In 1862, George Elliot, the novelist wrote: “The constantly heavy-clouded and often wet weather tends to increase the depression. I am inwardly irritable and unvisited by good thoughts”.
There were so many days in December when this description applied as the very thick, low cloud and days with fog occurred all too frequently. There were sixteen days when no UV light was measurable and thick fog, with visibility down to 100 metres, on four days.
December was mild and very dry, which climatologically is a relatively rare combination because typically mild Decembers are wet and cold Decembers are dry.
Although there were thirteen days with measurable precipitation the rainfall for the month amounted to just 22.6mm. The wettest day was the 10th when 8.5mm fell, over a third of the total for the month. This makes December 2016 the third driest December I have recorded since the station was started in 1984 and the driest month of 2016. It is no wonder that the Rivers Kennet and Og are running so low.
The 32-year average was 91.5mm, making a deficit of 68.9mm. The two previous very dry Decembers were in 1991 and 1988 with 21.8mm and 17.6mm, respectively. The record rainfall for December occurred in 2013 when 157mm was logged.
It is not surprising that the Rivers Kennet and Og are running so low as although November rainfall was above average the October total was very low. The rainfall for the whole of 2016 was 767 mm, which is 91% of the 32-year average or 72mm below.
Although there were eleven days when an air frost occurred, it was a mild month with the mean 0.7C above the long-term average. There were a couple of colder spells at the beginning and end of the month but twenty-one days when the maximum exceed the mean for December. The warmest day occurred on the 9th when the thermometer rose to 13.7C, which was 6C above the mean. The coldest night was measured on the 1st of the month when a minimum of -7.1C was recorded followed by -6.3C on the 2nd.
The peak barometric pressure occurred on the 27th with a reading of 1044.9mb and any wall barometer at home, accurately set, would have shown the arm far around to the right at the ‘Very dry’ setting. In fact it was the highest December barometric pressure I have recorded since 1991.
Many days were very calm as the intense high pressure dominated for much of the month. This resulted in many days with stagnant air and some days with hardly a movement of the air for extended periods. For example, on the 27th the anemometer measured a peak of just 5mph for the whole day with two very similar days when a maximum was 6mph, which cannot be classed as a gust of wind, just a brief movement of air. In contrast to this calm scene was a very breezy day that occurred on the 23rd when a maximum gust of 41mph was recorded.
To look on the bright side there fifteen days with strong sunshine, the sunniest occurring on the 29th with 5.77 hours.
The very dry Decembers of 1988 and 1991, as mentioned above, were followed by very dry Januaries with between a half and a third of the mean monthly rainfall. However, January 1989 was mild and January 1992 cold, so no consistent trend there. What will January 2017 bring?
