October 2017 – The 1st Half (Dry and Warm)

A recent run of unusually warm nights has pushed the mean temperature up to over 2°C above my very estimated LTA.

1st – 16th October
Mean minimum = 10.6°C
Mean maximum = 18.1°C
Mean = 14.4°C
Rain = 4.6 mm
Sunshine = 64.4 hours.

It has been the driest first half of any October I have recorded since before 2005 in what normally is one of the wettest months of the year. Sunshine levels just a little below normal after a few rather cloudy days, though only one day so far has been completely without any sunshine (13th). No grass frosts but that is nothing out of the ordinary as I don’t expect to see those appear until right at the end of the month or even into November.

Storm Ophelia (did the Met Office rename it to fit in with their protocol?) just gave a ‘not out of the ordinary’ windy day here with a maximum gust of 33 mph.

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Hurricane Ophelia Approaches

Hurricane Ophelia is on its way to the British Isles. By the time it arrives it will be an ex-Tropical storm rather than an actual hurricane but it is looking like a very severe storm. The latest models predict the centre of the storm will move up the west coast of Ireland with the strongest winds out in the Irish Sea, well away from us here in the South West. But it will still be windy with a huge swell developing bringing a large surf to even here at Sidmouth. Time to get the ol’ surfboard out.

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14th October – Mild Night

A minimum of 15.8C last night was the warmest October night since 16.9C on the 3rd October 2013. That was also the highest minimum October temperature I have recorded since before 2005.

As Hurricane Ophelia approaches the forecast is for even warmer nights with very high minimums for the time of year through Sunday night and into early Monday morning.

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Summer in October

October days do not get any better than today in what is turning out to be a lovely start to the month.

A maximum of 20.4C and nearly 8 hours of sunshine. With a DP around 15C and just a light, sea breeze made for a warm and sunny afternoon.

A few hours kip in the hammock allowed for the fading suntan to be topped up a little. Busy down on the beach, more like July than October.

Cool, misty mornings and fine, sunny afternoons have dominated the first 8 days of this month. No rain since the 2nd.

1st – 8th
Mean minimum = 8.4C
Mean maximum = 18.3C
Mean = 13.4C
Rain = 2.6 mm
Sunshine = 46.3 hours.

Average Sunny Interval Length

You might find the data below interesting (if the tabs don’t get all messed up). It is the average length of a sunny interval (in minutes) for here. Stephen Burt helped me put together a spreadsheet that calculates it from the electronic sunshine recorder.

It might be of use to determine cumulus development which should, in theory reduce the length of the sunny interval. I note that Stephen’s data from Reading was rather different in that his average sunny interval length was far, far shorter; almost dramatically so.

Sun Interval 2012 2013 2014 2015 2016 2017
Jan 51.4 26.7 27.3 44.0 45.2 75.8
Feb 61.8 28.2 28.1 59.4 31.2 52.7
Mar 139.5 39.3 98.2 67.1 85.7 63.5
Apr 56.6 60.8 74.8 174.4 65.5 93.2
May 116.8 101.1 88.8 48.5 119.0 104.6
Jun 41.5 104.0 110.8 100.3 51.4 143.2
Jul 99.5 263.5 91.9 56.6 76.2 101.6
Aug 70.0 90.1 51.7 49.2 121.6 72.3
Sep 76.7 50.9 93.6 121.1 49.4 44.1
Oct 46.1 49.6 46.1 79.5 90.3
Nov 48.7 55.2 49.5 29.4 78.9
Dec 47.6 43.0 70.9 23.7 42.9
Ave 71.4 76.0 69.3 71.1 71.4 83.5

I’ll sort the data to show and average sunny interval through each hour of the day. That might reveal any cumulus development through the year.

Average Sunny Interval Length Through the Day

The following data (for 2017) gives the time (in minutes) of the average length of sunny interval (when the sun is shining) for each hour of the day.

You can see that peak length in January is in the morning but then tapers off slowly but not hugely during the afternoon. February on the other hand is very different and that is probably down to a stronger sun and convective cloud forming. There is a brief morning peak then a reduction in interval length. March and April follow in a similar way but there is another peak a couple of hours before sunset. The summer months follow a similar pattern.

