Llansadwrn (Anglesey) Diary 'lights 2023

             

• January
• February
• March
• April
• May

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 usually 21-21 GMT. When averages are referred to (.) compares with the last decade and [.] with the new 30-y climatological average [1981-2010]. All data are subject to verification and amendment.

January 2023

January 1 - a fine morning and becoming brighter at the 0900 GMT observations after recent showers of rain. Visibility was very good there was not much in the way of snow on the Eryri Mountains except a few high patches and a sprinkling of fresh ice precipitation on the very tops. A red squirrel was at a feeding box and a raven was croaking on the tallest Scots pine no doubt having a good view of the surrounding countryside. The temperature was 6.1C an overnight minimum and on the grass there had been a minimum of 3.7C. Pressure 1001 mb was rising with low pressure over the UK with 994 mb over the North sea just off Tayside. The sky was darkening in the W with towering cumulus clouds developing over the mountains and to the NE over Liverpool Bay, cumulonimbus were in the vicinity. Llyn Tegid at Bala after much rainfall was full and overflowing flooding the carpark at the visitor centre [Max 8.5C Min 6.1C Rain 5.4 mm]. The 2nd began with little cloud in the sky and though the sun had not risen above cloud huggng the mountaintops brightness was increasing. There was little wind, smoke was drifting from the NW. Visibility was good, there had been a fresh fall of snow and was lying at 2500 ft. Pressure 1016 mb was rising in a ridge from Azores high 1030 mb. A skein of geese flew noisily overhead moving in a north-westerly direction. Rain at Bala (32.4 mm) helped to swell the water in Llyn Tegid keeping the car park underwater. Cloudier around noon, the afternoon had sunny spells turning cloudier with the SW'ly breeze picked up during the evening. The temperature rising reached 4.7C by midnight [Max 9.6C Min 1.2C Grass -1.7C Rain 0.8 mm]. The 3rd was mild overnight and began dull and wet the temperature at 0900 GMT in warm sector air 9.6C highest of the past 24h. A frontal wave was over SW Ireland associated with low 985 mb to the W over the Atlantic. At noon low 998 mb was over Shannon with a warm front over the Irish Sea. Spells of light occasionally moderate rain of 13h duration. Sunless. Wet in Snowdonia (Capel Curig 44.4 mm) [Max 11.4C Min 2.2C Rain 12.4 mm]. On the 4th pressure 1008 mb was rising with low 987 mb over the N North Sea with a cold front over the English Channel. Rain amounts continued to be substantial over North Wales with (40.4 mm) recorded at Lake Vyrnwy. We were in a strong moist SW'ly airflow as depressions pass over northeastwards. Patches of standing water were seen on the Cefni Marsh. Another sunless day [Max 10.8C Min 9.4C Rain 1.2 mm]. Another sunless day on the 5th continuing very mild began with poor misty visibility and intermittent slight drizzle. Pressure 1015 mb was falling with low 990 mb Shannon and a warm front over Anglesey,a cold front was situated off SW Ireland. With the jetstream over Britain another depression 951 mb was over the Atlantic to the W. The cold front passed over during the evening producing a 4C temperature fall as the low 975 mb approached the Western Isles of Scotland. At 1619 GMT the wind reached 40 mph and rain fell at up to 21 mm/h at 1836 GMT [Max 11.3C Min 8.7C Rain 11.8 mm]. The morning of the 6th began with an ugly red sky in the east then was overcast and dull, but it was dry though the ground was very wet even soggy. The last three days had been very mild, today was cooler after a minimum of 6.9C it was 8.2C at 0900 GMT. Red squirrels were running about the garden and visiting the feeding boxes helping themselves to monkey nuts or hazel nuts and hiding away or burying a number. If they don't return for them a few small hazel trees appear from time to time. Deep low 952 mb was to the W of Ireland and warm air returned between 18 and 23 GMT, maximum 11.2C at 2100 GMT, as a wedge of warm sector air passed through, followed strengthening wind and a spell of light rain through the night [Max 11.2C Min 6.9C Rain 6.0 mm]. At midnight on the 7th deep pressure 988 mb was falling with low 949 mb to the W with a cold front over the Irish Sea. The temperature was 10.1C at 0051 GMT before falling erratically and had reached 3.6C by 0900 GMT the wind also moderating. With low 955 mb W of Ireland pressure continued to fall. It was dull and wet the light rain and drizzle continued until 0930 GMT. Some weak sunshine then bright sunshine for a while before the afternoon turned dull with rain at times the temperature reaching a minimum of 6.8C at 1627 GMT. Pressure was lowest 986 mb at 1830 GMT. During the evening the temperature began rising and the wind strengthened again reaching 36 mph at 2145 GMT (Libanus 50.6 mm) [Max 9.5C Min 8.2C Rain 9.0 mm]. The 8th began wet with moderate to heavy rain and poor visibility. Pressure falling again was on 986 mb with complex low 955 mb to the NW. A frontal band over the Irish Sea was moving away by noon when the rain eased. The afternoon remaining cool and quite dull I spent it in the greenhouse cutting back the chrysanthemums that had finished flowering [Capel Curig 16.8 mm] [Max 6.5C Min 3.6C Rain 7.4C]. Showery rain with small ice pellets after midnight on the 9th brought the rainfall total at 0900 GMT to 12.4 mm for the past 24h. The sky was slowly clearing the moderate visibility improving with cumulus clouds developing by 0930 GMT. The sea was rough around the coast and there were pools of water on Cefni Marsh. The sun appeared around noon the temperature 7.3C at 1630 GMT [Valley 21.6 mm 3.6h] [Max 9.6C Min 3.6C Rain 12.4 mm].

The first snowdrops of the season were spotted on the 9th in the garden here at Gadlys a bit later than usual. The median date of flowering (data set 1994-2022) is the 4th of January. Last year they appeared on the 3rd of January. It's always nice to see the first ones pop up, sometimes we see them in snow, but not recent years.

The 10th was wet and windy with no sunshine. At 0900 GMT conditions were drenching and dark with zero solar radiation recorded a headlight was needed for the obs. It was milder with strong to gale force winds with gusts of 47 mph here at 1154 GMT and 50 mph at Gorwel Heights, Llanfairfechan. Warm sector air until 1700 GMT when a cold front that was over Ireland moved across (Capel Curig 60.6 mm) [Max 11.7C min 5.0C Rain 15.6 mm].

