month, resulting in a very cold but generally dry start to April, though with occasional snow flurries. From the 13th to the 25th the weather was much warmer, though often wet and windy in northern ad western districts. The last five days saw a northwesterly type in charge, bringing a return of rather cold weather with scattered showers of hail, rain and sleet. The monthly pressure chart shows a weak southwesterly flow over the UK, while the anomalous flow is south to southwesterly. Pressure anomalies varied between -3mbar in Shetland and the Western Isles, and +1mbar in East Anglia and Kent.
Mean maximum temperature during April ranged from 13.4°C at St James's Park (London) to 7.2°C at Dalwhinnie (Inverness-shire), while mean minimum temperature varied between 7.2°C at St Mary's (Isles of Scilly) and minus 0.3°C at Loch Glascarnoch (Wester Ross). Daytime temperatures ranged from close to the 1981-2010 normal in East Anglia to 2°C below in parts of western Scotland. Night-time temperature was 0.5-1.5°C below in all parts of the UK. The Central England Temperature (CET) of 7.4°C was 1.1°C below the long-term mean - equal lowest alongside April 2012 since 1989. In the last 100 years there were 19 colder Aprils, two with the same mean temperature, and 79 were warmer.
The highest maximum at a standard site (i.e excluding rooftop and mountain sites) in the UK was 23.0°C recorded at St James's Park (London) on the 25th, while the lowest minimum was minus 11.2°C at Braemar (Aberdeenshire) early on the 2nd. The lowest daytime maximum was 0.5°C at Lake Vyrnwy (Montgomeryshire) on the 1st, while the warmest night was that of the 13th/14th with a minimum of 12.3°C at Bodelwyddan (Denbighshire).
Rainfall averaged over England and Wales during April was 37mm which is 57 per cent of the average for the standard reference period 1981-2010. Averaged nationally it was much drier than April 2012 but much wetter than April 2011; in the last 100 years 17 Aprils were drier while 83 were wetter. The equivalent figures for Scotland were 71mm and 109 per cent of the normal amount, and for Northern Ireland 53mm and 92 per cent. Monthly totals at routinely-available sites varied between 348mm at Cluanie Inn (Wester Ross) and 4mm at both Nantwich (Cheshire) and Bramham (West Yorks). The heaviest daily fall was 64mm on the 17th at Broadford airfield (Isle of Skye) while 209mm fell between the 13th and 18th (six days) at Cluanie Inn.
Sunshine averaged over England and Wales during April was 181 hours which is 108 per cent of the 1981-2010 mean, appreciably sunnier than April 2012, but not as sunny as April 2011. In the last 100 years, 28 Aprils were sunnier while 72 were duller. The equivalent figures for Scotland were 192 hours and 120 per cent, and for Northern Ireland 211 hours and 121 per cent. Largest total in the UK was 238 hours at Tiree (Inner Hebrides) and the smallest was 99 hours at Eskdalemuir (Dumfriesshire).
Strongest winds during April occurred between the 13th and 18th with gusts to 73 knots at Aberdaron (Caernarfon) on the 18th.
By Philip Eden