Llansadwrn (Anglesey) Weather:
Monthly and Annual
Summary for 2004
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Llansadwrn (Anglesey) Weather:
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Wet throughout with 3 cold days at the end of the month
It was a wet month with 139.9 mm rainfall 134% of average or 143% of the 1971-2000 average. Ranking 18th wettest since 1928, it was the wettest January since 2000 (the wettest year on record) that had 145.2 mm. January 2000 ended a run of 3 very wet years, January 1998 had 103.5 mm and January 2999 had 193.4 mm. There were 4 falls over 15 mm; 15.7 mm on the 5th, 24.6 mm on the 15th, 27.6 mm on the 30th (the wettest day) and 17.8 mm on the 31st. These 4 days added up to 85.7 mm 61% of the total. With only 1 dry day there were 26 rain days (0.2 mm, or more) 7.4 more than average. There were 19 days with 1.0 mm, or more.
Temperatures were above average overall. The mean 5.7C was +0.3 but +0.8C on the 1971-2000 average. Highest maximum on the 7th was only 11.0C (-1.2) while the lowest minimum -2.1C on the 29th was (+0.5). There were 3 days (-2.4) with airfrost over 16.8 h duration, but 15 days had ground frost (+1.0). The mean soil temperature at 30 cm was 5.6C (+0.6) and 17 days were 5.6C, or more, so that grass grew well on my lawn and surrounding fields.
January 2003 was sunniest since 1980 with 142% of average. This January was dull with sunshine in short supply, RAF Valley reported 44.1h (+14.1). This was only 74% of the 30-y average. Sunniest day was the 29th with 6.9h; There were 12 sunless days with another 4 with 0.3h, or less.
Three days saw sleet or snow but no days with lying snow. Hail fell on 8 days. Snow grains on the 2nd, snow pellets on the 26 - 28th and ice pellets on 11th, 13th, 14th and 16th. Thunder was not heard although an active cold front passed over on the 28th.
A warm and very wet start, a dry middle with heavy snow at the end.
The first 4 days of the month had 83.7 mm of rainfall that was 68% of the total for the month. The most 33.4 mm fell on the 2nd with a duration of 13.2h. Although the middle part of the month was drier the month ended with 14.8 mm of melted snow. The 122.5 mm total (59.6 h duration) was 124% of the 10-year average but 164% and 162% of the 1971 - 2000 and long-term averages. It was the wettest February since 2003 and ranked 11th wettest on record here since 1929. The combined January and February total of 262.4 mm was the 9th wettest start to the year but was not quite as wet as in 2000 (288.6 mm) and that turned out to be the wettest year on record. But there were 11 dry days (days with trace amounts of dew and/or frost not included) this 5.4 days more than average. Rain days (0.2 mm, or more) were 15 (-3.9) while wet days (1.0 mm, or more) were 13 (-1.9). The number of days having 5 mm, or more, were 8 and this was +0.9 of average.
Temperature averages were mixed. The mean maximum of 7.9C was -0.6 of both averages while the mean minimum of 3.2C was (+0.3) but +1.1C compared with the 1971 - 2000 average. Thus the mean of 5.6C was (-0.2) but +0.3 on the 1971 - 2000 average. While February maximum temperatures were similar it is the minimums that are, over recent years, higher. The 5 days of airfrost were close to average and resulted in 27.8 h of frost. The lowest was -1.1C (+0.3) on the 26th. There were 16 days of ground frost (+2.8) with the lowest -5.0C on the 9th.
There were 6 days (+1.2) that saw hail in the month. On the 7/8th there were ice pellets and thunder was heard on the 7th. The 24 - 28th saw the most wintry weather since December 2000 with frequent snow and ice pellets. At 1740 GMT on the 25th there was a moderate shower of conical-shaped snow pellets that measured up to 10 mm diameter across the widest point. Snow fell on the 4 days 25 - 28th with snow lying at 09 GMT of 4 cm, 13 cm, 7 cm and 4 cm deep respectively. The 26th saw moderate snow, heavy at times, from 0720 GMT to 1130 GMT that was lying in places up to 17 cm deep. The number of days with lying snow equalled that of 1996 and 1991 but was no where near the 13 of 1979.
Despite 10 sunless days in the month RAF Valley reported 97.7h (+13.8) of sunshine some 118% of the 30-y average. The sunniest day was on the 29th with 9.9h and another 7 had 5h, or more.
March is one of the drier months and this year was no exception. With 55.1 mm, ranking 34th lowest in the records since 1928, it was 69% of average and had 11 dry days (+1.2). Rain days, those with 0.2 mm, or more, were 14 (-2.3). But there were 10 days (-1.4) with 1.0 mm, or more, and 3 (-2.2) with 5 mm, or more. Wettest was the 18th that had 13.8 mm but the 15th saw 12.2 mm and the 13th 10.4 mm.
The mean temperature of 7.0C was coolest since 2001. The highest maximum was 19.1C (+3.7) on the 31st while the lowest minimum was -2.0C on the 2nd. There were 5 days (+3.1) with air frost and the month had 34.3 h when the temperature was below freezing. Ground frosts numbered 13 and were just 1.8 above average. Snow fell on 3 days (+0.6) and hail <5 mm diameter fell on 4 days, the most in March since 1999. No thunder was heard.
