Royston (Iceni) Weather Station

Daily Weather Observations - March 2004

Temperatures and sunshine were both near to the long term average in March, but rainfall was below normal.

The cold and frosty weather at the end of February spilled over into the first few days of March and the lowest temperature of the month, -3.7°C, was recorded on 1^st March. The lowest grass minimum temperature of the month, -7.8°C, was also recorded on 1^st March. Only 4 further air frosts then occurred in the month, on 2^nd, 3^rd, 9^th and 12^th.

In contrast, the mildest night of the month was 15^th/16^th with a minimum temperature of 11.0°C. This was the culmination of a concerted rise in temperatures between 11^th and 16^th, but it then became gradually less mild over the next 10 days before another surge in temperatures up to the end of the month.

The highest daily maximum temperature in March was 18.5°C on 31^st, whilst the lowest daily maximum temperature of the month was 4.8°C on 11^th. The mean daily maximum temperature over the whole month was 10.5°C, which is 0.4°C above the 30 Year (1971/2002) average. The mean night minimum temperature was 0.3°C above normal at 3.6°C. This value was only 0.4°C higher than in February and 0.3°C higher than in January.

In total, 5 air frosts (as noted above) and 12 ground frosts were recorded in March. Air frost duration was 19.0 hours. Despite the mean temperature being marginally above average it was nonetheless the 2^nd coldest March (after March 2001) in the last 8 years. In general the temperature regime in March was unexceptional and no extremes were recorded.

The mean earth temperature at 30 cms depth as measured at 0900 GMT daily was 6.1°C, peaking at 8.4°C on 18^th and registering a lowest value of 2.4°C on 3^rd.

Although only 7 days in March were completely dry it was, in fact, a dry month with the total rainfall of 28.2 millimetres being only 66% of the 1971/2000 average for Royston. The number of "rain days" (0.2 millimetres or more) was 13, whilst on 9 of these days rainfall exceeded 1.0 millimetre. The wettest day of the month was 12^th when an early morning snow cover very quickly thawed, giving a rainfall equivalent of 7.3 millimetres.

Snow was observed to fall on 3 days (10^th, 11^th and 12^th) in March and hail observed to fall on 6 days (7^th, 13^th, 21^st, 22^nd, 23^rd and 24^th). This was the highest number of days with hail in March since records began at Royston (Iceni) Weather station in 1972. The hail on 21^st (at 1710 GMT) was accompanied by thunder and lightning (which severed readings from all of the weather station’s automatic instruments until restoration of the system later in the evening!). This was the only day in March with thunder. Rainfall duration in the month was 31.8 hours.

Sunshine struggled throughout the month to keep up with the average but over 20 hours sunshine on the last two days of the month raised the total of 102.5 hours to within 4% of the 1971/2000 average. The sunniest day of the month was 30^th with 10.2 hours sunshine, just exceeding the 10.1 hours on 31^st. Only 4 days (4^th, 5^th, 12^th and 27^th) in the month were completely sunless.

The most notable weather event in March was undoubtedly the gale which occurred in the afternoon of 20^th, mainly accompanied by bright sunshine! The maximum wind gust recorded was 71 mph at 1610 GMT, this being the highest wind speed in the month, and also the highest wind speed since the 71 mph recorded on 27^th October 2002. As might be expected, the 20^th registered the highest 24 hour (00/00 GMT) mean wind speed (16.4 mph) in the month. The lowest daily mean wind speed in March was 0.0 mph (to nearest 1 decimal point) on 1^st.

The analysis of daily wind directions as observed at 0900 GMT was NORTH 4 days, NE 4, E 1, SE 2, S 5, SW 8, W 4, NW 1, and CALM 2.

The mean MSL air pressure in March was 1020.1 mB, which is 5 mB above the average of the last 30 years. The pressure extremes in the month were 1039 mB on 1^st and 997 mB on 20^th.

The mean relative humidity in the month was 83.9%. The highest daily (00/00 GMT) mean relative humidity was 97.4% on 5^th and the lowest daily mean relative humidity was 70.0% on 2^nd. The absolute lowest relative humidity reading in March was 44% at 1345 GMT on 30^th.

Fog (visibility < 1000 metres) was noted at the 0900 GMT observation hour on just 1 day (5^th) in March. In fact, visibility was below the 200 metre threshold on this occasion.

The Winter (December 2003/January 2004) means held over from last month are as follows: The mean daily maximum temperature in Winter was 7.8°C (0.8°C above average), whilst the mean night minimum temperature was 3.3°C (1.0°C above average). Total rainfall was 178.3 millimetres (128% of average) and sunshine 202.7 hours (115% of average).

Richard Barker

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

5^th April 2004

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