Monthly summary January 2010

The very cold winter (December – February) continued into January 2010. Snow falling, in one form or another, was recorded on 10 days. The 50% snow cover at 0900 was noted on 14 days and for 12 consecutive days from 4th to 15th. The snow depth from each fall was averaged each day over several ground areas and the total for the month was 25cm. With low temperatures and strong winds the wind chill was significant on several days with -11°C and -12°C logged on the 9th and 7th respectively.  There were 22 days with air frost (equaling the record in 1985), the lowest occurring on the 7th when the thermometer dropped to -8.5°C (record low was of -13.3°C in 2009). For three days, 6th to 8th, the maximum temperature did not rise above freezing with a maximum of only -1.8°C on the 7th. To add to the picture fog was recorded at 0900 on 5 days.

This was the third coldest January I have observed with the mean temperature of 0.48°C some 3.6°C below the long-term average. Only 1985 (0.30C°) and 1987 (-0.15C°) were colder. The total rainfall, mostly falling as snow, was 81.4mm, which is 93% of the long-term average.

There has been a rising trend for January mean temperatures since the late 1980’s but the Januarys of 2009 and 2010 have reversed that trend.

Monthly summary December 2009

December began where November finished, with disturbed windy and wet weather. With wind from a southerly quarter from 1st to the 9th, temperatures were above average accompanied by heavy rainfall. As pressure rose and winds swung into a northerly quarter, temperatures dropped and air frost occurred. However, worse was to come as snow fell on the 16th, 17th, 19th and 21st. With strong winds the wind-chill factor was significant for several days dropping to -8°C on the 18th. A snow covering at 0900 of at least 50% was evident from the 20th to the 24th. Rain showers then fell on very cold ground producing sheet ice that covered everything and was extremely dangerous to pedestrians and drivers alike.

With a mean temperature of 2.26°C it was the third coldest December I have recorded, equal to 2001, but less cold than 1996 (2.18°C) and 1995 (1.75°C) and 2°C below the long-term average. It was the wettest December since 2002 with a total of 107.9mm which is 120% of the long-term average. Although the Spring months show a rising trend in temperatures, December is quite the opposite with the frequency and severity of air frosts increasing significantly.

The mean temperature for the year was almost identical to the long-term average of 9.6°C. It is of interest that the average for my records in the 1980’s is 8.9°C. The annual rainfall of 885mm was 105% of the long-term average.

Monthly summary November 2009

With just two days that were totally dry and almost record rainfall, November was a very disturbed month. Frequent low pressure systems crossed near or over the country and delivered substantial rainfall, a total of 171.8mm was the second highest on record and 193% of the long-term average. The wettest day was the 24th with 21.2mm but the 18th brought almost as much rainfall with 18.8mm. As a consequence of the frequent cloud cover the mean temperature was 1.7°C above the long-term average. Also of note was the total absence of any air frost, which has not happened since records began here in 1984. The other feature was the frequent strong winds which reached gale force on a number of occasions. The maximum gusts on the 24th, 13th and 14th were respectively, 42, 50 and 51mph.

Monthly summary October 2009

October brought us a variety of weather, from strong winds at the beginning and end of the month with intermittent dry spells and some periods of heavy rain. Some nights were topsy turvy with the thermometer rising over 4°C during the hours of darkness. From the 12th to the 14th we enjoyed a period of glorious sunshine, around 7 hours on some days, accompanied by light winds. However, cloud trapped under the high pressure arrived on the 15th, often referred to as anticyclonic gloom. The last ten days brought winds from a southerly direction, all the way from the Azores, which produced maxima well above the average for late October. The peak temperature was 18.1°C on the 6th.There were just two nights with frost, -0.5°C and -2.0°C during the early hours of the 13th and 18th respectively.

The mean temperature was 0.4°C above the long-term average and the total rainfall of 73.2mm was 82% of the long-term average. The UV levels are low at this time of the year, the peak occurring on the 3rd with a value of 3.6 MEDs. During this autumn month there were three days with 7.5 hours of bright sunshine, the 2nd, 8th and 12rh respectively.

Monthly summary September 2009

September has been such a contrast to previous months. A mild first eight days, with the wettest day of the month on the 3rd (8.3mm) changed when the jet stream at last moved north allowing pressure to build. The downside was the arrival of strong northeasterly winds, a maximum gust of 31mph occurred on the 16th, which were unpleasant and lasted until the 19th.  A light shower was noted on the 22nd and 23rd with the remainder of the month being warm and dry with very pleasant autumn sunshine.

The average temperature was 0.2° above the long-term average with no air frosts but a minimum of 2.7°C on the morning of the 27th. This was the driest September I have recorded and is identical to September 2003, which also had a total of 11.1mm and is just 17% of the long-term average. The figure for evapotranspiration, the amount of moisture that evaporates form the ground and plant life, was 59.2mm and explains why the ground is now so dry after a wet summer.