Royston (Iceni) Weather Station

Daily Weather Observations - February 2005

It was a dull but dry February in Royston, whilst the mean temperature was close to the average.

The month commenced with a cloudy but mostly dry first week. Over the first 6 days of February only 2.6 hours sunshine was recorded, but then on 7^th the sunniest day of the month occurred with 8.2 hours sunshine. After another sunny day on 8^th (5.3 hours sunshine) dull conditions returned for the next few days.

Sunshine amounts remained below average for the rest of the month, although two sunny days on 27^th and 28^th raised the month’s total sunshine value of 62.6 hours to within 14% of the 1971/2000 average. Over the whole month 8 days were completely sunless. It was the dullest February since at least 1998.

For the third successive month rainfall was below normal (see note at the end of this report re Winter rainfall). The February rainfall total of 27.1 millimetres was 77% of the 1971/2000 average. The number of "rain days" (0.2 millimetres or more) was 16, whilst on 8 of those days rainfall exceeded 1.0 millimetre.

The wettest day of the month was 10^th with 8.9 millimetres rainfall. Rainfall duration was a relatively high (for the rainfall total) 63.6 hours, indicating that much of the month’s rainfall was light in nature.

February was snow free until 19^th but with the exception of 25^th snow then fell on every day until the end of the month (making a monthly total of 9 days with snow falling). Amounts of snow were fairly small, however, and the greatest level depth of snow at the 0900 GMT observation hour was only 2 cm, on 22^nd. Snow was lying at 0900 GMT (ground more than 50% covered) on 4 other days in the last week of the month but snow depths were minimal and the snow thawed quickly.

Hail was also observed to fall on 21^st and 22^nd, and earlier in the month on 13^th and 15^th additionally.

Although the mean temperature in February was just 0.2°C below the 30 Year (1973/2002) average, this figure conceals mild conditions during the first half of the month and somewhat colder weather in the second half. For instance the mean daily maximum temperature from 1^st/14^th was 9.0°C, whereas the equivalent value for 15^th/28^th was only 4.5°C. The same comparison on the night minimum temperatures gives means of 4.2°C and –0.7°C respectively.

With regard to the month as a whole the mean daily maximum temperature was 6.8°C, which is 0.4°C below average. The mean night minimum temperature was 1.8°C which is precisely equal to the 30 Year average. Overall it was the coldest February since 1996, and only the 3^rd occasion in the last 10 years that February has been colder than average.

The highest temperature recorded in February was 12.2°C on 12^th. This is the lowest February absolute maximum temperature since 1996. The lowest temperature recorded in the month was –4.5°C on 28^th. The lowest grass minimum temperature of the month of –9.3°C also occurred on 28^th. Totals of air and ground frosts in February were 8 and 19 respectively.

The mean earth temperature at 30 cms depth as read at 0900 GMT daily was 5.4°C, peaking at 7.2°C on 12^th, and falling to its lowest value of 3.8°C on 28^th.

The mean wind speed in February was 3.0 mph. The maximum wind gust speed recorded was 48 mph on both 12^th and 13^th. The highest daily (00/00 GMT) mean wind speed was 14.3 mph on 12^th, whilst the lowest such value was 0.1 mph on 16^th.

Winds with a northerly component dominated the second half of February and this is reflected in the following analysis of wind directions as observed at 0900 GMT daily: NORTH 8 days, NE 2, E 0, SE 4, S 1, SW 3, W 4, NW 5 and CALM 1.

The mean MSL air pressure in February was 1020.7 mb, which is 5 mB above the 30 Year (1973/2002) average. The highest and lowest air pressure values recorded in the month were 1036 mB and 998 mB on 3^rd and 12^th respectively.

The mean relative humidity in the month was 88.6%. The highest daily (00/00 GMT) mean relative humidity was 98.6% on 24^th and the lowest daily mean relative humidity was 70.2% on 14^th. The absolute lowest relative humidity reading in February was 44% at 1325 GMT on 27^th.

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

This report concludes with a few summary statistics for the Winter (December/February) 2004/2005. The mean daily maximum temperature over the 3 months was 7.8°C, which is 0.8°C above average. The mean night minimum temperature was 0.7°C above average at 3.0°C. Total rainfall was 85.9 millimetres which is only 62% of normal. Sunshine totalled 219.0 hours, which is 125% of average. It was the driest Winter since 1991/1992. Winter 2004/2005 is ranked as only the 6^th mildest Winter in the last 10 years.

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

5^th March 2005

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