Royston (Iceni) Weather Station

Daily Weather Observations - October 2008

A sunny October was experienced in Royston, but both temperatures and rainfall were a little below normal.

The most significant features of the weather in October occurred near the end of the month. With regard to temperature, on 29^th the lowest minimum temperature (and first air frost in October) was recorded since October 1997. The temperature dipped to –2.5°C on this date and this was accompanied by a grass minimum temperature of –6.0°C, the lowest such value of the month.

The mean daily maximum temperature in October was 14.4°C, which is 0.2°C below the 30 Year (1976/2005 average). The mean night minimum temperature was 0.9°C below average at 7.1°C. It was the coldest October since 2003.

The lowest day maximum temperature in October was 7.4°C, not surprisingly also on 29^th. In contrast the highest night minimum temperature was 14.0°C on 13^th. Totals of 2 air frosts and 6 ground frosts were recorded in October. Air frost duration in October was 11.8 hours.

The mean earth temperature at 30 cms depth as recorded at 0900 GMT daily was 11.8°C. The highest and lowest earth temperature values in October were 14.4°C and 7.6°C on 1^st and 31^st respectively.

Another significant feature of the October weather was the snowfall which occurred during a period of heavy rainfall in the evening of 28^th. This was the first snowfall recorded in October since at least 1972, when records commenced at Royston (Iceni) Weather Station. Although this snow did not settle in Royston there were significant deposits elsewhere in North Hertfordshire and surviving snow patches were noted as late as 31st!

The aforementioned rain and snow on 28^th made this day the wettest day of the month with rainfall of 19.9 millimetres. At this point in the month rainfall had been running well below normal but by the end of the month the rainfall total of 53.2 millimetres was only 7% below the 30 Year (1971/2000) average.

The number of "rain days" (0.2 millimetres or more) in October was 15, whilst on 12 of these days rainfall equalled or exceeded 1.0 millimetre. Rainfall duration in the month was 49.4 hours.

October was a sunny month in Royston and total sunshine of 153.0 hours was 133% of the 1971/2000 average. The sunniest day of the month was 11^th with 9.8 hours sunshine. This came during a 5 day spell from 8^th to 12^th inclusive which aggregated 47.8 hours sunshine. Only 2 days (15^th and 20^th) were completely sunless in October. It was the sunniest October since 2003

The mean wind speed in October was 6.1 mph, whilst the maximum wind gust speed recorded was 46 mph on 1^st. The highest daily (00/00 GMT) mean wind speed was 12.4 mph, also on 1^st and the lowest daily mean wind speed was 0.9 mph on 31^st.

The analysis of wind directions as observed at 0900 GMT daily shows a bias towards winds with a westerly component, as follows: NORTH 1 day, NE 1, E 0, SE 1, S 4, SW 11, W 7, NW 6 and CALM 0.

The mean MSL air pressure in October was 1011.3 mB, which is 3.4 mB below the 1976/2005 average. The highest and lowest air pressure values recorded in October were 1029 mB on 9^th and 992 mB on 5^th and 30^th.

The mean relative humidity in the month was 87.8% with a highest daily (00/00 GMT) mean of 97.6% on 5^th and a lowest daily mean of 75.8% on 1^st. The absolute lowest relative humidity reading in October was 35% at various times during the afternoon of 11^th.

Fog (visibility < 1000 metres) was not noted on any day in October at the 0900 GMT observation hour.

Met. Observer, Royston (Iceni) Weather Station

5th November 2008

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