Llansadwrn (Anglesey) Weather:
Monthly and Annual
Summary for 2008
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Llansadwrn (Anglesey) Weather:
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Note: Values in (.) refer to the 10-y 1998-2007 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 the pop-up graphics.
The month began with near normal temperatures and air frosts, the rest was very wet with above average temperatures
Total rainfall was 189.9 mm (168%) of the 1998-2007 average and [194%] of the 1971-2000 average. It was the wettest January since 1999 that had 193.4 mm and ranking 3rd on the Llansadwrn record kept since before 1928. The wettest January was 1948 mm with 230.9 mm recorded at Treffos. Rainfall duration was 127.0 h. The 48.8 mm recorded on the 9th was the 3rd largest fall in a day I have measured at this station set up in 1979. Rain days with 0.2 mm, or more, numbered 23 (+3.0) and wet days with 1 mm, or more were 20 (+4.5). Days with 5 mm, or more were 12 (+4.7), but there were 6 completely dry days these (-1.0) of the decadal average. Soil remained close to its saturated water percentage 70% most of the month with standing water on 6 mornings.
The temperature record continues to show the effect of climate change. The monthly mean was 6.5C (+0.7) and a large [+1.6] of the 30-y climatological average. The mean maximum was 8.9C (+0.7) and [+1.5], the highest maximum was 10.9C (-1.1) and one of 12 days that had 10C, or more, in the month. The lowest maximum was 2.5C on the 3rd, this was a cold day (-1.5) of average, but the maximum was just 1.6C on the day, the 2.5C was recorded at 09 GMT the following day and by convention was credited to the 3rd. The mean minimum temperature was 4.1C (+0.7) and [+1.7]. The highest minimum was 9.4C (+0.4) on the 21st while the lowest was -0.5C (+1.1) on the 4th. The only other day to see an air frost was the previous day (3rd) with -0.3C. In all there were just 7.5h of air frost. Ground frosts numbering 12 were closer to normal (+0.3) with the lowest -3.7C (+2.1) on the 12th. The soil temperature at 30 cm was 6.4C and (+1.1) of average. There were 22 days on which the temperature was >= 5.6C or 42F, this is regarded as the minimum temperature for plant root growth. The soil surface was frozen on just 2 days, the 3rd and 4th.
The was small hail on 9 days, slight snow on 1 day, but no lying snow at 0900 GMT. A covering of snow pellets and snow lay for about 20 minutes from 1620 GMT on the 31st. No thunder was heard.
The period 11 - 19th had almost clear skies and night frosts
The month was outstanding for its sunshine with the Met Office at RAF Valley recording 120.8 h of sunshine on the Kipp & Zonen instrument. Since the Campbell Stokes 'glass sphere and card' instrument was consigned to the museum it has been difficult to compare the present reading with previous. Using the correction (see Notes 1 below) it was (153%) of average and sunniest since 1986 and ranked 5th sunniest on the Anglesey record since 1930. The sunniest day was on the 18th with 9.1 h, but the spell 11 - 19th had more than 8 h each day. It was not all sunshine as there were 7 sunless days spread over the beginning and end of the month.
Temperatures were above average, the mean in Llansadwrn was 6.1C (+0.7) and [+1.3] of the decadal and 30-y averages. The highest mean was on the 9th with 10.1C and the lowest 2.6C on the 17th. It was the maxima that excelled with the mean 10.4C highest since 1998 (10.5C) 2nd highest since before 1979 being the only 2-years into double figures. The highest maximum of 16.8C on the 11th (+4.4), in Föhn-like conditions with a relative humidity down to 34%, was the highest recorded at this station so early in the year (previously 16.5C on 10th January 1998), and the 2nd highest in February to the 17.2C recorded on the 28th in 1985. On the same day Trawsgoed in Ceredigion (it seems now to have a g in it and may a different location to the Trawscoed previously reported) had 16.1C, but not to be outdone on the 12th had a summer-like 18.2C while here it was only 14.1C. There was 16 days on which the temperature reached 10C, or more. The mean earth temperature at 30 cm was 5.8C (-0.2)
There were some frosty days too with air frost recorded on 5 days (+1.9), most since 2004. The mean minimum was 2.9C (-0.3) and [+0.8] indicating lower than in recent years, but higher than the climatological average 1971-2000. Lowest was -1.3C on the 18th which was on the average, and highest 8.0C (-0.3) on the 8th. There were 27.6 h of frost duration, most 10.2 h on the 17th. There were 19 (-0.2) ground frosts, close to the average of the last 10-years.
