Llansadwrn (Anglesey) Weather:
Monthly and Annual
Summary for 2009
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Llansadwrn (Anglesey) Weather:
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Note: Values in (.) refer to the 10-y 1999-2008 average; [.] refer to the 30-y 1971-2000 climatological average while {.} refer to the station LTA (long-term average) from 1979. All data are subject to verification and amendment. Javascript must be enabled to see pop-up graphics.
The beginning was cold with frozen ground while the middle was stormy and followed by some wintry weather
The main feature was the below average temperatures. The mean temperature 4.3C, lowest since 2001, was (-1.6) based on the decadal average and [-0.6] on the 30-y 1971-2000 average. January ranked the 8th coldest since before 1979. Following on from the end of December 2008, the beginning of the month had a week of below freezing minima with a mean for the month of 1.2C (-2.3) and [-1.2] of average, lowest since 1997 ranking 6th since before 1979. There were 8 air frosts (+4.6), highest since 2001, with the lowest minimum temperature -5.0C on the 6th. Frost duration was 109.8 mm, the highest number of hours (09-09 GMT) was 20.5 h on the 7th. The mean maximum temperature was 7.3C (-0.9) and [-0.1] equal lowest since 2003 ranking 12th since before 1979. The lowest maximum 1.4C (-2.5) was on the 6th while the highest 13.9C (+2.4) was on the 30th, 3rd highest in January at this station. There were 18 ground frosts (+6.2) with the lowest -9.7C recorded on the 6th. Soil temperature at 30 cm averaged 3.8C (-1.8) with 29 days below 5.6C (42F) a threshold deemed necessary for root growth. The ground surface was frozen for the first 10 days of the month when the soil temperature at 5 cm deep at 09 GMT got as low as -1.7C on the 6th and at 10 cm reached -0.1C on the 6th and 7th.
 "Number of days with gales recorded in December and January on Anglesey.")
There were storms with gale force winds between 10 - 11th and on the 15th. December 2006 and January 2007 combined had the highest number of gales (23) recorded on Anglesey since 1942. Since then low numbers have been recorded, this last December 2008 and January 2009 combined having 9 an anomaly of -0.9 from the mean 9.4 gales. High positive anomalies seemed to occur every 8 to 10 years and there has been an increase in number since the 1960's. December and January 2007 had the greatest positive anomaly of 13.6. An increase in storminess is a factor that might be linked to climate change and is one of the factors, along with temperature and rainfall, predicted by climate models likely to increase in the future.
Rainfall was 95.2 mm ((76%) and [97%] of average. A generally 'dry' month with 12 (+5.5) dry days, but there were 9 (1.6) days having 5 mm, or more. There were 18 (-2.4) rain days (0.2 mm, or more) and 14 (-1.8) wet days (1 mm, or more). The wettest day was on the 11th having 21.8 mm and the only other day to have double figures was the 16th with exactly 10.0 mm. Rainfall duration (0.1 mm, or more per hour) was 77.0 hours. Evaporation was low with the Piche evaporimeter recording 34.3 ml, or mm. The potential water balance (measured by lysimeter) was 89.6 mm.
Sleet or snow fell on 3 days (+1.6) and hail (all types) on 5 days (+1.2).
Sunshine duration recorded at RAF Valley totalled 60.5 h (102%) and [111%] of average. It was highest since 2006 with the sunniest day on the 26th with 7.2h. The were 11 sunless days with another 4 having 1 hour, or less. In Llansadwrn global solar radiation averaged 2.90 MJ m -2, highest was 6.37 MJ m -2 on the 26th and was lowest 0.46 MJ m -2 on the 4th.
A cold beginning with frequent showers of snow and snow pellets, a warmer second half
A dull month with sunshine duration recorded at RAF Valley only 46.8h, the lowest (K&Z adjusted values) since 1980 and 3rd lowest at Valley on record since 1940. The sunniest day was on the 4th with 7.8h; there were 9 sunless days with a further 7 having 1h, or less.
Colder than of late - the mean temperature was 4.9C, lowest since 1996 and the 11th lowest since before 1979 at this station. Below average on both the late decadal (-0.9) and 30-y 1971-2000 [-0.4) averages. The mean maximum was 7.5C (-1.1) and [-1.0], the highest 11.6C (-1.0) was on the 16th while the lowest 1.7C (-2.5) was on the 2nd. The mean minimum was 2.2C (-0.8) and [-0.1] showed the least deviation from average. The lowest minimum was -1.9C (-0.5) on the 4th and 8th and there were 8 (+4.5) days with air frost, most since 2003 (nine) and previously 1996 (twelve). There were 16 days with ground frost (+1.4), lowest was -5.3C on the 4th. The temperature of the soil at 30 cm averaged 4.9C (-1.9) with 17 days below the 5.6C (42F) plant growing threshold.
Driest since 1986 and ranking the 8th lowest rainfall since before 1928 in Llansadwrn. The 17.8 mm were just (19%) and [24%] of the averages. The wettest day had only 4.1 mm, this was on the 2nd. There were 5 (-1.6) dry days, 18 (+0.2) rain days and 8 (-5.5) wet days. At RAF Valley rainfall was only 8.4 mm (14%) , lowest since 1986 (6.9 mm) and ranking 2nd since records began in 1942. The most was just 1.2 mm on the 12th; there were 13 rain days, 3 wet days and 7 dry days.