While not as sunny as March 2003, RAF Valley reported 142.7h (+12.4). This was 121% of the 30-y average. Sunniest day was the 1st with 9.9h; 15 days saw 5 h, or more, but 6 were sunless.
Rainfall 50.5 mm was only 69% of average. It was the driest April since 1997 (30.8 mm) and ranked 29th in records since 1928. The beginning of the month saw small amounts of rainfall as did the beginning of the second half. The wettest day was on the 17th but that only had 11.4 mm. Days with or without some rainfall were all close to their averages. There were 10 (+0.2) dry days while 16 (-0.3) had rain of 0.2 mm, or more. There was a tendency towards lower amounts of rain as wet days, those with 1 mm, or more were 12 (-1.3) and only 3 (-2.6) had 5 mm, or more.
The monthly mean temperature (½ max + min) was 9.4C and this was 0.6C above average. The most significant was the mean minimum of 6.2C that was 1.1C above the 10-y average but a staggering 1.8C above the 30-y average. It was the highest on record at this station (since 1979). This was reflected in zero air frosts (-0.7) and only 2 slight ground frosts (-4.9). The mean maximum was 12.6C and this was very close to the 10-y (+0.1) and 30-y (-0.2C) averages. But there were 3 warm days 24/26th with the highest temperature 19.8C on the 24th and was 2.0C above average. There were 6 days <10C with the lowest 8.8C on both the 9th and 15th.
It was a dull month with only 119.8 h (-46.1) of sunshine reported at RAF Valley. This was but 68% of the 30-year average. There were only 2 days that had more than 10 hours. The sunniest day was on the 22nd with 11.9h, and the 26th had 10.6h. There were 2 sunless days and another 5 saw less than 1h.
 "Daily PE measurements by Piche and lysimeter, in April 2004 at the weather station."){kind=small}
Soil temperatures at 30 cm depth averaged 10.4C (+0.6) and was cooler than 2003 but ranked 3rd in the station records. Every day was >=5.6C a minimal temperature regarded as necessary for plant growth. Positive PE (potential evapotranspiration) values, measured by lysimeter, were frequent through the month with a total 34.3 mm accumulated at the end. There are often many negative values during winter months when rainfall is large and dew and frost frequent. Evaporation recorded by the Piche evaporimeter was 40.3 ml or 36.6 mm (calculated on the area of evaporating surface of my instrument). The graph, of this month, shows the closeness of the daily values. The fluctuations in plotted line of the lysimeter PE are due to rainfall occurring just before amount percolated is measured. It can take 4 to 6 hours for the water to percolate through the soil. This is why daily values are not usually reported; 2/3 days usually works quite well but can still show some fluctuation in very wet weather.
No thunder was heard during the month but ice pellets were recorded on 5 days (+1.4).
Last May (2003) was the wettest May in Llansadwrn on record having a total of 148.3 mm. This year, despite the wet start to the month with 39.3 mm in the first 8 days (84% of the total), the month ended with 47.0 mm, 71% of average. It was the driest May since 1998, that had only 25.3 mm, and ranked 25th driest on record since 1928. It brought the rainfall for the spring months (March - May) to 152.6 mm, driest since 1990 that had a total of only 80.2 mm, and ranked 16th driest on record. The wettest day was on the 3rd having 20.7 mm falling in 5.6 h. Wet days (those with 1.0 mm, or more) numbered 7 (-2.9) while there were 10 (-4.1) rain days (0.2 mm, or more). 
The main feature was the 18-day spell between the 9th and 26th. With only trace amounts on 3 days and 0.1 mm on the 11th it qualified as an absolute drought (according to the old official definition, no longer used, of a minimum of 15 days none credited with 0.2 mm, or more). The last absolute drought in May occurred in 1980, also 18 days. Before that it was necessary to look back to 1948 to find another, also 18 days.
The month finished with mean temperatures above average and frost-free. The mean 12.0C was (+0.3), and +0.5 of the 1971-2000 average, coolest since 2000 but 9th warmest overall since 1979. The highest mean of 15.6C occurred on the 28th and 29th while the lowest 8.4C was on the 9th. The mean maximum of 16.0C (+0.4) but only equalled the 30-y average. The warmest day was on the 27th that saw a temperature of 22.7C, one of the highest in Britain on the day. The lowest was 9.8C on the 8th this accompanying some other low temperatures at higher elevations in a few places in North Wales (e.g. Capel Curig and Rhyl 10C, Lake Vyrnwy 9C and Moel-y-Crio 8C). The mean minimum temperature of 8.0C was (+0.2) but +1.0C up on the 30-y average. Highestt was 13.0C on the 28th while the lowest was 3.5C on the 5th. This day also had the lowest grass minimum of the month 0.6C, thus no ground frosts were recorded here, but 3 were reported at Valley. The mean grass minimum was 5.8C close to the average (-0.1).