Rainfall of 68.9 mm , drier than the past 10-years (74%) and closer to the 30-year average [92%]. The wettest day, on the dull extra leap-year day 29th, had 16.3 mm. There were 10 (+3.8) dry days and 14 (-4.0) rain days. Wet days were 11 (-2.5) while days with 5 mm, or more, were 5 (-1.2).
There was snow sleet or snow and the 3 days with hail was (-2.9) of average. There was no thunder, but there were 3 days with gales.
The mean air temperature of 6.5C, lowest since 2006 ranking 10th since before 1979, was 0.7C below the average of the past 10-y but only 0.2C below the 1971-2000 average. The month was more like an average March experienced before the warming trend of the past 30 years. Locals were complaining of how cold it was, they were either too young or had short memories of how it used to be! The mean maximum was 9.8C (-0.7) and [-0.4], the highest maximum on the 31st was 14.6C and was (-1.9) of average. The lowest 6.8C occurred on 2 days the 22 and 23rd and were (+1.0) of the decadal average. The mean minimum 3.3C was again (-0.7), but spot on the 30-y average [0.0]. The highest minimum of 6.3C (-2.3) on the 2nd was lowest since 1984 that had 6.1C and the lowest -0.1C was highest on record since 1979 and the only day with air frost (-1.7). There were 11 (-0.3) ground frosts, interspersed through the month, with the lowest -3.8C (+2.6) on the 5th when 0.17 mm of dew and frost deposits were recorded. The mean temperature of the soil at 30 cm was 6.9C (-0.4), all above the 5.6C or 42F regarded as necessary for plant growth. Lawnmowers were out during the month, in the past they were not out until April!
Rainfall was 96.1 mm (131%) and [113%] of average, highest since 2006 and ranking 18th wettest in Llansadwrn since 1928. The largest fall was on the 15th with 20.6 mm. There were 4 (-5.6) completely dry days and 22 (+5.7) rain days. Wet days numbered 18 (+6.7) while those with 5 mm, or more 6 (+1.5). Evaporation measured by the Piche evaporimeter was 41.7 ml (or mm), evapotranspiration by lysimeter, increasing this month, with 19.6 mm. There were some windy days (21,22) with low relative humidity when Piche evaporation was 4.9 and 2.4 ml respectively. Despite increasing evaporation soil water remained close to saturation levels (water content 70% dry mass here) and several 'wet fields' near the weather station have had standing water on them most of the month. The wetness has made cultivation difficult although 2 or 3 of the drier fields have been ploughed and sown with barley. Local soils are of variable structure and most shallow of rather poor agricultural quality many being on glacial drift. The wettest areas should be mire (wetland) vegetation and there are a few examples of these that have survived, but many have been improved over the years and are difficult to maintain when it is wet. It is these fields that usually attract flocks of curlews and lapwings.
Sleet (larger amounts) , or snow (small amounts) were seen on 6 days (+3.8), but there was none lying. Small hail fell on 12 days (+7.6) and included 6 days with snow pellets and 6 days with ice pellets.
It was a windy month with 5 gales recorded at RAF Valley (9,10,11,12 and 28). The mean wind speed for the month was 18.1 mph with the highest 33.2 mph recorded on the 12th which also had the highest gust of 70 mph.