The mean temperature ended the month on 7.4C (+0.4) and [+0.6] of the averages and was highest since 2005 and ranked 11th. The mean maximum temperature was 10.8C (+0.5) and [+0.6], highest since 2005. The highest maximum 17.8C (+1.4) on the 19th was 3rd highest on this date and 4th highest in March at this station since before 1979. The mean minimum 3.9C (+0.2) and [+0.6] was again highest since 2005. The lowest minimum -1.1C (+0.9), was one of 4 air frosts in the month and most since 2006 (8). There were 11 days (-0.6) with ground frost, the same as in 2008 and least since 2006. Soil temperature at 30 cm averaged 7.3C (+0.2) with only 2 days (5,6) below the 5.6C (42F) threshold for plant growth.
Rainfall was 49.7 mm (73%) and [59%] of the decadal and 30-y averages, driest since 2002 and ranking 27th in Llansadwrn since before 1928. There were 12 (+3.1) dry days and 16 (-1.1) rain days. Wet days numbered 13 (+1.2) while there were 3 (-1.2) having 5 mm, or more. Wettest was the 9th with 11.5 mm followed by the 3rd with 10.3 mm.
Sunshine recorded at RAF Valley was 142.9 h duration (111%) and [135%] of average, ranking the 12th sunniest on the Anglesey record since before 1931 using the Kipp & Zonen adjusted values. Sunniest days were the 19th and 29th having 10.4h duration and the 18th and 20th with 10.3h. There were 4 sunless days with another 2 having less than 1 h. In Llansadwrn global solar radiation averaged 10.40 MJ m -2, highest was 19.56 MJ m -2 on the 29th and lowest 4.23 MJ m -2 on the 3rd.
Snow fell on 2 days (-0.8) and there was 1 cm of lying snow on the 4th (+0.2). Small hail fell on 5 days(-0.3).
With a mean temperature of 10.0C (+0.9) and [+1.4] of average it was highest since 2007 (11.3C) and ranks 4th highest since before 1979. The highest daily mean was 12.6C on the 24th while the lowest was 7.2C on the 28th.
The mean maximum was 14.1C (+1.4) and [+1.3] highest since 2007 (15.5C), ranking 6th, with the highest 18.7C (-0.2) of average on the 20th lowest since 2006; all daily maximums were 10C, or more. The lowest maximum 10.6C (+3.3) was on the 6th, 2nd highest on record beaten only by the 12.1C in 1980.
The mean minimum temperature was 5.9C (+0.4) and [+1.5] lowest since 2007 and ranking 7th since before 1979. The highest minimum was 9.7C (-0.2) on the 24th while the lowest was 2.4C (+2.0) on the 12th. The lowest grass minimum also on the 12th was -1.7C (+1.5) being 1 of 3 ground frosts in the month (2, 11, 12).
Earth temperatures at 30 cm averaged 10.5C (+0.3) with the minimum 9.0C on the 7th. At the end of the month temperatures in the profile down to 100 cm were all above 11C.
Rainfall for the month was 42.9 mm (54%) and [74%] of average, lowest since 2007 ranking 24th driest since before 1928. There were just 2 days (-3.8) with 5 mm, or more. The wettest day was on the 26th having 16.4 mm and the 28th had 10.7 mm. Wet days (>=1.0 mm) were 9 (-5.0) while rain days (>=0.2 mm) numbered 15 (-2.1). There were 10 (+0.6) dry days.
There were 2 days (+1.8) with thunder heard, the 15th and 25th. There was 1 day (-3.1) on the 25th with small hail, but large agglomerated clear ice (7 mm) was seen in Llanfairfechan.
It was a sunny month with 182 h of bright sunshine in Llansadwrn calculated from global solar radiation. The mean solar radiation was 15.38 MJ m -2, the highest 24.85 MJ m -2 was on the 18th while the least was 5.68 MJ m -2 on the 6th. At RAF Valley sunshine duration was 188.3 h (117%) of the last 10-y and [120%] of the 30-y average, sunniest days were the 19th and 20th with 13.0h each. There were 3 sunless days with another 4 having less than 1 h. April was sunniest since 2007 ranking the 11th sunniest April on the Anglesey record since before 1930.
Rainfall was 81.4 mm (114%) and [142%] of the decadal and 30-y averages respectively, largest since 2006 that had 124.7 mm ranking 23 since before 1928. All daily rainfalls were below 10 mm and only 3 (-1.8) reached 5 mm, or more, but there were significantly more rain (>=0.2 mm) and wet (>=1.0 mm) days. There were 9 (-2.7) dry days; 20 (+4.0) rain days and 19 (+7.0) wet days. The largest fall was 9.8 mm on the 17th.
It was a windy month, despite there being no gales reported at Valley. The mean wind speed (mws) was 16.5 mph, highest in May since 2003 and 8th highest since before 1956. The highest daily mws 28.7 mph was on the 18th, the lowest 6.8 mph was on the 29th. Other windy days were the 6th with 24.0 mph, the 7th 27.4 mph, the 8th with 25.1 mph and the 16th with 25.6 mph. The mean highest gust was 32.8 mb, the highest gust 50.7 mph on the 7th and 16th.
