Royston (Iceni) Weather Station

Daily Weather Observations - November 2010

November had commenced on a mild note including the highest temperature of the month, 17.2°C on 4^th. This was only the 3^rd occasion since 1972 that 17°C has been exceeded in November. On 5^th the night minimum temperature was as high as 14.8°C.

To illustrate the difference in temperatures between the first and last weeks of November the mean daily maximum temperature for 1^st/7^th was 13.4°C compared with 1.2°C for the 24^th/30^th. The comparable figures for the night minimum temperatures are 9.1°C for 1^st/7^th and –3.0°C for 24^th/30th.

Overall it was the coldest November since 1998. The mean daily maximum temperature in the month was 7.8°C, which is 1.9°C below the 30 Year (1976/2005) average whilst the mean night minimum temperature was 1.5°C below average at 3.4°C. Air frost was registered on 7 days and ground frost on 15 days in the month. The lowest grass minimum temperature in November was –10.5°C on 28^th. November was the 4^th consecutive colder than average month, although both September and October had only a marginally below average mean temperature.

The mean earth temperature at 30 cms depth as observed at 0900 GMT daily was 7.7°C, this element peaking at 11.9°C on 5^th and falling to its lowest value of 3.5°C on 30^th.

November was a dry month with a rainfall total of 31.4 millimetres, which is 65% of the 1971/2000 average, making it the driest November since 1999. The wettest day of the month was 5^th with 14.1 millimetres rainfall.

The number of "rain days" (0.2 millimetres or more) in November was 19, with rainfall reaching or exceeding 1.0 millimetre on 7 of these days. Small amounts of snow fell on 3 days (25^th, 27^th and 29^th) followed by a larger fall on 30^th giving a level depth cover of 2 cm at 0900GMT on that day. The ground had a complete snow cover at 0900 GMT on 1 other day (27^th) although it was of negligible depth.

Despite 6 days in November being completely sunless, the sunshine total for the month was only 3% short of the 1971/2000 average at 66.1 hours. The sunniest day of the month was 16^th with 7.4 hours sunshine. It was the dullest November since 2008 only

November was rather windy at times and 5 days in the month experienced a 24 hour mean wind speed over 10 mph, and maximum gust speeds over 30 mph. The maximum gust speed recorded in the month was 46 mph on 11^th. The highest daily (00/00 GMT) mean wind speed was 16.3 mph on 4^th whilst in contrast the lowest daily mean wind speed was 1.6 mph on both 20^th and 22^nd.

The analysis of wind directions as observed daily at 0900 GMT shows winds with a westerly component were in the ascendancy, as follows: NORTH 1 day, NE 4, E 0, SE 4, S 2, SW 5, W 7, NW 7 and CALM 0.

The mean MSL air pressure in the month was 1005.0 mB, which is 9.9 mB below the 30 Year (1976/2005) average. It is perhaps surprising to have a drier than average month with such a low mean pressure. The highest and lowest air pressure values in November were 1021.8 mB on 16^th and 966.4 mB on 8^th respectively.

The mean relative humidity in November was 87.4%. The highest daily (00/00GMT) mean relative humidity value was 94.8% on 20^th, and the lowest such mean value was 77.2% on 12^th. The absolute lowest relative humidity reading in the month was 64% at 1240 GMT on 3^rd and 0250 GMT on 12^th.

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