Lookback - October 01, 2014
September Lookback
Warm and very dry

By Philip Eden

The pressure for September 2014 was above normal in all parts of the British Isles, with pressure anomaly ranging from +8 mbar in Shetland to +2 mbar in the Isles of Scilly and Channel Isles. The anomalous flow over the British Isles was easterly over England, Wales, Northern Ireland and southern Scotland, and anticyclonic over northern Scotland. All parts of the country were rather warm, most of the country was dry or very dry too with percentages of less than 10 in northwest England and north Wales and 10-15 in south Wales, the Midlands and western Scotland. Sunshine duration over the country was within 20 per cent of the average in all regions.

Mean maximum temperature during September ranged from 21.5°C at St James's Park, Heathrow (both London) and also at Jersey airport (Channel Is), to 13.5°C at Fair Isle (between Orkney and Shetland), while mean minimum temperature varied between 14.8°C at St Mary's (Isles of Scilly) and 8.0°C at Dalwhinnie (Inverness-shire). Mean temperatures were between 0.2 and 2.5 degC above normal in all regions. The Central England Temperature (CET) of 15.3°C was 1.2 degC above the mean for 1981-2010 and - rarely - September was warmer than August; this was the warmest September since 2006, and in the last 100 years only three Septembers were warmer, two had the same mean temperature, while 95 were cooler.

The highest maximum at a standard site (i.e excluding rooftop and mountain sites) in the UK was 27.0°C at St Helier (Jersey) on the 16th, while the lowest minimum was minus 0.1°C at Katesbridge (Co Down) on the 8th. The lowest daytime maximum was 10.1°C at Loch Glascarnoch (Wester Ross) on the 7th, while the warmest night was that of the 16th/17th with a notably high minimum of 18.3°C at Jersey airport (Channel Is).

Rainfall averaged over England and Wales (note: not UK-wide) during September in a record stretching back to 1766 was 15.5mm which is just 20 per cent of the average for the standard reference period 1981-2010; this was the lowest September rainfall since 1959, and in the last 100 years only September 1959 was drier, while 99 other Septembers were wetter. (UK-wide it was the driest September since before 1910). The equivalent figures for Scotland were 38mm and 40 per cent of the normal amount, and for Northern Ireland 15mm and 20 per cent. Monthly totals at routinely-available sites ranged from 107mm at Lerwick (Shetland) to 1.0mm at Squires Gate (nr Blackpool, Lancs). The heaviest daily fall was 44.9mm on the 19th at Chesham (Bucks).

Sunshine averaged over England and Wales during September was 145.4 hours which is 99 per cent of the 1981-2010 mean, making this the sunniest September only since 2012, and in the last 100 years 49 Septembers were sunnier and 51 were duller. The equivalent figures for Scotland were 110 hours and 99 per cent, and for Northern Ireland 140 hours and also 114 per cent. Largest total in the UK was 273.7 hours at St Helier (Jersey), and the smallest was 63.5 hours at Lerwick (Shetland).

Strongest winds during September occurred on the 26th with gusts to 61mph at Kirkwall (Orkney) and at Lerwick (Shetland).

By Philip Eden

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