Royston (Iceni) Weather Station

Daily Weather Observations - November 2003

It was mild, sunny and very wet November in Royston.

Although the severe drought of late Summer and early Autumn in Royston showed signs of easing from mid-October, it was again mostly dry in the first half of November. Abundant rainfall then followed, particularly over the weekend 22^nd/23^rd when virtually continuous rainfall, albeit mostly light to moderate, was experienced over the whole 48 hours of the Saturday and Sunday. The rainfall total from this event was 48.5 millimetres which boosted the total for the whole month to 103.8 millimetres, which is 198% of the 30 Year (1971/2000) average.

It was the wettest November since 2000, and the wettest month of any since July 2002. The number of "rain days" (0.2 millimetres or more) in November was 16, whilst rainfall exceeded 1.0 millimetre on 14 of these days. The wettest day of the month was 22^nd (24 hours ended 0900 GMT on 23^rd) with 20.6 millimetres rainfall. The rainfall distribution in the two halves of the month was 1^st/15^th 18.5 millimetres and 16^th/30^th 85.3 millimetres, illustrating the transition to wetter conditions from mid-month as mentioned above. Rainfall duration over the whole month was 102.1 hours.

The November rainfall brought the year to date total up to 444.1 millimetres, but this is still 16% short of average for the January/November period.

After the relatively unusual experience in recent years of a cooler than average month (of any name) in October it was back to ‘normal’ in November with the mean temperature being 1.8°C above average. The mean daily maximum temperature in November was 1.7°C above the 30 Year (1973/2002) Royston average at 11.3°C, whilst the mean night minimum temperature of 6.6°C was 1.9°C above average.

The highest day maximum temperature recorded in November was 15.3°C on 6^th, and the lowest night minimum temperature recorded was 1.0°C on 27^th. In contrast the coldest day was 23^rd when a maximum temperature of 7.0°C occurred, and the mildest night was 18^th, experiencing a minimum temperature of 11.3°C.

No air frost occurred in November, this being about a 1 in 4 years event over the last 30 years. Only 2 ground frosts were recorded (compared with 13 in October) in the month, the absolute lowest grass minimum temperature being –2.0°C on 27^th. This was the highest such value in November since 1984. It was the mildest November in Royston since 1994.

The mean earth temperature at 30 cms depth as measured daily at 0900 GMT in November was 8.6°C. Although the earth temperature is normally falling at this time of the year, along with the air temperature, it actually rose from 8.6° on 1^st to a maximum of 10.0°C on 21^st before sinking to a minimum of 6.5°C on both 28^th and 29^th.

The exceptionally sunny conditions of 2003 continued in the first half of November and sunshine had reached the monthly average by 16^th. The next 7 days then produced only 1.1 hours sunshine, with 5 of these days being completely sunless! A sunnier last week then raised the monthly sunshine total to 92.2 hours, which is 138% of the 30 Year (1961/1990) average. At the end of November the year-to-date sunshine total was no less than 430.1 hours in excess of the annual average.

The sunniest day of the month was 7^th with 7.9 hours sunshine. The number of days without any sunshine at all was 6.

The mean wind speed in November was 4.5 mph. The highest daily (00/00 GMT) mean wind speed was 12.3 mph on 14^th whilst at the other end of the scale the lowest daily mean wind speed was 0.1 mph on 21^st. The highest wind gust recorded in the month was 46 mph on 14^th.

The analysis of daily wind directions as observed at 0900 GMT was NORTH 1 day, NE 2, E 0, SE 4, S 10, SW 9, W 1, NW 2, and CALM 1.

The mean MSL air pressure in November was 1011.7 mB, which is approximately 3 mB below the average of the last 30 years. The highest and lowest pressure values recorded in November were 1031 mB and 983 mB on 7^th and 26^th respectively.

The mean relative humidity over the month was 91.7%. The highest daily (00/00 GMT) mean relative humidity was 99.7% on 22^nd and the lowest daily mean relative humidity was 78.5% on 3^rd. The absolute lowest relative humidity reading in November was 56% at 1425 GMT on 3^rd, and 1335 GMT on 7^th.

Fog (visibility < 1000 metres) was observed at 0900 GMT on just 1 day (11^th) in November.

A few brief details for the Autumn (September/November) season as a whole conclude this report. The Autumn mean daily maximum temperature was 15.5°C, which is 1.3°C above average, whilst the mean night minimum temperature was 0.1°C below average at 7.3°C. This was the lowest Autumn mean minimum temperature since 1993. Total Autumn rainfall was 155.0 millimetres (93% of average), and sunshine 476.2 hours (149% of average). It was the driest Autumn in Royston since 1999 only.

Richard Barker

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

4^th December 2003

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