Royston (Iceni) Weather Station
Daily Weather Observations - November 2000
November 2000 Weather Review
Although November was a very wet month in Royston it was sunnier than average, whilst temperatures were a little above normal.
The main weather talking point this Autumn nationally has undoubtedly been the heavy rainfall experienced across the country, and although Royston has escaped the worst of the deluges which have affected some areas it has nonetheless been a very wet Autumn here. In fact, with an Autumn (September/November) rainfall of 334.1 millimetres (which is 211% of the 35 Year (1961/1995) average) it has been the wettest Autumn in Royston since rainfall records commenced in 1853, the rainfall even exceeding the total (319.1 millimetres) recorded in the very wet Autumn of 1974.
As regards rainfall in November only, the total for the month of 118.2 millimetres was over twice the normal at 225% of the 35 Year (1961/1995) average, making it the wettest November in Royston since 1970. The wettest day of the month was 5th with 22.6 millimetres, this being the wettest November day since 26th November 1983 when a daily rainfall of 27.6 millimetres was recorded. The number of "rain days" (0.2 millimetres or more) in the month was 20; of this total 18 days are classified as "wet days" with over 1.0 millimetre rainfall recorded.
Rainfall duration in November was 111.3 hours.
Thunder was recorded on 1 day (7th at 1458 GMT) in November, this being only the 4th November since 1972 thunder has been heard.
Temperatures in November were unexceptional with no high or low extremes, giving a mean temperature for the month 0.5°C above normal.
The mean daily maximum and minimum temperatures in November were 10.0°C and 5.1°C respectively, both these values being 0.5°C above the 25 Year (1973/1997) average.
The highest day maximum temperature recorded in November was 15.0°C on 28th. The lowest day maximum temperature was 6.5°C on 20th. The lowest temperature of the month was 0.0°C recorded on 15th. This means that no air frost at all was recorded at Royston (Iceni) Weather Station in November (or indeed the whole Autumn), but it is possible that lower lying parts of the town may have just registered an air frost on this date. In contrast, a minimum temperature of 9.5°C was recorded for the night of 28th/29th, the highest such minimum temperature of the month.
Even ground frosts were relatively few in number (3), the lowest grass minimum temperature registered being –3.1°C on 15th.
The mean earth temperature at 30 cms depth as observed at 0900 GMT daily was 7.5°C. The highest earth temperature recorded was 9.7°C on 1st whilst the lowest earth temperature was 6.0°C on 18th.
With both the high rainfall and rainfall duration values it is perhaps surprising that sunshine duration was above average, despite the month containing 6 days (9th, 11th, 23rd, 25th, 27th and 28th) which were completely sunless.
Total sunshine duration in the month was 84.6 hours, which is 127% of the 30 Year (1961/1990) average. The sunniest day was 1st with 7.4 hours sunshine, whilst 13th was almost as sunny with 7.3 hours sunshine.
The MSL air pressure was noteworthy in November for a record low mean value. The mean air pressure value for the month was 997.0 mB which is an exceptionally large 18 mB below normal, and is the lowest monthly mean for any month of the year since at least January 1972 in Royston. Furthermore November was the first month of any in this period to experience a mean value below 1000 mB.
The highest pressure reading of the month was a relatively low 1013 mB on 10th, whilst the lowest pressure reading of the month of 970 mB occurred just a few days earlier on 6th.
With November being dominated by low pressure, as might be expected it was a fairly windy month, but with the absence of any notable gales. The maximum wind gust speed recorded was 46 mph, on both 5th and 22nd. The mean wind speed in the month was 6.2 mph. The highest daily (00/00 GMT) mean wind speed was 12.5 mph on 26th, and the lowest daily mean wind speed was 1.3 mph on 14th.
Daily wind directions as observed at 0900 GMT were NORTH 0, NE 1, E 1, SE 3, S 6, SW 14, W 4, NW 1 and CALM 0.
The mean relative humidity in November was 90.6%. The highest and lowest daily (00/00 GMT) mean relative humidity values were 98.1% on 23rd and 80.5% on 26th respectively. The absolute lowest relative humidity reading of the month was 63% at 1310 GMT on 1st.
To expand on the Autumn (September/November) rainfall data quoted above, the mean daily maximum and minimum temperature values for the Autumn were 14.5°C (0.4°C above average) and 8.6°C (1.1°C above average) respectively. Total sunshine duration in the Autumn was 325.2 hours, which is 102% of average.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
7th December 2000
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