Weather Station

Anemometer

Our anemometer appears to have started to work again. It certainly wasn’t us out there at midnight when it started up again! I believe that we have an intermittent fault in our ISS, the main processor, which will probably need replacing. Fingers crossed that it continues to function in the mean time.

Amemometer Problems -Again!

Unfortunately our anemometer decided to “give up the ghost” at 00.20  last night during a spell of sustained winds peaking at 72mph. While it is still in situ and there is no visible reason why it should have stopped recording, this is the second time this has occured, the last time being December 2011 also during strong winds. The equipment we use, a Davis Vantage Pro2, is a scientific instument and meant to be more robust than it is actually proving to be, this being the third major fault in 4 years, the other being a faulty temperature sensor.

2013

2013 – Weather Summary

Published January 3, 2014

Overview

2013 was the windiest year ever recorded at this station. New highs were set for annual gale days, wind run and average wind speed . Despite the average temperatures for the year, new monthly lows occurred in 2 of the first 3 months, reflecting the fact that it had been the coldest spring for 50 years, In complete contrast, July was the driest and hottest month ever recorded with a new record high humidity of 100% and 10 consecutive days when temperatures exceeded 20°C.

After a brief summer, the cold, wet and windy conditions returned with the first snow fall ever to be recorded in November.  December ended the year in the same vein except it was the wettest and windiest month on record at the station. During the month a new high wind speed and lowest atmospheric pressurewere also recorded.

Summary

Despite its average temperatures January was dull, wet and very windy with gales towards the end of the month. During the gales that occurred on the 29th, winds gusted to 73mph with a wind speed of 49mph, the latter being a record for this station at the time.

February was breezy and also the coldest month on record at the time with the first air frosts  of the year. As this time last year, there was below average rainfall.

The beginning of March saw the jet stream passing over Spain which was even further south than in 2012. This allowed an Easterly air stream to develop bringing cold but bright conditions resulting in 9 air frosts but plenty of sunshine. In fact, March was the coldest month since our records began breaking all the records set in February. March was also very dry with lower than usual humidity and no snowfall despite nearby islands and many parts of the mainland suffering the worst snowfalls in living memory. The month ended with 9  consecutive days without rain.

April continued the cold, wet, windy conditions with Easterly winds in the early part of the month bringing the lowest temperature of the year (-3.3°C) and 6 of the 7 month’s air frosts during the first 8 nights. The continuing clear, dry conditions resulted in the  longest recorded dry spell of 15 consecutive days without rainfall, ending when 0.2mm of rain on the 6th. Winds then veered South, bringing higher temperatures which finally reached double figures on the 14th for the first time since early January.

May was  blustery and chill with below average temperatures reflecting the fact that nationally, it had been the coldest Spring for 50 years.  The month was gripped by Westerlies bringing rain, chill winds and very little sunshine. The temperature eventually rose above 15°C for the first time on the 7th  but the keen winds did not reflect this.

June was a particularly cloudy and breezy month. While not feeling particularly warm, the cloud had the effect of raising the average temperature by keeping night time temperatures high. Despite the cloud, June was dry with only 60% the average rainfall and surprisingly, it was also the sunniest month since our records began, due mainly to the long days.

In July, while most of the UK’s weather was dominated by high pressure and the majority of people sweltered in temperatures exceeding 30°C, we were shrouded in mist and fog with temperatures struggling to reach the mid teens. When the mists finally lifted, we recorded 100% humidity for the very first time. Clear skies and long hot and sunny days then followed with temperatures exceeding 20°C on 10 consecutive days. Despite the misty and humid conditions, July was the driest month on record. It was also the hottest month on record with all 4 mean temperature measurements being exceeded.

The dull, breezy conditions returned in August and continued throughout September with near average rainfall and less sunshine than previous years. Temperatures exceeded 20°C only twice in August and was hovering around double figures as a daily maximum by the end of September.

October bucked the cold trend by being the warmest October on record here at Askernish. It began with blustery southerly winds bringing moist and cloudy conditions, after which a high front brought light easterlies and a period of dry and calm weather. Mid moth saw cloud increasing from the South with increasing winds, rain, and lower temperatures with winds gusting to 49 mph towards the end of the month.

November was blustery with only a few rest bites, the strongest winds being towards the end of the month. The wind was a feature throughout the month with the wind gusts regularly exceeding 40mph. It  began dull, wet and windy with frequent showers, some turning to hail. Brief periods of sunshine and showers did occur, during which the wind was still a feature. The clearer skies during these brief rest bites resulted in lower temperatures at night with the first ground frost of the winter and the first snowfall to be recorded during the month of November.  The month ended with a return of the dull, showery, blustery conditions with winds peaking 54mph.

Blustery conditions continued throughout December with a continual succession of depressions sweeping in from the Atlantic. These depressions ensured that December was the wettest, dullest and windiest monthever recorded at this station. Winds were generally from the West or South and there were very few days when the wind did not exceed 30mph. These incessant winds resulted in 3 gale days, and the highest wind speed ever recorded at this station. Some of the severest weather occurred over the Christmas period with the lowest atmospheric pressure  ever recorded  here occurring early on Christmas Eve.

