The author: Dr. Donald Perkins (FRMetS) making observations at the weather station but, sometimes, is out and about.

Llansadwrn (Anglesey) Weather

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Logo: Llansadwrn Weather - Melin Llynnon, Ynys Môn

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Times are GMT (UTC, Z). Observations at this station [ ] are 24-h 09-09 GMT, some others { } occasionally refer to other 24-h periods, extremes (first indications) are given in bold and are usually 21-21 GMT. When averages are referred to (.) compares with the last decade and [.] with the 30-y climatological average [currently 1971 - 2000]. All data are subject to verification and amendment.

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January 2009


Ice on the beach at Llanfairfechan. 1st: A bright and frosty New Year with just a little cloud in the sky and a light E'ly breeze. Overnight the air temperature had fallen to -4.1C and on the grass to -8.2C. There were small ice crystals on the ground together with frozen previous deposits. There was a thick frost deposit on the grass minimum thermometer and on fallen leaves while ice crystals in the shade had grown some more. Frost deposited measured from 1 hour before sunset to 09 GMT was a WE (water equivalent) of 0.26 mm; there was 0.1 mm in the copper rain gauge. Visibility was very good with some mist and or smoke in the bottom of Valleys. The afternoon was cloudier, but the sky cleared again during the evening when it turned frosty. {Scilly Is 8.3C, Sennybridge -8.4C, Aberdaron 6.9h} [Rain 0.0 mm; Max 4.6C; Min -4.1C; Grass -8.2C]
2nd: It was a clear night with frost adding to the crystal growth with 0.19 mm water equivalent deposited by morning. Just before dawn the sky was still clear, but then cloud encroached so and was overcast soon after 09 GMT. Pressure was 1031 mb with high 1037 mb over the N of Scotland. The morning stayed cloudy, but the sky cleared in the afternoon leaving a line of stratocumulus over the mountains. There was moderate haze imparting an orangy colour colour to the setting sun. Another clear frosty evening. [Rain 0.0 mm; Max 3.1C; Min -2.3C; Grass -6.8C]
3rd: Clear sky overnight with air (-2.6C) and ground frost (-7.9C) keeping the shaded grassy areas of the garden a frosty white, but there was little hoar frost to be seen on taller vegetation. Pressure was 1032 mb with the high centred over Wales, a sunny day with the temperature -2.3C (dewpoint -5.7C) at 09 GMT rising to 4.7C by afternoon. Visibility was very good and there was little or no wind so that chimney smoke rose vertically, or sometimes drifted from the NE. One or 2 bonfires were lit in Llansadwrn in the afternoon and this smoke drifted from the NW. Frost remained all day in the shade and washing hung out to dry froze as stiff as boards. Later some cloud was spotted in the west this encroaching slowly during the evening so that the sky was overcast by 2200 GMT, but not before the grass minimum temperature had fallen to -8.0C. {Fair Isle 7.0C, Braemar -10.7C, Aberdaron 7.7h} [Rain 0.0 mm; Max 4.7C; Min -2.6C; Grass -7.9C]
4th: Overcast at dawn and the temperature had risen to 1.5C, but did not rise any further during the day that kept cloudy and sunless. There was a little rain at 1215 GMT on a narrow band heading south ahead of a cold front, I could see no ice precipitation here, but it fell as snow above 1000 ft on the mountains giving a light covering at 2500 ft. Another cold day in the south of Britain, the highest temperatures being in the north. {South Uist 8.3C, Benson -9.0C, Sennybridge -8.6C, Valley 0.0h} [Rain 1.2 mm; Max 3.2C; Min -2.3C; Grass -8.0C]
Icicles forming in a stream at Nant-y-coed, Llanfairfechan. 5th: There was precipitation from 0100 to 0400 GMT with a rapid rise in temperature at 0200 GMT to a 24-h maximum of 3.2C. There were marks on the hailometer indicative of snow pellets, but whether or not there was snow as well was uncertain. There was more snow on the mountains with fresh snow lying generally above 2000 ft and as low as 1000 ft near Ogwen. Pressure 1024 mb was rising with the high 1030 mb situated off Aberdeen, Scotland. The sky had cleared sufficiently for the temperature on the grass to fall to -4.0C and there was a glaze of ice on concrete paths. It was a sunny morning with the sky continuing to clear, the afternoon was clear and sunny with frost returning before dusk. {Scilly Is 8.2C, Milford haven 4.5C, Altnaharra -8.2C,Sennybridge -6.5C, Valley 6.2h} [Rain 0.0 mm; Max 4.0C; Min -0.6C; Grass -4.0C]
6th: With high pressure 1030 mb over southern Britain and cold air from Europe the cold and icy weather persisted. Overnight frost deposition on the ground was a WE of 0.17 mm. Frost penetration into the soil had reached at least 10 cm with the thermometers reading -1.7C at 5 cm and -0.1C at 10 cm depth. The 20 cm was reading 0.8C and falling at lower depths with 5.8C at 100 cm. In 1963 frost penetrated far enough into the ground in Bangor to freeze water pipes entering houses that were without water as a result for several weeks. It was a bright morning with much cirrus cloud and altocumulus encroaching; the temperature struggled to reach 1.3C before starting to fall soon after 1300 GMT and was freezing again by 1500 GMT. [Rain mm; Max C; Min -5.0C; Grass -9.7C]

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Graph of daily mean temperature: © 2008 D.Perkins. Graph of daily maximum and minimum temperatures: © 2008 D.Perkins. Graph of soil temperature at 30 cm depth: © 2008 D.Perkins. Graph of daily rainfall: © 2008 D.Perkins. Histogram of monthly rainfall compared with the long-term average: © 2008 D.Perkins. Histogram of accumulated monthly rainfall with comparisons: © 2008 D.Perkins. Graph showing net yield of a mown grass ecosystem at the weather station. Red graph is total yield; Green graph is rate of growth: © 2008 D.Perkins. Comparison of annual grass production since 2004: © 2008 D.Perkins. Soil moisture percentage (% dry mass): © 2008 D.Perkins. Histogram of potential evapotranspiration and water balance: © 2008 D.Perkins. Graph of msl pressure at 0900 GMT: © 2008 D.Perkins. Daily solar radiation in Llansadwrn (midnight to midnight): © 2008 D.Perkins.


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Large [260 KB] NOAA 12 visible image at 1623 GMT on 8 April 2002 showing a cloud-free British Isles. Courtesy of Michael Wienzek ( A rare cloud-free image of the British Isles captured by the NOAA 12 satellite at 1623 GMT on 8 April 2002.

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