Royston (Iceni) Weather Station
Weather Review - JANUARY 2000
The weather of the new millennium started off on a favourable note with a mild, dry and exceptionally sunny January. These features of the weather in Royston have been a common occurrence over the last few years so the new millennium has commenced in much the same way as the old one ended in terms of the weather conditions experienced.
The sunshine was undoubtedly the main highlight of the January weather in Royston. The sunshine total for the month was 86.8 hours which is approximately 160% of the long term average.
Only 5 days in the month were completely sunless whilst 7 days recorded over 5 hours sunshine. The sunniest day was 27th with 7.5 hours sunshine, closely followed by 21st with 7.2 hours.
January proved to be yet another month with above average temperatures but it was not as mild this year as in January of the two previous years. The mean daily maximum temperature was 7.6°C (45.7°F) which is 1.2°C above the 25 Year (1973/1997) average. It was a similar story with night minimum temperatures as the mean of 3.0°C (37.4°F) was 1.1°C above average.
The highest temperature of the month was 13.4°C (56.1°F) on 29th. Since 1973 this figure has only been exceeded in 4 years, 1975, 1983, 1998 and 1999. No really cold days occurred in January, the lowest day maximum temperature being 3.4°C (38.1°F) on 13th.
The lowest temperature recorded in January was –1.1°C (30.0°F) on 24th. This date saw 1 of only 5 air frosts in the month. This lowest minimum temperature was the highest such value in January in Royston since 1990 (which escaped with no air frost at all in January). The actual duration of air frost (i.e. the time the temperature remained below 0°C) over the whole month was a relatively modest 19.5 hours.
Ground frost was much more prevalent, however, and occurred on 14 nights. The lowest grass minimum temperature (which determines a ground frost if it falls below 0°C) was –5.6°C (21.9°F) on 25th.
The mean earth temperature at 30 centimetres (1 foot) depth as measured daily at 0900 GMT was 4.3°C (39.7°F). The highest earth temperature of 5.8°C (42.4°F) was attained on 8th whilst the lowest value of 2.8°C (37.0°F) occurred on 28th. The mild spell over the last 4 days of the month soon raised this to 5.6°C (42.1°F) by 31st, however.
January was a virtually snow free month in Royston, but a few flakes of snow in the morning of 13th, and again literally a few flakes of snow (accompanied by hail) just after noon on 22nd meant that the records will show 2 days with snow falling, even though there was absolutely no danger of snow settling on either occasion. Only in 3 years (1974, 1989 and 1990) has January been completely snow free in Royston.
The lack of snow was partly a manifestation of the lack of precipitation generally since the rainfall total could only manage to climb to 49.5% of the 35 Year (1961/1995) average. This is not good news for the water supply situation as Royston now enters its three driest months of the year. Total rainfall in January was 25.4 millimetres (1.00 inches), this being comprised of measurable rainfall (0.2 millimetres or more) on 14 days in the month. The wettest day of the month was 3rd with 5.9 millimetres (0.23 inches) rainfall. Rainfall duration was 35.0 hours in January.
January was not a particularly windy month in Royston except for 28th and 29th when maximum gusts of 46 mph occurred on both days. The mean wind speed over the whole month as determined from 5 minute observations was 5.8 mph. The windiest day overall was 29th with a 24 hour (00/00h) mean wind speed of 15.6 mph. At the other end of the scale the calmest day of the month was 24th with a mean wind speed of only 0.4 mph.
As regards wind direction the daily distribution of this element as observed at 09 GMT was N 2, NE 1, E 0, SE 0, S 4, SW 10, W 7, NW 6, and CALM 1.
A large anticyclone persisted just to the west of the British Isles for part of the month and contributed to the mean MSL air pressure being some 6 mb above average at 1022.5 mb. The highest air pressure value recorded was 1041 mb on 16th, whilst the lowest value recorded was 994 mb on 29th.
The mean relative humidity in January was 89.5%, ranging from a highest daily mean value of 96.2% on 17th to a lowest daily mean value of 82.1% on 28th.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
4th February 2000
Royston Crow (Corvus Cornix)
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