So it seems that in January it takes until early afternoon for convective cloud to form and reduce the length of sunny interval slightly. Whereas by February, the sun is strong enough to cause a reduction in sunny interval from 10:00 onwards.

Hour Jan Feb Mar Apr May Jun Jul Aug Sep
04:00 0.0 0.0 0.0 0.0 5.4 14.9 4.4 0.0 0.0
05:00 0.0 0.0 0.0 8.9 27.2 22.7 24.4 14.1 6.5
06:00 0.0 0.0 14.2 23.8 23.8 15.7 20.2 24.2 21.4
07:00 0.0 11.7 23.7 21.7 22.0 19.7 14.2 21.8 22.9
08:00 17.5 24.1 24.9 20.0 17.4 19.6 15.2 17.2 21.3
09:00 25.1 24.3 20.7 18.2 13.2 15.4 16.4 12.5 14.2
10:00 22.3 18.4 15.7 16.4 15.5 16.4 15.1 13.4 10.6
11:00 26.3 15.6 16.4 17.3 16.2 17.1 14.0 13.2 11.7
12:00 24.5 14.8 16.0 13.3 16.3 15.8 16.2 13.3 7.4
13:00 22.9 18.9 14.4 14.3 15.2 16.2 17.0 13.0 9.0
14:00 22.5 15.9 12.5 19.6 18.9 18.4 16.6 10.8 11.9
15:00 20.3 15.4 11.7 19.3 22.3 17.5 15.9 10.3 13.7
16:00 8.6 17.2 15.0 24.9 22.9 19.7 16.8 20.6 17.6
17:00 0.0 13.7 22.9 20.3 22.8 18.3 14.6 16.0 20.0
18:00 0.0 0.0 12.1 16.5 21.5 24.8 19.0 19.2 8.8
19:00 0.0 0.0 7.5 2.3 17.7 26.4 23.7 9.6 0.0
20:00 0.0 0.0 0.0 0.0 0.0 1.8 1.7 0.0 0.0

Summary for September 2017

Normally one of the best months of the year but not his time. Unusually cool, cloudy and wet.

Mean Max: 18.9ºC
Mean Min: 10.5ºC
Mean: 14.7ºC

High Max: 23.1ºC 4th
Low Max: 16.9ºC 16th
High Min: 16.6ºC 4th
Low Min: 3.4ºC 22nd
Grass Min: 1.2ºC 22nd

Days >20°C 6 Days
Days >15°C 30 Days
Nights >10°C 16 Days
Nights <5°C 3 Days

Rain Total (gauge): 87.1 mm
Rain Days >0.2 mm: 21 Days
Rain Days >1.0 mm: 15 Days
Max 24 hrs: 21.1 mm 3rd
Days without any rain: 9

Thunder Heard: 1 Day 16th
Hail <5 mm: 1 Day 16th
Hail >5 mm: 0 Days
Fog @ 9am: 1 Day 18th

Total Monthly Sunshine: 137.0 Hours
Most Sunshine in a Day: 12.2 Hours 1st
Average Daily Sunshine: 4.6 Hours
Sunless Days: 3 Days
Cloudless Days: 1 Day 1st
Total Possible Sunshine: 378.1 Hours
Percentage of Total Sun: 36%

Mean Soil Temp @ 30 cm: 16.8ºC
Mean Soil Temp @ 100 cm: 16.2ºC

Ave 10 Min Wind >39 mph: 0.00 Days
Calm: 7.12 Days
Mean Wind: 3.8 mph
Max Gust: 37 mph 12th
Mean Cloud Cover: 57%

Mean Pressure: 1014.0 hPa
Max Pressure: 1025.2 hPa 2nd
Min Pressure: 993.8 hPa 11th

Max Dewpoint: 19.7ºC 4th
Min Dewpoint: 3.0ºC 22nd
Mean Dewpoint: 12.2ºC

Max Humidity: 100% Several days
Min Humidity: 50% 1st
Mean Humidity: 86%