Statistical Summary

Temperature (°C):
Mean (1 minute)  9.2
Mean (min+max)   9.3
Mean Minimum     6.8
Mean Maximum     11.7
Minimum          -3.3    –     2 April
Maximum          24.3    –     20 July
Highest Minimum  15.7    –    22 July
Lowest Maximum   3.3    –     20 January
Air frosts       22

Rainfall (mm):
Total for year  910.2
Wettest day      24.0    –    14 November
High rain rate   61.0     –    22 October
Rain days        265
Dry days         100
Days above 20˚C  15
Days above 15˚C  84
Days below 0˚C  22
Days below -5˚C  0

Wind (mph):
Highest Gust     73.0    –     29 January
Average Speed    11.2        –       New Station Record High
Wind Run         97971.5 miles              –             New Station Record High
Gale days        5             –            New Station Record High
Predominant Direction  SSW

Pressure (mb):
Maximum          1039.29    –     25 November
Minimum          939.96    –     24 December               –               New Station Record Low

Days with snow falling         3
Days with snow lying at 0900   0

Total hours of sunshine        1085.0

Other station records set during the year included the lowest apparent temperature (-13.3°C) on the 14th Feb, highest minimum temperature (15.7°C) on 23rd July and the highest dew point (19.9°C) on the 21st August.

The highest daily wind run of 734.3 miles occurred on 29th Jan.

December 2013 – Summary

Published January 1, 2014

Overview

A blustery November was followed by a continual succession of depressions sweeping in from the Atlantic. These depressions, which lasted throughout the month of December, ensured that it was the wettest, dullest and windiest month ever recorded at this station. Winds were generally from the West or South and there were very few days when the wind did not exceed 30mph. These incessant winds resulted in 3 gale days, and the highest wind speed ever recorded at this station. Some of the severest weather occurred over the Christmas period with the lowest atmospheric pressure  ever recorded  here occurring early on Christmas Eve.

Summary
The first day of December was calm following a blustery November, but it proved to be the one and only time during the month. The first of the Atlantic depressions moved in on the 2nd bringing increased winds and overcast conditions. As it passed early on the 3rd, temperatures fell and the winds veered N and then slowly but steadily increased. These chill winds peaked around dawn on the 5th, gusting to 70mph when a wind speed of 49mph was recorded, equalling the station record. The only snowfall of the month occurred during this period.

The brisk North winds continued until the 7th when they veered towards the South bringing dull, wet, but warmer conditions, with no rest bite from the wind due to more Atlantic fronts. What followed were 11 wet and windy days with winds regularly gusting to 40, 50 or 60mph. Overcast conditions prevailed with rain, heavy at times, and very little sunshine. Winds eventually peaked during the early hours of the 19th,  gusting to 69mph when a wind speed of 50mph was recorded, a new station record.

The dull, wet and windy conditions continued through to the 22nd with many showers turning to hail.  The 23rd saw yet another deep Atlantic depression approaching when the atmospheric pressure began to drop rapidly. As the front passed with winds in excess of 60mph, an atmospheric pressure of 939.96mB was recorded late morning on the 24th, a new station record. Rain and strong winds persisted through to the end of the month with winds again regularly gusting 40 – 50 mph.

Despite all the wind and rain, temperatures in December were some 1.5°C above the average. All headline temperatures and averages were the highest recorded in a December, with a maximum temperature of 12.1°C occurring on the 10th.  There were no air frosts.

A total of 182.4 mm of rain fell during the month, a new station record. This rain fell on 31 rain days indicating that we experienced some rainfall on each and every day.

During the month there were 3 gale days, the average wind speed was 17.5mph with a  wind run of 12988.0 miles, all new records for this station. The highest gust was 70mph on the 5th and the highest wind speed recorded was 50mph on the 19th, the latter yet another record for this station.

As for sunshine, a total of 19.5 hours of sunshine were recorded on 16 sunshine days during December,  both new lows for this station

Statistical Summary

Temperature (°C):
Mean (1 minute)  7.4
Mean (min+max)   7.2
Mean Minimum     5.2
Mean Maximum     9.2
Minimum          0.9     –    on the 5th
Maximum          12.5     –    on the 10th
Highest Minimum  10.6     –    on the 12th
Lowest Maximum   5.2     –    on the 5th
Air frosts       0

Rainfall (mm):
Total for month  182.4        –       New Station Record High
Wettest day      16.8     –     on the 26th
High rain rate   50.8     –    on the 7th
Rain days        31
Dry days         0

Wind (mph):
Highest Gust     70.0     –    on the 4th
Average Speed    17.5                    –                 New Station Record High
Wind Run         12988.0 miles              –              New Station Record High
Gale days        3       –       New Station Record

Pressure (mb):
Maximum          1034.34     –    on the 1st
Minimum          939.96     –     on the 24th               –            New Station Record

Days with snow falling         1
Days with snow lying at 0900   0

Total hours of sunshine        19.5

November 2013 – Summary

Published December 1, 2013

November was blustery with only a few rest bites, the strongest winds being towards the end of the month. Despite the seasonal average temperatures, there were times when it felt cold due to the wind, the lowest wind chill being -6.8°C on the 19th. When it was calm, temperatures fluctuated around 10°C with a daily temperature range of only 0.5°C (10.9°C – 10.4°C) on the 25th, a record for this station. November was also a dry month with only 71.6mm of rain falling, some 40% below the 10 year average. There was also a smattering of snow overnight on the 18th, the first snow to be recorded in November at this station.