Sunshine duration at RAF Valley was 205.2 h (108%) and [106%] of average (K&Z adjusted data), lowest since 2007. The sunniest days were on the 30th with 15.5 h and 15.0 h on the 24th, 10 days in the month had over 10h duration. There were 4 sunless days with another 3 having 1h, or less. Global solar radiation in Llansadwrn averaged 18.03 MJ m -2, highest was 29.88 MJ m -2 on the 12th (Valley sunshine 14.6 h duration) and lowest 7.15 MJ m -2 on the 5th (sunless day at Valley).
The mean temperature was 11.4C (-0.6) and [-0.1] of average, lowest since 2005 (11.4C) ranking 13th since before 1979. Maximum temperature were especially at the beginning of the month well below average. The mean maximum was 15.1C (-0.6) and [-0.9] of average, lowest since 2005 (14.5C) ranking 9th since before 1979. Highest was 25.3C (+1.9) on the 30th, just 1 of 3 days with 20C, or more. Lowest was 10.8C (+0.2) on the 4th. The mean minimum was 7.6C (-0.7) but [+0.6] on the 30-y average, lowest since 2005 ranking 13th. The lowest minimum was 4.5C (+0.9) on the 12th while the lowest grass minimum was 2.0C (+1.7) on the 3rd.
Rainfall for the month was 67.1 mm, lowest since 2006 was (99%) and [101%] of averages. So a pretty average month and the total for the first 6-months of the year 354.3 mm keeping below the running total of the driest year here, 1945 with 390.4 mm. The largest fall was on the 26th having 15.1 mm, but the 17th had 14.7 mm these 2 days seeing 44% of the month's total. There were 5 (+0.3) days with 5 mm, or more. Wet days were 11 (+0.6) and rain days 14 (-0.8). There were 15 (+3.7) dry days. Evaporation was the highest of the year so far, PE measured by lysimeter was 69.1 mm and the potential water balance was -2.0 mm. That measured by the Piche evaporimeter housed in the Stevenson screen was 53.0 mm. Moisture content of the soil on the 23rd was 53.6% dry mass (the saturated water percentage is 70% and the permanent wilting percentage is 16%).
It was a very sunny month, at RAF Valley there were 234.7 h of bright sunshine recorded by the K&Z instrument. If the old Campbell-Stokes had been used then it might have recorded 184.5 h (see notes below). June was sunniest since 1975, that year having an adjusted 252.0 h duration (the Campbell-Stokes measurement was 305.4 h), and ranks 6th on the Anglesey record since before 1930. The sunniest day was on the 24th with 15.5h, the 1st had 15.4 h and the 2nd 15.0 h. There were 2 sunless days. In Llansadwrn mean global solar radiation measured 19.18 MJ m -2. Highest was 29.24 MJ m -2 on the 24th and lowest 5.96 MJ m -2 on the 6th.
The first 15-days of the month had a mean temperature of 13.0C and was (-0.3) of the decadal and [-0.6] of the 30-y monthly averages, this was despite the first 2 days with maxima over 20C. By the end the mean had crept up to 14.5C, highest since 2007 (rank 8 since before 1979), (+0.3) and [+0.9] of the averages. The last 9 days had maxima above 20C; the highest maximum was 26.3C (+1.2) on the 29th. The lowest maximum was 10.6C on the 6th, but this was reached at 09 GMT on the 7th. The maximum during the day on the 6th reached no more that 9.1C, a day that saw ice pellets in precipitation.
The mean minimum was 10.6C, highest since 2007 (rank 7), (0.0) and [+1.1] of average. The highest minimum was 16.1C (+1.1) on the 29th and the lowest 5.9C on the 12th that also had the lowest grass minimum 3.1C (-0.1).
Thunder was heard on the 26th and ice pellets were recorded on 2 (+1.7) days.
It was a quiet month with no gales. Valley recorded a low mean wind speed of 10.4 mph. Highest was 21.0 mph on the 17th with a high gust of 45 mph.
Rainfall of 135.8 mm (212%) and [214%] exceeded the long-term average for November, the wettest month of the year in Llansadwrn. It was largest fall in July since 1967, ranking 8 since 1928. The wettest day was on the 16th having 29.6 mm largest in July since 1996 when 30.7 mm fell on the 2nd, and 6th largest at this station since before 1979. There were only 5 (-7.0) dry days and 22 (+7.4) rain days. Wet days numbered 20 (+8.9) and there were 9 (+4.6) days having 5 mm, or more. With that much rainfall it was not surprising that the potential water balance was 77.1 mm and on the 27th soil moisture was 63% of dry mass, just 7% below saturation.
 "July rainfall in Llansadwrn, Anglesey 1928-2009."){kind=small}
The histogram of July rainfalls recorded in Llansadwrn from 1928 indicates that the years from the late 1970's to early 21st century had been relatively dry. Wet spells were in the late 1930's, mid 50's and late 60's. Are the late 00's ushering in another spell of wet Julys?
 "July rainfall anaomalies in Llansadwrn, Anglesey 1928-2009."){kind=small}
Looking at the anomalies, differences of each July from the mean, shows that between 1988 to 2006 there were just 3 above average. There were 7 wetter Julys in the period 1928 to 1967. At least the present wet July cannot be blamed on climate change as we have experienced several wetter ones previously.
