Royston (Iceni) Weather Station

Daily Weather Observations - November 2006

November 2006 was a month of excesses in Royston, with temperatures, rainfall and sunshine all being above average.

With November 2003 it was the equal 2^nd mildest November (after November 1994) since at least 1972. This month completed a very warm Autumn which set a new record for Royston (see details at the end of this report).

The mean daily maximum temperature in November was 11.9°C, which is 2.2°C above the 30 Year (1976/005) average. The mean night minimum temperature was 6.0°C, which is 1.1°C above average.

The temperature extremes in November were unexceptional, the first example being the absolute maximum temperature of 15.3°C (on 15^th). At the other end of the scale the lowest temperature recorded was –0.1°C on 2^nd, which just gave an air frost. This was the only air frost in November, and indeed in the whole Autumn. Air frost duration in November was only 0.2 hours.

The night of 24^th/25^th was the mildest of the whole month with a minimum temperature of 12.0°C. In contrast the lowest daily maximum temperature of the month was 8.4°C on 21^st.

The lowest grass minimum temperature in November was –3.5°C on 2^nd. A total of 5 ground frosts was recorded in November, with 4 of these being accounted for in the first 4 days of the month.

The mean earth temperature at 30 cms depth as observed at 0900 GMT daily was 9.1°C. The highest earth temperature recorded was 12.1°C on 1^st, whilst the lowest earth temperature was 7.9°C on 22^nd.

November commenced on a very sunny note with 44.1 hours sunshine being recorded over the first 6 days. The sunniest day of the month, 2^nd with 8.6 hours sunshine, occurred in this period. In fact, 2^nd was the sunniest November day in at least the last 9 years in Royston.

Total sunshine in November was 118.7 hours, which is 174% of the 30 Year (1971/2000) average. This was the highest November sunshine total in at least the last 9 years. Only 1 day (14^th) in the month failed to record any sunshine at all.

Despite a very dry start to November (only 1.7 millimetres rainfall in the first 9 days, and only 9.8 millimetres in the first 2 weeks) the second half of the month was much wetter and by the month end the total of 65.9 millimetres had exceeded the 1971/2000 average by 26%.

The number of "rain days" (0.2 millimetres or more) in November was 15, with the rainfall exceeding 1.0 millimetre on 11 of those days. The wettest day of the month was 17^th with 15.3 millimetres rainfall. Rainfall duration in the month was 41.6 hours. It was the wettest November since 2003 only.

A rare November thunderstorm occurred on 25^th during which thunder was heard repeatedly between 1130 and 1210 GMT. This was only the sixth November since 1972 in which thunder has been heard.

Winds with either a southerly or westerly component completely dominated November (i.e. on every day!) as shown by the following analysis of wind directions at 0900 GMT: NORTH 0 days, NE 0, E 0, SE 1, S 10, SW 9, W 9, NW 1 and CALM 0.

The mean wind speed in November was 3.7 mph. The highest daily (00/00 GMT) mean wind speed was 7.6 mph on 23^rd and the lowest daily mean wind speed was 0.0 mph (to nearest 1 decimal place) on both 2^nd and 3^rd. The maximum gust speed in the month was 44 mph on 20^th.

The mean MSL air pressure in November was 1011.3 mB, which is 3.5 mB below the 1976/2005 average. The highest and lowest pressure values recorded in November were 1035 mB and 976 mB on 10^th and 23^rd respectively.

The mean relative humidity in the month was 89.8%, the daily (00/00 GMT) mean peaking at 97.4% on 17^th and falling to a lowest value of 76.6% on 1^st. The absolute lowest relative humidity reading in November was 47% at 1220 GMT on 3^rd.

Fog (visibility < 1000 metres) was not observed at the 0900 GMT observation hour on any day in November.

AUTUMN (September/November) 2006: It was the warmest Autumn since at least 1972, with the mean temperature of 13.7°C exceeding the previous highest (2005) by 1.3°C! The mean daily maximum temperature of 17.1°C was 2.7°C above the 30 Year (1976/2005) average, whilst the mean night minimum temperature was 2.3°C above average at 10.2°C. Rainfall was 173.4 millimetres (104% of the 1971/2000 average), and sunshine was 442.1 hours (136% of the 1971/2000) average. It was the wettest Autumn since 2002, and the sunniest Autumn since 2003.

Richard Barker

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

5^th December 2006

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