November began dull, wet and windy. There were frequent showers, some turning to hail, and winds gusting to 43mph in the first 3 days. Sunshine and showers followed for the next 5 days although the wind was still a feature, gusting to 44mph on the 6th. The clearer skies resulted in more sunshine, 4.5 hours on the 4th , but lower temperatures at night with the first ground frost of the winter on the 4th and icy conditions early on the 9th.

The dull, showery, blustery conditions returned later on the 9th and continued until the 17th, with winds peaking 53mph on the 13th. Despite the windy conditions, it was warmer with a high of 11.6°C being recorded on the 15th and the 16th.

On the 18th, the wind veered towards North and temperatures began to fall. With winds gusting to 54mph and lower temperatures, a small smattering of snow fell overnight, the first to be recorded in November. Winds eased during 19th – 25th only gusting to 18mph, and it was brighter but colder with temperatures falling overnight to -1.5°C on the 21st, the first and only air frost in November.

With winds backing West on the 26th , the warmer, dull and blustery conditions returned once again with winds peaking 48mph during this period.

Temperatures were near average for the time of year with a Mean Temperature (1Min) of 7.2°C. There was 1 air frost on the 21st when temperatures fell to -1.5°C overnight.

71.6mm of rain fell during the month on 28 rain days. Despite the number of rain days, the total rainfall for the month was 40% below the 10 year norm.

The average wind speed was 11.6mph with a wind run of 8359.3 miles. The highest gust was 54mph on the 19th and the dominant direction was West.

The sun shone for more than 0.5 hours on 26 days resulting in 50.7 hours of sunshine during the month.

Statistical Summary – November 2013

Temperature (°C):
Mean (1 minute) 7.2
Mean (min+max) 6.9
Mean Minimum 4.4
Mean Maximum 9.3
Minimum -1.5 – on the 21st
Maximum 11.6 – on the 15th
Highest Minimum 10.4 – on the 26th
Lowest Maximum 5.0 – on the 21st
Air frosts 1

Rainfall (mm):
Total for month 71.6
Wettest day 7.6 – on the 22nd
High rain rate 28.6 – on the 27th
Rain days 28
Dry days 2

Wind (mph):
Highest Gust 54.0 – on the 19th
Average Speed 11.6
Wind Run 8359.3 miles
Gale days 0

Pressure (mb):
Maximum 1039.29 – on the 25th
Minimum 984.36 – on the 2nd

Days with snow falling 1
Days with snow lying at 0900 0

Total hours of sunshine 
50.7

Temperature and Humidity Censor Problems

Published November 22, 2013

We have been experiencing intermittent problems with our temperature and humidity readings over the past few months, but yesterday (21/11/2013) saw a prolonged period where the temperature readings were 69.9’C and 100% humidity!

It would appear that we have a “flaky” censor which needs replacing and we may well experience some more anomalous readings before it is delivered and can be fitted.

This is now the second major failure in 3 years and is something that I was not expecting with the Davis VP2 weather station. Davis has always been noted for their expensive weather stations but they are considered to be the best. With our experience here at Askernish, it would appear to us that the reputation of this company for reliability far exceeds what it’s equipment actually delivers.

My father would have likened them to the cavalry – they certainly know the meaning of the word “charge

Not only is there the expense, there is also the inconvenience of the down time and then having to correct the data. It weaves a complicated web and impacts on so many other measurements which are calculated internally by the software. There are many hours of “fun” ahead.

October 2013 – Summary

Published November 1, 2013

October 2013 was the warmest October on record here at Askernish with temperatures exceeding or equalling not only the headline temperature measurements (highest, and mean), but also the highest heat index (16.2°C), dew point (15.4°C) and apparent temperature (14.6°C) was recorded for the month of October. With several weather fronts moving through during the tail end of the month, the highest wind gust plus the highest and lowest pressures were also recorded for the month of October.

The month began with blustery southerly winds bring moist and cloudy conditions until 8th. Conditions improved from the 9th onwards when a high front brought a light east wind which cleared the skies resulting in a dry, calm period which continued until 16th. During this period there were up to 8 hours of warm sunshine per day and no rain for 6 days. In fact, only 4.4mm of rain fell in the first 16 days of the month.

Cloud began to increase from the 17th, bringing some rain, and it began to feel a little chill as the winds began to rise. Wet and blustery conditions then prevailed for the remainder of the month with winds gusting to 49 mph and 13.4 mm of rain falling on the 30th.

Rainfall for the month was 76.8mm, the majority of which occurred in the last 10 days of the moth. It fell on just 20 rain days, the fewest ever recorded in October.

The average wind speed was 11.1 mph with a wind run of 8283.4 miles reflecting the mid month lull. The highest gust was 49mph on 30th and the predominant direction was South.

Although feeling chill in the brisk winds, temperatures were higher than usual with the highest ever recorded in October (16.3°C) on 3rd. The mean temperatures were also high equalling those of October 2011.

The sun shone for more than 0.5 hours on 22 days resulting in 69.4 hours of sunshine during the month with a maximum of 7.9 hours on 12th.

Other records of note were the highest and lowest atmospheric pressures being recorded in October, a result of the many fronts that occurred during the month.

