Royston (Iceni) Weather Station

Daily Weather Observations - February 2004

Rainfall and sunshine were both close to the average in February, but the mean temperature was above average.

It was the 7^th February in the last 8 years with an above average mean temperature, the exception being last year when the mean temperature was just 0.1°C below average. However, the mean temperature this year conceals a period of exceptional warmth for the time of year at the beginning of the month and below average temperatures for most of the second half of the month.

This is illustrated by comparison of the means between the two halves of the month. The mean daily maximum temperature for 1^st/15^th was 10.5°C, which is 3.4°C above average for this period, whilst the equivalent value for 16^th/29^th was 5.3°C (2.3°C below average). Similarly, the mean night minimum temperature for 1^st/15^th was 6.7°C (4.7°C above average) and the mean night minimum temperature for 16^th/29^th was –0.6°C (2.2°C below average).

For the month as a whole the mean daily maximum temperature was 0.8°C above average at 8.0°C, whilst the mean night minimum temperature was 1.4°C above average at 3.2°C. The highest temperature of the month was 16.4°C on 4^th; other high daily maxima were 14.1°C on 2^nd and 15.2°C on 3^rd. Each of these temperatures was the highest recorded on its respective date in the last 32 years. In contrast the maximum temperature on 28^th was only 2.4°C and this was the lowest such value on this date since at least 1972.

Night minimum temperatures were also notably high in the early part of February, the highest for the month being 12.0°C on 4^th. The lowest temperature recorded in February was –4.0°C on 26^th and the lowest grass minimum temperature was –6.1°C, also on 26^th. Overall it was the mildest February since 2002 only.

Totals of 11 air frosts and 13 ground frosts were recorded in February. The air frost duration for the month was 95.8 hours.

The mean earth temperature at 30 cms depth as observed at 0900 GMT daily was 5.8°C. The highest and lowest earth temperature readings in the month were 8.5°C and 2.6°C on 5^th and 29^th respectively.

On average February is the driest month of the year in Royston, but after the dry February last year the rainfall total of 39.0 millimetres this year exceeded the 30 Year (1971/2000) average by 11%. The number of "rain days" (0.2 millimetres or more) was 14, whilst on 9 of these days rainfall was 1.0 millimetre or greater. The wettest day of the month was 5^th with 14.3 millimetres rainfall. Rainfall duration over the whole month was 46.3 hours.

The cold second half of February (see above) was accompanied by snowfall on 6 of the last 8 days of the month. However, amounts of snow were generally small and of the 3 days in this period on which the ground was more than half covered with snow at 0900 GMT the greatest snow depth measured was only 2 cm (on 29^th). The only other day in the month on which snow was observed to fall was on 8^th but the amount was minimal.

Snowfall in the afternoon of 28^th was accompanied by hail also, this being the only occurrence of hail in February.

For the first time in at least the last 7 years sunshine in February failed to exceed the normal. The sunshine total of 69.1 hours was 95% of the 1971/2000 average. It was a rather dull month until the last week when sunnier conditions helped boost the total to near the average. The 7 day period from 11^th to 17^th was particularly dull with 6 days being completely sunless and only 1.1 hours sunshine being recorded on the remaining day (15^th).

The sunniest day of the month was 25^th with 8.8 hours sunshine. The only other day with above 8 hours sunshine was 9^th (8.2 hours). The number of sunless days in the month was 7.

The mean wind speed in February was 4.6 mph. The highest daily (00/00 GMT) mean wind speed was 14.6 mph on 3^rd, whilst the lowest daily mean wind speed was 0.2 mph on both 12^th and 16^th. The highest wind gust speed recorded in the month was 48 mph on 8^th (at 0230 GMT).

The analysis of wind directions as observed daily at 0900 GMT was NORTH 4 days, NE 3, E 0, SE 0, S 0, SW 9, W 3, NW 9 and CALM 1.

The mean MSL air pressure in February was 1020.9 mB, which is 5 mB above the average of the last 30 years. The highest and lowest pressure values recorded in the month were 1037 mB and 998 mB on 9^th and 27^th respectively.

The mean relative humidity in the month was 85.8%, with the highest daily (00/00 GMT) mean relative humidity being 96.3% on 14^th and the lowest 67.8% on 8^th. The absolute lowest relative humidity reading in February was 48% at 1420 GMT on 8^{th ,} 1520 GMT on 25^th, and 1515 GMT on 26^th.

No fog (visibility < 1000 metres) was observed at the daily 0900 GMT observation hour in February.

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

6^th March 2004

Royston Crow (Corvus Cornix)

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