Llansadwrn (Anglesey) Weather
Diary summary 1998
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Llansadwrn (Anglesey) Weather
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A mild month with rainfall about average (106%).
Gales at the beginning of the month, on the 4th Valley (Anglesey) recorded a maximum gust of 66 kt (76 mph).
6th: Thunder heard at 2217 GMT. At 2245 there was a squally shower accompanied by ice pellets (H4). There were further showers of ice pellets in the night.
7th: Frequent showers of ice pellets (H4) and hail (H5) in the afternoon.
8-11th: Remarkable warm spell with temperatures exceeding those of any January in my records (20 years). Maximum temperatures of 12.0C on 8th, 12.5C on 9th, 16.5C on 10th and 14.6C on 11th were warm for any January. A maximum of 16.5C (the highest of the month and in any January at this site) occurred at 2230 GMT on the 10th. A low relative humidity of 46% occurred at about 01 GMT on the 11th, dew point was 4.3 C. There was a SE'ly Föhn wind blowing from the Snowdonia mountains at the time. Winds were force 5-6 most of the day. Evaporation from the Piche evaporimeter in the screen was 6.7 mls in the 24-hour period to 09 GMT on the 11th. This turned out to be the maximum 24-hour value in 1998. Minimum temperatures were 10.9C on the 10th and 13.4C on the 11th. The grass minimum on the 11th was 10.0C.
13th: The wettest day of the month with 11.9 mm and 12.4 h duration. The longest rainfall duration, however, was on the 18th (14.1 h) with 7.7 mm rainfall.
27th: The lowest grass minimum of the month was -6.9C which was the lowest of the year.
28th: The lowest air minimum of the month was -2.2C.
Differences between previous absolute values (which have all occurred in recent years) were maximum +2.2C on 1997; minimum +2.4C on 1990; mean +3.3C on 1996 and grass minimum +0.5C on 1990.
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The relatively warm weather continued this month. It was the warmest February in my records. The mean 7.9C exceeded that of 1990 by 0.8C.
Rainfall (53.1 mm) was the driest February since 1993 (30.8 mm) and was only the 25th driest on record in Llansadwrn since 1928. The last decade has been the wettest of the 7 decades giving a COL average of 54%. The long-term average, however, was 72% and the 1961-90 average 80%.
1st: The coldest day of the month, minimum -0.2C and only 4.0 h frost duration. The lowest grass minimum of -5.3C was also on this day.
6th: Heavy rain shower and hail (H5) in the evening around 2000 GMT
10-25th: A warm spell of 16 days when the maximum was 10C or more. The absolute maximum for the month of 15.0C occurred on the 15th.
15/16th: A moderate fall of beige coloured dust (probably originating from the Sahara) was seen at 09 GMT on the 16th. It was covering most flat surfaces, including my car, and concentrated at the edges of greenhouse glass and gutters. Only 0.1 mm rainfall was recorded from the 15th. Winds were mainly S-SW and the lowest relative humidity of 56% was recorded together with a maximum of 15.0C between 1300-1400 GMT. It is probable that the dust was deposited about this time with a few spots of rain.
18th: There were ice pellets melting on the ground at 0900 GMT and was followed by frequent showers of snow pellets.
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Again a warm month, the warmest March on my 20-year record. The mean minimum was 5.6C (+1.6C) warmer than 1990 (5.1C). The mean of 8.4C was warmer than both 1990 and 1997 (both 8.3C). There were no air frosts in the month (-1.8 average), but there were 8 ground frosts (-0.9 average). Ice pellets fell on the 1st, 4th and 5th. There was no thunder heard in the month (-0.5 days of average). It was a wet month with 152.4 mm (173% of average), the 4th wettest in records since 1928. The wettest March was in 1981 with 205.9 mm. Rainfall this March was concentrated in three 48-hour periods that comprised 81% of the total for the month.
2/3rd: Rainfall 53.1 mm
5/6th: Rainfall 29.6 mm
24/25th: Rainfall 41.6 mm
19th: Intense high pressure of 1044.9 mb, the highest of the year.
15-22nd: No measurable rain fell in this period. There were only 14 rain days (0.2 mm or more) in the month, -4.8 days of average.
31st: The highest maximum of the month 15.7C. Flower buds of bluebells were beginning to appear.
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April was a very wet month over many parts of the UK. Many areas had over 200% of average, some parts of central and NE England having more than 300% of average. Llansadwrn was comparatively dry with 88.3 mm (129% of average). There have been 16 wetter April's since 1928 and 5 of them with falls >100 mm. It was the coldest April here since 1989 and the fifth coolest on my 20-year record.
