Royston (Iceni) Weather Station
Daily Weather Observations - March 2001
March 2001 Weather Review
The weather in March was somewhat disappointing for the first month of Spring – it was cold, dull and wet.
As has happened frequently in the national news in recent months the rainfall once again made the headlines. In Royston the 12 months ended March 2001 have been the wettest 12 months ended March since rainfall records began here in 1853. During this period a total of 955.3 millimetres rainfall has been recorded, which is 164% of the 30 Year (1971/2000) annual average for Royston.
As regards the rainfall for March alone this totalled 87.2 millimetres, which is 205% of the 1971/2000 average. The number of "rain days" (0.2 millimetres or more) was 22, whilst the number of days with 1.0 millimetres or more was 18. The wettest day of the month was 16th with 12.9 millimetres rainfall. Rainfall duration in the month was 105.3 hours. It was the wettest March in Royston since 1979.
A heavy snow shower in the early evening of 2nd was enough to give a 2 cm snow cover at the 0900 GMT observation hour on 3rd, but the lying snow did not persist beyond that day. A further snowfall in the morning of 21st gave difficult driving conditions in the "rush hour" period, but again the snow cover did not last long due to milder air soon moving over the region turning the precipitation to rain.
Snow was observed to fall, albeit in small amounts, on 3 other days in March, 1st, 18th, and 20th. In addition to the lying snow on 3rd and 21st as mentioned above, there was also a light snow cover at 0900 GMT on 1st, but with negligible depth. Hail was recorded on just 1 day (2nd) in March.
The mean temperature in March was below average (although by only 0.6°C), making March the second month in the last 3 months with below average temperatures, this pattern being an unusual occurrence in recent times.
March commenced on a cold note with sharp frosts from 2nd to 5th. On 3rd the lowest minimum temperature (-5.1°C) of the month was recorded, along with the lowest grass minimum temperature of –11.1°C. Both these values were the lowest recorded in March since 3rd March 1986. Overall it was the coldest March since 1996, after a run of 4 years each with a significantly milder than average March.
The highest temperature recorded in March was 16.9°C on 31st. At the other end of the scale the temperature achieved a maximum value of only 2.8°C on 17th, and 3.0°C on 1st.
The mean daily maximum temperature in March was 9.0°C, which is 0.9°C below the 25 Year (1973/1997) Royston average. The mean daily minimum temperature in the month was 0.4°C below average at 2.7°C. Totals of 6 air frosts and 12 ground frosts occurred in March, whilst air frost duration was 66.1 hours.
The mean earth temperature at 30 centimetres depth as measured at 0900 GMT daily was 5.8°C. The earth temperature monthly extremes ranged from 2.9°C on 6th to 8.0°C on 31st.
The first half of March was quite sunny and by 15th sunshine of some 63 hours had been recorded, compared with the average for the whole month of 103 hours. However, the second half of the month was very dull, and only managed to increase the sunshine total by another 25 hours. Given that the sunniest day of the month, 30th with 10.0 hours sunshine, occurred in this latter period the daily average sunshine for the other 15 days between 16th and 31st was only 1 hour!
For the record the actual sunshine total in March was 88.4 hours, which is 82% of average. Other sunny days (apart from 30th as mentioned) were 5th and 6th with 9.7 and 8.3 hours sunshine respectively. The number of days in the month with NIL sunshine was 7.
Although strong winds can often be a feature of the March weather it was not so this year and the maximum gust speed recorded in March this year was ‘only’ 37 mph (on 31st). In terms of mean wind speed over the whole 24 hour period from midnight, 31st was also the windiest day of the month overall with a mean wind speed of 9.9 mph. The calmest day of the month was 15th with a mean wind speed of 0.6 mph. The mean wind speed over the whole month was 4.2 mph.
The daily wind directions as observed at 0900 GMT were NORTH 5, NE 7, E 1, SE 4, S 1, SW 6, W 3, NW 1, and CALM 3.
Following the trend to lower pressure values over recent months the mean MSL Air Pressure in March was some 12 mB below average at 1003.3 mB. This was the lowest mean value recorded in March since at least 1972. The highest and lowest pressure readings in March were 1019 mB on 5th and 6th, and 990 mB on 28th and 29th, respectively.
The mean relative humidity in March was 87.9%. The highest daily (00/00 GMT) mean relative humidity was 97.8% on 8th, whilst the lowest daily mean relative humidity was 74.7% on 30th. The absolute lowest relative humidity reading in March was 45% at 1555 GMT on 30th.
Fog (visibility less than 1000 metres) was not noted at the 0900 GMT observation hour on any day in March.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
5th April 2001
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