The soil temperature at 30 cm depth was 13.9C and an impressive (+0.6) on the average. At the beginning of the month the daily temperature was 12.2C and this rose to 15.5C on the last day. The highest was 16.0C on the 28th. Evaporation began rather slowly in wet weather at the beginning of the month, this was followed by several overcast or misty days (9 - 13th) when there was little. Evaporation increased in the second half of the month during dry and sunny weather. By Piche total evaporation for the month was 43.1 ml, while by lysimeter potential evapotranspiration was 54.3 mm. There was a negative water balance of ( - ) 7.2 mm. Soil moisture was 59 litres per sq. m (of 10 cm depth) on the 27th April and this dropped to 41.5 litres per sq. m on the 27th May. The dry weather slowed the growth of grass at the end of the month.
There was one gale, soon after midnight on the 4th. But then wind speeds were below average and on 5 mornings it was calm at 09 GMT. At RAF Valley the mean wind speed was 9.2 (-3.6) mph. No thunder was heard, but there was a fall of ice pellets also on the 7th.
Sunshine was close to the average. At RAF Valley 229.3 (+2.3) h were recorded and was 99% of the 30-year average. The sunniest day was on the 23rd with 15.0h. There were only 2 sunless days, on the 8th and 11th with another 3 having <1.0 h. The last 17 days were the sunniest with 172.8 h that was 75% of the total.
For the third consecutive month temperatures were above average. For rainfall it was the fourth consecutive month below average despite some heavy accumulations elsewhere.
The monthly mean of 14.4C ranked 8th highest and was +0.9C on the average. Although cooler than 2003 (15.0C) it was the warmest previously since 1993. The mean minimum of 10.8C (+0.8) ranked 3rd and only lower than June 2003 (11.3C), highest on record, and equal to 1982 (10.8C). With cloud filled high-pressure and low-pressure systems predominating, nights were mostly cloudy preventing much radiative cooling. An exception was the night of the 18/19th with a minimum of 5.8C and 3.4C on the grass, both lowest of the month. Maximum temperatures were above average, with 18.0C (+0.9) ranking 8th highest, but the absolute maximum of 23.6C on the 14th was -1.4C of it's average. The best spell of maximums was between the 13th and 16th, but failed to make 4 consecutive days of 20C, or more, as the 15th reached only 18.0C. The 7th saw an isolated 20.3C bringing the total of days with 20C, or more, to 4.
Rainfall was 52.3 mm 71% of average and 79% of the 30-y 1971-2000 average. It was drier than Junes of 2002 and 2003, but wetter than 2000 and 2001. To the 18th the total was only 8.5 mm and continued on the dry spell of May. Most of the rainfall, 43.8 mm (84%), fell over the last 13 days. But this was nothing like the large falls experienced elsewhere. There were no heavy 24-h falls, the wettest was on the 29th having 9.4 mm. There were 9 (-2.2) completely dry days with 17 (+2.0) rain days. Wet days were 11 (+0.6) while those with 5 mm, or more, totalled 4 (-0.7).
 "Graphic of PE and PWB up to 18 June 2004."){kind=small}
Evaporation rates were moderately high through the month. Up to the 18th potential evapotranspiration (PE) was 40.4 mm. This ran the negative potential water balance (PWB) of -7.2 mm in May into the -16.7 mm of June, a total of -39.1 mm. Soil moisture on 6 June was 40.4 litres per sq. m (of 10 cm depth) this falling to 34.2 litres per sq. m on the 15th, almost as low as the 33.1 litres per sq. m seen on 28 August 2003. Garden plants and crops needed to be irrigated and vegetation on roadside verges and around rocky outcrops turned yellow. There was no wilting ; "Graph showing net primary production of the grass ecosystem at the weather station."){kind=small}
seen on deeply rooted mature trees, but the growth of shallow rooted grass was slowed, being limited by moisture. By the end of the month further rainfall only partially restored the water balance to -16.7 mm. But soil moisture had increased a little to 36.7 litres per sq. m by the 28th. Grass quickly turned greener, but growth was still limited. The first 6 months of the year, however, with 423.5 mm rainfall, shows a positive water balance of 384.4 mm.
Thunder was heard on the 7th; there were no hail falls.
Sunshine recorded at RAF Valley was 173.6 h which was only 86% of average. The sunniest day was on the 25th with 15.5h with another 5 days having >10 h.. While there were no sunless days 6 saw <2 h.
A very dull and cloudy month with few sunny days. There were 140.5h of sunshine recorded at RAF Valley which was 75% of average (72% of the 30y average) lowest since 1957 ranking 5th. The sunniest day was on the 5th with 13.1h and only 4 others saw more 10, or more, hours. These were 13th with 10.7h; 18th with 12.2h; 23rd with 11.2h and the 31st with 11.7h. There were 5 sunless days with another 4 having less than 1h. The five days from the 24th to 29th saw 0.0, 0.0, 0.1, 1.5, and 0.1h.
After 3 warmer than average months July was cooler with the mean 14.9C almost a degree (-0.9) below average. It was lowest since 2002 (14.7C) ranking 9th since before 1979. The mean maximum 18.1C (-1.3) was also lowest since 2002. The warmest day was the 29th with a temperature of 21.4C, but this was lowest since 1998 ranking 4th since before 1979 and was a massive 4.3C below average. The coolest day was on the 8th with 13.5C (-1.2). Even the mean minimum of 11.7C was -0.5 below average. There were no really warm nights with the highest minimum 14.5C seen on the 28th. But there were few cold nights, only 4 went below 10C, with the lowest 8.1C (-0.1) on the 5th which also had the lowest grass minimum of 5.2C (-0.4). There were 9 days spread throughout the month on which the maximum reached 20C, or more, with 2 pairs consecutive on the 20/21st and 28/29th. The temperature of the soil at 30 cm had a mean of 16.7C (-0.8C) and was lowest since 1996.