The mean temperature was 15.8C close to the averages (-0.1) and [+0.2]. The greatest anomaly was in the mean maximum temperature of 19.0C [(-0.5)] on both averages, this despite the 28.1C (+2.0), highest since 2006, recorded on the 1st and 25.6C on the 2nd, the only 2 days with hot (for here) 25C, or more. There were 9 days with 20C (warm for here), or more. The mean minimum was 12.5C (+0.2) and [+0.8] with the highest minimum 18.0C on the 2nd. The lowest minimum was 8.1C (-0.2) on the 10th that also saw the lowest grass minimum of 5.2C (-0.2). The mean temperature of the soil at 30 cm was 17.6C this was spot on the decadal average.
At RAF Valley 175.8 h of sunshine were recorded [(104%)] of average sunniest since 2007 ranking 21 on the Anglesey record since 1930. The sunniest day was on the 25th having 13.6h, one of only 4 days this month to see 10 h, or more. There was just 1 sunless day (16) and another with just 0.1h (11). It was a windy month with a mean wind speed of 25.1 mph, the highest in July since 1988 and ranking 5 since 1956. The highest mws were 27.4 mph on the 28th, 26.6 mph on the 22nd, 26.5 mph on the 26th and 23.3 mph on the 31st. There were, however, no gales. The mean highest gust was 30.2 mph with the highest 49.5 mph recorded on the 28th. Mean solar radiation at Llansadwrn, where there were 2 sunless days, was 16.97 MJ m -2 with the highest 25.27 MJ m -2 on the 23rd and the lowest 10.03 MJ m -2 on the 17th.
August 2008 was the dullest on record here, this year had more sunshine but with 136.0 h duration recorded at Valley was only (90%) of the decadal and just [83%] of the 30-y averages. Lowest since 2007 it ranked 18 on the Anglesey record since 1930. The sunniest day was on the 5th with 12.1 h duration, but there were only another 3 seeing 10h, or more. These were the 6th with 11.0h, the 7th with 10.5h and the 24th with 11.3h. There were 4 sunless days. In Llansadwrn 8 days were judged sunless, being nearer the mountains with greater cloud cover this is understandable. On the coast at Valley the sky often clears a little whereas it does not here. Solar radiation averaged 14.44 MJ m -2 d -1 (August 2007 was only 11.01 MJ m -2 d -1 ), highest was 22.70 MJ m -2 on the 5th and the lowest 4.91 MJ m -2 on the 31st.
Winds in August were mostly from the S and SW. At 09 GMT wind direction was S on 14 and SW on 13 mornings. A very windy month with moderate to high sustained wind speeds; the mean wind speed (mws) at Valley was 17.5 mph, highest since the exceptionally windy August of 1985 (20.6 mph) and 2nd highest on record since 1956. The 31st had a mws of 28.6 mph and only 4 days (7, 11-13) had mws of 10 mph, or less. Valley did not report any gales although winds were often of gale-force on the mountains and higher ground. The highest gust was 52 mph recorded on the 20th and the mean gust speed was 34 mph. The winds caused problems for the annual Menai Strait Regattas and several days races had to be curtailed or rearranged.
 "Mean wind speed anomalies in July and August 1956-2009: Source Met Office Valley."){kind=small}
Both July and August have seen high mean wind speeds that should have been good for wind power generation on the island. Combining the 2 months Valley data the mws was 16.4 mph, highest since 1985 with 16.8 mph and 1970 with 16.5 mph. July and August combined had the 3rd highest mws since before 1956.
Rainfall ended the month with a total of 112.1 mm (116%) and [139%] of average and was largest since 2004 ranking 24 since 1928. The wettest day was on the 30th with 16.2 mm, the 30th and 31st contributed 30.9 mm 35% of the total. Another wet day was the 23rd with 16.0 mm; there were 8 days (+1.6) with 5 mm, or more. Rain days were 19 (+1.4) and wet days 17 (+3.9). With 7 (-1.2) dry days the month was drier than August 2008 that had just 3 days.
The mean temperature was 15.6C (-0.1) of the decadal average of average, highest since 2005 ranking 11 since 1979. Compared with the 30-y climatological average (1971-2000) it was [+0.3] indication of a continuing warming trend. The mean maximum was 18.7C (-0.5) and [-0.6] that below both averages.
 "Days in August having a temperature of 20C, or more."){kind=small}
The highest maximum was 21.8C (-3.5) on the 6th, lowest since 1992 and 3rd lowest since before 1979, there were no really warm or hot days as experienced in the SE of England. There were, however, 8 days that had between 20.0C and 21.8C. August 2007 had just 3, the lowest on record was 2 in 1985. The lowest maximum was on the 28th having 15.0C (-0.1).
The mean minimum was 12.6C (+0.3) and a large [+1.2] anomaly based on the 30-y average. This was lowest mean minimum since 2007, but ranked 7th highest since 1979. This reflects the large amount of cloud cover in the month and lack of clear nights. The highest minimum was 16.6C (+0.4) on the 19th while the lowest was on the 22nd was 9.3C (+0.8). This was only 1 or 2 sub-10C nights, the other 9.5C on the 29th. The grass minimum readings averaged 10.7C (+0.3), the lowest on the 29th was 6.0C was (+0.6). On 18 nights the temperature on the grass did not fall below 10C.
