Davis Vantage Vue AWS at Gorwel Heights in Llanfairfechan.

Llansadwrn (Anglesey) Weather:
Monthly and Annual
Summary for 2021

Logo: Llansadwrn Weather - Melin Llynnon, Ynys Môn




January 2021

A wet month with spells of wintry weather throughout

Above average rainfall and below average temperatures

A wet month carrying on from the record breaking wet 2020. The 180.6 mm of rainfall this month (169%) & [175%] of the new averages, even wetter than last, largest since 2008, ranking 7th in Llansadwrn records since 1928. The largest fall was on the 18th having 31.5 mm. There were 9 falls (+1.4) of 5 mm, or more; and 15 (-2.0) wet days. Rain days were 24 (+1.3); day days 7 (-1.3); and just one, he 31st, had no precipitation (-2.8) of average. Rainfall duration totalled 169 wet hours.

Rainfall at Gorwel Heights totalled 205 .0 mm (223%) & [230%] of averages, wettest on record since 2011. The wettest day was on the 20th with 34.2 mm, 29.4 mm fell on the 18h and 28.6 mm on the 19th, the three days totalling 92.2 mm 45% of the monthly total. Days with 5 mm, or more, were 11; wet days were 17; rain days 22; and dry days 9. Rainfall duration totalled 173 wet hours.

It was the coldest January since 2010. The mean temperature 4.1C (-1.4) & [-1.3] of the new averages, lowest since 2010 and ranking 6th in station records since 1979. The mean maximum 6.4C (-1.6) & [-1.5] ranked 5th in station records. The highest maximum 10.0C on the 19th (-1.9) equal lowest (2011) since 2010, the lowest 2.7C (-0.9) on the 8th lowest since 2013. The mean minimum 1.8C (-1.3) & [-1.1] equal lowest (2011) since 2010 ranked 12th. The lowest minimum was -2.2C on the 9th and lowest since 2014 (-2.8). There were 8 air frosts, most since 2013 (10), with 46.5h of frost. There were 21 ground frosts (+3.9) most since 2015 (25) with the lowest -9.2C (-2.9) on the 7th lowest since 2009 (-9.7C).

The mean temperature at Gorwel Heights was 4.8C January lowest station record (-1.5) & [-1.4]. The mean maximum 6.6C was a January low station record with the highest 12.2C on the 28th second lowest on record 2019 (11.4C) The lowest maximum 2.3C on the 8th was fourth lowest (0.5C in 2013). The mean minimum 2.9C was lowest on record, the lowest -0.8C on the 9th was third lowest. There were 3 days of air frost but only 7.2h fell below freezing.

The wintry month in Llansadwrn had 12 days (+5.5) of small hail, most since 2015. Sleet or snow fell on 6 days equal 2019, most since 2013. There were no days (-0.6) with snow lying at 0900 GMT, least since 2019 (2), there were 10 in 2010.

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February 2021

Above average temperatures, rainfall and sunshine

A month of contrasts the beginning cold and wintry the end milder, wet and windy

The mean temperature in the first half of the month 4.2C was below average (-1.7) & [-1.4], but by the end with a spell of very mild weather ended on 6.1C (+0.2) & [+0.5] of averages, lowest since 2018, but ranked 16th highest in station records. The mean maximum was 8.6C with the highest maximum 12.5C on the 20th and the lowest 1.7C on the 9th -2.6C based on the decadal average. The mean minimum was 3.6C with the highest 9.1C on the 20th and the lowest -2.1C on the 11th. There were 6 days of air frost of 53.3h duration. There were 12 days with a ground frost (-3.0), the lowest -7.3C on the 11th (-1.3) of average.

At Gorwel Heights the mean temperature was 6.8C [(+0.6)] of averages, equal highest with 2014 since 2011. The mean maximum was 9.3C highest since 2019 (12.0C), the highest maximum was 14.3C on the 23rd second only to Rhyl's 15.0C, it was only 11.2C in Llansadwrn. The mean minimum was 4.2C lowest since 2018, the lowest minimum -2.3C on the 13th, frost duration was 71.5h, there were six air frosts in a spell from the 9-14th.