If the above were not bad enough the rainfall of 82.2 mm was 147% of average. It was the wettest July since 1992 and ranked 27th wettest since before 1928. The wettest day was on the 16th with 18.3 mm. Rain days (0.2 mm, or more) totalled 19 (+4.9) while there were 13 wet days (1.0 mm, or more) and 5 days had 5 mm, or more (+1.0). But it was not all bad as there were 7 (-0.6) dry days most of them were sunny too!
Thunder was heard on the 6th for about an hour from 2220 GMT and there were some ice pellets fell on the 8th. The mean wind speed, recorded at Valley, was 11.8 mph with the windiest day having 18.6 mph on the 8th. The wind strength was generally light to moderate but became fresh to strong on the 8th when there was a maximum gust of 42 mph. The wind at 09 GMT here was mostly from the S to NW direction (21 days).
; "Click for graphic of monthly rainfall accumulated January to August."){kind=small}
It was a wet month having 138.6 mm, the wettest August since 1992 (149.2 mm). It was wetter than August 2000 (132.4 mm) and brought the total for the year up to 688.1 mm, not far short of that in 2000 (718.2 mm) that went on to be the wettest year in Llansadwrn on record since 1928 1 . This year ranked 9th wettest, but 1956 and 1957 each had more than 200 mm (more than 8 inches). The highest recorded here was 230.4 mm (more than 9 inches) at Gadlys Cottage in 1957.  "Graphic of August rainfall anomalies at Llansadwrn."){kind=small}
The month was in complete contrast to last year that had only 16.8 mm while only 9.2 mm was recorded in 1995. Comparison with different averages reveals a further contrast. August was 199% of the average of the last decade (1994-2003) and 172% of the 30-y climatological average (1971-2000). Against the long-term average (1928-2003) it was only 155%. The wettest day was on the 16th when 20.6 mm fell, but there were 10 days (+5.0) with 5 mm, or more, while 5 of these were over 10 mm. Rain days were 23 (+9.2) and wet days 16 (+5.6). Rainfall duration (measured >0.1 mm per hour) was 60.5h.
 "Graphic of August mean temperature anomalies at Llansadwrn."){kind=small}
All temperatures were above average. The mean of 17.0C was +0.9 of the 10-y average but +1.7 of the 1971-2000 average. It equalled that of 2003 and was highest since 1997. The graphic shows the mean temperature anomalies (difference from the 1979-2004 mean). The largest positive anomaly was in August 1995 [+3.1C] while the largest negative anomaly was in 1986 [-2.4C]. While there is a just discernible upward trend in these data, the plotted regression line (dotted) is not statistically significant.
The mean minimum was 13.4C that was +2.0C of the 30-y average while the mean maximum of 20.6C was +1.3. The highest maximum was 27.7C (+1.3) on the 2nd while 26.4C occurred on the 1st. The lowest maximum of 13.5C was on the 20th. The 2nd saw the highest minimum of 17.4C. There were only 3 days <10C; the lowest 7.7C on the 21st, 9.6C on the 22nd and 8.3C on the 31st. The lowest grass minimum 4.8C was seen on the 31st.
It was a very dull month with poor amounts of sunshine. RAF Valley reported 155.6 h of sunshine only 78% of the 10-y average. It was the dullest August since 1985 (153.5 h) ranking 12th lowest since before 1946. The sunniest day did have 11.5 h on the 7th and the only other day over 10 h was the 1st with 11.3 h. But there were no sunless days and only 3 recorded <1 h, so most days did see some sunshine.
It was a fairly humid month with an average of 89% recorded at 09 GMT. Although wind speeds were a little above average, and temperatures above average, rates of evaporation were below average. The Piche evaporimeter showed 32.1 ml (-8.2) and the lysimeter PE was 48.6 mm (-4.5). There was a water balance of 90.0 mm.
Thunder was heard on 4 days and was +2.4 of the average.
1: An analysis of autumn rainfall 1928-2000
A dry and sunny beginning that turned very wet, dull and cooler on the 10th lasting to the month's end
It was a very wet and dull month overall. Although the first 9 days received only 2.5 mm of rain the total for the month was 165.8 mm, over 84.2h duration, some (166%) of average. The long-term average was similar but compared with the 1971-2000 climatological average it [180%]. It was wetter than last September that had 159.7 mm and was wettest since 1999 that had 174.3 mm. Before then it is necessary to look back to 1976 when, following the dry summer, 180 mm fell. It was even wetter than September 2000, with 139 mm, that was the wettest year here on record. Since 1928 it ranks the 9th wettest September. The wettest ; "Click for graphic of monthly rainfall accumulated January to September."){kind=small}
was 220.7 mm seen in 1935. Interestingly that year went on to have a wet October 208 mm and a wet November 160 mm, but December was a bit drier with 58 mm! All this rain in the month brought the total for the year to 854 mm just a few mm short of the total in 2000. Will 2004 rival the record breaking 2000?