Early on the 17th the ground was covered white with a rare form of small soft hail. It was cold, below freezing -1.4C at 0900 GMT and the hail had not melted. Overnight the air temperature was at a minimum -2.4C at 0700 GMT and on the grass it had fallen to -5.7C, the soil surface was frozen hard with the temperature at 5 cm depth 1.0C. There was some hoar frost on vegetation and rime on the rims of copper raingauges. It was then sunny with 5 oktas of cumulus and cirrus with cumulonimbus over the Eryri mountains. Pressure 990.5 mb was rising with a complex of lows around the UK. Over the S Norwegian Sea 969 mb and 982 mb over the coast of Brittany. Pressure was high 1037 mb NW of the Azores and 1030 mb E of the Black Sea. The snowline on the Carneddau was at 2000 ft with a 30% cover at 1500 ft. The fall of soft hail had not marked the well covered hailpad, usually even small snow pellets leave a fine etching of the aluminium surface. Examination of the still frozen hail under a lens and photograph (left) revealed that the hail was an aggregation of ice crystals of the ordered of 1 mm diameter each composed of tiny diamond shaped crystals of the order of a tenth of a millimetre (100 micrometres). Usually such small ice crystals would have melted before reaching the ground. Later larger conical shaped snow pellets fell at 1400 GMT followed by some small snow flakes and again from 1500 GMT with large flakes of snow enough to cover the ground. The wind was NNW'ly and wintry showers were coming off the North Channel and Irish Sea on to North Wales and sometimes through the Cheshire gap. The afternoon precipitation caught many off guard and traffic in Llanfairfechan was brought to a standstill especially with no gritting on Valley Road and Gorwel where vehicles were stranded overnight [Max 5.8C Min -2.4C Grass -5.7C Pptn 4.6 mm]. Another cold night and on the morning of the 18th snow was lying locally at 0900 GMT up to 1 cm thick. The snowline on the Carneddau was at 750 ft with 30% cover above 550 ft. The wind was WNW'ly and pressure 998 mb rising with low 978 mb over the North Sea not quite so cold air in circulation reaching us from Norway, the Baltic and the Continent. Glimpses of sunshine in the afternoon, sleet showers at times and a moderately heavy shower of wet snow pellets around 20 GMT (Trawsgoed 16.8 mm) [Max 5.5c Min -1.6C Grass -4.5C Pptn 1.4 mm]. The sky was clearing on the morning of the 19th after a fall of snow pellets that almost covered the cold ground and remnants of yesterday's snow. The snowline on the Carneddau Mountains was at 2000 ft with 30% snow cover at 750 ft. A sunny afternoon [Max 5.3C Min -1.0C Grass -6.0C Pptn 0.8 mm]. There had been no ice precipitation overnight and with an air temperature of -0.9C and -5.2C on the ice covered grass on the 20th the soil temperature at 5 cm had fallen to 0.8C. Remnants of snow and hail were frozen on the ground and crunchy underfoot, there was ice on water. Fine and bright with just 3 oktas cumulus and cirrus clouds [Valley 7.6h] [Max 7.9C Min -0.9C Grass -5.2C Pptn nil]. The 21st was fine, sunny and cold at 0.8C at 0900 GMT with slight hoar frost on vegetation. Brief drumming by woodpeckers was heard in the wood. Visibility was very good, but fog was prevalent in England with visibility down to 100 m in Pershore. Pressure was on 1020 mb with a ridge to S Britain from S Norway 1037 mb [Max 7.1C Min -1.0C Grass -5.6C Pptn nil].

After five nights of air frost there was none recorded on the 22nd though with a touch of ground frost -0.7C. Icy remnants had disappeared here, but snow was still lying at 2000 ft on the mountains with remnants at 500 ft. The soil surface was soft and the temperature at 5 cm had risen to 3.9C and there was some submerged ice in water. I had not been collecting much percolate from the lysimeter in recent days it being frozen. Today it had thawed and I collected 145 ml equivalent to 2 mm of precipitation. It was a fine cloudy morning with good visibility, mist and fog was prevalent except around Irish Sea coasts, SW England and NE Scotland. Pressure was on 1031 mb in a slim high pressure area from the Baltic 1040 mb. Contrasting temperatures in the UK today warmer in the north colder 'ice days' in the south (Achnagart 10.9C lo max Chertsey -0.5C Benson min -9.7C and 14.8 mm Weybourne 7.4h Valley 0.0h) [Max 7.3C Min 0.7C Grass -0.7C Pptn nil]. The 23rd began frost-free, cloudy but dry. A mistle thrush was singing in a nearby tree. Pressure remains high on 1035 mb the ridge from the Baltic high 1041 mb persisting. With low airflow in the high pressure particulates air pollution was high in parts of England and wind turbine electricity generation low. Mist and fog was again widespread in central and southern England. Contrasting sunshine and temperatures again (Cassley 12.2C Goudhurst 1.7C Santon Downham min -9.8C Eskdalemuir 5.4 mm Weybourne 7.7h Valley nil) [Max 8.7C Min 5.7C Grass 2.8C Pptn tr].

The month ended with a total of 137.9 mm of rainfall (120%) & [133%] of averages, most since 2021 ranking 27th highest in Llansadwrn since 1928. The mean temperature 6.2C lowest since 2021 and the 10th highest in January station records since 1979. Despite 8 sunless days, sunshine recorded at RAF Valley was 66.5h (136%) & [118%] of averages, lowest since 2021 and 18th on the Anglesey record since 1931.

February 2023

February 1 - a dull day, but it was breezy with wind turbines generating 45% of the UK's electricity demand. Pressure was on 1024 mb with low 980 mb over the S Norwegian Sea while pressure was high 1035 mb over the Atlantic off Cap Finistrerre. A dull and damp day with slight drizzle at times, also sunless but the only day to be so in the month [Max 8.6C Min 6.0C Grass 0.8C Pptn 0.2 mm]. Continuing mild on the 2nd with no overnight frost the result of a wedge of warm air from mid-Atlantic reaching our shores. Pressure was on 1025 mb with pressure high 1035 mb over the Charente Maritime, France. Dull and damp again after recent drizzle fine spots continued on the wind though the sun did appear from time to time later [Max 9.9C Min 7.1C Grass 3.6C Pptn trace]. The 3rd began under grey skies with poor visibility in misty drizzle of no volume under a frontal band over the N Irish Sea. Pressure 1031 mb was rising quickly and the afternoon was drier with a little sunshine breaking through. The Algerian iris Iris unguicularis has been flowering profusely this winter. We have not seen so many flowers. An evergreen rhizomatous perennial native to N Africa and SW Asia flowers here in late winter (left). The fragrant beautifully marked deep violet flowers are best picked for the house when just opening as they are a favourite of slugs, and there are plenty around even in winter (right) [Max 10.5C Min 8.6C Grass 6.9C Pptn trace Valley 1.6h]. It was a dry morning on the 4th, but skies were overcast. A mistle thrush was singing in the wood and there were two wood pigeons foraging for beech mast. Pressure was a high 1036 mb with the system 1040 mb over S Britain, Brest and Bay of Biscay. Cloudy everywhere at first, but the afternoon brightened and there were sunny spells before rain came along in the evening g on a cold front, but did not fall as snow on the mountains of Eryri where only a few snow patches are surviving the mild weather [Max 9.8C Min 7.7C Grass 6.0C Pptn 1.7 mm Valley 0.0h]. The 5th began much brighter and cooler with an overnight ground frost and a light E'ly wind. Pressure was 1046 mb with the high 1048 mb over N Wales. Yesterday's cold front was over N France. With 4 oktas of cirrus clouds and contra visibility was very good and the day was fine and sunny [Max 8.3C Min 2.7C Grass -1.5C Valley 5.9h].