Temperature (°C):

Mean (1 minute) 10.9
Mean (min+max) 10.8
Mean Minimum 8.5
Mean Maximum 13.1 – Highest ever recorded in October
Minimum 2.8 – 10th
Maximum 16.3 – 3rd – Highest ever recorded in October
Highest Minimum 13.7 – 6th – Highest ever recorded in October
Lowest Maximum 10.4 – 31st – Highest ever recorded in October
Air frosts 0

Rainfall (mm):

Total for month 78.6
Wettest day 13.4 – 30th
High rain rate 61.0 – 22nd
Rain days 20 – Fewest ever recorded in October
Dry days 11

Wind (mph):

Highest Gust 49.0 – 30th – Highest ever recorded in October
Average Speed 11.1
Wind Run 8283.4 miles
Gale days 0
Predominant Direction S

Pressure (mb):

Maximum 1034.04 – 10th – Highest ever recorded in October
Minimum 966.82 – 27th – Lowest ever recorded in October

Days with snow falling 0
Days with snow lying at 0900 0

Total hours of sunshine 69.4

Days with recorded sunshine 28
Days with more than 0.5 hrs sunshine 22

Monthly summaries – briefer than usual

Published October 14, 2013

Apologies for the rather brief monthly summaries of late. This has been due to the weather station being “unmanned” for almost 3 months. Normal service will be resumed as soon as possible

September 2013 – Summary

Published October 14, 2013

Summary for September 2013

Temperature (°C):
Mean (1 minute) 12.3
Mean (min+max) 12.6
Mean Minimum 10.2
Mean Maximum 15.0
Minimum 4.3 – 5 September
Maximum 19.7 – 24 September
Highest Minimum 13.5 – 3 September
Lowest Maximum 11.4 -16 September
Air frosts 0

Rainfall (mm):
Total for month 87.4
Wettest day 24.0 – 14 September
High rain rate 23.2 – 17 September
Rain days 25
Dry days 5

Wind (mph):
Highest Gust 48.0 – 15 September
Average Speed 10.0
Wind Run 7229.9 miles
Gale days 0

Pressure (mb):
Maximum 1027.33 – 10 September
Minimum 987.03 – 15 September

Days with snow falling 0
Days with snow lying at 0900 0

Total hours of sunshine 71.4

August 2013 – Summary

Published October 13, 2013

Highlight of the month was a record dew point of 19.8°C on the 21st. This after the previous record high was superseded twice during the month of July.

Temperature (°C):
Mean (1 minute) 13.9
Mean (min+max) 14.2
Mean Minimum 11.9
Mean Maximum 16.6
Minimum 8.1 – 7th July
Maximum 21.1 – 22nd July
Highest Minimum 14.4 – 1st July
Lowest Maximum 14.6 – 28th July
Air frosts 0

Rainfall (mm):
Total for month 71.6
Wettest day 14.0 – 20th July
High rain rate 47.4 – 10th July
Rain days 25
Dry days 6

Wind (mph):
Highest Gust 43.0 – 30th July
Average Speed 9.7
Wind Run 7217.3 miles
Gale days 0

Pressure (mb):

Maximum 1024.83 – 27th July
Minimum 989.68 – 17th July

Days with snow falling 0
Days with snow lying at 0900 0

Total hours of sunshine 
81.4

July 2013 – Summary

Published October 13, 2013

While most of the UK’s weather was dominated by high pressure and the majority of people sweltered in temperatures exceeding 30’C, we in the Uists were shrouded in mist and fog with temperatures struggling to reach the mid teens until the middle of month.

The mists finally lifted and cleared on the 18th when we recorded 100% humidity for the very first time. What then followed were clear skies and long hot and sunny days with temperature exceeding 20°C on 10 consecutive days. Indeed, the lowest temperature recorded on the 22nd of 15.7′C was the highest minimum temperature recorded at this station. The high humidity also resulted in the highest ever dew pointbeing recorded on 2 separate occasions, first on the 11th (18.8’C) and then again on 19th (19.7’C).

Despite the misty and humid conditions, July was the driest month on record with only 23.8mm of rain falling. It was also the hottest month on record with all 4 mean temperature measurements being exceeded.

Temperature (°C)
Mean (1 minute) 14.9 – Station Record – Highest Monthly Average 
Mean (min+max) 15.3 – Station Record – Highest Monthly Average 
Mean Minimum 12.3 – Station Record – Highest Monthly Average 
Mean Maximum 18.3 – Station Record – Highest Monthly Average 
Minimum 9.7 – 6th July
Maximum 24.3 – 20th July
Highest Minimum 15.7 – 22nd July – Station Record – Highest Minimum Temperature
Lowest Maximum 12.7 – 2nd July
Air frosts 0

Rainfall (mm)
Total for month 23.8 – Station Record – Lowest Monthly Rainfall
Wettest day 4.6 – 3rd July
High rain rate 16.6 – 3rd July
Rain days 16
Dry days 15

Wind (mph)
Highest Gust 36.0 – 4th July
Average Speed 7.0
Wind Run 5168.5 miles
Gale days 0

Pressure (mb)
Maximum 1036.48 – 8th July
Minimum 993.13 – 2nd July

Days with snow falling 0
Days with snow lying at 0900 0

Total hours of sunshine 120.4

Gremlins in the Works

Published July 29, 2013

On July 28th 2013 at 10:11BST, our weather station was indicating an external temperature of 69.9′C. Preliminary investigations indicated that the temperature sensor may be faulty as all the associated readings (apparent temperature, wind chill, humidity, etc) were also corrupt.

