Llansadwrn (Anglesey) Weather

Latest Diary Tenth Year

April

27th: At midnight frontal cloud stretched from W of Iberia through St George's Channel and Irish Sea to Norway, associated with low 987 mb over the Norwegian Sea. At 09 GMT pressure 1014 mb was falling slowly in a slack pressure area and it was calm. It was one of those mornings that had Anglesey enveloped in low cloud and mist. There was 100% relative humidity and visibility very poor, 1 km. All thermometers in the screen were reading 9.8C, as they should after resetting the maximum and minimum. It was calm and a good time to check that all were reading the same and agreeing with the NPL certificated thermometer. With 100% RH the dry and wet bulbs read the same, in fact they were all acting as wet bulbs. Blackbirds and thrushes were singing, the males having little to do at the moment with females sitting on eggs. There was little change until late in the afternoon when the sky brightened from the W and some sunshine broke through by 16 GMT, but it did not last long and the evening was dull once again. With the morning very dull, despite a little sunshine, solar radiation was 7.02 MJ m^-2 2nd lowest of the month. The evening turned cloudy again and there was a moderate shower of rain from 2230 GMT and continued showery through the night [Rain 8.9 mm; Max 12.0C; Min 9.5C; Grass 8.9C]
28th: Overcast with slight rain up to 09 GMT. Pressure 1001 mb was falling with low 997 mb over the Norwegian Sea and frontal wave low 995 mb off NE Scotland. The showery trough over Anglesey and N Ireland was just starting to move away. There were puddles of water around the garden and visibility moderate in rain and mist. A blackcap and chiffchaff were singing strongly in the trees. By afternoon the sky was clearer and there was plenty of sunshine and clear visibility. Snow patches on the mountains are now confined mainly to the NE flank of Carnedd Llewelyn. The evening was clear and on the grass the temperature went down to 0.6C. [Rain 1.3 mm; Max 12.7C; Min 6.5C; Grass 3.3C]
29th: A sunny morning with a light NE'ly breeze. Visibility was very good >50 km affording fine views of mountains and Lleyn Peninsula. Pressure 996 mb was falling within complex low-pressure with low 992 mb to the N of Scotland and low 988 mb over the Celtic Sea. Pressure was high 1024 mb over Finland and W Russia. During the day the low moved over SW England and brought rain, on an occluded front, there and to South Wales with Milford Haven recording {30.4 mm}. The morning here was mostly sunny then cloudier by noon. The afternoon had some good sunny spells before showery rain developed around 1500 GMT. As the front moved N there was moderate rain from 2200 GMT. {Crosby 16.3C, Valley 13.8C, Tiree Is 12.9h, Valley 9.5h, Milford Haven 30.4 mm}[Rain 10.5 mm; Max 13.5C; Min C; Grass C]
30th: With the low 986 mb at midnight slow-moving over SW England moderate rain continued until 0400 GMT. By morning there was a fresh fall of snow on the mountains above 2700 ft. It was a dull morning, although pressure 988 mb was rising and the slight rain eased by 11 GMT the morning remained dull. The afternoon had further slight rain from 1500 to 1930 GMT and the day was sunless with the temperature rising to only 7.7C. Before midnight there were a few holes in the cloud sheet. [Rain 2.4 mm; Max 9.2C; Min 6.0C; Grass 5.5C]

The month ended with a rainfall total of 86.2 mm (110%) and [149%] of the monthly averages. The mean temperature was 8.3C (-0.8) and [-0.3], the mean maximum was 11.9C [(-0.9)] on both averages while the mean minimum was 4.7 (-0.8) but [+0.3] of the 30-y average. Sunshine duration at Valley was 168.2 h (105%) [107%] K&Z adjusted averages.