The wettest day was on the 12th with 30.0 mm, it was the 3rd of 3 days that in in all had 69.4 mm. Other very wet days were on the 16/17th with 34.5 mm; the 19th with 15.9 mm and the 29th with 12.9 mm. There were in all 13 wet days (1.0 mm, or more) close to the average but 10 of them had 5.0 mm, or more, and this was 2.9 days more than average. This means that the month had heavier falls than usual. It is seen also in the number of rain days 20 (0.2 mm, or more) that were 4.1 days less than average, and the number of dry days 5 (-4.8).
Evaporation was below average. As measured by the Piché evaporimeter evaporation 33.9 mls was -4.7 of average. Potential evapotranspiration (PE) measured by lysimeter was 29.6 mm and this was -7.1 of average. The potential water balance (PWB) was 135.7 mm this a massive +73.5 mm.
The beginning of the month was sunniest. At RAF Valley more than 10 h of sunshine were recorded on the 5 days of the 1st and 6 - 9th. The sunniest was 12.2 h on the 7th but the 8th was not far behind with 12.1 h. The remainder of the month was poor for sunshine and finished with 131.4 h. This was just 95% of the average of the last 5 years but did poorly against the 10-year average 86% and 30-year average 93%. It was the dullest September since 1968 ranking 30th.
 "Graphic of September mean minimum temperature anomalies at Llansadwrn."){kind=small}
The monthly mean temperature was 14.4C and was modestly (+0.4) of the 10-year average but a large [+1.0] of the 1970-2000 climatological average. Once again it was the minimums that were highest and averaging 11.5C were (+0.9) and [+1.8]. There have now been 8 consecutive Septembers with above average minimum temperatures. Although there were 5 maximums at the beginning of the month, highest 24.6C (+4.8), the remainder of the month was rather cooler. The lowest maximum on the 21st was 13.5C but this was (+3.4) higherer than usual. The lowest minimum was 7.4C on the 15th (+4.1) much higher than usual while the lowest grass minimum 4.9C on the 25th was also (+4.1).
It was a windy month with 5 days of gales, the average for October is about 2.
 "October rainfall totals in Llansadwrn 1928-2004."){kind=small}
 "October rainfall anomalies at Llansadwrn: Differences are from the 1928-2004 average."){kind=small}
With 246.2 mm (9.7 inches) it was the 2nd wettest October on record in Llansadwrn and wettest since 1967 that had 257.9 mm. It was the 7th October to have 200 mm, or more, well spread out since 1928. There is, as yet, no evidence of a climate change effect in these October monthly data. Look at 1935 and 1938 for comparison with 2000 and 2004, and the larger falls seen in 1954 and 1967. It was the third largest fall, however, of ANY month and coming 3rd to the 250.5 mm that fell in November 2000, the wettest year on record in Llansadwrn.
The wettest day was on the 22nd having 86.0 mm, the largest daily fall recorded at this station. This amount fell far short of the Llansadwrn record of 137 mm on 10th August 1957 that fell in 3 hours during a thunderstorm, one of the heaviest falls recorded in the British Isles. The 86 mm followed 3 days 19 - 21st of rain that totalled 47.5 mm. In the week 18 -24th total rainfall was 152.5 mm (6.0 inches). Falling on already moist soil runoff was large and this quickly led to extensive flooding around Llansadwrn, and nearby Beaumaris, where there was much damage to property (see Diary entry for more information about other areas of Anglesey and North Wales that were affected). During the month there were 10 days (+2.3) had 5 mm, or more, and 9 of them saw more than 10 mm. So that there were a large number of heavy falls. There were 19 days (+2.7) wet days with 1.0 mm, or more and 21 days (+1.1) with 0.2 mm, or more. There were 4 (-4.3) completely dry days 8 - 11th but these followed 2 wet days on the 3/4th that had a total of 40.5 mm.
Evaporation PE (Potential Evapotranspiration) 26.7 mm by lysimeter and 28.2 mm by Piche Evaporimeter for the month was insignificant compared with the huge PWB (Potential Water Balance) of 219.5 mm.
It was another fairly dull month with 97.2 h of sunshine recorded at RAF Valley. This was 88% of the 10-y average but 91% of the 30-y average. The sunniest day was on the 8th having 9.9h. There were 5 sunless days and another 3 saw 1h, or less. It was the dullest October since 1980 ranking 21st.
Temperatures were close to the 30-y 1970-1990 averages with the mean 10.5C (-0.1). But they were lower than has been experienced over the last decade when the mean was (-0.8C). Both maximum 13.5C (-0.8) and minimum 7.5C (-0.7) were similar. Warm days were at a premium and at the beginning of the month 15.6C was seen on the 3rd and 15.9C on the 7th. But the highest were at the end of the month; 16.7C the warmest day on the 28th and 16.0C on the 29th the only days making 16C, or more. The highest maximum was 3.1C below average. All the overnight minimum temperatures were below 10C, again the highest 9.9C was at the end of the month on the 30th. The lowest minimum was 4.2C on the 26th while the lowest grass minimum was 0.6C on the 14th. The mean soil temperature at 30 cm depth was 11.7C (-0.6).
There were 4 days with thunder, 3.5 days more than average. There were ice pellets on the 7th and a heavy fall of large hail (more than 7 mm diameter) after midnight on the 16th. Both of these events were associated with thunder storms. There were 5 very windy days, with 2 gales experienced at the weather station on the 4th and 21st.
