Royston (Iceni) Weather Station
Daily Weather Observations - November 2004
November 2004 Weather Review
November 2004 was a little milder than normal in Royston, whereas rainfall and sunshine were close to average.
The most noteworthy feature of the November weather was probably the snowfall which occurred on 18th. After a wet day the rainfall suddenly turned to snow at around 1900 GMT and the ground quickly became snow covered. At 0900 GMT the next day a 4 cm level depth of snow was measured. Night frosts and cold days on 19th and 20th maintained the snow cover at this depth until 0900 GMT on 20th, but a milder spell which set in on 21st removed any lingering traces of snow.
This (19th) was the earliest date in Autumn with snow lying since at least 1972, but it was only 1 day in advance of snowfall lying in both November 1988 and November 1985. The total rainfall and rainfall equivalent of snow on 18th was 28.3 millimetres, making 18th not only the wettest day in November by a large margin but also the wettest November day since at least 1972.
This rainfall event made up one-half of the total November rainfall of 57.2 millimetres, which amount is 109% of the 1971/2000 average. The number of "rainfall days" (0.2 millimetres or more) in November was 15, whilst on 8 of these days rainfall exceeded 1.0 millimetre. Despite the slightly above average rainfall in the month it was nonetheless the driest November since 2001. Rainfall duration in November was 76.8 hours.
The warmer than average conditions of recent years continued in November. It was not only the 6th successive warmer than normal November but also the 10th warmer than average month so far this year (July being the exception, but with a mean temperature only 0.2°C below average!).
The mean daily maximum temperature in the month was 10.2°C, which is 0.6°C above the 30 Year (1973/2002) average. The mean night minimum temperature was 1.0°C above average at 5.7°C. It was the coldest November in Royston since 2001, however.
The highest temperature recorded in November was 14.2°C on 3rd. This is not a particularly high temperature when compared with November in past years and it was, in fact, the lowest absolute maximum temperature in the month since 1987. The lowest temperature recorded in the month was –1.0°C on 20th. The lowest grass minimum temperature in November of –6.1°C was also recorded on this date.
Air frost occurred on 3 days in November and air frost duration was 21.7 hours. The number of ground frosts recorded in the month was 8.
The mean earth temperature at 30 cms depth as observed daily at 0900 GMT was 9.2°C, the earth temperature peaking at 11.5°C on 2nd, and falling to a minimum value of 6.8°C on 21st.
Despite 10 days in November being completely sunless, the 70.5 hours total sunshine in the month still managed to exceed the 30 Year (1971/2000) average by 4%. The sunniest day was 13th with 7.7 hours sunshine. Sunshine exceeded 7 hours on 11th and 19th also.
November was a relatively calm month and the mean wind speed of 2.4 mph was the second lowest such value (after May) so far this year. The highest daily (00/00 GMT) mean wind speed in the month was 10.2 mph on 17th and the lowest daily mean wind speed was 0.2 mph on 20th. The highest wind gust speed recorded in November was a relatively modest 37 mph on 17th.
The analysis of wind directions as observed at 0900 GMT daily shows a bias towards directions with a westerly component, as follows: NORTH 2 days, NE 2, E 0, SE 2, S 4, SW 7, W 10, NW 2 and CALM 1.
The mean MSL air pressure in November was 1022.1 mB, which is 7 mB above the 30 Year (1973/2002) average. The highest and lowest air pressure values in the month were 1038 mB and 1005 mB on 14th and 18th respectively.
The mean relative humidity over the whole month was 90.6%. The highest daily (00/00 GMT) mean relative humidity value was 98.6% on 2nd, whilst the lowest such value was 74.9% on 13th. The absolute lowest relative humidity reading in November was 52% at 1440 GMT on 13th.
Fog (visibility < 1000 metres) was not observed at the 0900 GMT observation hour on any day in November.
This report concludes with a few summary details of the Autumn (September/November) 2004 weather. The mean daily maximum temperature was 15.2°C, which is 1.0°C above average. The mean night minimum temperature was 8.5°C, which is 0.8°C above average. Rainfall was 86% of average at 142.6 millimetres, whilst sunshine totalled 357.6 hours (10% above average). It was the warmest Autumn since 1995, although Autumn 2001 had the same mean temperature. It was the driest Autumn since 1999.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
8th December 2004
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