Sunshine duration at RAF Valley totalled 127.8h with 5 sunless days and just 0.1h and 0.6h recorded 2 others. Sunniest days were on the 17th with 10.7h and 27th with 10.2h. The 17th was the brightest day in Llansadwrn with global solar radiation reaching 17.52 MJ m-2. The dullest day was on the 20th with 3.07 MJ m-2. The mean daily solar radiation was 9.35 MJ m-2. Estimated sunshine duration was 125.2 h with 8 sunless days.
The mean temperature 8.3C was -0.9 of the 10-year, but just -0.3C of the 30-year average. So a little cooler than we have been experiencing of late, but much nearer Aprils of past years. The mean maximum was 11.9C [(-0.9)] the same on both averages. The highest maximum 19.2C (+0.6) was on the 22nd and the 23rd with 16.0C were the only days to have more than 15C and there were 8 sub-10C days, scattered through the month, with the lowest 5.7C on the 6th. The mean minimum was 4.7C (-0.8) and [+0.3] clearly showing the contrast between the last decade and the climatological 1971-2000 average. The lowest minimum was -0.1C on the 6th the only air frost of the month, was for such a short time that the chart recorder used for determining hours of frost did not record it. The bi-metallic strip temperature recorder responds slower than the standard mercury thermometer. There were 11 days of ground frosts (+4.9) of average with the lowest -4.4C (-1.3) on the 8th. Soil temperature at 30 cm averaged 9.5C (-0.7), lowest 8.2C on the 7, 9 and 10th and highest 11.2C on the 25, 27 and 30th. All 6 soil thermometers (5 cm to 100 cm) registered more than 10C for the first time this year on the 23rd.
Rainfall was 86.2 mm spread throughout the month, largest falls 11.0 mm on the 12th and 10.5 mm on the 29th. There were 5 (-4.3) dry days and 21 (+3.8) rain days. Wet days numbered 18 (+4.1) while there were 7 (+1.4) with more than 5 mm. Evaporation by the Piche was 35.1 ml (or mm) and by the lysimeter 37.5 mm. There was a potential water balance of 48.7 mm, the soil remaining close to the saturated water percentage of the local soil (70%) through the month. Moderate amounts of rainfall left standing on 9, 15, 27 and 30th and it was pretty wet underfoot at other times putting work on the garden vegetable plot on hold.
At RAF Valley sunshine duration was 168.2 h (105%) and [107%] of average. Sunniest day was on the 16th with 11.3h and there were 3 sunless days. Here sunshine based on the solarimeter reading was also 168 h with 7 sunless days. The mean global solar radiation was 13.92 MJ m-2. Highest was 23.20 MJ m-2 on the 16th and lowest 5.36 MJ m-2 on the 21st.
The mean temperature 13.6C was (+1.7) and [+2.1] when based on the 10-y and 30-y averages respectively and was the highest recorded at this station since before 1979 beating 1990 with 13.4C into 2nd place. The highest mean of the month 20.1C was on the 8th and the lowest 9.4C on the 19th with the only other sub-10C 9.5C on the 1st. The mean maximum temperature was 17.4C (+1.8) and [+1.4] ranking 6th highest here with 1990 holding on to the record with a mean of 19.2C. The highest maxima were 25.1C (+1.7) on the 8th and 25.0C on the 7th, again not as high as the 27.6C recorded in 1990 or the 26.4C in 1989. In 1990 there were 4 days with 25C, or more. At Valley the mean maximum temperature was 17.5C, the highest on record, with 24.9C on the 8th. In Llansadwrn there were 6 days on which the temperature reached 20C, or more, equal highest since 2001 ranking 8th. The mean minimum here was 9.7C (+1.5) and [+2.7], and at Valley 10.3C, both highest on record. The lowest minimum was 4.8C (+1.1) on the 1st of the month while at Valley it was 5.8C on the 19th (5.1C here). The highest minimum was 15.4C on the 4th, second highest in May, and highest this early in the year since records began in 1979 (17.0C on 17 May 2002) while at Valley it was 14.0C. The mean grass minimum was 7.5C (+1.3) while it was 7.4C at Valley. The lowest grass minimum was 1.7C (+1.4) on the first and 1.9C on the 19th when Valley recorded their lowest of 1.3C. Soil temperatures at 30 cm depth increased through the month, beginning 10.4C and ending 15.5C. The mean soil temperature was 14.4C (+0.8)
Rainfall was 33.4 mm (48%) and [58%], the lowest total since 1998 (25.3 mm) ranking 14th driest since before 1928. The wettest day was on the 4th with 8.3 mm. There were 17 (+5.6) dry days, 11 (-5.1) rain days and 9 (-2.9) wet days.