As time progressed it also became clear that other physical readings such as wind run, not associated with temperature were also corrupt. The stations software was rebooted when all temperature associated readings reverted to zero, humidity was 100%, wind run ceased to be recorded AND other internal calculations such as maximum solar radiation, which is software driven, were also corrupt.

Further investigations revealed nothing when at 18:20BST, everything normalised and has remained so thus far.

It is to be hoped that “the gremlins have left the building”, but I’m not too sure. Having been singularly unsuccessful in determining the root cause, the problem is likely to re-occur.

In the mean time, some nonsensical temperatures remain in the records. Unfortunately, it may be some time before these are normalised as they weave a complex path around the data and are sometimes difficult to completely remove from our records.

Record High Humidity

Published July 18, 2013

While the rest of the UK sweltered in the recent heat wave, we in The Uists have been shrouded in mist and fog blowing in off the Atlantic for almost a week. Yesterday, the 17th July was particularly bad with thick fog lingering all day and persisting throughout the night.

During the morning of the 18th, the fog slowly cleared and temperatures began to rise and at 09.09 BST, we recorded a relative humidity of 100% for the very first time.

June 2013 – Summary

June was a particularly cloudy month and, while not feeling particularly warm, it had the effect of raising the average temperature by keeping the night time temperatures high. Despite the cloud, June was also relatively dry with only 60% the average rainfall and surprisingly, was also the sunniest month since our records began; due mainly to the long days. The winds were also a feature with the highest June wind gust, wind speed and wind run recorded at this station.

The month began feeling chill with temperatures struggling to reach double figures. Warmer weather finally arrived on the 3rd but the cloud did not clear until 5th when the temperature exceeded 20’C for the first (and thus far the only) time this year. The warm dry weather continued until 11th during which time there were 16.2 hours of sunshine on both the 8th and 9th, a station record.

The 11th saw 15.2mm of rain which was the only significant rainfall of the month. From this time onwards, the weather was a mixture of cloud (bringing some occasional mist), showers, sunny intervals and increasing winds. While temperatures struggled to reach 15°C, the cloud kept night time temperatures high resulting in a daily temperature difference of less than 3°C on many occasions. While the dry overcast conditions prevailed, there was 8.8mm of rainfall on 21st and 14.8 hours of sunshine on 17th.  The wind was also a feature during this period, peaking on 23rd with gusts of 41mph and a wind speed of 29mph (10 minute average) being recorded.

Rainfall for the moth amounted to 38.2mm which fell on 14 rain days, only 5 of which exceeded 0.2mm.

The average wind speed for the month was 9.0mph and the wind run was 6503.5 miles.  A peak gust of 41mph recorded on 23rd, all records for the month of June. The predominant wind direction was SW.

The sun shone for more than 0.5 hours on 26 days resulting in 166.7 hours of sunshine during the month, a station record.

The average temperature for the month was 12.7°C making this the warmest June recorded at this station, despite the month having a distinct chill to it. The maximum temperature of 20.7°C on 5th was the highest recorded in June at this station.

Temperature (°C):
Mean (1 minute)          12.7
Mean (min+max)         12.7
Mean Minimum            10.0
Mean Maximum           15.5
Minimum                       6.3       7th June
Maximum                      20.7     5th June
Highest Minimum        12.5       27th June
Lowest Maximum       12.3      1st June
Air frosts       0

Rainfall (mm):
Total for month         38.2
Wettest day             15.2   11th June
High rain rate           11.6     21st June
Rain days                  14
Dry days                   16
Days ≥ 0.2mm          14
Days ≥ 2.0mm           5
Days≥ 20.0mm          0

Wind (mph):
Highest Gust                   41.0     23rd June
Average Speed               9.0
Wind Run                    6503.5 miles
Gale days                           0

Pressure (mb):
Maximum                    1033.39     3rd June
Minimum                     991.54      22nd June

Days with snow falling                      0
Days with snow lying at 0900           0

Total hours of sunshine                   166.7     Station Record

May 2013 – Summary

May was  blustery and chill with below average temperatures reflecting the fact that nationally, this has been the coldest Spring for 50 years.

The month began in an Easterly airflow bringing overcast conditions resulting in rain, chill winds and very little sunshine. A brief respite was experienced on the 7th when the winds turned Southerly and the temperature rose above 15°C for the first time this year , but the keen wind did not reflect this.

The chill winds and dull conditions continued until 14th when a west wind prevailed  bringing less cloud and rain but more sunshine, with temperatures eventually rising into double figures on a more regular basis. Even so, it still felt chill in the blustery winds that continued throughout the month.

Conditions did improve from the 28th onwards when winds eased in the afternoon allowing the temperature to rise to 16.9°C on the 29th when 15.9 hours of sunshine were also recorded on that day.

Rainfall for the month was 71.4mm which fell on 25 rain days. The average wind speed was 11.7mph with a peak gust of 46mph on 26th. The wind run was 8725.4 miles.

The average temperature was 9.0°C with a low of 0.7°C recorded on 3rd and a high of 16.9°C recorded on 29th, the warmest day of the year so far.

