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%) & [181%] 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; wt 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) & [-1.5]. 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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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 6.4
Mean min 1.8 1.8
Mean 4.1 4.1
Anomaly~ -1.4 0.2
Anomaly 30-y -1.3 0.4
High max 10.0 10.0
Date 19 .
Low max 2.7 2.7
Date 8 .
High min 7.3 7.3
Date 28 .
Low min -2.2 -2.2
Date 9 .
Grass min -9.2 -9.2
Date 7 .
.
MSL Pressure at 09 GMT (mb) 1011 1011
Highest 1030 1030
Date 15 .
Lowest 976 976.0
Date 21 .
.
Means at 0900 GMT .
Air temperature (C) 3.8 3.8
Dew point (C) 1.8 1.8
RH% 93 93
Soil temperatures (C) .
.
5 cm 3.5 3.5
10 cm 3.9 3.9
20 cm 3.9 3.9
30 cm 4.9 4.9
Anomaly~ -0.9 -6.4
50 cm 5.6 5.6
100 cm 6.9 6.9
Anomaly~ -0.7 -4.7
.
Rainfall (mm) .
.
Rain tot 180.6 180.6
Rain % ave~ 169 15
Rain % 30-y 175 16
Days 0.0 1 1
Days <0.2 7 7
Days >=0.2 24 24
Days >=1.0 15 15
Days >=5.0 9 9
Max fall 31.5 31.5
Date 18 .
Highest rate (mm/h) 18 18
Date 18 .
Average rain per hour (mm) 1.1 1.1
.
Evaporation .
.
Piche (mls/ mm) 16.3 16.3
Lysimeter PE (mm) 8.5 8.5
AWS ET calculated 9.3 9.3
.
Weather (days) .
.
Air frost 8 8
Ground fr 21 21
Sl/snow 6 6
Sn lying 0 0
Thunder 0 0
Hail <5 mm 12 12
Hail >=5 mm 0 0
Fog at 09h 2 2
Gales in SE Anglesey 0 0
.
Wind direction at 09h (days) .
.
N 5 5
NE 4 4
E 3 3
SE 1 1
S 1 1
SW 8 8
W 6 6
NW 1 1
Calm 2 2
.
Wind speed mph .
.
Daily mean 6 6.0
Highest daily mean 15.3 15.3
Date 19 .
Mean gust 19.5 19.5
Highest gust 40 40
Date 19 .
.
AWS records of rainfall and frost .
.
Wet hours (with 0.2 mm,or more) 169 169
Frost duration (h) 46.5 46.5
.
Cloud cover at 09h. Mean % 81 81
.
Global solar radiation (MJ m-2) .
.
Llansadwrn
Sol rad mean 2.52 2.52
Maximum 5.31 5.31
Date 25 .
Minimum 0.86 0.86
Date 13 .
Brightest hour W/sq m 309 309
during hour beginning GMT 12 12
on day 23 .
Sunless days 11 11
.
Sunshine (h) .
[ ~ missing days are derived] .
Valley 41.1 41.1
Average %~ 80 3
Average 30-y 73 3
Sunniest 6.3 6.3
Date 25 .
Sunless days 13 13
.
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 [1981-2010] MetO Llanfairfechan DataPoint & Gorwel 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 6.6
Mean min 2.9 2.9
Mean 4.8 4.8
Anomaly (2011-2020) * -1.5 -6.6
Anomaly [1981-2010] # -1.5 -5.9
High max 12.2 12.2
Date 28 .
Low max 2.3 2.3
Date 8 .
High min 8.1 8.1
Date 28 .
Low min -0.8 -0.8
Date 9 .
.
MSL Pressure at 09 GMT (mb) 1012 1012
.
Highest 1031 1031
Date 15 .
Lowest 976 976
Date 21 .
.
Means at 0900 GMT
Air temperature (C) 4.5 4.5
Dew point (C) 2.6 2.6
RH% 86 86
.
Rainfall (mm)
.
Total 205.0 205.0
% (2011-2020) * 223 18
% [1981-2010] # 181 19
Max fall 34.2 34.2
Date 20 .
Highest rate (mm/h) 21 21
Date 27 .
.
Wet hours (with 0.2 mm, or more) 173 173
Average rain per hour (mm) 1.2 1.2
.
Days <0.2 9 9
Rain >=0.2 22 22
Wet >=1.0 17 17
Days >=5.0 11 11
.
Weather (days) .
.
Air frost 3 3
Frost duration (h) 7.2 7.2
Wind direction at 09h (days) .
.
N 5 5
NE 2 2
E 1 1
SE 6 6
S 3 3
SW 11 11
W 1 1
NW 0 0
Calm 2 2
.
Mean mph 4.4 4.4
Highest daily mean mph 18.8 18.8
Date 31 .
Mean gust 21.1 21.1
Highest gust 52 52
Date 16 .
.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

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.



Designed and written by Donald Perkins © 2021

Page first dated 5 February 2021

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