Sunshine duration at RAF Valley totalled 232.3 h while the estimated duration in Llansadwrn was 221 h. At valley the sunniest day was on the 31st with 15.5 h and there were 2 sunless days (26,28) while the 9th had 0.1h and the 17th 0.4h. Global solar radiation at Llansadwrn was a mean of 18.74 MJ m-2 with the highest 27.09 MJ m-2 on the 18th and the lowest 6.38 MJ m-2 on the 9th.
Rainfall for the first 16 days was only 7.5 mm (11% of average) and the moisture content of surface soil (0-5 cm) fell to 30.4% dry mass, the permanent wilting percentage for the local soil is 15.2% and no wilting was seen although plants in the garden required irrigation.
 "Potential monthly evaporation and soil water balance up to 16 June 2008.")
The second half made up for the lack of water in the first with heavy falls on the 17th (14.3 mm), 17th (22.6 mm), 21st (18.6 mm) and 26th (40.7 mm). The latter was the largest fall in a day at this station since 1979, and in Llansadwrn since 1929 when records began. The month ended with 123.5 mm (168%) and [186%] of average, just exceeding the 122.1 mm of 2007 and was wettest since 1998 and ranking 9th  "Top 10 previous wettest years in Llansadwrn with June subtotals."){kind=small}
. There were 13 (+2.6) dry days and 16 (+0.3) rain days (0.2 mm, or more). There were 12 (+1.1) wet days (1 mm, or more) and 6 days had 5 (+0.9) mm, or more . Potential evapotranspiration (PE) to the 16th (last day of dry spell) measured by lysimeter was 49.3 mm resulting in a negative potential water balance (PWB) of 41.8 mm. The month ended with a PE of 69.3 mm and a positive PWB of 54.2 mm.
The mean temperature of 13.5C, equal lowest since 2002, was 0.1C lower than May and was 1.0C lower than average of the past 10 years. It was much closer to the 1971-2000 average just 0.1C lower. The mean maximum 17.2C, 0.2C lower than May, was [(-0.5)] compared with both averages. The highest maximum 22.8C (-2.4) was on the 9th and with the 22.0C on the 8th were the only two reaching 20C, or more. The mean minimum 9.7C was (-1.6) and [+0.2] with the highest minimum 13.0C (-2.0) on the 25th and lowest 6.0C (+0.1) on the 13th. The mean grass minimum 7.7C was also down on the average (-1.2), the lowest 3.3C (+0.2) was on the 16th; at RAF Valley there was a ground frost -1.4C.
Sunshine duration reported by the Met Office at Valley was 206.3h (125%) and [122%] of average (Kipp & Zonen adjusted values), sunniest since 2006 the 14th sunniest June on the Anglesey record since before 1930. The sunniest day was on the 8th having 15.2h. There were 2 sunless days and another 4 had <1 hour. In Llansadwrn sunshine base on the solarimeter reading was 209 h. The mean solar radiation was 18.16 MJ m-2, the highest was 28.34 MJ m-2 on the 8th and the lowest 6.56 MJ m-2 on the 25th when there was the record heavy rain.
