Speleotrove weather analyses

Prestwick RNAS, 18:00 to 20:00, 1997–2020

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Met Office station 1007: Prestwick RNAS, Ayrshire (KA9 2); OS grid reference: NS 369276.
Coordinates: N55°30'54" W4°35'06" (55.515 -4.585), elevation 27 m.
Note: gusts not recorded in 13 out of the 24 years, 0.5% 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.

	Apr	May	Jun	Jul	Aug	Total
≤ 5 mph	1	1	1	2	2	7	2%
≤ 10 mph	4	8	9	9	8	38	10%
≤ 15 mph	8	18	17	18	15	76	21%
≤ 20 mph	9	21	20	20	17	86	24%
≤ 30 mph	9	21	21	21	17	88	24%
≤ 40 mph	9	21	21	21	17	89	24%
any wind	9	22	21	21	17	89	24%

‘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 −0.1 −0.1
≤ 10 mph +0.1 +0.3 −0.1 −0.1 +0.2
≤ 15 mph +0.2 +0.3 −0.1 +0.3
≤ 20 mph +0.1 +0.1 +0.1 −0.1 −0.1 +0.1
≤ 30 mph +0.1 +0.1 −0.1 −0.1
≤ 40 mph +0.1 +0.1 −0.1 −0.1
any wind +0.1 +0.1 −0.1 −0.1
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	13	30	28	28	24	0	0	0	0	123	34%

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	17	17	19	20	22	21	21	21	20	19	17	16	230	63%

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	5	5	5	3	3	3	3	3	6	5	6	6	51	14%
≤ 10 mph	13	12	13	12	11	12	14	13	15	15	14	15	158	43%
≤ 15 mph	19	18	22	24	24	25	27	25	24	23	21	20	272	74%
≤ 20 mph	23	22	27	27	29	29	30	30	27	27	25	24	319	87%
≤ 30 mph	28	26	30	30	31	30	31	31	29	30	28	28	352	96%
≤ 40 mph	30	28	31	30	31	30	31	31	30	31	30	30	361	99%

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

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