 "Summer rainfalls in Llansadwrn, Anglesey."){kind=small}
Rainfall was 315.0 mm (138%) and [150%] of average. The largest since 2007 and ranking 14th since before 1929. The wettest summer was in 1957 with 443.9 mm, but that included the record thunderstorm fall of 127 mm on the 10th August. The previous year, however, also recorded 416.7 mm - two 400 mm summers in a row! Other notable wet years were 1965 with 355.8 mm, 1954 with 369.2 mm, 1938 with 388.2 mm and 1931 with 362.0 mm. So wet summers are not that unusual, particularly before 1970. In recent years up to 2006 we enjoyed rather more dry summers than wet, since then we have had 3 wet summers, but not as wet as they might have been due to the average amount of rain in June.
Summer mean maximum temperatures were 18.7C (-0.1) and [-0.1] close to the averages. The mean minimum was 11.9C was close to the 10-y average (+0.2), but well above [+1.0] the 30-year average . The mean was 15.3C (+0.1) and [+0.5] of average, an indication of the continuing warming trend.
A wet and windy first week then mostly dry sometimes sunny with clear nights when heavy dew formed
It was a dry month overall the 42.6 mm, least since 2002, was (36%) and [46%] of average. It was the 10th driest September in Llansadwrn since 1928. The wettest day was on the 2nd with 17.6 mm followed by the 8th with 10.2 mm. The 2nd and 8th, the only having over 10 mm, constituted 65% of the month's total. There were 12 (-5.2) rain days and just 5 (-7.9) wet days; there were 3 (-4.6) days with 5 mm, or more. Days with no precipitation were 9 (+0.1) and dry days with less than 0.2 mm were 18 (+9.1), highest in September since 2002 (22) and most in any month since May 2008. The dry days included 5 days when dew had condensed on the funnel.
 "Dewfall in September measured by drosometer.")
Net dew, measured by drosometer on 20 days in the month, totalled 3.4 mm, largest was 0.3 mm on the 9th when a trace was observed in the bottle of the raingauge. On the 6th, in drier air conditions, nil dew was recorded by this method. On nights that it rained measurements of dew were not possible by this method. Total precipitation, rainfall and dew, was 42.9 mm. The lysimeter throughput includes rainfall and dewfall, less any evaporation. Potential evapotranspiration PE (usually calculated using the standard raingauge observations) was 26.3 mm to which could be added the 3.4 mm of dew to obtain a more accurate value. The amount of dew measured by drosometer (a net amount) is likely to be less than the actual, unknown, amount of dew condensing in the lysimeter.
The potential water balance PWB was 16.3 mm. Soil moisture on the 6th was 62% dry mass and was 57% dry mass on the 30th when soil was crumbly, but still moist.
The mean temperature was 13.7C (-0.7) of the decadal and [+0.3] of the 30-y climatological (1971-2000) average. This was highest since 2006 (16.3C) and worked about about even in the ranking since 1979. The month at times appeared cool in the daytime and this was because the maximum temperatures were often on the low side. The highest maximum 19.5C on the 18th, was lowest since 1992 ranking only 4th since 1979, this was a large (-4.4) anomaly compared with the past 10-years and -3.4 over this stations 30-years records. The lowest maximum 14.2C on the 14th was in contrast (+0.9) and +1.2 over 30-years. Ranking 13th highest, and equal highest since 2007, was the mean minimum of 10.6C. Highest and on the low side was 14.1C (-1.1) on the 8th while the lowest 7.6C(+0.7) was again above average. The lowest grass minimum of 5.0C (+2.0) also occurred on the 24th.
Sunshine duration recorded at Valley 127.1 h, highest since 2006, was [(101%)] of both averages. The sunniest day was on the 9th having 12.1h, the first day of a spell of 5 days (9 - 13) having 10h, or more, duration each day (no other days had 10h). There were 3 sunless days.
The mean wind speed (mws) was 12.7 mph (-0.7) with the windiest day on the 21st having a mws of 25.1 mph. Other windy days were the 3rd with a mws of 23.5 mpg (highest gust 50 mph) and the 8th with a mws of 24.5 mph (highest gust 46 mph). There were no gales reported at Valley, but there were strong to gale-force S to SW'ly winds around Irish Sea coasts and mountains on the 8th. Gale force 8 was reported at Aberdaron and Capel Curig where a gust reached 57 mph. In Llansadwrn the blustery wind was near gale-force 7/8 around 09 GMT.
The outstanding feature of the month must be the overall warmth. The mean temperature was 12.2C, highest since 2006 ranking 4th since 1979. Positive compared with both the decadal (+0.9) and 1971-2000 [+1.6] averages. The mean maximum of 15.2C ranked 6th since 1979 and had anomalies of (+0.9) and [+1.4]. The absolute maximum for the month 19.3C was not outstanding having an anomaly of (-0.3) and was lowest since 2001, but was notable because it occurred on the 29th of the month, a record here for the highest temperature recorded in the year. The lowest maximum was 11.5C, lowest since 6 June but highest since 2006 ranking 5th highest on October since 1979. The lowest minimum was 4.7C (+1.0) on the 9th when the grass minim fell to 1.8C, but this was not the lowest as 0.9C (+1.1) was recorded on the 17th.