 "January to July rainfall anomalies 1929-2008")
Rainfall was 81.5 mm (131%) and [128%] of average, least since 2006 (26.7 mm) as 2007 had 120.4 mm, and ranking 31st wettest since before 1929. It brought the total for the year so far to 679.5 mm, most since 1958 (720.8 mm) and ranking 2nd. The largest fall 17.6 mm was on the 28th. There were 5 days with 5 mm, or more (+0.8). Dry days were 7 (-4.8) while rain days were 19 (+4.3) and wet days 13 (+1.8).
The mean temperature was 15.9C (-0.2) and [+0.3], highest since 2004 with a mean of 17.0C, ranking 9th since before 1979. The highest mean 17.6C was on the 25th and the lowest 7.8C on the 20th . The mean maximum temperature was 19.5C (+0.2) and [0.0], the highest maximum was 26.0C on the 24th (+0.5) and the lowest 13.5C on the 11th (-1.5). The mean minimum was 12.3C (-0.2) and [+0.3) of average. The lowest minimum 7.8C (-0.6) was on the 20th, but the lowest grass minimum 5.2C was the next day, the 21st.
There were 3 days with thunder (+1.9), but no hail was observed.
Sunshine duration at RAF Valley was 166.0 h (100%) and [98%] of the averages, lowest since 2005 that had 158.1 h, but ranking 28 out of 78 on the Anglesey record (Kipp & Zonen adjusted values). The sunniest day was the 27th with 14.5 h, there were 2 sunless days and another 4 days with <1 h . Global solar radiation at Llansadwrn averaged 14.92 MJ m-2 , highest was 25.97 MJ m-2 on the 21st while the lowest was 5.85 MJ m-2 on the 17th. Estimated sunshine duration was 183 h with 4 sunless days.
Llansadwrn (Anglesey): Monthly weather data for 2008.
Anomaly ~ is based on the 1998-07 average.
Anomaly 30-y is based on the 1971-2000 average.
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Jan Feb Mar Apr May Jun Jul Year
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Air temperatures (C)
Mean max 8.9 10.4 9.8 11.9 17.4 17.2 19.5 13.6
Mean min 4.1 2.9 3.3 4.7 9.7 9.7 12.3 6.7
Mean 6.5 6.6 6.5 8.3 13.6 13.5 15.9 10.1
Anomaly~ +0.7 +0.7 -0.7 -0.9 +1.7 -1.0 -0.2 .
Anomaly 30-y +1.6 +1.3 -0.2 -0.3 2.1 -0.1 +0.3 .
High max 10.9 16.8 14.6 19.2 25.1 22.8 26.0 26.0
Date 13 11 31 22 8 9 24 .
Low max 2.5 6.1 6.8 5.7 12.0 13.2 13.5 2.5
Date 3 17 22,23 6 17 12 11 .
High min 9.4 8.0 6.3 9.7 15.4 13 17.6 17.6
Date 21 8 2 26 4 25 25 .
Low min -0.5 -1.3 -0.1 -0.1 4.8 6.0 7.8 -1.3
Date 4 18 18 6 1 13 20 .
Grass min -3.7 -7.5 -3.8 -4.4 1.7 3.3 5.2 -7.5
Date 12 18 5 8 1 16 21 .
Atmospheric moisture means
RH (%) 92 86 84 86 75 78 82 83
Dew point (C) 5.1 3.0 3.5 5.4 9.6 9.9 12.6 7.0
Soil temperatures (C)
5 cm 5.5 4.1 5.5 8.5 15.2 16.6 17.2 10.4
10 cm 5.8 4.8 5.6 8.2 13.7 15.2 16.4 10.0
20 cm 5.8 5.0 6.2 9.0 14.3 15.7 16.9 10.4
30 cm 6.4 5.8 6.9 9.5 14.4 15.8 17.0 10.8
Anomaly ~ +1.1 -0.2 -0.4 -0.7 +0.8 -0.3 -0.5 .