May

1st: A cloudy morning with 1 or 2 blue patches appearing as the cloudbase lifted. The temperature at 09 GMT was 8.7C and had just been on 9.2C, the maximum of the past 24-h. Pressure 1001 mb was rising and visibility was good. There were sunny spells in the afternoon with the sky clearing over Anglesey leaving a line of stratocumulus clouds over the mountains of Snowdonia, similar views can be seen left (across a field of cattle) and right (across a field of sheep). Take your pick! [Rain 2.7 mm; Max 14.2C; Min 4.8C; Grass 1.7C]
2nd: There were showers of rain from 05 GMT that accumulated 2.7 mm by 09 GMT. With 6 oktas of cumulus clouds the morning began brightly with a gentle S'ly breeze. Pressure 1017 mb was rising slowly; the temperature was 11.3C, dewpoint 7.6C, and visibility was very good >30 km. Pressure was high 1024 mb to the SE over central Europe and low 987 mb W of Iberia with trough to W of Ireland giving us a S'ly flow of air. Another mostly sunny day with mainly cumulus clouds and an increasing amount of cirrus in the afternoon. Later the cumulus decreased and the evening was mostly sunny. [Rain 0.0 mm; Max 15.6C; Min 6.1C; Grass 2.3C]
3rd: A bright morning with 6 oktas cover of altostratus and altocumulus clouds. The blue of the sky was looking milky as there was suspended Saharan dust high in the atmosphere. Pressure was 1019 mb with high 1030 E North Sea and low 978 mb W of Ireland. The wind was light to moderate SE'ly and cloud tended to burn off giving some long spells of sunshine. The temperature reached 21.1C, highest of the year so far, in a Föhn-like wind with the relative humidity a low 48%, but observer Keith Ledson at Red Wharf Bay recorded 23.1C just before a sea breeze set in. Evaporation by Piche evaporimeter was 5.3 mm in the 24-h 09-09 GMT. It was a warm sunny evening, later there were some spots of dusty rain. [Rain trace; Max 21.1C; Min 8.6C; Grass 6.0C]
4th: Overcast with moderately high mainly altostratus cloud. It had been a warm night with the air minimum not falling below 15.4C, second highest in May and highest this early in the year since before 1979 (17.0C on 17 May 2002). There had been a slight deposition of light reddish-brown dust associated with initially with dry deposition including pollen and then a few spots of rain. In previous days deposits have been greyish (grime) with yellow (pollen). At 0900 GMT pressure 1017 mb was rising and the temperature was 17.7C, dewpoint 11.1C. There were a few more spots of rain and dust from 0915 GMT and the morning kept overcast. There was further moderate rain in the afternoon as 2 cold fronts passed over before brightening up soon after 1500 GMT. Further light reddish-brown dust (MUNSELL ® 5YR 7/3) had been deposited in the rain without much pollen. Trajectory analysis, using the HYSPLIT model at the NOAA Air Resources Laboratory, indicated that parcels of air arriving over Llansadwrn at 15 GMT had come from a pool of N African dust around the Canary Islands. Soon after the sky cleared rapidly giving a sunny end to the day. [Rain 8.3 mm; Max 18.8C; Min 15.4C; Grass 12.2C]
5th: An almost clear sky except for a little cloud well south of the Snowdonia Mountains. Noctilucent clouds were seen for the first time this season in Northern Ireland at 03 GMT, too early for me. Mist was blowing across fields from sea fog in the Irish Sea and Red Wharf Bay penetrating Malltraeth Marsh and Afon Nodwydd valley, but here up on the Llansadwrn ridge were were in sunshine. Pressure 1027 mb was rising and the day was sunny, but there was a cool NE'ly off the sea and this kept the temperature down to 15.5C. Later in the afternoon some cumulus clouds were seen over the mountains. An orange tip butterfly was seen around the garden and the first red admiral, possibly arrived here on the S'ly winds that brought the dust yesterday. Solar radiation was 26.84 MJ m^-2 and Valley recorded 9.4 h of sunshine. {Capel Curig 19.7C} [Rain 0.0 mm; Max 16.5C; Min 6.7C; Grass 2.8C]
6th: The morning had hazy (with dust and smoke) sunshine with 5 oktas of cirrus clouds. There was a light ENE'ly breeze and the temperature at 09 GMT 16.5C had exceeded yesterday's daytime temperature. Pressure 1024 mb was falling with high 1031 mb E North Sea and low 989 mb W of Ireland. There was a clear sky most of the day, some convergent cloud developed over the station for a while, but the S'ly won and the temperature reached 24.1C with relative humidity falling to 42%. The temperature, exceeding any last year, was the highest recorded since 21 September 2006 with 26.2C. Soil moisture determined today was 67% dry mass, a little drier at just below the saturated water level of 70%. The evening and night were mostly clear. [Rain 0.0 mm; Max 24.1C; Min 11.1C; Grass 7.3C]
7th: A fine sunny morning with smoke and dust haze. Pressure was 1020 mb and there was a light ENE'ly breeze. A cloudier day, with some weak convective clouds seen mainly to the W and S. Here the battle between the cool NE'ly off the sea and warmer S'ly air took place over the weather station in the afternoon. The effect was variable, the cloud coming and going , but the S'ly held long enough for the temperature to rise to 25.0C, highest so far. To mark the occasion the local flock of house martins were seen and heard chattering overhead for the first time this season. Our complement of migrating birds is nearly complete, only the spotted flycatcher is missing, but with declining numbers in recent years we will be lucky to see one. There are tiny goldcrests and goldfinches about the garden nesting somewhere in the shrubs and trees. It was a warm mostly clear evening with bats flying at dusk, a light shower of rain was reported in Llanfairfechan associated with some showery rain in S Snowdonia. [Rain 0.0 mm; Max 25.0C; Min 11.5C; Grass 8.3C]
8th: More of the same, almost clear sky and sunny with 21.0C at 09 GMT. A little cloud during the afternoon at times and with gusty S'ly breeze the temperature rose to 25.1C. By 1800 GMT frontal cloud, associated with low 998 mb W of Ireland, was seen encroaching. {Kinlochewe 25.3C, Valley 24.9C} [Rain 0.2 mm; Max 25.1C; Min 15.1C; Grass 10.9C]
