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April 2010A dry and sunny month with temperatures above the 30-year averageA cold and wet beginning then turning sunny,warmer and very dry with a drought between 7 - 23rdThe first 15 days had rainfall of 18.4 mm (25%) and [32%] of the month's average and by the end of the month had risen to just 20.8 mm, lowest since 1984, (28%) and [36%] of average ranking 7 since 1928. The 17 days between 7 - 23rd had no measurable rain and qualified, under former terminology, as an absolute drought. The wettest day on the 4th had 11.1 mm, and the only one to have more than 5 mm (-4.4). Wet days were 3 (-9.9) and rain days 8 (-8.4). Dry days (<0.2 mm) were 22 (+8.4) and those with no precipitation 17 (+7.2). Evaporation rates were 58.3 mm by Piche evaporimeter and 49.8 mm PE measured by lysimeter. The potential water balance was -29.0 mm. On the 27th soil moisture measured under grass had fallen to 43% dry mass from over 61% at the beginning of the month.The mean temperature 8.2C was below and both the decadal (-0.9) and 30-y [-0.4] averages. By the end of the month the mean temperature was 9.1C (-0.1) and [+0.5], lowest since 2006. The mean maximum was 13.4C [(+0.6)] of average, the highest maximum was 18.8C (0.0) on the 24th and the lowest 9.5C (+2.0) on the 2nd. The mean minimum was 9.1C below the decadal average (-0.7) but above the 30-y average [+0.4]. The lowest minimum was 0.4C (-0.3) on the 1st, so no air frosts, but there were 10 (+3.7) ground frosts with the lowest temperature on the grass -4.2C on the 22nd, unusually quite a spread in the dates of these minima. The mean soil temperature at 30 cm deep was 9.9C (-0.3) It was the sunniest April since 2007, the 222.9 h duration recorded at Valley was the second highest on the Anglesey record since 1930, (137%) and [142%] of average. The sunniest day on the 16th had 12.8h, there were no sunless days.May 2010Exceptionally sunny, rather dry, but mean temperatures below averageDry and cool at the beginning, highest temperatures after mid-month with most rainfall at the end.An exceptionally sunny month at Valley the 271.9 h sunshine duration {(140%)} of both Kipp & Zonen adjusted averages. Despite 2 sunless days it was the sunniest May on the Anglesey record since 1930, beating the previously sunniest 1977 that had 257.7h (K &Z adjusted value). The sunniest day was on the 23rd with 14.7h.  "Sunshine duration anomalies in May 1931 - 2010.")
May is second only to April being the driest month of the year, and rainfall this month was true to form with 28.6 mm (39%) of the decadal and [50%] of the 30-year average, lowest since 1998 (25.3 mm) ranking 8 since 1928 in Llansadwrn. The wettest day was the 31st having 7.5 mm, but only because of the statistical curiosity in that a days rainfall is totalled between the hours of 09 - 09 GMT. The 31st rain fell after midnight on the 1st June! The 28th had 6.9 mm. Days with no precipitation totalled 18 (+6.5) while dry days with <0.2 mm were 20 (+5.4). Rain days were 11 (-5.4) and wet days were 7 (-5.7). Just 2 days had >5 mm (-2.6). Evaporation totals were moderately high with the Piche evaporimeter recording 61.9 (ml) mm and the lysimeter a PE value of 73.5 mm. Potential water balance (PWB) was -44.9 mm. The potential water deficit (PWD) was 52.6 mm. Soil moisture sampled under grass fell from 37.5% dry mass (DM) on the 4th to 24.2% DM on the 28th. The permanent wilting percentage for the local soil is 15.2%. On the 23rd leaves on some tall mature sycamores were wilting during the afternoon. There were 4 warm days (>20C) between 20 - 23rd, the highest was 24.8C (+1.1) on the 23rd. In a rather cool month temperatures on these days failed to bring the mean temperature 10.8C up to the averages so finished (-1.1) and [-0.7]. The highest mean was 19.9C on the 23rd while the lowest was 7.2C on the 9th. The mean maximum 14.9C was (-0.7) and [-1.1], the highest 24.8C on the 23rd the lowest 10.2C (-0.4) on the 11th. The mean minimum was 6.7C (-1.5) and [-0.3], the lowest 2.5C (-1.1) was on the 12th that also recorded the lowest grass minimum temperature of -0.5C (-0.8). There were 3 days of ground frost (+2.3), but no air frosts. The mean soil temperature at 30 cm deep was 13.2C (-0.4). There was no thunder, but there were 2 days (+0.5) with small hail (snow pellets) and 2 days (+2.0) on which sleet fell (2nd and 11th). June 2010Sunny, warm and mostly dryWet days beginning and end, otherwise warm and sunnyApart from 2 wet days June was very dry. On the 7th there was 14.3 mm and on the 28th 26.1 mm fell in a thunder storm, these accounting for 92% of