Llansadwrn (Anglesey) Weather Observations from the observer's spreadsheet Usually updated on a Monday, but may be updated at other times.

Key to observations.

CLIMATOLOGICAL OBSERVATIONS AT LLANSADWRN, ANGLESEY, FOR SEPTEMBER 2024
	<---09 GMT--->					<-------Air temperature-------->							<---Soil temp--->			<---Earth temp--->			<--State Grd.-->				Rain	Sol	<-------Weather------->						Press	Pptn	Fr.	Pch
DD	N	dd	ff	V	ww	Temp	Dpt	RH	Max	Min	Mean	Gmin	5cm	10cm	20cm	30cm	50cm	100cm	E	C	Gr	SS	mm	MJ/m2	S	L	H	T	G	F	mb	W hrs	hrs	evap
1	8	E	2	6	02	16.4	14.2	87	19.6	14.6	17.1	11.5	17.0	16.7	17.2	17.2	16.9	16.1	0	0	1	0	54.4	5.22							1016	15	0.0	0.4
2	8	NE	1	5	61	16.1	15.9	99	18.0	16.1	17.1	14.5	17.0	17.0	17.1	17.3	17.0	16.2	2	3	3	0	4.6	3.59							1009	10	0.0	0.2
3	6	W	1	6	01	13.4	12.6	95	15.8	11.2	13.5	8.4	16.0	15.5	16.5	16.8	16.9	16.4	1	2	3	0	1.8	10.02							1014	2	0.0	0.6
4	8	SW	2	5	25	11.6	10.7	94	15.3	8.2	11.8	5.0	14.0	14.3	16.1	16.8	16.8	16.2	1	2	3	0	0.2	9.32							1019	3	0.0	0.7
5	8	NE	4	7	02	14.7	13.3	91	17.7	10.0	13.9	7.5	14.7	14.8	15.9	16.3	16.5	16.1	1	2	3	0	tr	4.68							1021	1	0.0	1.0
6	7	NE	2	5	04	16.6	15.6	94	23.4	14.5	19.0	12.5	17.0	16.2	16.0	16.2	16.0	16.0	1	0	1	0	0.0	18.21							1013	0	0.0	1.7
7	9	E	1	4	04	17.7	16.6	93	22.1	14.9	18.5	13.6	17.3	16.5	17.1	17.2	16.7	16.2	1	0	1	0	0.1	17.74							1011	1	0.0	1.0
8	8	NE	1	5	04	16.4	15.8	96	16.6	15.8	16.2	15.2	17.4	17.4	17.5	17.7	17.0	16.0	1	2	3	0	tr	2.67							1005	0	0.0	0.6
9	7	NW	1	7	012	12.8	9.8	82	17.4	11.2	14.3	9.2	15.0	15.2	16.3	16.9	16.8	16.1	1	0	1	0	0.1	11.86							1014	1	0.0	2.0
10	8	SW	3	5	02	13.7	11.6	87	14.8	12.8	13.8	11.7	14.8	15.2	16.2	16.8	16.8	16.2	1	0	1	0	4.3	7.13							1006	12	0.0	0.8
11	7	W	3	6	01	10.3	8.7	90	14.3	8.1	11.2	5.2	12.5	13.0	15.0	16.1	16.3	16.1	1	2	3	0	2.6	9.01			4	T			1010	5	0.0	1.0
12	5	NW	3	7	03	9.2	8.1	93	15.1	6.4	10.8	3.3	12.1	12.0	14.3	15.2	16.0	16.0	1	2	4	0	0.7	12.50			4				1017	2	0.0	1.4
13	3	NE	2	7	01	9.6	8.4	92	15.7	6.1	10.9	2.6	12.2	11.7	13.9	14.9	15.8	15.9	1	0	1	0	0.0	12.80							1029	0	0.0	3.0
14	7	SW	5	6	02	14.9	12.2	84	17.8	9.6	13.7	9.1	13.7	13.7	14.6	15.0	15.5	15.6	1	0	0	0	10.6	13.96					1		1027	8	0.0	2.8
15	8	SW	3	4	61	14.1	12.8	92	14.9	13.8	14.4	11.8	14.5	14.7	15.0	15.0	15.3	15.5	1	2	3	0	15.0	3.01			4				1023	6	0.0	0.4
16	4	00	0	8	02	13.1	11.7	91	20.3	9.2	14.8	5.5	14.2	13.0	14.3	14.8	15.2	15.3	1	2	3	0	0.0								1030		0.0
17
18
19
20
21
22
23
24
25
26
27
28
29
30
N	87	%
Means---->						13.8	12.4	91	17.4	11.4	14.4	9.2	15.0	14.8	15.8	16.3	16.3	16.0						9.45							1017
Totals----->																							94.4	141.72	0	0	3	1	1	0		66.0	0.0	17.6
MEANS AND AVERAGES AT LLANSADWRN, ANGLESEY FOR SEPTEMBER 2024
Differences from 2014-2023 average* & from 1991-2020 average**.
Air temperature (C)							*	**		Weather (No. days occurrence)						*		Wind direction (days)								Rainfall (mm)						*	**
	Mean maximum					17.4	-0.5	0.1			Sleet/ snow falling				0	0.0			N			0					Total				94.4	91	93	%
	Mean minimum					11.4	0.2	0.7			Snow lying (at 09 GMT)				0	0.0			NE			5					Largest fall				54.4
	Mean (max+min)/2					14.4	-0.2	0.4			Hail <5 mm				3	2.4			E			2
	Highest maximum					23.4	-0.3				Hail >=5 mm				0	{All types}			SE			0				Evaporation (mm)
	Lowest maximum					14.3	1.1				Thunder heard				1	0.5			S			0					Lysimeter				PE	0.0
	Highest minimum					16.1	-0.1				Gales				1	n.a.			SW			4					Monthly total				PWB	77.0
	Lowest minimum					6.1	-0.9				Fog (at 09 GMT)				0	n.a.			W			2									PWS	81.1
	No. days <0.0C					0	0.0			Rainfall (No. days occurrence)									NW			2									PWD	-4.2
Grass minimum mean						9.2	0.9				No pptn		0.0 mm		3	-6.1			Calm			1					AWS				ET	20.1
Lowest minimum						2.6	-0.1				Dry		< 0.2 mm		7	-2.1											Piche				P I	17.6
	No. days <0.0C					0	0.0				Rain		>= 0.2 mm		9	-8.4			Check days			16
Earth temperature 30cm						16.3	0.5				Wet		>= 1.0 mm		7	-5.7			This month			30
													>= 5.0 mm		3	-3.9