It was a wet month in Llansadwrn where rainfall totalled 146.6 mm (143%) & [182%] of averages, lowest since 2019, ranking the 8th wettest February in Llansadwrn records since 1928 The wettest day was on the 23rd when 50.6 mm fell over 23h duration, the second highest February daily total in station records since 1979 only beaten by the 55.3 mm recorded in 2020 when the months total reached a record 250.6 mm. There were 3 days (-2.0) with no precipitation, 11 (+2.4) dry days; 17 (-2.7) rain days; 15 (+1.8) wet days; and 9 (+2.8) had 5 mm, or more.

It was drier at Gorwel Heights, the total rainfall 95.8 mm, lowest since 2019, (113%) & [128%] of averages. The wettest day was on the 23rd with 18.4 mm over 21h duration. Rainfall duration during the month was 104h. Dry days were 13; rain days 15; wet days 12; and 8 days had 5 mm, or more.

A very windy month at Gorwel Heights with a mean wind speed of 8.8 mph, the highest 25.4 mph on the 12th and 23.3 mph on the 23rd. On 10 days high gusts of more that 40 mph were recorded, highest recorded were 57 mph on the 18th; 58 mph on the 19th; 63 mph on the 20th and 64 mph when significant structural damage occurred in the village of Llanfairfechan.

In Llansadwrn snow fell on 2 days and small hail on 7 days.

Sunshine at RAF Valley totalled 92.8h, sunniest since 2019 ranking the 20th sunniest February on the Anglesey record back to 1931. The sunniest day was on the 28th with 10.1h duration, there were 7 sunless days.

Winter 2020/21

Second wettest winter on record in Llansadwrn. Temperatures below the station averages.

Winter seasonal averages Anomalies
10-y 30-y
Temperature (C)
Mean maximum 7.6 -1.0 -0.4
Mean minimum 3.1 -0.5 0.0
Mean 5.4 -0.7 -0.2
Rainfall (mm) 510.6 139% 156%

 

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March 2021

Temperatures and rainfall above average, a little duller than average

Wet and wintry at times, above average temperatures at the end of the month

Another wet month with 124.7 mm bringing the total so far this year to 451.9 mm, but 64.7 mm below last year's total. Wettest in March since 2019 and (151%) & [159%] of averages. The wettest day was on the 14th with 30.0 mm while 23.8 mm fell the next day resulting in standing water on garden and fields. Despite this there were 8 days (+0.6) with no precipitation and 13 dry days (+0.1). Rain days were 18 (-0.1); wet days 11 (-3.5); and 6 days (-2.4) had 5 mm, or more. It was drier in Llanfairfechan at Gorwel heights with 90.0 mm (103%) & [109%] of averages. The wettest day was on the 9th having 13.4 mm with 12.6 mm falling on the next day. The 27th had 12.0 mm and the 28th 11.2 mm. There were 15 dry days; 16 rain days; 13 wet days; and 8 had 5 mm, or more. Rainfall duration (wet hours) was 92h at Gorwel Heights and 99h in Llansadwrn.

It was wintry at times with sleet falling on the 11th and 26th. Hail fell on 3 days (-2.3) of average. A windy month with gales in the area on 5 days.

Temperatures were a little above normal with the mean 7.4C (+0.5) & [+0.4] of averages, highest since 2019 ranking 15th since 1979. The mean maximum was 10.3C with the highest maxima 18.6C on the 30th and 16.8C on the 31st the only two >15C. There were 15 days <10C the lowest maximum 5.6C on the 4th. The mean minimum was 4.4C (+0.8) & [+0.7] of averages. There were 2 air frosts this month the lowest -1.0C on the 6th the other -0.6C the previous day. There were 7 ground frosts, significantly (-8.0) of average, the lowest -6.4C on the 6th was (-1.7). A little warmer in Llanfairfechan at Gorwel Heights with the mean 7.9C [(+0.4)] highest since 2014. The highest maxima were 17.7C on the 30th highest since 2014 and 16.1C on the 31st. The mean minimum was 5.3C equal highest (2019) since 2017. There were no air frosts the lowest 0.8C on the 7th.