the 47.7 mm total rainfall, lowest since 2006, for the month (75%) and [72%] of average. The were 23 (+7.6) dry days and 7( (-7.6) rain days. There were just 2 days over 5 mm (-2.5). The 14-days from the 14th to 27th had no measurable rain, missing out on the 15-days required for a drought as in April. Rainfall for the first 6 months of the year was 286.4 mm the least in Llansadwrn since 1929 (283.7 mm). Potential evaporation measured by the Piche evaporimeter was 63.2 mm and by lysimeter 77.1 mm. The potential water balance was -29.4 mm. Soil moisture on the 17 June was 26% dry mass. It was the sunniest June at Valley since 1975. The 251.7 h duration, (142%) and [149%] of average, was the 3rd highest on the Anglesey record since before 1930 using Kipp & Zonen adjusted values. The sunniest day was on the 15th with 15.3 h. There were 14 days with sunshine of 10h, or more. There was 1 sunless day at Valley on the 6th. Temperatures were above the averages. The mean maximum was 19.0C (+1.1) and [+1.3]. The highest maximum was 24.5C (-0.8) on the 26th and the lowest 13.9C (+0.7) on the 1st. The mean minimum was 11.0C (+0.3) and [+1.5]. The highest was 14.6C (-0.6) on the 27th and the lowest 7.2 (+0.9) on the 20th. The 20th also had the lowest grass minimum temperature of 3.8C (+0.4). Thunder was heard on the 13th when heavy rain and ice pellets fell in Llanfairfechan. On the 29th there was heavy thunder and lightning on a cold front that passed over just after midnight. Disruptions to power supplies were experienced in a large part of SE Anglesey, including Beaumaris. Heaviest rain fell in nearby Red Wharf Bay and Pentraeth. July 2010The wettest July on record in Llansadwrn, dull with mean temperature close to averageSome rain throughout the month, no falls very large. Sunniest at the beginning, maximum temperatures below average
It was a cloudy and rather dull month with 121.4 h of sunshine recorded at RAF Valley, (73%) and [72%] of the Kipp & Zonen adjusted averages. It was the 9th dullest July on the Anglesey record since 1930. The sunniest day was on the 3rd with 12.2 h and there were 6 sunless days with another 3 having <1.0 h. The mean temperature was 15.7C, lowest since 2007 close to the averages (-0.1) and [+0.1] so middle of the road. This hid the differences between maximum and minimum values. The mean maximum 18.7C lowest since 2007, and ranking 11th, was (-0.6) and [-0.8] with the highest 22.1C on the 26th a large (-4.1) below average. The mean minimum was 12.7C highest since 2006, and ranking 6th, was (+0.4) and [+0.1]. The lowest minimum 10.0C on the 17th was (+1.8). The lowest grass minimum on the 5th was 6.2C (+0.9). There were 3 days with gales with 2 spanning overnight on the 15/16th causing widespread damage to ash trees on Anglesey and moored boats in the Menai Strait, and around western coast of Gwynedd and Anglesey. Thunder and lightning occurred on the 14th and 22nd. August 2010Only half the average rainfall, temperatures well down and sunny at timesRainfall of 51.3 mm was lowest since 2003 ranking the 14th driest August in Llansadwrn since 1928. Just (51%) of the decadal and [64%] of the 30-y averages there were 9 (+1.2) days without precipitation and 14 (+0.8) dry days (<0.2 mm). The wettest day was on the 19th with 12.8 mm. Rain days were 17 (-0.8) and wet days 10 (-3.3). There were 2 (-4.6) with 5 mm, or more. Potential evaporation measured by Piche was 41.5 mm while the lysimeter recorded 37.0 mm. The potential water balance was 14.3 mm and soil moisture under grass averaged 47.1% dry mass varying little through the month. Temperatures were all below average with the mean air temperature 14.6C (-1.1) and [-0.7] lowest since 1993 ranking 8th since 1979. Warm days were few and far between with 5 days reaching 20C, or more. The mean maximum 17.9C was (-1.2) and [-1.4] with the highest 21.0C on the 22nd (-3.9) of the average. The lowest maximum was 14.7C on the 30th this (-0.4) of average. The mean minimum was 11.4C (-1.0) and [0.0} with the lowest 7.2C on the 31st. The lowest grass minimum also on the 31st was 2.8C (-2.7). Sunshine at RAF Valley was 175.0h duration, (115%) and [107%] of the Kipp & Zonen adjusted averages.Highest since 2005 and ranking 20th on the Anglesey record since 1930.. The sunniest day was on the 15th with 12.4h and there were another 4 days having 10h, or more. There was 1 sunless day. Monthly data 2010
AcknowledgementI am grateful to Geraint Roberts, at the Met Office RAF Valley, for supplying the Valley observations.
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 "July rainfall totals in Llansadwrn 1928 -2010.")