Note: Any peaks seen on the PE graph are due to recent rainfalls having not yet percolated through the soil. This method is not good for daily measurements, but good results are obtained over 3 days (allowing time for percolation) and on a monthly basis. The lysimeter also measures dew and depositions of frost, and is a better raingauge than one with a rim at 30 cm high. In winter, when evaporation from the ground is low, negative values are sometimes seen and indicate an accumulation of dew and frost, and more rain than measured by a standard raingauge. In summer, when evaporation is high and rainfall less, the lysimeter still measures dew and more rain than the standard gauge, but the effect is less noticeable. The daily graph is show here for it's interest and you can read more about this 'classic' method of measuring evaporation here.

 

KEY: OBSERVATIONS AT 09 GMT DD date; N cloud (oktas, 9=obscured); DD wind direction (8 sectors, 00=calm); ff wind speed (Beaufort scale); V visibility (0 dense fog, 1 thick fog, 2 fog, 3 moderate fog, 4 very poor, 5 poor, 6 moderate, 7 good, 8 very good); WW present weather SYNOP code (eg. 01 cloud decreasing, 02 sky not changing, 03 cloud increasing, 04 smoke haze, 05 haze) Temperatures (degC); Temp dry bulb temperature; Dpt dewpoint; RH relative humidity (%); soil temperatures are under bare soil and earth under grass; SS snow depth (cm); Press air pressure, aneroid (mb). For state of the ground E, concrete C, and grass Gr codes consult the page on 'Recording Atmospheric Depositions on Grass'. =0 bare soil very dry and cracked; +2 local flash flooding. 24 hour observations... Max maximum temperature (degC) beginning 09GMT; Min minimum temperature ending 09GMT; Gmin grass minimum temperature (degC) ending 09GMT; Pch Evap Piche evaporation (ml) beginning 09GMT; Rain rainfall beginning 09GMT (mm); Pptn W hrs number of hours with precipitation 09-09GMT; trace <0.05 mm; tr trace of rain; tr dw trace of dew; tr fr trace of frost; Fr. hrs hours of frost (09-09GMT). Sol MJ/m2 Global Solar Radiation (MJ per m2) 00-00 GMT. Monthly observations... PE Potential evapotranspiration, PWB Potential water balance, PWS Potential water surplus, PWD Potential water deficit. Weather: days with... s slight or S heavy snow/sleet falling; L >=50% snow cover at 09GMT; H categories of hail: 1 ice crystals, 2 snow grains, 3 snow pellets, 4 ice pellets, 5 hail 5-9 mm, 6 hail 10-19 mm; up unidentified precipitation; t slight or T heavy thunder heard; G Gales (Beaufort land scale) refer to the area; Fog any hour 1, 09 GMT 9.

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