Total sunshine for the month was 131.2 hours and there were 23 days on which the sun shone for 0.5 hours or more.  The sunniest day was the 29th when 15.9 hours of sunshine were recorded, a record for this station.

Summary of the month

Temperature (°C):

Mean (1 minute)          9.0
Mean (min+max)         9.3
Mean Minimum            6.5
Mean Maximum          12.0
Minimum                        0.7     3rd
Maximum                      16.9     29th
Highest Minimum          11.3     7th
Lowest Maximum           8.6     3rd
Air frosts          0

Rainfall (mm):

Total for month          71.4
Wettest day                17.0     2nd
High rain rate             30.8     31st
Rain days                      25
Dry days                         6

Wind (mph):

Highest Gust               46.0     26th
Average Speed          11.7
Wind Run                  8725.4 miles
Gale days                      0

Pressure (mb):

Maximum          1024.86     1st
Minimum           991.50     13th

Days with snow falling                      0
Days with snow lying at 0900          0

Total hours of sunshine              131.2
Days exceeding 0.5 hours          23

April 2013 – Summary

For once, our weather here this month followed the national trend and that being the wettest, windiest and coldest April since our records began. On the bright side (literally), it was the month with the most recorded hours of sunshine, there being only 1 day with none being recorded  (11th) and a maximum of 12.1 hours recorded on 9th.

The month began under the influence of the northerly airstream that brought the bright, dry, if colder weather. It was during this period we recorded the lowest temperature of the year (-3.3°C) but 11.9 hours of sunshine on the same day (2nd) with 6 of the 7 month’s air frosts in the first 8 nights.  It was also during this period when our longest recorded dry spell of 14 consecutive days without rainfall ended when 0.2mm of rain fell on the 6th.

The cold, dry, bright weather continued in an easterly airstream from the 7th until the 13th when the winds veered south and we experienced our first significant rainfall  (10mm) on that day. The winds remained in the south and west until the end the month bringing sunshine and showers but temperatures remained low. It was not until 14th that temperatures reached double figures (11.2°C) for the first time since 7th January.

From the 14th onwards, the month continued with strong winds, sunshine and showers, and temperatures struggling to reach double figures. Despite the sunshine, the blustery conditions created a wind chill factor near to freezing or below on many occasions giving a keen edge to the wind. The average temperature for the month was 6.4°C, some 2.4°C below the 10 year average.

There were 21 rain days in total resulting in 66mm of rain which is 1mm below the 10 year average for April. Winds were blustery, especially in the second half of the month resulting in an average wind speed of 11.3mph with the highest gust being 52mph on 14th. The wind run was 8163.6 miles.

There were a total of 163.5 hours of sunshine during the month, a record for this station. The sun shone for more than half an hour on 29 days with a high of 12.1 hours on 9th. The month ended with 19 consecutive days with more than 0.5 hours of sunshine.

Summary for April 2013

Temperature (°C):
Mean (1 minute)          6.4
Mean (min+max)         6.3
Mean Minimum             3.3
Mean Maximum            9.4
Minimum                       -3.3       2nd April
Maximum                      11.4         7th April
Highest Minimum       8.1         19th April
Lowest Maximum        6.5         11th April
Air frosts            7

Rainfall (mm):
Total for month       66.0
Wettest day           10.0       13th April
High rain rate        14.2       21st April
Rain days             21
Dry days              9

Wind (mph):
Highest Gust          52.0       14th April
Average Speed         11.3
Wind Run              8163.6 miles
Gale days             0

Pressure (mb):
Maximum               1028.08      3rd  April
Minimum               979.48        15th  April

Days with snow falling             0
Days with snow lying at 0900       0

Total hours of sunshine             163.5
Days with recorded sunshine        29
Days with more than 0.5 hrs recorded sunshine      29

March 2013 – Summary

March 2012 heralded the beginning of a fabulous year of weather for us here in the north-west of Scotland, while the rest of the UK suffered the wettest year on record. With the jet stream once again as low as southern Spain, it meant that this March followed a very similar pattern to that of last year. Could it be that history is about to repeat itself?

One major difference between this March and last was the predominant wind direction. With the jet stream being even further south this year, it allowed an Easterly air stream to develop bringing much colder conditions. This cold weather was made bearable due to the clear skies that easterlies tend to bring which ultimately resulted in plenty of sunshine. In fact March was the not only the sunniest since we started recording solar radiation last August,  but also the coldest since our records began. This means that 3 of the last 4 months have progressively lowered the 4 averaged temperatures.

March was also very dry with lower than usual humidity and no snow! This was very much surprising and most fortunate considering that some nearby islands and indeed many parts of the mainland suffered the worst snowfalls in living memory. The month ended with 9  consecutive days without rain which coincides almost exactly with our longest ever recorded dry spell of 12 days, which ended on April 2nd last year.

Summary of the Month

March started where February had left off with lower than average temperatures and dull for the first 9 days, although this period was to be the warmest. Temperatures failed to reach double figures all month and indeed struggled to reach 9°C, doing so only on two occasions, the 2nd (9.5°C) and 7th (9.2°C). In fact, temperatures have only reached double figures 4 times this year, and those were in the first 7 days of January. March went on to be the coldest month recorded here superseding all  4 averaged temperature measurements  set only last month.

