Royston (Iceni) Weather Station

Daily Weather Observations - November 2002

Autumn ended on a mild and wet note with November temperatures and rainfall both being well above average, whilst sunshine for the month was marginally above normal.

Although no really wet days were experienced in November the high frequency of days with rainfall ensured that it turned out to be a very wet month with almost twice the average rainfall.

In fact, the number of "rain days" (0.2 millimetres or more) totalling 22 was the highest in November since 1974. Of this total no fewer than 20 days were classified as ‘wet’ days with 1.0 millimetre or more rainfall.

Total rainfall in November was 98.0 millimetres, which is 187% of the 30 Year (1971/2000) average for Royston. It was only the wettest November for 2 years, since in November 2000 a rainfall total of 118.2 millimetres was recorded.

The wettest day of the month was 6^th with 12.8 millimetres rainfall. Rainfall duration over the whole month was a very high 115.8 hours, which exceeds the previous highest monthly figure this year (62.3 hours in October) by a wide margin.

In the afternoon of 24^th a thunderstorm tracked north-eastwards across southern England, crossed London, and reached Royston at about 1730 GMT giving several claps of thunder. However, the centre of the storm passed to the east of Royston and the rainfall of 5.5 millimetres could well have been higher had its track been a little further to the west. It was only the 5^th occasion in the last 30 years that thunder has been heard in Royston in November (the other years being 1973, 1974, 1991 and 2000).

November was a very mild month with a mean temperature 1.8°C above the 25 Year (1973/1997) average for Royston. This was achieved without any notably high temperatures, the highest temperature of the month (15.4°C on 2^nd) having been exceeded in November in 15 of the last 30 years. In contrast, the lowest day maximum temperature of the month was 7.9°C on 25^th.

The lowest temperature recorded in November was 1.5°C on 18^th. Another indication of the mildness of the month is the fact this is the highest November minimum temperature since 1974. The warmest night of the month was 5^th/6^th with a minimum temperature of 12.3°C. The lowest grass minimum temperature in November was –2.4°C on 18^th, resulting in the only ground frost of the month. This is the lowest ground frost total in November since at least 1972 when records began at Royston (Iceni) Weather Station. It was the 8^th November without air frost in this period.

The mean daily maximum temperature in November was 11.1°C, which is 1.6°C above the 25 Year (1973/1997) average. The mean daily minimum temperature was 2.0°C above average at 4.4°C. It was the mildest November since 1997.

The mean earth temperature at 30 cms depth as measured at 0900 GMT daily was 9.0°C. The highest and lowest earth temperatures in the month were 11.2°C on 3^rd, and 7.6°C on 19^th, 25^th and 27^th respectively.

Despite November being a very damp month with a total of 7 days which had no sunshine at all, the sunshine total for the month, 71.4 hours, held up well and was, in fact, 7% above average. Even so it was the dullest November in at least the last 5 years.

The sunniest day in November was 4^th with 7.9 hours sunshine. Only 2 other days reached 7 hours sunshine, 3^rd with 7.0 hours and 18^th with 7.2 hours.

Fortunately there was not a repeat in November of the severe gale of October 27^th and the highest wind gust recorded in the month was 46 mph on 14^th. The mean wind speed throughout the whole month was 3.9 mph.

The highest daily (00/00 GMT) mean wind speed in November was 8.8 mph on 8^th, and the lowest 0.0 mph on 17^th.

The analysis of daily wind directions as observed at 0900 GMT daily was NORTH 0 days, NE 0, E 1, SE 5, S 9, SW 7, W 3, NW 1, and CALM 4.

The mean MSL air pressure in November was 1004.5 mB (10 mB below average). The highest air pressure value in the month was 1024 mB on 5^th, whilst the lowest was 968 mB on 14^th.

The mean relative humidity in November was 94.5%, with an absolute lowest reading of 64% at 1400 GMT on 7^th. The highest daily (00/00 GMT) mean relative humidity was 99.8% on 25^th, whilst the lowest daily mean relative humidity was 82.2% on 7^th.

Fog (visibility < 1000 metres @ 0900 GMT) was recorded on 4 days (13^th, 16^th, 25^th and 26^th) in November. On 16^th and 25^th the visibility was below 200 metres at 0900 GMT.

This report is concluded with the summary temperature, rainfall and sunshine data for AUTUMN (September/November) 2002. The mean daily maximum and minimum temperatures in Autumn were 14.9°C (+0.7) and 8.1°C (+0.5) respectively. Total rainfall was 201.5 millimetres (121%), and total sunshine 327.5 hours (103%). It was the driest Autumn since 1999.

Met. Observer, Royston (Iceni) Weather Station

6^th December 2002

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