50 cm 6.9 6.6 7.4 9.6 14.1 15.6 16.7 11.0
100 cm 7.7 7.5 7.9 9.4 12.9 14.7 15.5 10.8
Rainfall (mm)
Rain tot 189.9 68.9 96.1 86.2 33.4 123.5 81.5 679.5
Rain % ave~ 168 74 131 110 48 168 131 57.2
Rain % 30-y 194 92 113 149 58 186 128 66.1
Days, dry 6 10 4 5 17 13 7 62
Days >=0.2 23 14 22 21 11 16 19 126
Days >=1.0 20 11 18 18 9 12 13 101
Days >=5.0 12 5 6 7 1 6 5 42
Max fall 48.8 16.3 20.6 11.0 8.3 40.7 17.6 48.8
Date 9 29 15 12 4 26 28 .
Evaporation
Piche (mls) 21.6 35.7 41.7 35.1 72.3 49.3 45.2 300.9
Lysimeter PE (mm) -4.7 10.3 19.6 37.5 70.3 69.3 57.8 260.1
Weather (days)
Air frost 2 5 1 1 0 0 0 9
Ground fr 12 19 11 11 0 0 0 53
Sl/snow 1 0 6 3 0 0 0 10
Sn lying 0 0 0 0 0 0 0 0
Thunder 0 0 0 0 1 0 3 4
Hail <5 mm 9 3 12 8 0 1 0 33
Hail >=5 mm 0 0 0 0 0 0 0 0
Fog at 09h 1 1 0 0 0 0 0 2
Gales 8 3 3 0 0 1 0 15
Wind direction at 09h (days)
N 0 0 5 4 0 2 3 14
NE 1 3 4 3 15 5 1 32
E 2 5 1 7 6 0 2 23
SE 1 0 0 1 5 1 4 12
S 12 5 4 5 4 9 11 50
SW 8 10 8 8 1 10 4 49
W 5 3 7 0 0 1 3 19
NW 1 1 2 0 0 2 1 7
Calm 1 2 0 2 0 0 2 7
Autographic records of rainfall and frost duration (h)
Rain 127.0 45.6 72.8 81.2 32.3 64.0 51.4 474.3
Frost 7.5 27.6 0.2 0.0 0.0 0.0 0.0 35.3
Cloud cover at 09 GMT
Mean (%) 83 62 76 81 61 79 81 75
Global solar radiation (MJ m-2) and sunshine duration (h)
Llansadwrn
Sol rad mean 1.68 6.10 9.35 13.92 18.74 18.16 14.92 11.84
Maximum 4.85 10.95 17.52 23.20 27.86 28.34 25.97 28.34
Date 24 19 17 16 19 8 21 .
Minimum 0.05 1.48 3.07 5.36 6.02 6.56 5.85 0.05
Date 23 29 20 20 28 26 17 .
* ESD (h) 51 90 125 168 221 209 183 1046
Sunless days 14 6 8 7 4 2 4 45
Valley
Sunshine (h) 42.7 120.8 127.8 168.2 232.3 206.3 166.0 1064.1
Average % ~ 69 153 104 105 125 125 100 74
Sunniest 5.7 9.1 10.7 11.3 15.2 15.2 14.5 15.2
Date 3 18 17 16 31 8 27 .
Sunless days 11 7 5 3 2 2 2 32
# C-S (h) 45.8 129.2 137.9 189.2 275.9 250.1 199.3 1227.3
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Jan Feb Mar Apr May Jun Jul Year
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I am grateful to Robert Jones, Observer/ Admin. Officer 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.
* ESD is an experimental Estimated Sunshine Duration. It was calculated using a relationship derived by fitting Llansadwrn global solar radiation and Valley sunshine duration data to a linear regression equation.
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These pages are designed and written by Donald Perkins © 2008 Page first dated 2 February 2008 http://www.llansadwrn-wx.co.uk
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