Things began to change on the 10th when the easterly air stream exerted it’s influence resulting in the first of 9 air frosts  and the lowest temperature of the year (-3.1°C) on 11th. With clearer skies there were more hours of sunshine but temperatures struggled and the wind chill gave a raw edge which lasted until the end of the month. The only significant rainfall was a brief spell of 5 days when the majority of the months rain fell, with 12.4mm and 7.8mm falling on the 14th and 16th respectively. Total rainfall for the month was 34.6mm, some 60% below the 10 year average.

It remained bright, sunny and chill with occasional showers until the 22nd when winds increased and remained a constant East, the rain stopped and the sun shone. This coincided with the heavy snowfalls and massive disruptions experienced on the mainland and some nearby islands, but not us! A few occasional very light snow flurries fell on the 23rd and 24th but not enough to count as snowfall. The month ended with 9 consecutive days without rainfall, clear skies resulting in plenty of sunshine, low temperatures and air frosts, but with the humidity falling as low as 44%, there were no ground frosts.

The winds eased towards the end of the month but it still had a very raw edge only made bearable by the sunshine, up to 9 hours a day. There were 23 days when the sun shone for more than 30 minutes and a total of 127 hours of sunshine were recorded during the month, the latter beginning a record for our station.

As already mentioned the predominant wind direction was East with only 6 days not having an easterly element. The wind run was 7974.2 miles with an average speed of 10.7mph and a high gust of 45mph.

March 2013 Stats

Temperature (°C):
Mean (1 minute)                    4.3               Station record – lowest ever monthly averaged temperature
Mean (min+max)                   4.4              Station record – lowest ever monthly averaged temperature
Mean Minimum                      2.0              Station record – lowest ever monthly averaged temperature
Mean Maximum                     6.9              Station record – lowest ever monthly averaged temperature
Minimum                                -3.1     11th
Maximum                                9.5      2nd
Highest Minimum                    5.8      6th
Lowest Maximum                    4.3     23rd
Air frosts                                   9

Rainfall (mm):
Total for month                     34.6
Wettest day                          12.4     14th
High rain rate                        43.4     12th
Rain days                              16
Dry days                                15

Wind (mph):
Highest Gust                        45.0     9th
Average Speed                   10.7
Wind Run                          7974.2 miles
Gale days                              0

Pressure (mb)
Maximum                         1035.70    1st
Minimum                            990.15    17th

Days with snow falling                 0
Days with snow lying at 0900      0

Total hours of sunshine         127.0           Station Record – most hours of sunshine

February 2013 – Summary

Very briefly, February was the coldest month since records began at this station with all 4 avearaged temperature measurements being the lowest ever recorded. As this time last year, there was below average rainfall, some 21.8mm below the 10 year average.

Summary for February 2013

Temperature (°C):
Mean (1 minute)                      5.0          Staion Record
Mean (min+max)                     5.0         Station Record
Mean Minimum                        2.7         Station Record
Mean Maximum                      7.4          Station Record
Minimum                                 -2.6         1st  February
Maximum                                 9.6       3rd  February
Highest Minimum                    7.1      16th  February
Lowest Maximum                   4.2     22nd  February
Air frosts                                    5

Rainfall (mm)
Total for month                     56.0
Wettest day                          16.6      13th  February
High rain rate                        21.2      13th  February
Rain days                               18
Dry days                                 10

Wind (mph):
Highest Gust                         66.0      3rd  February
Average Speed                    10.9
Wind Run                           7349.9 miles
Gale days                                1
Predominant direction           S

Pressure (mb):
Maximum                     1038.98     26th  February
Minimum                      984.09      4th  February

Days with snow falling                   1
Days with snow lying at 0900       0

Total hours of sunshine                                    57.2
Days with more than 0.5 hrs of sunshine        19

January 2013 – Summary

Here is a brief summary of January’s weather.

It was, overall a very windy month – we broke the record for wind run – the figure for january was 10,009.0 miles – the first time wind run has been over 10,000 miles for a month – the previous highest figure was 9,382 miles which was during November 2011.

The gale that we had over the 28th/29th/30th January was pretty ferocious and we recorded a high wind gust of 73mph at 17:29 on the 29th January. At around the same time the record for 10 minute average wind speed was broken too, this was recorded as 49mph.

As well as being windy, the month was also dull – we recorded 6 consecutive days with less than half an hour sunshine each day. To add to our winter misery January was also pretty wet – although, the 128.6mm of rain that fell during the month wasn’t much above the 10 year average figure for January which stands at 118.4mm.

The average temperature for the month at 6.2′C (1 minute mean) or 6.0′C (min + max mean) was about on a par with the 10 year average which is 6.1′C

A high temperature of 10.4′C was recorded during a mild period at the beginning of the month and temperatures, unlike the rest of the UK, didn’t quite drop below zero with a low temperature of 0.1′C recorded on the 23rd January.

We had no snow during the month.

There were 20 days when the sun shone, of these we received more than half an hour’s sunshine on 16 days. The total hours of sunshine for the month was 27.