With some clear sky overnight there had been a moderate ground frost on the morning of the 6th the grass minimum recorded -5.0C, there was frost on the grass and the soil surface was just frozen. Soil temperature at 5 cm depth was 2.8C. There was a light SSW'ly breeze with a few cirrus and cumulus clouds. Pressure was 1042 mb with high 1044 mb SE England. A sunny day here with low pollution, in England there was mist and fog with raised particulate AQI values [Max 8.4C Min 0.5C Grass -5.0C Pptn trace Valley 3.3h]. Another fine morning on the 7th with a little more cloud (5/8) including cirrocumulus and cumulus. The wind was variable, mainly WSW and visibility was moderate with haze. Mist and fog was again affecting central England where high particulates in the air were recorded. The temperature at 0900 GMT was 5.4C, a raven was croaking in the tall Scots pine and the woodpecker was drumming loudly nearby. There was a ridge of high-pressure over S Britain from SE European high 1046 mb it was 1039 mb here. There was a weak cold front over NI and W Scotland where there was a little rain. Sunny spells in the afternoon [Max 9.9C Min 3.3C Grass -0.7C Pptn nil Valley 2.6h]. A cloudier morning on the 8th with 6 oktas cumulus and cirrus clouds. There was a cool SSW'ly breeze the overnight ground frost had disappeared from the grass the temperature being 5.1C in weak sunshine. Visibility was moderate with some haze (AQI 3.4) while there was fog in S Britain with -5C temperature with visibility down to 100 m in places high AQI 8-10 central England. Pressure 1033 mb was falling with low 952 mb over the Norwegian Sea. Pressure was high 1048 mb SE Europe and 1034 mb N Azores. There were tight isobars to the |NWS with storm force winds affecting Scotland and the Northern Isles. A sunny afternoon with light breezes here [Max 7.7C Min 2.5C Grass -3.0C Pptn 0.6 mm Valley cloudy with fog 0.2h]. Hardly a cloud in the sky on the 9th, I spotted a small cumulus cloud over the mountains. Frosty overnight with the grass minimum -4.7C with silver frost and frost still at 0900 GMT with ice on water. Visibility was good, but misty. Particulate levels were moderate to high in SE England with a band of frontal cloud over the S and English Channel. Pressure was high 1035 mb to the SW with a ridge extended to S Ireland and SW Britain it being 1034 mb here [Max 9.8C Min 0.6C Grass -4.7C Pptn trace Valley 8.2h].

The 10th found a warm front over the Irish Sea associated with low 969 mb SE Greenland. Pressure 1034 mb was steady with high 1042 mb over Austria. Dull, breezy and damp with drizzle similar weather prevalent all along the western fringe with SE England sunny [Max 9.3C Min 1.2C Grass -2.2C Pptn 0.45 mm Valley 0.9h]. Another sunless day on the 11th with spells of slight rain and drizzle or slight showery rain. It being so mild I put several chrysanthemum pots with fresh shoots outside the greenhouse to slow their development [Max 9.4C Min 6.9C Grass 7.3C Pptn 0.1 mm Valley 0.0h]. A fine morning on the 12th with brightness increasing. The Austrian high 1040 mb had a ridge to N Wales and N England with pressure here 1037 mb. A very nice day with a light S'ly breeze. The temperature at Gogerddan, W Wales, reached 12.4C. Hive bees were humming on the flowering heathers on the sunny sheltered rockery banks and a few large early bumblebees about as well. Visibility was good and there was little snow to be seen on the mountaintops of Snowdonia. There were a few snow patches surviving with two on Carnedd Dafydd near the cliffs of Ysgolion Duon, the Black Ladders [Max 10.7C Min 6.4C Grass 4.5C Pptn nil Valley 2.9h]. The sky was clear overnight this leading to a white ground frost on the morning of the 13th of -3.6C. There was not a cloud to be seen at 0900 GMT and it was calm. Inversion mist was hanging over the Cefni Marsh and some valley bottoms this clearing to give a sunny day. Sunniest was Aberporth with 8.9h and warmest Kew Gardens 13.6C [Max 11.8C Min 1.3C Grass -3.6C Pptn nil Valley 8.6h]. The 14th began cloudier, there were a few lenticular clouds, with moderate hazy visibility with a light to moderate S'ly breeze. The temperature at 0900 GMT was 10.7C. The day was fine and bright with little sunshine, there was a spell of rain in the morning, the afternoon was brighter when the temperature rose to 13.6C and 16.1C at Gorwel Heights in Llanfairfechan. At Gogerddan, W Wales, 16.4C was reached [Max 13.6C Min 1.5C Grass -3.6C Pptn 0.2 mm Valley 0.3h].

The first 14 days of the month were very dry with only 3.2 mm rainfall (3%) & [4%] of averages. Also mild with the mean temperature 6.9C (+1.0) & [+1.3] of averages.

On the 15th there was a cold front over the Irish Sea and it was a bleak day with a moderate SSW'ly wind. Visibility was poor with slight showers of rain. Pressure had fallen and was 1017 mb, but was still high 1038 mb in SE Europe [Max 9.4C Min 8.5C Grass 2.4C Pptn 9.8 mm Valley 1.9h]. A frontal-wave low 1011 mb at Shannon moved over Ireland to the North Channel at midnight there was a burst of heavy rain at 0108 GMT and strong wind at 0304 GMT. On the 16th at 0900 GMT in low cloud fog was thick (code 1, less than 100 m) with slight to moderate drizzle. The temperature was 8.6C and the wet bulb in the Stevenson screen also read 8.6C, 100% humidity. There was a triple point over the Severn estuary associated with the North Channel low. Yesterday's cold front was over France. The fog was slow to lift, a damp and sunless day. At midnight deepening low 987 mb was at Rockall, this had been named storm Otto by the Danish Weather Services (Hawarden 14.6C & 2.7h) [Max 10.5C Min 6.5C Grass 4.5C Pptn 0.4 mm Valley 0.0h]. Pressure 1019 mb was rising on the 17th with storm Otto 981 mb now at Wick deepened further reaching 978 mb when over S Sweden at 1800 GMT. Overcast with poor visibility in mist and rain in the morning, brightening by afternoon with a little sunshine. The first flowers had appeared on the dwarf white Rhododendron on the rockery bank (Pershore 17.2C Achnagart 39.2 mm) [Max 12.6C Min 8.6C Pptn 4.5 mm Valley 2.1C]. Another mild day on the 18th overnight the air minimum was 9.2C and the temperature rose to 10.7C in the afternoon. Dull and damp with slight rain and/ or drizzle with poor visibility. Low Otto 981 mb was now over the Baltic [Max 10.7C Min 9.2C Pptn 0.3 mm Valley 0.0h]. Similar weather on the 19th, mostly cloudy with a WSW'ly wind the cloud had orographic waves to the SE at 0900 GMT. Occasionally brighter, but little in the way of sunshine after its brief appearance rising over the Carneddau Mountains at 0758 GMT. Pressure 1028 mb was rising with complex low 975 SW Iceland and high 1032 mb 500 miles W of Cap Finisterre. A woodpecker spent a little time weakly drumming on the top of the electricity pole and a dark red squirrel was taking hazel nuts from a nearby feeder. Spent the afternoon in my workshop making some new Piche tubes. The markings on the old ones I had made using plastic laboratory pipettes had faded making reading difficult especially with old eyes. The new ones are very clear! (Usk 14.8C) [Max 9.8C Min 4.9C Grass 0.5C Pptn trace Valley 0.0h]. The dark squirrel met me on the path to the Stevenson screen the morning of the 20th, I don't know who was most surprised. After recent intermittent drizzle the sky did look brighter to the SE for a while before returning to intermittent drizzle, we have been getting a lot of drizzle lately of little volume when measured. We were in a W'ly airflow with low 967 Norwegian Sea and high 1034 SE Europe. Two cold fronts straddled Britain while Wales had a slow-moving warm front. The temperature 8.8C (dewpoint 8.0C 95% RH) rose to 10.4C mid-afternoon when the sun broke through [Max 10.4C Min 7.4C Pptn trace Valley 6.1h].