A mild fairly dry month that was cold and wet in the middle.
 "Anglesey sunshine anomalies in Novembers 1946-2004."){kind=small}
A very dull month with record low sunshine recorded at RAF Valley. With only 27.7 h of sunshine (48% of average) made it the dullest November since records began in 1946. The were 14 days with no sunshine at all and another 9 days had less than 1 h. The sunniest day, and only 1 seeing more than 5h, was on the 10th having 5.8h. The mid 1960's and late 1980's saw sunny Novembers, but since 1990 they have been increasingly gloomy.
The 92.7 mm rainfall was 68% of the average of the last decade and 74% of the long-term and 30-y averages. It was the 20th driest November on record since 1928. The 4 dry days were close to average and there were 23 (+0.9) rain days. Wet days were 17 and close to average while days with 5 mm, or more, were 7 (-1.9). The wettest day, and only day exceeding 10 mm, was on the 18th and had 19.1 mm. It was wettest since 2000, that had 153.6 mm, and brought the total amount of rain for the year up to 1192.8 mm, the 6th largest accumulation to the end of November. Rainfall for the autumn (September to November) totalled 504.7 mm some 153% of average.
Temperatures continued the trend of above average minimums partly reflecting the cloudiness (86%). Lacking many clear nights there were only 4 ground frosts (4 below average) and the lowest (-2.2C on the 29th) was above average (+0.7). The mean minimum of 6.3C was +0.6 but was a larger +1.1 when based on the 30-y 1971-2000 average, an indication of a warming trend in recent years. Lack of sunshine contributed to low maximum temperatures with the mean 10.4C -0.5 but +0.4 on the 30-y average. The highest maximum was 12.9C on the 4th and this was -2.6 of the average.
The cold spell 18 - 20th saw above average sleet and snow (+2.5) but the 2 days that saw hail was -2.5 of average. There was no thunder heard and no gales in the month.
Briefly cold in the second half of the month with a white Christmas.
The month was mostly mild with the mean temperature 6.3C (+0.7) and close to the 30-y average [+0.8]. It was warmest since 1998 (6.7C) and ranked 6th warmest since 1979. Mean of the maximum and minimum temperatures 8.7C and 3.9C respectively were similarly (+0.7) and [+0.8]. The highest maximum on both the 8th and 14th was, however, only 10.9C and lowest since 1990 and -2.1C of the average. It was one of the 8th coolest observed in December since 1979. The lowest minimum was -1.5C on the 20th and was the only day to have airfrost, -1.9 of the average. There were 17 days with ground frost, this was +2.8 of the average. The mean temperature of the soil at 30 cm depth was 6.9C and +0.6 of average. Only 6 days saw a temperature of 5.6C, or less, this being the temperature regarded as necessary for plant growth. Grass continued to grow through the month and there were several plants still in flower in the garden.
Rainfall was 127.2 mm 104% of average but 112% of the long-term average. It was drier than December 2003 that had 136.5 mm and 2000 that had 153.6 mm and ranked 28th. There were 6 dry days (+1.0) and 19 (-1.4) rain days (0.2 mm, or more). There were 17 (+0.8) wet days (1.0 mm, or more) while those having 5 mm, or more, were average. The wettest day by far was the 21st that had 31.9 mm. The 15th with 12.8 mm, the 27th with 14.0 mm and the 30th with 14.6 mm were the only other days with 10 mm, or more. Soil moisture levels continued close to saturation point so that when there was significant rainfall standing water readily occurred.
There were 45.0 h of sunshine recorded at RAF Valley and was 84% of the 10-y average. There were 13 sunless days and another 6 saw less than 1 h. The total sunshine was boosted by three sunny days, the 7th and 19th had 5.9 h and were the sunniest but the 15th was not far behind with 5.8 h. Other notable sunny days were the 2nd (4.7 h), 21st (4.3) and 26th (4.8). These 6 days comprised 31.4 h and were 70% of the month's total.
The 20th saw heavy thunder and lightning, snow pellets, ice pellets and sleet and snow. Christmas day (25) saw snow pellets and snow that gave a covering of almost 1 cm at 09 GMT in the morning. There were ice pellets seen in the evening as well. Just after midnight on Boxing Day following heavy thunder and lightning there was a moderate fall of 16 mm diameter hailstones. In total hail was observed on 6 days in the month, this +0.8 of average. The 2 days with thunder was +1.2 of the average for the month.
Overall it was a wet year and with a total of 1320.0 mm it was the wettest since 2000 that had 1483.9 mm, the wettest year on record. This year ranked 5th wettest since 1928 and at the end of October, when a total of 1100 mm had accumulated, looked in a position to challenge for that dubious title. But a drier than ; "The wettest years in Llansadwrn since records began in 1928."){kind=small}
average November (92.7 mm, 68%) and a near average December (127.2 mm, 104%) ended the race. January, August, September and October were the wettest months. October with 246.2 mm, 208% of average, was the wettest. It also had the wettest day when 86.0 mm fell on the 22nd causing extensive flooding (see Diary entry for more information). It was the largest fall recorded at this station, but fell far short of the Llansadwrn record of 137 mm on 10th August 1957 that fell in 3 hours during a thunderstorm. In contrast March to July were drier than average, May was the driest (47.0 mm, 72%) while April (55.1 mm) was drier than average (68%). June too with 52.3 mm was 72% of average. An 18-day spell between the 9th and 26th in May qualified as an absolute drought (according to the old official definition, no longer used, of a minimum of 15 days none credited with 0.2 mm, or more). The last absolute drought in May occurred in 1980, also 18 days. There were 89 (-23) completely dry days in the year, a little better than 2000 that had 84. There were 223 (+17) rain days (0.2 mm, or more) and 167 (+10) wet days (1.0 mm, or more). Days with 5 mm, or more were 80 (+5).