Sunshine duration recorded at Valley was 87.6h (88%) and [92%] of the averages. The highest, and only day to reach double digits, was 10.0h on the 12th. There were 5 sunless days. In Llansadwrn the mean solar radiation was 9.21 MJ m -2 d -1, the highest was 15.72 MJ m -2 on the 5th and the lowest 3.95 MJ m -2 on the 30th.
Rainfall totalled 91.8 mm, (58%) and [82%] of the averages, lowest since 2007 ranking 26th since 1929. The wettest day was on the 6th having 37.1 mm while 17.3 mm was credited to the 31st, although it fell after midnight. These 2 days made up 59% of the month's total. Days with no precipitation were 13 (+5.9) while dry days (<0.2 mm) were 15 (+4.8). Rain days numbered 16 (-4.8) and wet days 13 (-3.6). There were just 4 days (-5.1) with 5 mm, or more.
Sunshine duration recorded at RAF Valley totalled 42.5 h (86%) and [94%] of average. This was the lowest since 2006 and was about evens in the ranking on the Anglesey record since 1930. The sunniest day was on the 12th clocking up 6.1h duration; there were 8 sunless days
Wet and windy throughout
Rainfall of 261.9 mm (192%) and [209%] of average was the most recorded in Llansadwrn in November since the exceptionally wet autumn 2000 when 250.5 mm was recorded and before 1928 when observations began. Parts of Britain, especially Cumbria where Seathwaite in Borrowdale with 314 mm in 24-h had the highest rainfall ever recorded. The total rainfall for the month at Grasmere was 743 mm; at Shap Fell 623 mm; and Capel Curig was not far behind with 611 mm while in Llanberis 469 mm was recorded. Here only October 2008 with 282.8 mm had more and was most in any month since records began here. It is significant of current climate trends that the 2 wettest months have occurred within 13 months and 4 of the 5 largest falls since November 2000. The wettest day was on the 13th having 28.8 mm one of the 17 (+7.8) days to have 5 mm, or more. There were 26 (+8.2) wet days (>=1.0 mm and 27 (+4.8) rain days (>=0.2 mm).
The mean temperature of 8.6C (+0.3) and [+1.3] of average was highest since 2007 ranking 7th since 1979. The highest mean 12.5C was on the first and the lowest 4.6C on the 28th. The mean maximum was 10.9C (+0.1) and [+0.8] of average, highest since 2007 ranking 8th. The highest maximum was 14.8C on the 1st and the lowest 5.7C on the 30th; 20 days had 10C, or more. The lowest maximum was 5.7C on the 30th. The mean minimum was 6.2C (+0.5) and [+1.7] of average, highest since 2004 and ranking 5th. The highest minimum 10.7C occurred on the 20th and the lowest 2.6C on the 28th so there were no air frosts. There were 3 ground frosts with the lowest -0.4C earlier in the month on the 9th giving 210 ground frost-free days in the year. There were 12 (+7.1) days on which small hail fell, the most in November since before 1979 beating the 11 days recorded in 2000. A windy month with 9 days with gales reported at Valley. The mean wind speed was 21.9 mph, highest since 1986 ranking 5 since 1956. Windiest was the 19th with a mws of 42.7 mph. Sunshine duration was 50.8 h (95%) and [89%] of average, least since 2004. The sunniest day was on the 9th with 5.3h duration. There were 5 sunless days. Rainfall at Valley was 229.4 mm with 33.2 mm recorded on the 13th, 30.0 mm on the 1st and 27.0 mm on the 19th.
Despite the record rainfall in November the autumn 2009 total ranked only 19th wettest in Llansadwrn since before 1928. With 396.3 mm (131%) and [120%] of average it was lowest since 2007 and far lower than the record autumn 2000 total of 612.1 mm.
The mean temperature was 11.5C and was (+0.2) and [+1.1] of average and, like the summer, indicative of the continuing warming trend.
A wet, but warm beginning with ice pellets turning colder from mid- month with frequent snow pellets and sleet/ snow showers
A taste of Decembers of old with 12 days having sleet or snow (+10.1) on the average of the past decade and highest since before 1979 when records were first kept here. Just a taste because there was only 1 day with lying snow at 09 GMT on the 19th, up to 2 cm on the 19th, (+0.1) on the average of the past 10-y. There was plenty of hail too, total hail days were 12 (+5.5) broken down into 1 day with large snow pellets (conical 7 mm diameter) and 11 with small hail (<5 mm). These consisted of 7 days having ice pellets and 4 days exclusively having snow pellets, 6 days if the day with large ones was included and another day when ice pellets were recorded as well (ice pellets take precedence when both occur). The 12 days were the highest recorded in December since 1979, beating the previous highest 11 in 1999 and 2000. No thunder was heard, the last time thunder was heard in December was in 2006 (3).
The mean temperature 4.1C (-1.8) and [(-1.5} of average, lowest since 1996 (4.0C) ranked 5th lowest since before 1979. The mean maximum 6.6C (-1.6) and [-1.3], lowest since 1995 (6.1C) ranked 3rd lowest. The highest maximum 11.5C on the 8th was (-0.6) while the lowest 1.8C, on the 18th, was (-1.1). The mean minimum 1.5C, lowest since 1996 (1.2C) ranked 5th lowest. The highest 6.3C (-0.6) was on the 9th while the lowest -1.7C (+0.5) was on the 20th. There were 10 air frosts (+6.4) highest since 1996 (12), but there were 20 in 1981, ranked 6th highest. The lowest grass minimum was -5.2C also on the 20th. There were 18 days with ground frosts (+2.9) equal lowest since 2007 and ranked 7 since before 1985. There were 22 ground frosts in 2008, 2001 and 1989.