A dry and fine morning on the 21st and continuing mild with a wedge of warm sector air off the Atlantic associated with low 989 mb W of Rockall. Visibility was very good under moderately high altostratus. A cold front lying to the W of Ireland edged closer through the day arriving over the Irish Sea at midnight [Max 9.3C Min 7.4C Pptn 3.8 mm Valley 0.0h]. Cooler by the morning of the 22nd with a little rain that fell as snow on the mountains. In the wood wild garlic is shooting and will soon be large enough to use as salad. Also growing are the bluebells which have leaves about 5 cm tall. It was a clear evening and we had a wonderful dark sky view of the new Moon in close conjunction with Jupiter and Venus. Towards midnight a tawny owl was hooting [Max 7.1C Min 5.3C Grass 3.9C Pptn 4.4 mm Valley 0.5h]. Clear skies overnight resulted in a touch of ground frost -1.0C on the grass with white frost. By 0900 GMT on the 23rd all frost had disappeared the temperature rising from the 2.4C minimum at 0816 GMT. Very good visibility with lying snow above 2500 ft on the Carneddau and Black Ladders. Pressure 1025 mb was rising again in a ridge to Liverpool Bay and central N England from Atlantic-high 1034 mb W of the Scilly isles, It was sunny in northern Britain as here, but cloudy and wet in southern Britain. Solar radiation recorded today was 13.44 MJ m ^-2 , highest of the month [Max 8.8C Min 2.4C Grass -1.0C Pptn 0.9 mm Valley 8.3C]. Pressure 1016 mb was falling again on the 24th and frontal bands associated with low 990 mb over the Baltic were making progress south over Britain. Milder, the morning was very damp and unpleasant with snow thawing on the mountains with sleet of wet snow on the highest summits. Drier by afternoon clearing with a little sunshine late in the day. A magnitude 3.7 earth tremor occurred at 2359 GMT in South Wales near Crickhowel and was felt 100 miles away (Murlough 12.8C Benson -4.7C) [Max 10.8C Min 2.7C Grass -1.5C Pptn 0.1 mm Valley 1.0h].

With the sky clearing overnight there was a ground frost but no white was seen on the 25th at 0900 GMT. A sunny morning with a few cumulus clouds developing over mountains to the S later fair-weather clouds were over the weather station in a cool NE'ly breeze. Pressure was steady on 1022 mb with high 1025 mb 500 miles W of the Western Isles of Scotland. With low 989 mb over the Baltic we had a northerly airflow from the Atlantic via Iceland. The jetstream was well south with a string of depressions heading for the Strait of Gibraltar before being blocked and turning north. Fine and dry here, it was colder with with marine convection bring rain to the east of Britain (Helens Bay max 10.2C lomax Braemar 2.8C Tiree 9.6h) [Max 7.3C Min 2.6C Grass -1.6C Pptn nil Valley 7.1h]. Very fine morning on the 26th the E'ly breeze feeling rather chilly. Pressure 1031 mb was rising with high 1034 mb Scotland. Weak sunshine at first with cirrus and altocumulus clouds increasing, sunny spells developed later [Max 8.2C Min 3.2C Grass -0.2C Pptn nil Valley 4.9h]. The morning of the 27th was fine and dry with 6 oktas of cumulus clouds and an E'ly breeze picking up. With high 1040 mb over Scotland pressure here was steady on 1016 mb. Pressure was low 950 mb S Greenland and 1001 mb western Mediterranean [Max 7.3C Min 3.3C grass -1.2C Pptn 1.0 mm Valley 0.6h]. Snow had been at a premium this month, but this morning the 28th fresh snow had fallen on the Eryri Mountains lying above 2250 ft on the Carneddau and Nant Ffrancon Pass. Yr Wyddfa was well covered, but less at fallen towards Drum in the E of the range and was a higher altitude. Pressure was on 1038 mb with the Scottish high 1041 mb at Cape Wrath. Snow had fallen in parts of the Mediterranean including Spain and Morocco as a result of storm Juliette 998 mb over the Balearic Islands. Here, recent light showers of rain gave way to sunny spells [Max 8.7C Min 4.6C Pptn 0.3 mm Valley 2.2h].

The month ended with rainfall of 28.7 mm (25%) & [32%] of averages, lowest since 2009 making it one of the 13 driest Februarys on record in Llansadwrn since 1928. Temperatures finished above the averages with the mean 7.2C (+1.3) & [+1.6] of averages highest since 2019 and ranking 3rd in station records since 1979. It was generally a dull month with sunshine at RAF Valley 69.7h (81%) & [89%] of averages.

