Royston (Iceni) Weather Station
Daily Weather Observations - January 2003
January 2003 Weather Review
The year commenced with a fairly sunny but very wet January, whilst the mean temperature was close to average.
The outstanding weather event of the month was undoubtedly the heavy snowfall which occurred during the afternoon and early evening of 30th. An area of snow moved in on a strong wind from the north after a sunny start to the day and gave a 15 cms level depth of snow in Royston. This was the heaviest snowfall recorded in Royston in any month since 8th February 1991. The strength of the wind enhanced the penetrative effect of the snow and tree trunks, branches and twigs right down to ground level were coated with a thick layer of snow which made a resplendent scene in the bright sunshine in the morning of 31st.
.In addition to 31st the ground was more than 50% covered with snow at 0900 GMT on two other days in the month, 9th and 10th, but was only 1 cm deep on 9th and of negligible depth on 10th. Although snow was recorded as falling on 6 days in the month, only the snowfall on 30th was of a significant nature.
Snowfall aside, it is really the precipitation in the form of both rainfall and snowfall in January which made the headlines. The month commenced with heavy rainfall on both 1st and 2nd which, after the wet end to December, unusually left a few patches of standing water on arable farmland in the normally well drained chalk soils of the countryside around Royston.
It was, in fact, the wettest New Year’s Day in Royston in at least the last 30 years. Rainfall of 23.0 millimetres not surprisingly made it the wettest day of the month. The number of "rain days" (0.2 millimetres or more) in January was 20, whilst on 12 of these days rainfall exceeded 1.0 millimetre. Total rainfall in the month was 98.0 millimetres, which is 191% of the 30 Year (1971/2000) average. It was the wettest January in Royston since 1995. Rainfall duration in January was 90.5 hours.
Hail was observed to fall on 2 days, 4th and 28th, in the month.
The first sunshine of the month did not occur until 4th, ending a run of 6 consecutive days without any sunshine, and a run of 9 consecutive days with only 0.5 hours sunshine! After that matters improved somewhat and by the end of the month 67.5 hours sunshine had been accumulated, which is 25% above the 30 Year (1961/1990) average.
Despite the higher than normal sunshine it was nonetheless the dullest January since 1998. The sunniest day of the month was 11th with 6.9 hours sunshine. The number of completely sunless days in the month was 7.
Although the mean temperature in January was about average this statistic conceals some notably cold and mild spells. Mild conditions at the start of the month soon gave way to a cold and frosty spell in which the temperature plunged to its lowest value (-5.7°C on 8th) for 6 years. This was the lowest temperature recorded in January, whilst in contrast the night minimum temperature on 27th was as high as 8.4°C.
A very mild spell occurred from 25th to 27th but temperatures in Royston were not as high as the record values experienced in Scotland on 26th and SE England on 27th. The highest temperature of the month in Royston was 13.4°C on 27th ; whilst high for January it was not exceptional, having been exceeded in January last year, and equalled or exceeded in 5 other years in the last 30 years.
The lowest daily maximum temperature in January was 0.1°C on 7th, whilst on 8th the temperature could only manage a maximum of 0.2°C.
The mean daily maximum temperature in January was 6.6°C, which is precisely on the 30 Year (1973/2002) average for Royston. The mean night minimum temperature was 0.2°C above average at 2.3°C. The lowest grass minimum temperature in the month was –8.8°C on 8th. Totals of 11 air frosts and 12 ground frosts were recorded in January. Air frost duration in January was 186.3 hours. The mean earth temperature at 30 cms depth as measured at 0900 GMT daily was 4.7°C. The highest and lowest earth temperatures recorded in January were 7.3°C and 2.4°C on 2nd and 13th respectively.
The mean wind speed in January was 5.7 mph. The highest daily (00/00 GMT) mean wind speed in the month was 12.0 mph on 28th whilst the lowest daily mean wind speed was 0.3 mph on 11th. The highest wind gust speed in the month was 48 mph on 30th.
The monthly analysis of wind directions as observed at 0900 GMT daily was NORTH 2 days, NE 4, E 1, SE 1, S 4, SW 8, W 6, NW 3, and CALM 2.
The daily (00/00 GMT) mean air pressure reduced to mean sea-level in January was 1015.6 mB, which is about average. The highest and lowest air pressure values recorded in the month were 1039 mB and 976 mB on 11th and 2nd respectively.
The mean relative humidity in January was 90.7%. The daily (00/00 GMT) mean relative humidity values ranged from a highest value of 97.9% on 10th to a lowest value of 78.2% on 29th. The absolute lowest relative humidity reading in January was 63% at 1335 GMT on 7th.
Fog (visibility <1000 metres) at the 0900 GMT observation hour was not observed on any day in January.
Richard Barker
Richard Barker
Met. Observer, Royston (Iceni) Weather Station
5th February 2003
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