Speleotrove weather analyses

Wittering, 18:00 to 20:00, 1997–2020

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Met Office station 583: Wittering, Cambridgeshire (PE8 6); OS grid reference: TF 042026.
Coordinates: N52°36'40" W0°27'32" (52.611 -0.459), elevation 73 m.
Note: gusts not recorded in 5 out of the 24 years, 0.6% of daylight visibility records missing, 0.3% of daylight wind records missing.

This is the analysis for the average of 24 years (1997–2020).
Time slot: 18:00 to 20:00 (two hours); click below for any-hour analysis, or a different start time, or for whole day analysis (all times are GMT):

any-hour 06:00 08:00 10:00 12:00 14:00 16:00 18:00 all-day

‘Flyable days’ analysis

This is the number of days in each month, on average, for which (in this timeslot) the visibility was adequate, and there was no bad weather, and the wind speed was less than or equal to that shown on the left.

	May	Jun	Jul	Aug	Total
≤ 5 mph	1	2	2	1	6	2%
≤ 10 mph	7	8	8	4	27	7%
≤ 15 mph	17	17	19	9	62	17%
≤ 20 mph	21	21	22	11	75	20%
≤ 30 mph	22	21	23	11	78	21%
≤ 40 mph	23	22	23	11	79	21%
any wind	23	22	23	11	79	22%

‘Total’ shows the total flyable days, on average, in a year, and the same as a percentage.

Trend analysis

This is the average change (per year, over the 24 years) in the average number of days in each month for which (in this timeslot) the visibility was adequate, and there was no bad weather, and the wind speed was less than or equal to that shown on the left.

For example, if a value of +0.5 is shown for a given month then that implies that since 1997 the number of flyable days in that month has increased by (on average) half a day per year.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
≤ 5 mph
≤ 10 mph +0.1 −0.1 −0.2 −0.1 −0.3
≤ 15 mph +0.1 −0.1
≤ 20 mph +0.2 +0.1 −0.1 +0.2
≤ 30 mph +0.2 −0.1 +0.2
≤ 40 mph +0.2 +0.1 −0.1 +0.2
any wind +0.2 +0.1 −0.1 +0.3
Empty cells indicate negligible change; ‘Total’ shows the sum of the trends over the whole year.

Visibility analysis

This is the number of days in each month, on average, for which (in this timeslot) the visibility was adequate. That is, for the entire timeslot:

both hours were daylight (no more than 30 minutes before sunrise or after sunset)
horizontal visibility was at least 5000m (UK VFR rules » for class F or G »)
cloudbase was above 1000′ or less than 6/8 coverage.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total
Good days	0	0	0	0	29	29	29	14	0	0	0	0	101	28%

Bad weather analysis

This is the number of days in each month, on average, for which (in this timeslot) no bad weather occurred. That is, for the entire timeslot, there was no rain, hail, snow, snow on the ground, icing conditions, thunderstorms, etc.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total
Good days	21	19	22	22	24	22	23	23	24	23	21	21	265	73%

Wind speed analysis

This is the number of days in each month, on average, for which (in this timeslot) the maximum (gust) wind speed was less than or equal to the value shown on the left.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total
≤ 5 mph	3	3	3	2	2	3	2	3	4	5	3	4	36	10%
≤ 10 mph	12	11	12	10	10	11	11	12	15	16	13	12	145	40%
≤ 15 mph	22	19	22	22	23	24	25	25	25	25	24	22	279	76%
≤ 20 mph	26	24	28	28	29	29	30	30	29	28	27	27	333	91%
≤ 30 mph	29	27	30	30	30	29	31	31	30	30	29	30	356	97%
≤ 40 mph	30	28	31	30	31	30	31	31	30	31	30	30	363	99%

Please send any comments, questions, or corrections to me, Mike Cowlishaw, at mfc@speleotrove.com.

	May	Jun	Jul	Aug	Total
≤ 5 mph
≤ 10 mph	+0.1	−0.1	−0.2	−0.1	−0.3
≤ 15 mph	+0.1		−0.1
≤ 20 mph	+0.2	+0.1	−0.1		+0.2
≤ 30 mph	+0.2		−0.1		+0.2
≤ 40 mph	+0.2	+0.1	−0.1		+0.2
any wind	+0.2	+0.1	−0.1		+0.3