March 2023

March 1 - began dull with spots of rain and moderate visibility. St. David's Day, there were plenty of daffodils in flower in the garden this year and a good crop of leeks on the vegetable patch. The jetstream was well south of the UK over Africa. Pressure was high 1042 mb between Scotland and Iceland and here 1036 mb. The cloud was thin enough at times for some weak sunshine and the odd glimpse of clear sunshine to break through. Breezy at times. [Max 7.2C Min 4.0C Grass 1.0C Pptn 0.5 mm] [Hawarden 8.9C & 1.6h Lake Vyrnwy 2.3C & 2.0 mm]. On the 2nd it was fine and bright after slight showers of rain overnight. At 0900 GMT there was a light E'ly breeze and a temperature of 4.8C. Some noisy seagulls passed over and there was a red squirrel at the feeding box. Pressure was steady on 1029 mb with high pressure 1036 mb to the north. Pressure was low 1005 mb over the Med [Gibraltar 16.5C/9.7C 10.6h] and 990 mb over Svarlbard [-2.5C -5.2C 35 cm snow]. The afternoon had a little sunshine and visibility was good when snow could be seen on the Carneddau with snow lying at 2650 ft. [Max 7.3C Min 4.0C Grass 0.9C Pptn nil] [Milford Haven 9.5C Lake Vyrnwy 1.6C NSR St Athan 6.9h].The 3rd began mostly cloudy with breaks in the altostratus near the mountains resulting in crepuscular rays spread widely across the range. Pressure was on 1032 mb with remaining high 1034 mb from Iceland to the N of Scotland and Northern Ireland. A dull but dry day and a cool NNE'ly breeze and with no sunshine the maximum temperature was 5.6C. [Max 5.6C Min 2.4C Grass -2.0C Pptn nil] [Valley 6.3C Trawsgoed -5.6C NSR Aberdaron 0.5h]. The 4th was again cloudy there had been no overnight frost, visibility was very good. Pressure was high on 1034 mb here with a cold front over NW Scotland associated with low 983 mb over the Baltic. The temperature at 0900 GMT 4.4C, a great spotted woodpecker had found a very resonant tree branch nearby and there was loud drumming. The day was dry, but sunless. [Max 4.6C Min 3.0C Grass 0.8C Pptn nil] [Pembrey Sands 6.7C Sennybridge 0.7C NSR Sunless] Pressure had been falling slowly and at 0900 GMT on the 5th was 1022 mb. The centre of the high 1027 mb was now over the Atlantic W of Ireland. The day began dry with good visibility, but by 0915 GMT it had begun to rain and visibility had become poor. It was a day of slight rain showers and glimpses of sunshine. The maximum temperature reached 8.6C in the afternoon, highest in Wales, but Killowen NI had 11.4C. Began taking cuttings of new shoots coming on the autumn flowering greenhouse chrysanthemums. After flowering they are cut down leaving about 4 inches or so of old stem. New shoots form at the base of these shoots if you are lucky, they are best otherwise they may form on the old stems. I root three or four cuttings, trimmed to just under a node and dipped in Clonex liquid rooting hormone, around the edge of a 3 inch clay pot, plastic pots are no good for the job, in a 50:50 mixture of vermiculite and potting soil. The pots are stood on the greenhouse bench kept moist and sprayed with water should the sun come out [Max 8.6C Min 3.2C Grass 1.5C Pptn 1.3 mm] [Valley 7.9C Lake Vyrnwy 0.1C Bodelwyddan 11.6 mm Valley 1.0h].

The 6th began dull with low cloud on mountain slopes good visibility turning misty with rain or drizzle at times. Pressure 1006 mb was falling, there was a low 998 mb over the North Sea off Wick and a cold front N Irish Sea. Very dull under thick cloud with slight rain or drizzle, occasionally trying to brighten. The cold front crossed N Wales around noon when the temperature was 7.2C, then falling slowly reaching 2.8C at 2200 GMT. Caernarfon Airport reported snow late evening [Max 7.2C Min 4.3C Pptn 3.8 mm] [Milford Haven 9.6C Lake Vyrnwy 0.9C Pptn St Athan 22.0 mm & 1.1h Valley 0.0h]. An early shower of snow pellets and snow on the 7th left remnants scattered about. Snow was lying on the Snowdonia Mountains above 1500 ft, 50 cm deep in places, with 30% cover at 1250 ft and some as low as 250 ft. Bright at 0900 GMT with cumulus clouds developing and a cumulonimbus in the vicinity with sunny spells. Heavy snow in South Wales and Scotland with many schools closed. A sunny and warm afternoon if out of the north wind. Dug up a good helping of leeks from the vegetable plot, steamed for dinner they were of excellent flavour [Max 6.5C Min -0.2C Grass -3.9C Pptn nil] [Mumbles Head 8.1C & 4.0 mm Lake Vyrnwy -0.9C Aberdaron 7.6h Valley 6.7h]. After a cold night with air and ground frosts on the morning on the 8th it was fair and dry. The soil surface was soft, not frozen, and was 3.0C at 5 cm depth, but there was ice on water Fine and cold with weak sunshine and good visibility though haze increasing. Pressure was on 993 mb with Atlantic-low 969 mb having frontal bands were affecting S England and the Channel and N France with sleet and snow, and 975 mb Baltic with an associated warm front over West Country to Thanet. It was generally sunny over N Britain with a temperature range of -11C N Scotland, -15C over snow, to +11C in S England. Snow was lying at 1650 ft on the Carneddau and Moel Eilio and mountains of Llyn had white caps, snow fell in Llanfairfechan and we had intermittent ice crystals and small snow flakes blowing on the E'ly wind during the afternoon. [Max 3.6C Min -1.6C Grass -6.2C Pptn 0.2 mm] [Valley 4.8C Capel Curig -4.2C Pptn St Athan 12.6 mm Valley 2.1h Lake Vyrnwy 7 cm snow]. More snow fell overnight and at 0830 GMT on the 9th the MetO had issued yellow warnings for snow and ice, but issued an amber snow warning for North Wales and Shropshire from noon. A dusting of snow was evident on cold surfaces early and it snowed moderately from 0730 GMT, but little settling on warm ground. Snow fell at sea level including Rhosneigr and had settled on higher ground including the A5 at Ogwen at 1000 ft. Visibility was poor in snow and the temperature 0.7C (dewpoint -0.5C), RAF Valley was on RED. UK temperature range this morning N to S was -15C to +12C. Capel Curig reported 25 cm; Lake Vyrnwy 17 cm; Sennybridge 4 cm; and Bala 3 cm of snow. Heavy snow and blizzards on the mountains all day, in N Wales the Horseshoe Pass A542 and Pentrefoelas to Llyn Brenig A542 were closed and parts of N England were also badly hit. There was an ice-day at Lake Vyrnwy. Snow on the M62 brought traffic to a standstill resulting in 7 hours delays and Leeds and Bradford airport was also affected [Max 4.3C Min 0.6C Grass -1.7C Pptn 19.3 mm] [Milford Haven 11.6C Lake Vyrnwy -0.6/ -1.8C Aberdaron 24.6 mm Mona 15.2 mm St Athan 0.1h].