9-14th: A very showery period, I recorded 30 showers on the autographic raingauge, mostly ice precipitation. The most significant were:
12th: Moderate fall of ice pellets at 0608 GMT; 4-5 mm diameter snow pellets at 1520 GMT; a moderate/heavy fall of large conical hail (H5) at 1745 GMT which almost covered the ground.
13th: Snow pellets at 0735 GMT; snow at 0825 GMT; moderate/heavy ice pellets (H4) at 0827 GMT followed by frequent further snow showers.
14th: Ice pellets followed by snow from 1440-1600 GMT, but no accumulation on the ground. A further snowstorm from 1710-1830 GMT led to an accumulation of between 1-2 cm of lying snow. In a strong N-NE'ly wind the thermometer screen became filled with blown snow and a temperature of 0.0C recorded. An accurate digital thermometer, however, indicated a temperature of -0.9C during the storm. Ronaldsway (Isle of Man) reported 11 cm of lying snow and Moel y Crio in Flintshire up to 30 cm of level snow.
15th: Snow was still lying at 0630 GMT, but by 0900 GMT it had all melted so no lying snow was recorded!
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May was a dry month with only 25.3 mm of rain (42% of average). It was the driest month of the year and was the fifth driest May in records since 1928. Drier years were 1939 (19.0 mm); 1970 (22.9 mm); 1990 (22.8 mm) and 1991 (22.2 mm). Temperatures were above average with the mean maximum 17.1C (+0.8C) and mean minimum 8.9C (+1.6C).
4th: Lowest minimum of the month 5.0C was the warmest in May on my 20-year record.
13th: Highest maximum 24.8C was the third highest in 20 years of records.
14th: Thunderstorm from 0208 GMT for about 20 min and thunder heard again at 0640 GMT.
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In contrast to May, June was a very wet month (the wettest of the year) with a total of 182.9 mm (312% of average). Central, South and North Wales had over 300% of average rainfall. Llansadwrn was the third highest percentage listed in the Bulletin of the Climatological Observers Link No. 338 for June 1998. In terms of rainfall amount, however, it was placed 18th highest in the UK. It was the second largest rainfall in June in Llansadwrn since records began in 1928. Only 1935 with 196 mm was wetter, but this included a day with 91 mm! This June 7 days contributed most rain. 1/2nd (31 mm); 8th (23.1 mm); 13th (28.6 mm); 17th (31.5 mm) and 22/23rd (28.9 mm). Some local flooding of fields and roads occurred, especially on the 23/24th. The mean maximum temperature of 16.5C was -1.4C of average while the mean minimum of 10.3C was +0.7C of average.
1st: 1115 GMT, thunder preceded by heavy rain.
6th: Thunder at 0535 GMT.
12th: Lowest minimum of the month 4.0C.
19th: Only 1 of 2 days with a maximum of 20C, or more. Maximum 23.3C.
20th: Highest maximum of the month 24.1C.
27th: Ice pellets in a heavy shower at 05 GMT.
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The month began mainly dry which, after the very wet June, was very welcome. The first 2 days were sunny but then settled into a mainly cloudy regime. It remained a cool, unsettled and disappointing month. Rainfall was 62.8 mm (103% of average) but only 85% of the 1961-90 average. Temperatures were below average with the mean maximum of 17.5C (-2.4C). The absolute maximum of 20.1C on the 16th was the lowest in July on my 20-year record. The previous low was 20.4C in July 1988. With large amounts of cloud cover nights did not cool very much, the mean minimum was 11.8C (-0.1C of average). The lowest minimum was 8.8C on the 13th. There was no thunder or hail during the month.
22nd: 14.6 mm rainfall, the most in a day this July.
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Temperatures and rainfall were about average for August. The mean maximum was 19.2C (-0.5C) and the mean minimum 11.8C (-0.2). Rainfall of 69.9 mm was 95% of average but only 77% of the 1961-90 average.
9th: Maximum of 27.9C was the highest of the year. Largest temperature range of the year (13.4C) beating that on 13 May by 0.1C.
23rd: Rain or drizzle most of the day with thunder from 1608 GMT and lightning strikes nearby at 1619 GMT. Spells of heavy rain resulting in 13.1 mm, the largest fall in the month. Further thunder heard at 1815 GMT.
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The beginning of the month was rather wet and on the 10-12th turned cool giving the impression that summer was over. Pressure increased between 20-25th (highest 1035.2 mb on the 21st) giving us an 'Indian summer'. Maximum temperatures were 20C or more on the 6 days (highest 23.5C on the 20th) with much sunshine (Valley, Anglesey 10.3 h on the 21st). In terms of the mean temperature 14.7C (+1.3C) and mean minimum 11.1C (+1.4C) it was the warmest September in my records at Llansadwrn. The mean maximum of 18.2C (+1.2C) was equal to that of 1996 and was only exceeded by that in 1991 by 0.2C. Rainfall was 89.9 mm (120% of average), 98% of the 1961-90 average. There were 8 days with falls of 5 mm or more.