It was a dull year with 1404.6 hours of bright sunshine recorded at RAF Valley. This was 85% of the 10-y average and similarly 87% of the 1971-2000 average. It was the 2nd dullest year in records back to 1947.  "Annual sunshine anomaly at Valley, Anglesey, 1947-2004."){kind=small}
It is necessary to look back to 1958 with 1379.4 hours for the dullest. November with only 27.2 hours had the least sunshine lowest recorded back to 1946. January, however, with 44.1 hours was the sunniest since 1980 and was 142% of average while December with 45.0 hours was 84% of average. May with 229.3 hours was the sunniest month of the year, but this was very close to the average so was not exceptional at all. It was a poor summer for sunshine; June managed 173.6 hours, but this was only 86% of average. August with 155.6 h of sunshine (78%) had the least since 1958 (153.5 h).
 "Plot of annual mean temperatures 1979-2004."){kind=small}
 "Annual mean temperature anomaly 1979-2004."){kind=small}
The mean temperature was 10.4C (+0.1) but was +0.5 when based on the 1971-2000 average. It was the lowest since 2001 (9.9C), but since records started in 1979 ranked 9th highest. The highest mean was 22.5C on the 2 August; the lowest was 0.6C on 26 February. There were 197 days with a mean of 10C, or more. These were most since 1999 (202) and ranked 2nd highest since 1979. There were 62 days with 15C, or more but only 2 had 20C, or more (not unusual here). The histogram shows the mean plotted over the 26-years of station records. Fitted to a linear regression the temperature increases over the period by about 1C an indication the warming that has taken place in recent years. The other graphic shows the mean anomaly (differences from the 1979 -2004 mean) over the same period. Since 1989 there have been 8 years with an anomaly of +0.5C, or more, 2004 with +4.5C just did not quite make it.
The mean minimum temperature 7.4C showed the greatest anomaly (+0.3) and +1.0 on the 30-y average. While these data indicate a warming trend in recent years, a contributing factor this year was the large amount of cloud cover at night acting as a blanket and minimising radiative cooling at night. The highest minimum was 17.4C (+0.2) on the 2 August while the lowest of -2.1C (+1.8) was on the 29 January. There were 14 airfrosts, fewer than in 2003 that had 21, twice the fewest on record (7) recorded in 2002 and ranked 6th lowest since 1979. The year was airfrost-free from 12 March to 19 December. Days with minimums less than 5C were 102 and less than 10C were 263. There were 67 ground frosts, less than in 2003 (82), but more than in 2002 (57). The lowest was -6.5C recorded on 29 January. It was ground frost-free from 18 April to 18 November.
Maximum temperatures were close to the averages. The mean maximum was 13.4C (-0.1) and was on the 1971-2000 average. The highest 27.7C (-0.1) was on 2 August while the lowest was 2.2C (+0.4) on 26 February. There were 274 days on which the maximum was 10C, or more, and 144 saw 15C, or more. The number of days with 20C, or more, were 35 lowest since 2002 (55) and only 2 days reached 25C, or more .
Thunder was heard on 13 days and was the most since 1983 (16) and 2000 (12). There were 35 days with hail (all types) and was the most since 2000 (45) and ranked 4th highest. These included 3 days with hail 5 mm, or more diameter. On 25 February there was a fall of 10 mm diameter conical-shaped snow pellets; on 16th October hail of 7 mm diameter and on 26 December stones of 16 mm diameter. Sleet or snow fell on 15 days, the most since 2001 (18). After 2 years with no lying snow to record 2004 saw 6 days. This was the most since 1996 (7). There were gales on 17 days.
Llansadwrn (Anglesey): Monthly weather data for 2004.
