Royston (Iceni) Weather Station

Daily Weather Observations - April 2006

April 2006 was yet another dry month in Royston, but was a little warmer than average, with sunshine near normal.

After a run of 5 consecutive months with below average temperatures this trend was reversed in April with the mean temperature actually being above average. However, it was still the coldest April since 2001, this being more of a testament to the mild nature of April in recent years rather than indicating any particularly cold conditions in April this year.

The mean daily maximum temperature in April was 13.8°C, which is 0.7°C above the 30 Year (1976/2005) average. The mean night minimum temperature was also 0.7°C above average at 5.2°C.

The highest day maximum temperature recorded in April was 17.5°C on 27^th. It is noteworthy that this was the lowest absolute maximum temperature in April since 1989. The lowest night minimum temperature in the month was –3.0°C on 5^th, whilst the lowest grass minimum temperature was –6.9°C, also on 5^th. This was the lowest grass minimum temperature in April since 1996.

Totals of 2 air frosts and 5 ground frosts were recorded in April. Air frost duration over the course of the month was 14.2 hours.

The mean earth temperature at 30 cms depth in April was 10.1°C, ranging from a lowest value of 7.6°C on 12^th to a highest reading of 12.5°C on 28^th.

The dry spell which commenced at the end of November 2004 intensified during April and it was only the rainfall during the night of 30^th April/1^st May which prevented April from being a very dry month. In the event total rainfall in April was 32.8 millimetres, which is 74% of the 30 Year (1971/2000) average.

The number of "rain days" (0.2 millimetres or more) in April was 14, with rainfall equalling or exceeding 1.0 millimetre on 9 of these days. The wettest day of the month was 30^th with 12.9 millimetres rainfall. Whilst this was not a particularly heavy rainfall it nonetheless made 30^th April the wettest day of the year so far. Rainfall duration in the month was 43.6 hours. No snow was observed to fall in April, but hail did occur on 1 day (4^th). It was the driest April since 2003 only.

The first half of April was very sunny and by 15^th sunshine duration of 87.5 hours had been recorded. The second half of the month was more cloudy, however, and aggregate sunshine only reached 53.6 hours in this period. The final sunshine total for the month was 141.1 hours, which is 97% of the 30 Year (1971/2000) average.

The sunniest day in April was 5^th with 12.6 hours sunshine. This was the only day to exceed 10 hours sunshine. Only 1 day (15^th) in the month was completely sunless. It was the dullest April since 2001.

The mean wind speed in April was 3.0 mph. The windiest day was 2^nd with a 24 hour (00/00 GMT) mean wind speed of 8.3 mph. In contrast the calmest day of the month was 15^th with a mean wind speed of only 0.2 mph. The maximum wind gust speed recorded in April was 46 mph on 2^nd.

The analysis of wind directions as observed daily at 0900 GMT was NORTH 5 days, NE 2, E 2, SE 1, S 2, SW 7, W 8, NW 3 and CALM 0.

The mean MSL air pressure in April was 1013.4 mB, which is 1.5 mB below the mean of the last 30 years. The highest and lowest pressure values in April were 1026 mB and 1001 mB on 28^th and 1^st respectively.

The mean relative humidity in April was 78.2%, ranging from a highest daily (00/00 GMT) mean of 90.7% on 25^th to a lowest daily mean of 61.0% on 6^th. The absolute lowest relative humidity reading in April was 31% at 1530 GMT on 5^th.

Fog (visibility < 1000 metres at 0900 GMT) was not recorded on any day in April.

Met. Observer, Royston (Iceni) Weather Station

4th May 2006

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