Sunshine at RAF Valley totalled 114.4h (88%) & [95%] of averages. The sunniest day was on the 1st of the month with 10.3h and there were 7 sunless days.

 

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Monthly data 2021

Llansadwrn (Anglesey): Monthly weather data summary for 2021
Anomaly ~ is based on the 2011-20 average.
Anomaly 30-y is based on the 1991-2020 average.
.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Air temperatures (C)
.
Mean max 6.4 8.6 10.3 8.4
Mean min 1.8 3.6 4.5 3.3
Mean 4.1 6.1 7.4 5.9
Anomaly~ -1.4 0.2 0.5 0.2
Anomaly 30-y -1.3 0.5 0.4 0.4
High max 10.0 12.5 18.6 18.6
Date 19 20 30 .
Low max 2.7 1.7 5.6 1.7
Date 8 9 4 .
High min 7.3 9.1 9.7 9.7
Date 28 20 29 .
Low min -2.2 -2.1 -1.0 -2.2
Date 9 11 7 .
Grass min -9.2 -7.3 -6.4 -9.2
Date 7 11 6 .
.
MSL Pressure at 09 GMT (mb) 1011 1011 1021 1014
Highest 1030 1043 1038 1043
Date 15 27 17 .
Lowest 976 986 977 976.0
Date 21 2 11 .
.
Means at 0900 GMT .
Air temperature (C) 3.8 5.4 6.9 5.4
Dew point (C) 1.8 3.5 5.5 3.6
RH% 93 88 91 91
Soil temperatures (C) .
.
5 cm 3.5 4.6 6.9 5.0
10 cm 3.9 4.9 6.8 5.2
20 cm 3.9 4.9 6.9 5.2
30 cm 4.9 5.9 7.6 6.1
Anomaly~ -0.9 0.2 0.4 -5.2
50 cm 5.6 6.1 7.8 6.5
100 cm 6.9 6.9 8.0 7.3
Anomaly~ -0.7 -0.1 0.1 -4.4
.
Rainfall (mm) .
.
Rain tot 180.6 146.6 124.7 451.9
Rain % ave~ 169 143 151 37
Rain % 30-y 175 162 159 39
Days 0.0 1 3 8 12
Days <0.2 7 11 13 31
Days >=0.2 24 17 18 59
Days >=1.0 15 15 11 41
Days >=5.0 9 9 6 24
Max fall 31.5 50.6 30.0 50.6
Date 18 23 14 .
Highest rate (mm/h) 18 36 58 58
Date 18 16 25 .
Average rain per hour (mm) 1.1 1.2 1.3 1.1
.
Evaporation .
.
Piche (mls/ mm) 16.3 31.1 31.0 78.4
Lysimeter PE (mm) 8.5 17.3 34.5 60.3
AWS ET calculated 9.3 21.8 33.3 64.4
.
Weather (days) .
.
Air frost 8 6 2 16
Ground fr 21 12 7 40
Sl/snow 6 2 2 10
Sn lying 0 0 0 0
Thunder 0 0 0 0
Hail <5 mm 12 7 3 22
Hail >=5 mm 0 0 0 0
Fog at 09h 2 0 0 2
Gales in SE Anglesey 0 6 5 11
.
Wind direction at 09h (days) .
.
N 5 0 1 6
NE 4 0 3 7
E 3 5 3 11
SE 1 5 2 8
S 1 8 3 12
SW 8 7 11 26
W 6 2 6 14
NW 1 0 2 3
Calm 2 1 0 3
.
Wind speed mph .
.
Daily mean 6.0 7.6 7.5 7.0
Highest daily mean 15.3 17.7 22.7 22.7
Date 19 23 28 .
Mean gust 19.5 24.6 22.2 22.1
Highest gust 40 50 49 50
Date 19 23 10 .
.
AWS records of rainfall and frost .
.
Wet hours (with 0.2 mm,or more) 169 125 99 393
Frost duration (h) 46.5 53.3 10.3 110.1
.
Cloud cover at 09h. Mean % 81 69 78 76
.
Global solar radiation (MJ m-2) .
.
Llansadwrn
Sol rad mean 2.52 5.29 8.11 5.31
Maximum 5.31 11.62 16.38 16.38
Date 25 28 30 .
Minimum 0.86 1.54 1.52 0.86
Date 13 20 10 .
Brightest hour W/sq m 309 488 629 629
during hour beginning GMT 12 12 12 12
on day 23 28 24 .
Sunless days 11 7 9 27
.
Sunshine (h) .
[ ~ missing days are derived] ~2 .
Valley 41.1 92.8 114.4 248.3
Average %~ 80 114 88 16
Average 30-y 73 118 95 17
Sunniest 6.3 10.1 10.3 10.3
Date 25 28 1 .
Sunless days 13 7 7 27
.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