>

Snow continued to fall on the 10th at all levels with some drifting taking place at higher levels. Snow on the ground at the weather station at 0900 GMT measured 2 cm with further accumulations on the Snowdonia Mountains. Capel Curig reported 27 cm, Lake Vyrnwy 15 cm; Hawarden and Bala 5 cm. In N England Thorncliffe, Staffordshire 23 cm and Bingley, West Yorkshire 14 cm. The blue flowers of Glory-of-the-snow covering the rockery banks were poking through the snow (below left) [Max 6.6C Min 0.3C Grass -0.6C Pptn 0.3 mm] [Milford Haven 7.3C Lake Vyrnwy -2.1C Capel Curig 11.8 mm Aberdaron 8.2h Valley 7.1h]. On the 11th pressure 1009 mb was falling slowly with high-pressure over Normandy 1011 mb. Low 991 mb was W Norway and low 986 mb Baltic, St Petersburg. Though temperatures below zero were recorded overnight no measurable deposition of frost on the ground was recorded, concrete and vegetation were dry, there were remnants of snow in places. Weak sunshine at first through altostratus cloud with some glimpses of sunshine later the temperature rising to 6.0C. By afternoon the temperature was falling as precipitation was seen in the west at 13 GMT there was sleet that turned to snow by 1400 GMT for a while at 3.0C, but did not settle. Thereafter the temperature rose reaching 8.8C before midnight [Max 9.0C Min -1.2C Grass -5.6C Pptn 4.8 mm] [Trawsgoed 9.8C Capel Curig -6.1C Porthmadog 14.4 mm Aberporth 0.56h Valley 0.0h]. At midnight on the 12th with a frontal-wave low NW of Malin Head 992 mb a trough developed over Britain with occluded front from the Isle of Man to Kent. The temperature at 0900 GMT was a mild 9.0C and there was a moderate SW'ly breeze. Visibility was poor, with fog reported at valley, but cloud was thinning and there was some sunshine. The temperature rose quickly to 11.9C before noon here and 13.8C at Gorwel Heights, the cloud thickened in the afternoon and there was some rain. The wind strengthened during the evening with . Mountain snow had rapidly thawed leaving areas of broken snow above 850 ft with almost unbroken areas around the summits of the Carneddau [Max 11.9C Min 2.7C Pptn 22.8 mm] [Northolt 14.6C Hawarden 12.8C Lake Vyrnwy 0.0C Capel Curig 45.6 mm Hawarden 2.2h]. In a change in the weather the 13th was wet and windy with gales around the coast and high ground. Pressure was on 979 mb with Atlantic-low 976 mb SW of Ireland. Windy gusts of 62 mph at Mumbles Head and 60 mph in Capel Curig where also very wet. Large accumulations of rainfall in Eryri, Llyn Tegid at Bala again flooding the car park at the Park Offices [Max 9.7C Min 9.0C Pptn 13.0 mm] [St Athan 13.7C Hawarden 12.8C Lake Vyrnwy 7.6C Capel Curig 54.2 mm Bala 41.6 mm]. On the 14th the weather had turned colder again with fresh snowfalls on the mountains as low as 1250 ft in places. The temperature at 0900 GMT was 4.1C after a minimum of 1.9C at 0755 GMT. Visibility was good with moderate haze and it was fine and sunny. Pressure 1006 mb was rising with Atlantic-high 1025 mb off S Iberia. Low 967 was over the Gulf of Bothnia in the Baltic [Max 8.9C Min 1.9C Grass -1.7C Pptn 1.0 mm] [Mumbles Head 10.0C Lake Vyrnwy 0.7C Trawsgoed 6.0 mm Aberdaron/ Valley 6.6h]...

The first 15 days of the month were wet with 74.4 mm rainfall (82%) & [95%] of averages. Also cold with the mean temperature 4.8C (-2.0) & [-2.2] of averages.

Wet and windy on the 16th, but turned very mild. Air temperature approached 10C at midnight and was 10.2C at 0900 GMT and rather blustery. After intermittent light to moderate rain there was 7.4 mm in the raingauge. Visibility was poor and it was still raining, it wasn't bothering the red squirrels, but I didn't care for it. Three individuals Darky, Red and Patch preeminent at present.. Complex Atlantic-low 976 mb to the SW with tight isobars on the chart, gust of 54 mph at Capel Curig this morning. We were in warm sector air, but a cold front was charted over the Celtic Sea [Max 10.6C Min 4.3C Pptn 1.0 mm] [Hawarden 13.0C Sennybridge 6.7C Capel Curig 19.2 mm 0.0h]. Fine, bright and breezy to begin the 17th with a UK temperature range this morning 4-13C. Pressure was on 999 mb with Atlantic-low 983 mb off SW Ireland. An occluded front over the Irish Sea was associated with a low just off S Norway 988 mb. Sunny spells and light showers otherwise pleasantly warm, 16.3C recorded in Llanfairfechan and Pershore provisionally highest in UK [Max 14.2C Min 9.1C Pptn 1.2 mm] (Pershore 16.3C) [Bodelwyddan 15.7C Lake Vyrnwy 6.7C Capel Curig 6.2 mm Hawarden 4.9h Valley 1.5h]. Showers of rain overnight, but a bright morning on the 18th with some weak sunshine. Visibility was a misty moderate to good with fog around the west coast with some drizzle. Temperatures around the UK between 6-13C rising to 13.8C here in sunshine at 1349 GMT. With cumulus clouds in the vicinity the afternoon turned showery [Max 13.8C Min 8.6C Pptn 1.8 mm[ [Bala 13.1C Trawsgoed 6.6C Hawarden 5.8 mm Valley 3.4h]. Dry with some clear sky overnight and with little wind a touch of ground frost. Becoming cloudy on the 19th by 0900 GMT with a light WSW'ly breeze. Weather cooler and fair in a minor ridge of high-pressure 1017 mb from Spain 1025 mb. A brief sunny spell before noon then with the wind strengthening some rain late afternoon and evening [Max 7.8C Min 3.2C Grass -1.6C Pptn 9.6 mm] [Hawarden 11.2C Lake Vyrnwy 2.4C Capel Curig 16.4 mm St Athan 6.4h Valley 3.6h]. The 20th began dull with intermittent slight rain and poor visibility, but milder again. At 0900 GMT with sky overcast it was 9.9C the UK range 0-13C. Twin Atlantic-lows 987 mb and 981 mb were stationed W of Ireland with pressure here steady on 1013 mb. There was a moderate SSW'ly breeze, the afternoon continued dull and sunless with poor visibility and fog around the north coast of the island. The white flowers of Blackthorn had appeared in hedgerows in Llansadwrn, a bit behind coastal parts of Anglesey. Records kept since 1996 though variable show a weak trend towards earlier flowering, possibly some 15 days earlier in recent years [Max 11.6C Min 5.1C Pptn 3.6 mm[ [Hawarden 15.4C Lake Vyrnwy 3.4C Pembrey Sands 13.4 mm 0.0h].

A mostly cloudy morning on the 21st with poor misty visibility. Pressure was 1003 mb with complex low 972 SW Iceland and a cold front along the spine of Britain. A shower front was over Wales and the day was blustery with the SW'ly wind strengthening to gale force. Strong gusts recorded 45 mph here and 46 mph at Gorwel Heights. Later Capel Curig reported 71 mph with a cold front over the Irish Sea the low 970 mb to the north-west [Max 12.0C Min 9.1C Pptn 14.0 mm] [Hawarden 14.2C Lake Vyrnwy 7.5C Valentia 34.0 mm Capel Curig 28.2 mm Valley 4.5h] [Ny Alesund -19.0C/ -20.9C Snow 49 cm; Tromso 0.4C/ -2.9C Snow 140 cm].

It was a fine and bright morning on the 26th I had been listening out for a chiffchaff due to arrive back and I was rewarded today. At 0912 GMT I heard one. It was spot on the median date calculated since first recorded here in 1999. The earliest date is 19 March 2012 and the latest 12 April 2001. Major weather events seem to affect the arrival date, they are quite variable from year to year, there is no trend for earliness in the data set (graphic). Pressure 1007 mb was rising rapidly, there was a complex low 998 mb making its way through the SW Approaches to Calais. It was raining in SE England [Max 10.7C Min 5.4C Pptn trace] [Milford Haven 13.0C Bala 2.5C Capel Curig 1.2 mm Valley 7.5h].

