Lookback - October 01, 2012
September Lookback
A cool month; very wet towards the end

By Philip Eden


Changeable westerly winds affected the UK until the 22nd, although amounts of rain in East Anglia and the Southeast were very small. A deep depression, spawned by Tropical Storm "Nadine", affected the country between the 23rd and 25th and produced large amounts of rain, triggering flooding in many parts of Britain. Westerlies resumed at the month's end.


Mean maximum temperature during September ranged from 20.0°C at Swanscombe (Kent) to 12.1°C at Lerwick (Shetland), while mean minimum temperature varied between 13.0°C at St Mary's (Isles of Scilly) and 5.9°C at Aboyne (Aberdeenshire). Daytime temperatures ranged from exactly average in East Anglia to 1.3 degC below in western Scotland, whereas night-time temperatures were typically 0.0-1.5 degC below the average in all regions. The Central England Temperature (CET) of 13.1°C was 1.0 degC below the mean for 1981-2010 - the lowest in September since 1994. In the last 100 years 25 Septembers were colder and 75 were warmer.


The highest maximum at a standard site (i.e excluding rooftop and mountain sites) in the UK was 29.3°C recorded at both Writtle (Essex) and Cambridge on the 9th, while the lowest minimum was minus 4.1°C at Braemar (Aberdeenshire) early on the 23rd. The lowest daytime maximum was 7.7°C at Tredegar (Monmouthshire) on the 23rd, while the warmest night was that of 9th/10th with a minimum of 16.8°C at St James's Park (London).


Rainfall averaged over England and Wales during September was 89mm which is 108 per cent of the average for the standard reference period 1981-2010. It was the wettest September for four years; in the last 100 years just 39 Septembers were wetter while 61 were drier. The equivalent figures for Scotland were 94mm and 114 per cent of the normal amount, and for Northern Ireland 101mm and 126 per cent. Monthly totals at routinely-available sites varied between 356mm at Cluanie Inn (Wester Ross) and 25mm at Wych Cross (Sussex). Until the 22nd amounts of rain were moderate to small especially in East Anglia and the Southeast, but over the 3-day period, 23rd-25th, widespread heavy rain triggered serious flooding, and 131mm fell at Ravensworth (North Yorks).


Sunshine averaged over England and Wales during September was 171 hours which is 118 per cent of the 1981-2010 mean, making this the sunniest September since 2003. In the last 100 years, just 11 Septembers were sunnier while 89 were duller. The equivalent figures for Scotland were 130 hours and 114 per cent, and for Northern Ireland 142 hours and 116 per cent. Largest total in the UK was 196 hours at Manston (Kent) and the smallest was 63 hours at Kinlochewe (Wester Ross).


Strongest winds during September occurred on the 25th with gusts to 63 knots during a northeasterly gale at Inverbervie (Kincardineshire).


By Philip Eden


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