Llanfairfechan, Gorwel Heights observations

Gorwel Heights (73 m), Llanfairfechan (Conwy): Monthly weather data summary 2021
Anomalies based on [1991-2020] # & 10-y averages (2011-2020) *
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Air temperatures (C)
.
Mean max 6.6 9.3 10.6 8.8
Mean min 2.9 4.2 5.3 4.1
Mean 4.8 6.8 8.0 6.5
Anomaly (2011-2020) * -1.5 0.6 0.4 -4.8
Anomaly [1991-2020] # -1.4 0.6 0.4 -4.5
High max 12.2 14.3 17.7 17.7
Date 28 23 30 .
Low max 2.3 1.1 5.6 1.1
Date 8 9 4 .
High min 8.1 10.1 10.3 10.3
Date 28 20 29 .
Low min -0.8 -2.3 0.8 -2.3
Date 9 13 7 .
.
MSL Pressure at 09 GMT (mb) 1012 1012 1021 1015
.
Highest 1031 1043 1038 1043
Date 15 27 6 .
Lowest 976 986 976 976
Date 21 2 11 .
.
Means at 0900 GMT
Air temperature (C) 4.5 6.4 7.7 6.2
Dew point (C) 2.6 2.8 5.3 3.6
RH% 86 77 82 82
.
Rainfall (mm)
.
Total 205.0 95.8 90.0 390.8
% (2011-2020) * 223 113 103 34
% [1991-2020] # 230 128 109 35
Max fall 34.2 18.4 13.4 34.2
Date 20 23 9 .
Highest rate (mm/h) 21 103 29 103
Date 27 23 25 .
.
Wet hours (with 0.2 mm, or more) 173 104 92 369
Average rain per hour (mm) 1.2 0.9 1.0 1.1
.
Days <0.2 9 13 15 37
Rain >=0.2 22 15 16 53
Wet >=1.0 17 12 13 42
Days >=5.0 11 8 8 27
.
Weather (days) .
.
Air frost 3 6 0 9
Frost duration (h) 7.2 71.5 0 78.7
Wind direction at 09h (days) .
.
N 5 1 1 7
NE 2 3 1 6
E 1 5 2 8
SE 6 3 2 11
S 3 12 10 25
SW 11 3 7 21
W 1 0 0 1
NW 0 0 0 0
Calm 2 1 8 11
.
Mean mph 4.4 8.8 4.6 5.9
Highest daily mean mph 18.8 25.4 14.9 25.4
Date 31 12 10 .
Mean gust 21.1 32.5 21.2 24.9
Highest gust 52 64 50 64
Date 16 23 28 .
.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year
Days wind 31 28 31 0 0 0 0 0 0 0 0 0 90

Acknowledgements

The Met Office at RAF Valley kindly supplied observational data from 1942 to 2011. Current data (provisional) are gathered from SYNOP reports and METAR, any missing observations are initially derived from nearby stations to complete the record, up to date figures are later gathered from the Met Office website. I am grateful Ivor McLean former Met Officer at RAF Valley for early Holyhead sunshine and various other observations; David Lee for use of his observations from Gorddinog; and Gordon Perkins (BlueTractorSoftware) for observations at Gorwel Heights and providing additional observations.



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Page first dated 5 February 2021

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