Rainfall (including ice precipitation) totalled 116.9 mm (90%) and [1-2%] of average, highest since 2007 ranked 38th since before 1928. The wettest day was on the 5th with 18.7 mm. There were 2 days (-5.4) with no precipitation and there were 6 dry days (<0.2 mm) (-5.5). Rain days were 25 (+5.5) and wet days 17 (+0.6). There were 8 days (-1.5) having 5 mm, or more.
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 "No. days in the year exceeding 20C & 25C at Llansadwrn 1979-2009.")
There were 34 days that reached, or exceeded 20C, in the year, most since the 66 in 2006 and 1990 that were the highest number recorded at this station. Just 5 days reached 25C, or more, that's 2 more than 2008 and 5 times the zero of 2007 one of 3 years since 1979 to achieve that distinction |
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Llansadwrn (Anglesey): Monthly weather data for 2009.
Anomaly ~ is based on the 1999-08 average.
Anomaly 30-y is based on the 1971-2000 average.
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
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Air temperatures (C)
Mean max 7.3 7.5 10.8 14.1 15.1 18.3 19.0 18.7 16.7 15.2 10.9 6.6 13.4
Mean min 1.2 2.2 3.9 5.9 7.6 10.6 12.5 12.6 10.6 9.1 6.2 1.5 7.0
Mean 4.3 4.9 7.4 10.0 11.4 14.5 15.8 15.6 13.7 12.2 8.6 4.1 10.2
Anomaly~ -1.6 -1.0 +0.4 +0.9 -0.6 +0.3 -0.1 -0.1 -0.7 +0.9 +0.3 -1.8 -0.2
Anomaly 30-y -0.6 -0.4 +0.6 +1.4 -0.1 +0.9 +0.2 +0.3 +0.3 +1.6 +1.3 -1.5 +0.3
High max 13.9 11.6 17.8 18.7 25.3 26.3 28.1 21.8 19.5 19.3 14.8 11.5 28.1
Date 30 16 19 20 30 29 1 6 18 29 1 8 1 Jul
Low max 1.4 1.7 6.8 10.6 10.8 10.6 15.7 15.0 14.2 11.5 5.7 1.8 1.4
Date 6 2 3 6 4 6 17 28 14 18 30 18 6 Jan
High min 7.5 6.5 7.5 9.7 12.3 16.1 18.0 16.6 14.1 12.8 10.7 6.3 18.0
Date 12 27 12 24 30 29 2 19 8 28 20 9 2 Jul
Low min -5.0 -1.9 -1.1 2.4 4.5 5.9 8.1 9.3 7.6 4.7 2.6 -1.7 -5.0
Date 6 4,8 4 12 12 12 10 22 24 9 28 20 6 Jan
Grass min -9.7 -5.3 -5.2 -1.7 2.0 3.1 5.2 6.0 5.0 0.9 -0.4 -5.2 -9.7
Date 6 4 4 12 3 12 10 29 24 17 9 20 6 Jan
Atmospheric moisture means
RH (%) 88 89 86 80 79 77 86 85 88 87 90 91 86
Dew point (C) 1.6 2.5 4.7 6.3 8.1 11.3 13.0 13.3 11.4 9.7 6.6 1.9 7.5
Soil temperatures (C)
5 cm 2.6 3.7 6.1 9.7 12.7 17.1 17.3 16.4 13.9 11.4 7.8 2.9 10.1
10 cm 3.0 4.0 6.1 9.2 11.8 15.9 18.8 16.0 13.7 11.5 8.2 3.3 10.1
20 cm 3.0 4.2 6.7 10.1 12.4 16.3 17.5 16.9 14.8 12.3 9.0 4.0 10.6
30 cm 3.8 4.9 7.3 10.5 12.6 16.4 17.7 17.2 15.2 12.9 9.8 5.1 11.1
Anomaly ~ -1.8 -1.0 +0.2 +0.3 -1.1 0.2 0.0 -0.3 -0.1 0.4 0.6 -1.4 -0.3
50 cm 4.6 5.4 7.6 10.6 12.4 15.9 17.4 17.1 15.4 13.4 10.5 6.3 11.4
100 cm 6.0 6.2 7.9 10.1 11.7 14.6 16.3 16.3 15.3 13.7 11.5 8.0 11.5
Rainfall (mm)
Rain tot 95.2 17.8 49.7 42.9 81.6 67.1 135.8 112.1 42.6 91.8 261.9 116.9 1115.4
Rain % ave~ 78 19 73 54 114 99 212 116 36 58 192 90 92.7
Rain % 30-y 97 24 59 74 142 101 214 139 46 82 209 102 108.5
Days 0.0 12 5 12 10 9 15 5 7 10 13 1 2 101
Days <0.2 13 10 15 15 11 16 9 12 18 15 3 6 143
Days >=0.2 18 18 16 15 20 14 22 19 12 16 27 25 222
Days >=1.0 14 8 13 9 19 11 20 17 5 13 26 17 172
Days >=5.0 9 0 3 2 3 5 9 8 3 4 17 8 71
Max fall 21.8 4.1 11.5 16.4 9.8 15.1 29.6 16.2 17.6 37.1 28.8 18.7 37.1
Date 11 2 9 26 17 26 16 30 2 6 13 5 6 Oct
Evaporation
Piche (mls) 34.3 17.4 33.3 52.4 58.9 53.0 50.5 51.9 37.6 38.4 29.8 21.4 478.9
