Monthly summary March 2011

March began with very cold days and several nights with air frost, which combined with strong winds produced several days with significant wind chill of -5°C and -7°C on the 5th and 7th respectively. It was only when we reached the 8th did temperatures recover to near normal monthly temperatures. As pressure rose from mid-month so did the occurrence of warm days with light winds, which were very pleasant for March. The maximum temperature was 18.3°C on the 25th.

The mean temperature was 0.3°C above the long-term average which was principally due to the mean maximum being +1.3°C whereas the mean minimum was -0.6°C. This was the driest March I have recorded. The total of just 12.7mm was almost 3mm less than the previous record of 15.6mm that fell in March 1997.

My recent analysis of wind speeds over the last ten years show that there have been significant changes, especially since 2008. The average annual wind speed for the years 2001 – 2006 fluctuate between 4.3mph and 4.6 mph. However, the years 2008/09/10 produced falling values of 3.9mph, 3.3mph and 3.1mph respectively. I discovered that during the winter season the incidence of 20mph+ gusts had fallen by four and 30mph+ gust by three. A recent meteorological report suggested that these falling values over the last three years or so were due to “a spell of subdued westerlies with a weak and contorted middle-latitude jet stream”.

background