Royston (Iceni) Weather Station

Daily Weather Observations - November 2005

Temperatures and rainfall were both a little below average in November in Royston, but it was a very sunny month.

November was a classic month of two halves, firstly very mild and rather wet, and then unseasonably cold and much drier.

To illustrate the sudden dip in temperatures around mid-month the mean daily maximum temperature from 1^st/15^th was 13.4°C whilst the equivalent value for 16^th/30^th was 5.2°C. The mean night minimum temperatures showed a similar anomaly: 1^st/15^th 7.5°C, 16^th/30^th 0.3°C (this latter mean minimum temperature value is lower than the 30 Year (1973/2002) average for any winter month!).

The mean daily maximum temperature for the whole month was 9.3°C, which is 0.3°C below the 30 Year (1973/2002) average. The mean night minimum temperature was 3.9°C, which is 0.8°C below average. The highest temperature of 17.5°C in November was reached on 2^nd, making this the warmest November day in Royston since 2^nd November 1984. In contrast, the lowest day maximum temperature in the month was 3.0°C on 25^th. Overall it was the coldest November in Royston since 1998.

The coldest night of the month was 17^th/18^th when minimum and grass minimum temperatures of –2.3°C and –5.5°C respectively were recorded. Two very mild nights occurred in November, firstly 5^th/6^th with a minimum temperature of 12.8°C, and later 10^th/11^th with a minimum temperature of 12.9°C. Totals of 8 air frosts (highest since 1996) and 11 ground frosts (highest since 1998) were recorded in November.

The earth temperature at 30 cms depth as observed at 0900 GMT daily dropped dramatically during November from a highest value of 13.0°C on 1^st to a lowest value of 5.0°C on 30^th. The mean earth temperature for the month was 8.4°C.

After a wet start to the month drier conditions prevailed in the second half of November. Rainfall from 1^st/15^th was 39.0 millimetres compared with just 7.5 millimetres for 16^th/30^th. The November rainfall total was 46.5millimetres, which is 89% of the 1971/2000 average. The number of "rain days" (0.2 millimetres or more) in the month was 13, with rainfall on 9 of these days exceeding 1.0 millimetre. The wettest day of the month was 2^nd with 18.6 millimetres rainfall. It was the driest November since 2001.

Despite a very dull end to November the sunshine total of 108.5 hours was nonetheless 59% above the 1971/2000 average, due mainly to sunshine of 99.1 hours in the period 1^st/21^st. With a record breaking sunshine total then in prospect the period 22^nd/30^th could only muster 9.4 hours. The highest daily sunshine amount was 7.7 hours on both 1^st and 7^th. It was the sunniest November since at least 1998.

In anticyclonic conditions the air stagnated over the country just after mid-month giving a remarkable 5 day sequence from 18^th to 22^nd inclusive where the 24 hour (00/00 GMT) mean wind speed each day was 0.0 mph (to nearest 1 decimal place). Daily maximum gust speeds of 5, 2, 9, 2, and 5mph respectively were recorded  on each of these days. The highest daily (00/00 GMT) mean wind speed in the month was 10.0 mph on 3^rd. The highest wind gust speed of 44 mph was also recorded on this day.

The analysis of wind directions as observed at 0900 GMT daily shows NORTH 1 day, NE 0, E 0, SE 0, S7, SW 7, W 8, NW 3 and CALM 4.

The mean MSL air pressure in November was 1014.9 mB, which is about average, with highest and lowest pressure readings of 1040 mB and 986 mB on 22^nd and 25^th respectively.

The mean relative humidity in November was 91.2%, with a highest daily (00/00 GMT) mean value of 98.9% on 22^nd, and a lowest daily mean value of 80.1% on 25^th. The absolute lowest relative humidity reading in November was 51% at 1310 GMT on 1^st.

Fog (visibility < 1000 metres @ 0900 GMT) was recorded on two days (19^th and 22^nd) in November.

For AUTUMN (September/November) 2005 the mean daily maximum temperature was 15.8°C (+1.6), the mean night minimum temperature was 8.9°C (+1.3), rainfall was 169.4 millimetres (102%), and sunshine 407.7 hours (126%). It was the warmest Autumn (despite the colder than average November) since at least 1972 in Royston, and the wettest since 2002 only. The number of days with thunder (5) was the highest since 1984.

Richard Barker

Met. Observer, Royston (Iceni) Weather Station

5^th December 2005

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