The 29th began dull with spots of rain and drizzle blowing on the moderate SSE'ly wind. Pressure 1004 mb was falling quickly with complex low 973 & 975 mb over the Atlantic W of Ireland. A triple point was over the Scilly isles with an occlusion over the Severn estuary while a cold front was over SW Ireland. Heard the chiffchaff singing rather weakly once or twice. Blustery at times with slight rain in the morning the temperature here reached 13.3C at 1114 GMT. In Llanfairfechan it reached 16.9C at 1127 GMT highest of the year so far, the provisionally the highest reported in Britain on the day. The blustery afternoon, 32 mph at 1642 GMT, remained dull with more rain coming along in the evening turning heavy 33 mm/h at 2129 GMT [Gorwel Heights 16.9C Gorddinog AWS 16.9C] (Derryln Cornahoule 16.2C Libanus 23.6 mm) [Max 13.3C Min 7.8C Pptn 15.5 mm]...

A wet month with rainfall of 146.6 mm (161%) & [187%] of averages, largest since 2019 making it one of the sixth wettest on record in Llansadwrn since 1928. Mean temperatures finished close to the averages similar to February with the mean 7.1C (+0.3) & [+0.1] of averages lowest since 2020. It was generally a dull month with sunshine at RAF Valley 85.6h (66%) & [71%] of averages.

April 2023

April 1 - began with the first native bluebells appearing in the wood latest since 2020, but five days earlier than the median date. Records kept since 1996 though variable like blackthorn show a weak trend towards earlier flowering, some 12 days earlier in recent years It was a fine morning with weak sunshine very good visibility, but by 0900 GMT haze was developing. The temperature was 8.4C, dewpoint 7.3C, and there was a light NE'ly breeze with broken altocumulus cloud overhead and a few cumulus clouds developing. There are flowers on our damson tree and the Black Hamburg vine in the greenhouse has new shoots developing. The UK temperature range this morning was 4C in Scotland and 11C in the Scilly Isles. Pressure 1008 mb was rising quickly in a ridge to the W of Ireland 1025 mb developing from Atlantic-high 1029 mb off the Gibraltar Strait. A fine sunny afternoon [Max 11.6C Min 6.7C Grass 3.5C Rain nil] (Cardiff 15.1C)...

A great day on the 8th in the garden, quite like summer. The morning began with 4 oktas cirrus and cirrostratus with little or no wind then settling into a SSE'ly. Pressure 1025 mb was rising with high 1037 mb S Norway. Unsettled in the Med with low 1013 mb over the Tyrrhenian Sea. Brewing up for later was low 966 mb SE Greenland with a cold front just W of Shannon. Mostly sunny in the afternoon, bees and butterflies were about, the temperature in a Föhn-like wind off the mountains reaching a pleasant 16.9C AWS at 1404 GMT with humidity falling to 46%, the theoretical possible temperature calculated on a 6C air temperature on Yr Wyddfa reaching here was also 16.9C. Further east Gorddinog AWS had 16.4C, Gorwel Heights 15.3C and Bodelwyddan 15.5C and west Mona 15.7C [Max 16.9C Min 12.6C Grass 1.7C Rain nil] [Kinlochewe 17.3C Hawarden 16.0C & 10.4h Bala -1.5C NSR Valley 7.5h]. The 9th began very fine with very good visibility although the sky was mostly covered with altostratus and a little cumulus there was weak sunshine. No overnight frost the temperature was 13.3C with 63% RH in a light SSE'ly breeze. Pressure was high 1037 mb over Scandinavia, but pressure here 1018 mb was falling with deepening low 959 mb SE Greenland and a rain bearing cold front W Ireland. The wind strengthened gusting 24 mph in the afternoon and there were slight showers of rain in the late evening [Pembrey Sands 15.4C Hawarden 2.2C St Athan 12.2 mm Lake Vyrnwy 4.9h].

The 12th was both the wettest and coolest day of the month. Snow had fallen on the mountains of Eryri and was lying at 1000 ft at Llyn Ogwen and smaller amounts covered the lower slopes of the Carneddau above 850 ft. Snow had also fallen in the Isle of Man. At 0900 GMT here there was some patchy snow on the ground in places following heavy precipitation of sleet and snow 7.8 mm/h at 0841 GMT, the temperature was 2.3C, the lowest of the past 24h, and visibility poor. Pressure was on 982 mb falling to 979 mb at 1039 GMT with twin depressions 978 mb S Ireland and 972 mb N Scotland. Strong to gale-force winds in the west particularly in South Wales with Mumbles Head reporting f9 56 mph mws and gusts of 71 mph. Here the wind was moderate to strong southerly. At 1046 GMT there was more heavy ice precipitation 18.8 mm/h and at 1150 heavy snow pellets covered the ground to a depth of 2 cm. Sferics were recorded over the Severn estuary, Gloucester and N Devon, the London area and Edinburgh [Max 8.8C Min 2.3C Grass 1.4C Pptn 9.2 mm] [St Athan 10.5C Lake Vyrnwy 0.1C Capel Curig 17.7 mm Bala 3.4h Valley 3.0h].

The first 15 days of the month had 32.4 mm rainfall (72%) & [49%] of averages. Temperatures were a little below the averages the mean 8.5C (-0.7) & [-0.6].

The 16th began overcast after recent rain the visibility very good under the cloudsheet. There had been a fall of light coloured Saharan dust in the rain and the air was clear from the haze of recent days. I collected a sample from an observing surface (pinkish white to light reddish brown, looked paler when dry, photo left). Backward trajectory analyses using the HYSPLIT air transport model on the NOAA ARL website indicated that parcels of air arrived over Llansadwrn between 1000 m and 2000 m above ground level (AGL) at 09 GMT today originated over the Sahara desert had taken the 'clean-air' Atlantic-route. In particular parcels of air air at 1750 m AGL or 1919 m above sea level (ASL) over Algeria (graphic right) on the 7th April arrived at the North Atlantic coast of Morocco on the 10th. Dust had been raised over the Sahara in recent days, heavy in the east, and plumes were carried over the foothills of the Anti-Atlas Mountains in southern Morocco then blowing out to sea. Parcels of air were carried over the Canary Islands south-westwards to mid-Atlantic before moving north-eastwards past the Azores and over Ireland to reach Anglesey on the 16th having travelled about 10,830 km. Last year Diary 22 April 2022 light to dark reddish grey dust had reached Anglesey by a Mediterranean east European route, contaminated by particulate pollutants, having travelled about 9000 km [Aberporth 15.1C & 3.2h Lake Vyrnwy 4.8C Aberdaron 3.6 mm Valley 0.0h] [Max 14.2C Min 7.1C Rain nil].