9th: There was a shower of light rain at 0300 GMT that left paths damp in places in the morning and another deposition of the fine north African reddish-brown dust. There was also local gritty dust and tree pollen that is now appearing in increasing amounts. An overcast sky with poor visibility and a slight S'ly breeze at 09 GMT. The temperature was 14.8C and with 5 cm depth soil temperature of 16.0C soil and concrete were dry. Pressure was 1012 mb in a slack area over Britain with decaying frontal cloud over the west. The day was sunless and very dull but kept dry. Early purple orchids are flowering, the example right was found growing on a roadside in Anglesey. [Rain 0.0 mm; Max 17.2C; Min 13.4C; Grass 12.1C]
10th: Little change although pressure 1018 mb was rising. We still had moderately high frontal cloud overhead, stretching from Lands End to Cape Wrath. Lightning struck a house in Flint at 0045 BST knocking a hole in the bedroom wall of a sleeping 3-year old boy who was unharmed. Most electrical equipment in house in the road was damaged. South Wales also hit by the storms was subjected to heavy rain and hail (stones up to 20 mm were reported in Chepstow), there were flash floods in Swansea, Chepstow and Cardiff. Here it was a lot quieter with just a few spots of rain just after 0900 GMT and the radar showing patchy rain over parts of South Wales and the west. The cloud was a little thinner and it was brighter during the day, but visibility was poor in the haze. By afternoon the sun was breaking through and there were sunny spells before evening. It was sunnier and a lot warmer in SE England. {Hertsmonceux, Sussex 27.3C, Valley 17.6C, Sennybridge 10.2C, Norwich AP 15.1h} [Rain trace; Max 18.5C; Min 11.2C; Grass 10.6C]
11th: Some clearer sky overnight and dew on the grass by morning. It was bright with mostly high cirrus clouds the front having moved westward. Pressure 1021 mb was rising and the temperature at 09 GMT was 15.7C (dewpoint 13.6C) in a light NE'ly breeze. Visibility was just good in smoke and dust haze with north African dust and photochemical smog, the blue of the sky was milky. The Met Office issued a severe weather warning of heavy rain for Wales and NW England. The NOAA 18 satellite image at 1310 GMT shows the convective clouds developing over Wales and Cumbria. The east coast of Scotland and NE England was affected by 'the Haar', fog off the North Sea. . In the event thunderstorms developed over Wales and moved north through the afternoon. Distant thunder was first heard to the SE at 1335 GMT, rumbling increased almost continuously through the afternoon with the sky darkening. At 1528 GMT a flash of cg lightning was seen close SE of here and soon after we had some slightly dusty rain, then the storm suddenly abated and apart from another rumble at 1850 GMT ceased. {Great Malvern 27.5C, Hawarden 25.1C, Capel Curig 5.2 mm} [Rain 2.4 mm; Max 20.8C; Min 10.6C; Grass 8.2C]
¤ 12th: A fine sunny morning with a veil of cirrus clouds, visibility was good with light haze and the sky seemed a little bluer. The temperature was 18.7C (dewpoint 12.7C). Moderately high levels of ozone were being reported from several parts of Wales developed from the action of bright sunlight on pollutant aerosols in the atmosphere. The day was mostly sunny with the NE'ly wind increasing to force 3/4 during the afternoon. {Trawsgoed 24.7C, Valley 12.2 h} [Rain 0.0 mm; Max 21.7C; Min 12.8C; Grass 8.4C]
13th: Another sunny morning with hardly a cloud to be seen. Visibility was good but the haze was moderate and high levels of ozone were being reported. The air is still dusty and the blue of the sky looked milky. It was windier with the NE'ly force 4/5, but the day was mostly sunny. With the soil surface looking dry soil moisture, in the top 5 cm under grass, has fallen to 57% dry mass. [Rain 0.0 mm; Max 16.8C; Min 10.2C; Grass 8.4C]
14th: Visibility had improved and was very good >30 km) with much of the sky overhead and to the N much bluer than of late with the dust moving away to the west. Pressure 1018 mb was falling with high-pressure 1026 mb around the Faeroes declining. Pressure remains low in the Bay of Biscay and, with low 1006 mb near Cape Finisterre, much of the Mediterranean region has been having rather cloudier, cooler and wetter weather than here. Associated frontal cloud would slowly head north through the day bringing unsettled weather to south-west England. Here it was another sunny day, somewhat cooler in the moderate NE'ly breeze the temperature reaching 15.6C. Haze built up again during the day, by afternoon the faintly coloured haze was seen up to 4000 ft against the backdrop of the Snowdonia Mountains and darker over Liverpool Bay. Solar radiation measured 26.70 MJ m^-2, a little less than the 26.84 MJ m^-2 on the 5th, with little or no haze. A mostly clear and dry evening and night. {Milford Haven 21.4C, Valley 14.5h} [Rain 0.0 mm; Max 15.6C; Min 8.8C; Grass 7.5C]
15th: Clear overnight with the air minimum falling to 7.1C and 6.0C on the grass that might have been lower had not the NE'ly f4 breeze persisted. I had moved potted most tomato plants back into the greenhouse just in case. A sunny morning, little change except a little of the southern frontal cloud could be seen, but at the moment associated rain was well S of here. Pressure 1012 mb was falling with the low 1006 mb still near Cape Finisterre. The afternoon was mostly sunny although some high cloud passed across the sky to the SW, and the NE'ly force 4/5 making it cool, but pleasant out of the wind in a sheltered spot in the garden. The northwest did best for sunshine and temperatures. After 18 GMT further cloud encroached, but again it was moderately high and there was no rain. {Castlederg 18.8C, Hawarden 18.1C and 3.3C, Stornoway 15.1h, Valley 12.7h, St Mawgan 32.2 mm} [Rain 0.0 mm; Max 15.1C; Min 7.1C; Grass 6.0C]

