Royston (Iceni) Weather Station

Daily Weather Observations - February 2009

It was a dull and wet (mostly as snow) February in Royston, but with near average temperatures.

Although the mean temperature in February was almost up to the 30 Year (1976/2005) average this statistic hides a month of two distinct halves. This is illustrated by a mean temperature of 1.0°C for the period 1^st/14^th, compared with the equivalent figure of 7.7°C for the period 15^th/28^th.

The temperature did not reach 10°C until 16^th, giving a consecutive period of 55 days since 23^rd December 2008 when 10°C was not reached. This is the longest such period with the temperature consistently remaining below 10°C since records commenced at Royston (Iceni) Weather Station in 1972.

The first two weeks of February were unusually cold (and snowy) but not severe. The lowest day maximum temperature in the month was 0.6°C on 6^th, whilst the lowest night minimum temperature in February was –4.5°C on 3^rd. The lowest grass minimum temperature in the month was –9.0°C, also on 3^rd. In contrast the highest daily maximum temperature in the month was 14.4°C on 27^th, and the highest night minimum temperature was 7.5°C on 20^th.

The mean daily maximum temperature in February was 6.9°C, which is 0.3°C below the 30 Year (1976/2005) average. The mean night minimum temperature was precisely on the 30 Year average at 1.8°C. Totals of 10 air frosts and 14 ground frosts were recorded in February, and air frost duration was 122.2 hours. It was the coldest February since 2006 only.

The mean earth temperature at 30 cms depth as recorded at 0900 GMT daily was 3.9°C. The highest and lowest earth temperature values were 6.9°C on 28^th and 2.3°C on 13^th, 14^th and 15^th respectively.

February 2009 will be mainly remembered for the snowfalls during the first two weeks resulting in the most significant snowfall event in Royston in any month since February 1991. A continuous snow cover existed from 2^nd to 15^th inclusive, reaching a maximum depth of 12 cm on 7^th as measured at the 0900 GMT observation hour. (Note: Daytime snow melt in preceding days will have reduced this depth somewhat).

Snowfall occurred on 8 days in total in February, whilst snow was lying (ground more than half covered with snow @ 0900 GMT) on 14 days. This was the highest number of days with snow lying in any month since February 1991.

As already indicated much of the precipitation in February fell as snow and the month’s rainfall total (rainfall equivalent of snow plus rainfall) was 64.9 millimetres, which is 185% of the 1971/2000 average. The number of "rain days" (0.2 millimetres or more ) was 15, with rainfall exceeding 1.0 millimetre on 8 of these days. The wettest day of the month was 9^th with 19.6 millimetres rainfall (snow melt). This was the wettest February day since 7^th February 2001, and the 3^rd wettest February day since at least 1972. It was the wettest February in Royston since 2001.

The February sunshine total of 65.6 hours was 10% below the 1971/2000 average, and was, in fact, 20.1 hours below January 2009, and no less than 79.4 hours below February last year! The sunniest day of the month was 21^st with 9.7 hours sunshine. The number of completely sunless days in February was 7.

The mean wind speed in February was 3.8 mph. The highest and lowest daily (00/00 GMT) mean wind speed values were 8.0 mph and 0.4 mph on 10^th and 18^th respectively. The highest wind gust recorded in the month was 35 mph on 10^th.

The mean MSL air pressure in the month was 1012.6 mB (4 mB below the 1976/2005 average), with highest and lowest values of 1031 mB on 20^th and 21^st, and 975 mB on 10^th respectively.

The mean relative humidity in February was 90.9%. The highest daily (00/00 GMT) mean relative humidity was 99.7% on 2^nd, and the lowest daily mean relative humidity was 78.8% on 28^th. The absolute lowest relative humidity reading in February was 51% at 1340 GMT on 1^st.

Fog (visibility < 1000 metres) was observed at the 0900 GMT observation hour on just 1 day (7^th) in February.

WINTER (December/ February) 2008/2009: It was the coldest Winter in Royston since 1995/1996. It also had the highest number of days with snow lying since 1995/1996. The mean daily maximum temperature in Winter was 6.1°C, which is 0.9°C below average. The mean night minimum temperature in Winter was 0.8°C below average at 1.5°C. Total rainfall in Winter was 136.4 millimetres (98% of average), and total sunshine was 239.8 hours (136% of average).

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

6^th March 2009

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