Just before and after midnight on the 17th fog developed, but had cleared by morning the sky overcast. Pressure was on 1029 mb in a ridge to Brittany from high 1036 mb S Norway. Remnants of frontal cloud/ fog over the North Sea were impinging upon the east coast of England. Dull and damp at first becoming brighter in the afternoon and feeling warm in sunshine before turning cooler as 'haar' mist encroached from the east. Later in the evening thick fog developed [Max 15.1C Min 8.2C Rain nil] [Kinlochewe 21.1C Gorddinog AWS 17.1C Milford Haven/ Gorwel Heights 16.1C Lake Vyrnwy 7.7C NSR Aberporth 2.2h Valley 0.6h]...

Pressure 1015 mb was falling rapidly on the morning of the 21st with the moderate NE'ly producing quite a wind chill 4.4C in the early hours. At 0900 GMT the temperature was 10.3C dewpoint 7.9C the sky with cumulus and altocumulus had been clearing becoming bright, but now cloud was increasing again. Visibility was poor with thick haze. The UK temperature range 4C Sennybridge to 15C in Cumbria and the north. Pressure was high 1033 mb over S Norway while Atlantic-low 978 mb was N of the Azores. Detached occluded cloud was charted lying over Wales and East Anglia to the North Sea and then circling to the Cote d'Azur. No precipitation was found in the raingauges, the ground had looked slightly damp about 0700 GMT, but had dried quickly. A deposit of light reddish grey dust was collected at 0900 GMT. An area of rain over central and South Wales was heading northwards becoming patchy by midday. A shower of rain at 1300 GMT measuring 0.2 mm brought more of the same light to dark reddish grey dust, another sample was collected at 1400 GMT. The University of Athens SKIRON model midnight analysis chart indicated an area of dust over northern Britain. Backward trajectory analyses using the HYSPLIT air transport model on the NOAA ARL website indicated that parcels of air arrived over Llansadwrn between 1500 m and 1750 m above sea level (ASL) at 07 GMT today originated over the Mediterranean Sea 12-14th, with the 1500 m ASL trajectory parcels over the coast of Algeria and Tunisia on the 11th. Heavy dust had been raised over the Sahara Desert in recent days some of this blowing over the sea visible on satellite images. The dust had taken an east European route, similar to the 22 April 2022 event, this time passing over Greece on the 14th , lingering over the Black Sea 15-17th when furthest 3200 km away, Ukraine 18-19th, Poland 20th and The Netherlands on the 20th, and moving rapidly over the North Sea to Britain reaching Anglesey today after a distance of some 6786 km [Max 13.2C Min 6.6C Rain 0.0 mm] [Hawarden 14.1C Pembrey Sands 3.0C Lake Vyrnwy 5.6 mm Aberdaron 3.0h Valley 2.9h].

The 29th began mostly cloudy, but fine and warm with a temperature of 14.0C at 0900 GMT. The UK temperature range this morning was 3C in the north and 16C in the south. Pressure was high 1021 mb SE England with pressure here 1020 mb. Pressure was low 1006 mb over the Baltic and 987 mb SE Greenland. With little rain in the past 5 days the soil surface had dried and on the vegetable plot was good to work (Pershore College 20.2C)[Max 19.1C Min 9.7C Grass 6.8C Rain 8.6 mm] [Trawsgoed 19.2C Sennybridge 2.6C Pembrey Sands 8.2 mm Aberporth 7.2h Valley 3.1h]. At midnight on the 30th fog developed before light to moderate rain fell from 02 GMT, highest rate 7 mm/h at 0410 GMT. It had stopped raining by the time of the 0900 GMT observation when the sky was overcast with moderate misty visibility and breezy. Rainfall for the past 24h was 8.6 mm the second largest fall of the month. There was a low n1010 mb off the Western isles of Scotland with occluded fronts over the Irish Sea. Glimpses of sunshine between 13 and 14 GMT. Light showery rain in the evening [Max 13.9C Min 10.2C Rain 1.2 mm] [Hawarden 16.9C Sennybridge 8.2C Trawsgoed 19.8 mm Aberporth 2.9h Valley 0.1h]

The month ended with rainfall of 53.0 mm (118%) & [81%] of averages, largest since 2019. Temperatures finished a little above the averages with the mean 9.4C (+0.2) & [+0.3] of averages lowest since 2021 and ranking 16th highest in station records since 1979. A fairly sunny month with sunshine at RAF Valley 166.1 h (90%) & [101%] of averages, the sunniest day 13.3h on the 20th.

May 2023

The first 15 days of the month were on the dry side with 18.2 mm rainfall (25%) & [27%] of monthly averages. Temperatures were above one degree above averages the mean 12.7C.

The 16th began mostly cloudy with a light ESE'ly breeze. Pressure was on 1028 mb within high pressure area 1030 mb Shannon. Frontal bands N of Scotland associated with low 1001 mb over the Norwegian Sea. Low 995 mb over Italy named Storm Minerva with torrential rain causing devastating flood damage to property and 9 deaths in the Po Valley, including in Ravenna. The River Po is fed from several high mountain lakes. Rimini reported 96 mm, Bologna 74 mm rainfall. Some sunny spells here in the afternoon and keeping dry [Max 16.3C Min 5.8C Grass 3.7C] (Usk 19.5C)

The 20th began with a few clouds, some cirrus and cumulus clouds started bubbling up over the mountains, but subsided later. A new bird record for the station list when two red kites were spotted overflying at 0900 GMT. Reported around Anglesey for a while the first sighting here. The temperature was 16.8C and there was a gentle ESE'ly breeze. A warm and sunny day the temperature rising to 19.0C, but in Porthmadog 21.5C was recorded [Max 19.0C Min 9.8C Rain nil]. The warmest day so far this year on the 21st with 20.4C recorded at the station and 23.3C in Porthmadog the latter highest in the UK so far this year. Beginning mostly cloudy, but bright with good hazy visibility, pressure was steady on 1025 mb. A large Atlantic-high 1034 mb stretched from SE Nova Scotia past the Azores with a ridge to the Western Isles linking the UK to Baltic high 1030 mb. A cold front lay over Ireland with associated cloud affecting Irish Sea coasts. The cloud burnt back by the afternoon which was sunny. Air particulate levels were slightly elevated, PM2.5 4.0 µg per m^-3 here, around Irish Sea coasts, moderate in the Netherlands and parts of Europe. Ozone levels were moderate with 24-h mean Marchlyn Mawr reservoir 2100 ft where an instrument recording ozone (Air Quality in Wales) 24-h mean measured 79 µg per m^-3 [Max 20.4C Min 10.6C Rain nil] (Porthmadog 23.3C Sennybridge 1.3C)

5.1#

Latest AWS observations Last year's Diary, for previous Diaries consult the site map Snowdonia Snowline for the current season Daily Observations, usually updated bi-monthly Monthly & annual summary with analyses 2023 Temperature graphs, daily and monthly rainfall histograms, accumulated rainfall total and more, all on a page for 2022 The observer's choice of forecasts, satellite imagery, severe weather, natural hazards and more