Royston (Iceni) Weather Station
Daily Weather Observations - January 2002
January 2002 Weather Review
The year commenced with a mild, dry and sunny January in Royston.
Continuous sunshine prevailed for the first 4 days of January but was interspersed by sharp night frosts. Sunshine from 1st to 4th accounted for 50% of the normal sunshine for January but unfortunately this bright start to the year did not last as the next 4 days were completely sunless!
However, by the end of the month 68.0 hours sunshine (which is 25% above the long term average) had been accumulated. Despite this total being above average it was, in fact, 28 hours less than in January last year, and also the lowest January total since 1998. Sunshine in January 1998 was also a little above average so now January in Royston has been sunnier than average in 5 consecutive years.
The sunniest day in January was 19th with 7.2 hours sunshine. The next sunniest day was 3rd with 6.9 hours sunshine. A total of 8 days in the month had no sunshine at all.
After the cold start to the month it became progressively milder with no further air frosts after 4th. It was the mildest January in Royston since 1990, although the mean temperature was equal to that in 1993.
The mean daily maximum temperature in January was 8.6°C, which is 2.2°C above the 25 Year (1973/1997) average for Royston. The highest temperature recorded in the month was 13.5°C on 27th; at the other end of the scale the lowest day maximum temperature was 2.2°C on 2nd.
The mean daily minimum temperature in the month was 4.4°C, which is 2.5°C above the 25 Year mean. The lowest temperature recorded in January was –3.5°C on 4th. In contrast, the night minimum temperature on 21st was as high as 11.5°C.
The lowest grass minimum temperature in the month was –7.9°C on 2nd. Totals of 4 air frosts and 8 ground frosts were recorded in January. Air frost duration for the whole month was 40.6 hours.
The mean earth temperature at 30 centimetres depth as observed at 0900 GMT daily was 4.7°C. Along with the air temperature this showed a steady increase through the month from a minimum of 1.9°C on 5th and 6th to a maximum of 7.5°C on 28th and 31st.
Although the last 2 years have been very wet in Royston (and heavy rainfall countrywide has made the national headlines on a number of occasions in that time) it may be surprising to note that January was the 3rd successive month in Royston with below average rainfall. The January rainfall total was 33.2 millimetres, which is 65% of the 30 Year (1971/2000) average for Royston. It was the driest January since 2000 only, however.
The number of "rain days" (0.2 millimetres or more) in January was 14. On 10 of these days 1.0 millimetre or more of rainfall was recorded. The highest 24 hour rainfall total was a somewhat modest 7.2 millimetres on 26th.
Probably the most significant feature of the January precipitation was that the month was completely snow-free. This is only the 4th occasion in January in the last 30 years in Royston that this has happened (the other years with a snow-free January being 1990, 1989 and 1974).
Rainfall duration in January was 44.5 hours.
The strength of the wind tended to increase as the month progressed resulting in a very windy spell near the end of the month (which continued into early February). The maximum wind gust recorded in January was 58 mph on 28th (after a wind gust of 51 mph had been recorded on 26th). The mean wind speed for the whole month was 6.8 mph.
The highest daily (00/00 GMT) mean wind speed was 16.5 mph on 28th, whilst the lowest daily mean wind speed was 0.1 mph on 8th.
The analysis of wind directions as observed daily at 0900 GMT is as follows: NORTH 0 days, NE 0, E 0, SE 4, S 8, SW 12, W 5, NW 0, and CALM 2.
In contrast to January last year (when pressure was some 9 mB below average) the mean MSL air pressure this January of 1018.9 mB was about 3 mB above average. The highest pressure value recorded in the month was 1040 mb on 1st and the lowest value was 977 mB on 24th.
The mean relative humidity in January was 91.1%. The highest daily (00/00 GMT) mean relative humidity value was 99.3% on 5th, whilst the lowest daily mean relative humidity value was 78.7% on 28th. The absolute lowest relative humidity reading in January was 63% at 1855 GMT on 24th.
Fog was not a feature of the January weather in Royston and was recorded on only 2 days (6th and 10th) at the 0900 GMT observation hour.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
6th February 2002
Royston Crow (Corvus Cornix)
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