(~ Based on the 1994-03 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 8.0 7.9 10.4 12.6 16.0 18.0 18.1 20.6 17.2 13.5 10.4 8.7 13.4
Mean min 3.3 3.2 3.6 6.2 8.0 10.8 11.7 13.4 11.5 7.5 6.3 3.9 7.4
Mean 5.7 5.6 7.0 9.4 12.0 14.4 14.9 17.0 14.4 10.5 8.4 6.3 10.4
Anomaly~ +0.3 -0.2 -0.1 +0.6 +0.3 +0.9 -0.9 +0.9 +0.4 -0.8 +0.1 +0.7 +0.1
High max 11.0 12.5 19.1 19.8 22.7 23.6 21.4 27.7 24.6 16.7 12.9 10.9 27.7
Date 7 3 31 24 27 14 29 2 8 28 4 8,14 2 Aug
Low max 4.3 2.2 5.6 8.8 9.8 13.7 13.5 13.5 13.5 10.3 6.1 4.8 2.2
Date 26,27 26 11 9,15 8 24 8 20 21 20 18 19 26 Feb
High min 9.0 10.2 8.7 9.5 13.0 14.2 14.5 17.4 15.0 9.9 10.5 9.1 17.4
Date 8 4 16 24 28 10 28 2 4 30 17 23 2 Aug
Low min -2.1 -1.1 -2.0 2.0 3.5 5.8 8.1 7.7 7.4 4.2 1 -1.5 -2.1
Date 29 26 2 17 5 19 5 21 15 26 20 20 29 Jan
Grass min -6.5 -5.0 -5.9 -0.2 0.6 3.4 5.2 4.8 4.9 0.6 -2.2 -5.2 -6.5
Date 29 9 1 6,17 5 19 5 31 25 14 29 20 29 Jan
Atmospheric moisture means
RH (%) 92 88 85 83 83 83 85 89 88 90 92 93 88
Dew point (C) 4.2 3.2 3.9 6.6 9.3 11.5 12.3 14.3 11.9 8.2 7.8 5.3 8.2
Soil temperatures (C)
5 cm 4.5 4.4 5.8 9.7 14.1 16.6 16.7 17.4 14.3 9.7 8.2 5.4 10.6
10 cm 4.9 4.8 5.8 9.4 13.0 15.7 15.8 17.1 14.3 10.1 8.5 5.8 10.4
20 cm 5.4 5.6 6.3 9.8 13.4 15.9 15.9 17.6 15.0 11.0 9.2 6.4 11.0
30 cm 5.6 6.1 6.7 10.4 13.9 16.1 16.7 18.1 15.7 11.7 9.6 6.9 11.5
50 cm 6.3 6.7 7.0 10.3 13.6 15.8 16.3 17.8 16.0 12.4 10.2 7.7 11.7
100 cm 7.3 7.4 7.3 9.8 12.5 14.7 15.3 16.7 15.7 13.0 10.9 8.8 11.6
Rainfall (mm)
Rain tot 139.9 122.5 55.1 50.5 47.0 52.3 82.2 138.6 165.8 246.2 92.7 127.2 1320.0
Rain % ave~ 144 114 73 68 72 72 147 199 166 208 68 104 120
Days, dry 1 11 11 10 16 9 7 5 5 4 4 6 89
Days >=0.2 26 15 14 16 10 17 19 23 20 21 23 19 223
Days >=1.0 19 13 10 12 7 11 13 16 13 19 17 17 167
Days >=5.0 7 8 3 3 4 4 5 10 10 10 7 9 80
Max fall 27.6 33.4 13.8 11.4 20.7 9.4 18.3 20.3 30.0 86.0 19.1 31.9 86.0
Date 30 2 18 17 3 29 16 16 12 22 18 21 22 Oct
Evaporation
Piche (mls) 22.0 30.0 36.4 40.3 43.1 41.1 42.3 32.1 33.9 27.7 18.7 18.9 386.5
Lysimeter (mm) -1.9 2.8 13.0 34.3 54.3 69.0 53.3 48.6 29.6 26.7 8.2 7.3 345.2
Weather (days)
Air frost 3 5 5 0 0 0 0 0 0 0 0 1 14
Ground fr 15 16 13 2 0 0 0 0 0 0 4 17 67
Sl/snow 3 4 3 0 0 0 0 0 0 0 3 2 15
Sn lying 0 4 1 0 0 0 0 0 0 0 0 1 6
Thunder 0 1 0 0 0 1 1 4 0 4 0 2 13
Hail <5 mm 8 5 4 5 1 0 1 0 0 1 2 5 32
Hail >=5 mm 0 1 0 0 0 0 0 0 0 1 0 1 3
Fog at 09h 0 0 1 0 1 0 0 2 0 1 1 0 6
Gales 3 3 3 0 0 0 0 0 5 1 0 2 17
Wind direction at 09h (days)
N 0 2 4 2 6 4 3 1 4 2 6 3 37
NE 3 7 1 3 2 1 4 3 2 1 1 2 30
E 0 3 5 1 0 0 0 2 1 7 1 1 21
SE 2 0 2 2 2 0 0 4 2 5 0 0 19
S 3 4 7 8 6 9 5 5 5 5 4 2 63
SW 7 5 5 5 2 5 8 5 5 4 6 10 67
W 10 2 2 3 4 6 3 3 5 5 6 5 54
NW 5 2 3 3 4 5 5 4 4 1 6 5 47
Calm 1 4 2 3 5 0 3 4 2 1 0 3 28
Autographic records of rainfall and frost duration (h)
Rain 96.0 59.6 34.4 46.5 39.9 39.8 57.0 60.5 84.2 130.8 94.2 73.6 816.5
Frost 16.8 27.8 34.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.4 85.3
Cloud cover at 09 GMT
Mean (%) 82 72 75 75 78 83 85 78 72 71 86 74 78
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I am grateful to Robert Jones, Observer/ Admin. Officer at the Met Office RAF Valley, for providing data quoted from Valley.
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These pages are designed and written by Donald Perkins: Copyright © 2004 Page first dated 2 February 2004 http://www.llansadwrn-wx.co.uk
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