12th: Rainfall 13.5 mm, the largest fall in a day this month. ice pellets fell together with heavy rain during the evening.
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A wet and stormy month with 6 days of gales. Valley, Anglesey recorded 8 days of gales, more than twice the average for October. Rainfall of 156.8 mm was 152% of average (136% of the 1961-90 average). There were 25 rain days (0.2 mm or more) +6.6 days of average; 22 wet days (1.0 mm or more); and 11 days with 5 mm or more (+3.6 days of average). Rainfall of 156.8 mm, the second largest monthly total of the year, was the wettest October since 1987 (198 mm) and the thirteenth wettest in records since 1928. Temperatures were near average with the mean maximum 13.5C (-0.4C) and mean minimum 7.7C (+0.1C).
16th: Earth tremor (2.6 on the Richter scale) largest since 2.9 tremor in 1994 but much smaller than the 5.4 we experienced on 19 July 1984.
16-28th: A very blustery end to the month with strong SW-NW gales on the 16th, 17th, 20-21st, 23rd and 27th. Valley recorded maximum gusts of 68 mph on the 20th and 66 mph on the 24th.
22nd: Highest maximum of the month 15.6C was the lowest on 20-year record. Previously the lowest was 16.0C in 1992.
29-30th: Frequent showers of ice pellets.
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Rainfall was 117.9 mm (106% of average) and 96% of the 1961-90 average. There were 22 rain days (0.2 mm or more) which were +1.5 days of the average. Temperatures were a little below average with mean maximum 9.9C (-0.5C of average) and mean minimum 4.5C (-0.2C of average). There was no air frost in the month (-0.2 days) but there were 14 ground frosts, which were above average (+4.8 days). There were 5 days of gales and 6 days when ice pellets fell (+3.6 days). Thunder was heard on 2 days (2-3rd).
8th: Highest maximum 15.4C during a mostly sunny day.
16th: Lowest minimum 1.0C also the lowest grass minimum of -3.0C.
22nd: The smallest temperature range of the year (0.4C). Maximum of 6.9C and minimum of 6.5C.
27th: 15.7 mm rainfall, most in a day this November.
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Temperature means were a little above average with a mean maximum of 9.2C (+1.4C) and a mean minimum of 4.2C (+1.3C). The total rainfall of 117.7 mm was almost the same as in November. It was near average, but because the soils have been at maximum water capacity for some weeks, even moderate falls have resulted in much runoff and local flooding. Several fields have had water standing in them and some local roads have suffered minor flooding from time to time. There were 3 days with air frost and 10 days with a ground frost.
24th: 16.0 mm rainfall, most in a day this month.
26th: A very stormy day with the S-SW wind reaching gale force 8 by noon. The pressure dropped to about 981 mb by 1700 GMT and it became increasingly windy (force 9-10) with strong gusts. Valley recorded a maximum gust of 78 mph. While not as severe as the Christmas Day storm of last year (1997), some minor structural damage occurred and several trees were brought down in the area. Unlike last year our electricity supply was unaffected!
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The overall impression of 1998 was that we had a wet year and a poor summer. It was in fact the wettest year with 1216 mm of rain since 1967, which had 1378 mm. It also had the most rain days with 233 of 0.2 mm or more, and wet days with 181 of 1.0 mm or more. It is interesting that this wet year has followed only 2 years after 1996 which was the driest for many years with 794 mm. June, usually one of our best summer months, was particularly wet (183 mm), it was the wettest month of the year and second wettest June in the records since 1928. Only June 1935 was wetter! The wettest days of the year were 2 March with 34.1 mm, 13 June with 28.6 mm and 17 June with 31.5 mm. It was, however, a mild year with only 9 air frosts (13 days below average) and was frost-free from 2 February to 5 December. The number of days of ground frosts (60) were only 6 below average. There were 33 days on which hail fell of less than 5 mm diameter. This was about twice the average. There were only 3 days on which hail fell of 5 mm or more. Thunder was heard on 9 days, 3 more than average. Sleet or snow was seen to fall on 7 days, 5 days less than average. There was no snow lying at the observation hour of 0900 GMT. The mean maximum temperature was 13.6C (+0.1 of average) and the mean minimum was 7.5C (+0.8 of average).
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Last updated: 28 March 1999. This page is maintained at http://www.llansadwrn-wx.co.uk
© 1998 - 1999 Donald Perkin. All Rights Reserved.