Lysimeter PE (mm) 5.6 7.8 15.3 42.2 43.9 69.1 58.7 40.5 26.3 17.4 1.1 2.2 330.1
Weather (days)
Air frost 8 8 4 0 0 0 0 0 0 0 0 10 30
Ground fr 18 16 11 3 0 0 0 0 0 0 3 18 69
Sl/snow 3 6 2 0 0 0 0 0 0 0 0 12 23
Sn lying 0 0 1 0 0 0 0 0 0 0 0 1 2
Thunder 0 0 0 1 0 1 2 0 0 0 3 0 7
Hail <5 mm 6 6 5 0 2 2 1 1 0 0 12 11 46
Hail >=5 mm 0 0 0 0 0 0 0 0 0 0 0 1 1
Fog at 09h 1 0 1 0 0 0 0 0 0 0 0 0 2
Gales 4 0 1 1 0 0 0 1 0 1 7 1 16
Wind direction at 09h (days)
N 0 2 1 1 0 2 1 1 0 2 2 0 12
NE 3 1 0 3 4 9 1 0 6 1 1 8 37
E 2 3 0 2 1 4 1 0 3 1 1 3 21
SE 4 4 1 6 3 1 2 1 2 6 3 2 35
S 11 3 6 11 8 4 10 14 3 7 6 4 87
SW 5 8 10 5 10 3 9 13 9 9 10 4 95
W 3 1 7 1 2 4 2 2 4 1 4 3 34
NW 1 2 3 0 1 1 5 0 1 1 1 4 20
Calm 2 4 3 1 2 2 0 0 2 3 2 3 24
Autographic records of rainfall and frost duration (h)
Rain 77.0 26.2 52.1 41.2 71.2 40.2 86.6 81.0 39.7 54.6 164.1 104.5 838.4
Frost 109.8 85.0 10.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 35.2 240.3
Cloud cover at 09 GMT
Mean (%) 63 73 69 63 66 71 85 79 82 79 78 72 73
Global solar radiation (MJ m-2) and sunshine duration (h)
Llansadwrn
Sol rad mean 2.90 5.30 10.40 15.38 18.03 19.18 16.97 14.44 13.20 9.21 5.20 2.80 11.08
Maximum 6.37 8.84 19.56 24.85 29.88 29.24 25.27 22.7 22.08 15.72 8.99 4.74 29.88
Date 26 4 29 18 12 24 23 5 9 5 9 28 12 May
Minimum 0.46 2.38 4.23 5.68 7.15 5.96 10.03 4.91 5.48 3.95 1.68 1.11 0.46
Date 4 15 3 6 5 6 17 31 8 30 19 7 4 Jan
Sunless days 10 12 3 4 9 2 2 8 3 3 5 7 68
Valley
Sunshine (h) 60.5 46.8 142.9 188.3 205.2 234.7 175.8 136.0 127.1 87.6 50.8 42.5 1498.2
Average % ~ 102 55 111 117 108 137 104 90 101 88 95 86 104
Sunniest 7.2 7.8 10.4 13.0 15.5 15.5 13.6 12.1 12.1 10.0 5.3 6.1 15.5
Date 26 4 19,29 19,20 30 24 25 5 9 12 9 12 vs
Sunless days 11 8 4 3 4 2 1 4 3 5 5 8 58
# C-S (h) 64.8 50.1 154.2 211.8 243.7 284.5 211.0 159.8 145.6 98.2 55.7 45.8 1725.2
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
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I am grateful to Geraint Roberts, at the Met Office RAF Valley, for supplying the Valley data.
#. Valley sunshine duration, since August 2005, has been measured using a Kipp & Zonen electronic sensor. This gives sunshine durations that are different to the previous Campbell-Stokes instrument. A conversion factor 1 has been applied to estimate what the Campbell-Stokes (C-S) duration might have measured for comparison. The electronic sensor measures less sunshine than the Campbell-Stokes instrument, it varies throughout the year and is about 20% less in summer and 7% less in winter. Averages have been computed using estimated equivalent Kipp & Zonen sunshine durations.
References
1: Prior J. (2006). Sunshine measurement. Weather 61, p. 77.
2: Kerr A. & Tabony R. (2004). Comparison of sunshine recorded by Campbell-Stokes and automatic sensors. Weather, 59 (4), pp. 90-95.
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These pages are designed and written by Donald Perkins © 2009 Page first dated 23 February 2009 http://www.llansadwrn-wx.co.uk
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 "Graph of annual mean temperature and anomalies 1979-2009.")
 "Annual rainfall statistics at Llansadwrn 1929-2009.")
; "Monthly rainfall accumlated through the year with comparisons."){kind=small}
 "Annual Anglesey sunshine duration anomaly 1930-2009.")