The first 15 days were mostly sunny with sunshine duration at RAF Valley a provisional 142 h 75% of the May LTA and already exceeding that recorded in May 1998. It was dry with rainfall 13.6 mm (19%) and [24%] while the mean temperature was 14.7C (+2.8) and [+3.2] of the monthly averages.

16th: Overcast with moderately high altostratus cloud with weak sunshine. Pressure was 1010 mb and the NE'ly lighter this morning was force 2. The jetstream continues fragmented in the north and is running south of the Gibraltar Strait over north Africa. Weather is unsettled in the Mediterranean region with rain affecting both southern Europe and north Africa. The slow-moving complex low-pressure near Biscay and occluded frontal cloud over Wales gave rain, heavy in some places in the south-west, and here a mostly cloudy sometimes bright, and dry day until around midnight. The cool NE'ly persisted with a maximum temperature of 13.0C. {Castlederg 18.4C, Hawarden 14.8C, Cardinham 21.8 mm, Tiree 8.6h} [Rain 0.5 mm; Max 13.0C; Min 9.3C; Grass 6.8C]
17th: A spell of drizzle from midnight and a shower of rain about 05 GMT amounted to just 0.5 mm. There were a few holes in the cloud about 0830 GMT, but these had disappeared by 09 GMT. Soil and concrete were dry, the temperature of the soil (15.0C at 5 cm deep) ensured evaporation of the small amount of rain. Pressure was 1010 mb and we still had the NE'ly breeze. The day was overcast and sunless with a maximum temperature of 12.0C, but as a low maximum higher than last year's 10.4C on the 27th and still highest since 6 May 1990 with 13.4C . There was slight rain from 1600 GMT until midnight. {Lusa 16.0C, Pembrey Sands 15.7C, Altnaharra 2.5C, Camborne 18.0 mm, Stornoway 15.1h} [Rain 2.9 mm; Max 12.0C; Min 9.4C; Grass 8.6C]
18th: A bright start with the sky clearing. Pressure 1017 mb was rising with a ridge of high-pressure extending from the high 1037 mb over N Greenland. Pressure remains low 1004 mb over the Mediterranean. A sunny morning, and yes we still had the NE'ly breeze force 3/4. [Rain mm; Max C; Min 7.4C; Grass 6.0C]

Last month's diary Diary since January 2008 Daily Observations, usually updated bi-monthly Monthly summary and further analysis of the observations in 2008 Monthly summary and further analysis of the observations in 2007 Snowdonia snowline for 2007/2008, usually updated twice weekly in season The observer's choice of forecasts, satellite imagery and more Temperature graphs, daily and monthly rainfall histograms, accumulated rainfall total and more, all on a page for 2008 The Observer's Wx Bookshelf Location map and satellite image (use mouse, left click and hold to drag the image) 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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