Summary for January 2013

Temperature (°C):
Mean (1 minute)                           6.2
Mean (min+max)                          6.0
Mean Minimum                            4.4
Mean Maximum                           7.6
Minimum                                        0.1          23rd January
Maximum                                     10.4           2nd January
Highest Minimum                          9.1            4th January
Lowest Maximum                         3.3          20th January
Air frosts                                          0

Rainfall (mm):
Total for month                          128.6
Wettest day                                 20.0           26th January
High rain rate                             17.4            29th January
Rain days                                      26
Dry days                                          5

Wind (mph):
Highest Gust                               73.0           29th January
Average Speed                         13.5                    Station record
Wind Run                            10009.0 miles            Station Record
Gale days                              1
Predominant direction         S

Pressure (mb):
Maximum                      1029.26     4th January
Minimum                         967.73    29th January

Days with snow falling                   0
Days with snow lying at 0900        0

Total hours of sunshine                  27.0
Days with more than 0.5 hrs          16

 

2012

December 2012 – Weather Summary

December was a month where the weather pattern swung between clear, bright, sunny spells to overcast, wet and windy conditions, each lasting for several days at a time until the winds arrived at the end of the month.

December started with clear skies, light winds and sunny spells resulting in 5 air frosts in the first 7 days. The clouds gathered from 8th onwards with increasing winds and rain culminating in very dull, overcast, wet and windy conditions on 13th and 14th. Clear skies and sunny periods returned for next 3 days with a further 2 air frosts, only for the very overcast, wet and windy conditions to return for 19th -22nd. During these 4 days, there was no measurable sunshine and 28.6mm of rain fell on the 22nd, both new records for this station. Clearer weather returned from the 23rd with sunshine and showers with the winds gaining strength over the following days culminating in gales on 28th and 29th. On the 28th winds gusted to 80mph (Force 12) with an average wind speed of 48mph (Force 9), the wind run for the day being 661.5 mileThe wind gust and wind run were records for this station. Windy conditions with sunshine and showers then continued until the end of the month.

While temperatures were relatively high during the wet and overcast periods, the clearer spells resulted in lowering the overall temperature,  reducing the monthly (1 minute) average temperature to 5.4°C making December the coldest month on record.

Rainfall was a little above average for the month for the first time this year at 117.8mm which fell on 27 rain days.

The wind speed averaged 11.9mph with a wind run of 8829.9 miles and a high gust of 80mph, the predominant direction being South. The sun shone for a total of 50.3 hours during the month. There were a total of 21 days when it shone for more than 30 minutes , the sunniest being the 4th with 4.3 hours of sunshine.

Decemebr 2012 weather statistics

Temperature (°C):
Mean (1 minute)  5.4                         –    Station recordlowest ever mothly avearage temperature
Mean (min+max)   5.2                        –    Station recordlowest ever monthly average temperature
Mean Minimum     2.9
Mean Maximum     7.6
Minimum          -1.7             10 December
Maximum          11.1           28 December
Highest Minimum  7.2        23 December
Lowest Maximum   3.9        1 December
Air frosts       7

Rainfall (mm):
Total for month  117.8
Wettest day      28.6            22 December     –    Station record
High rain rate   46.2            22 December
Rain days        27
Dry days         4

Wind (mph):
Highest Gust     80.0            28 December    –    Station record
Average Speed    11.9
Wind Run         8829.9 miles
Gale days        2                                              –    Station record – most recorded in any 1 month

Pressure (mb):
Maximum          1032.41     10 December
Minimum            973.05      14 December

Days with snow falling                   0
Days with snow lying at 0900        0

Total hours of sunshine             50.3

November 2012 – Weather Summary

Where October announced the onset of winter, November confirmed it’s arrival with below average temperatures, frosts and the first snow on the high ground.

The month started where October had left off with some sleet and snow showers during the first 4 days and even a thunder storm during the night of the 2nd. The first snows on Ben Mhor were seen on the 3rd. Although the temperatures rose a little after that, they remained below average for this time of year giving a chill edge to the wind at times.

While the rest of the UK experienced heavy rainfall towards the end of the month, here the skies cleared and the winds faded from the 24th onwards resulting in some very bright, sunny and calm days. As a consequence, temperatures were low resulting in frosts at night and when clouds did develop, they lay heavy at times during the final days of the month.

Despite the flooding that occurred elsewhere in the UK, the rainfall for November was again below average, this time by some 21 mm with 108.4 mm falling on 28 rain days.

November was a chill month at times with the average temperature (1 min) only reaching 8.9°C, almost 2°C below the 10 year average. 11.4°C was the highest temperature recorded on the 13th but temperatures fell below zero on 4 occasions, the lowest being -2.1°C on the 27th.

The winds were lighter than previous years, this being due in part to the exceptionally calm spell during the final days of the month which saw most of the clearer skies  and frosts.  The average wind speed was 10.1 mph with a wind run of 7235.5 miles.  The highest gust of 52 mph was recorded on the 20th and the predominant wind direction was SW.

The sun shone for a total of 43.1 hours during the month. There were 23 days when the it shone for more than 30 minutes, the sunniest being the 25th with 3.7 hours of sunshine.

October 2012 – Weather Summary

October brought the month on month record breaking sequence to end, but it did bring the first taste of winter with the first frosts, below average temperatures and the first, albeit brief, sleet/snow.

The northerly airflow experienced this October kept the average temperature  down to 7.8°C, some 3°C below the 10 year average. The clearer skies  experienced with these northerly airflows also gave rise to the first frosts, there being 3 air frosts in total with the lowest  temperature  being -1.0°C on the 26th. The highest temperature recorded during the month was 13.6°C on the 21st.

October did continue the trend of below average rainfall with 64.8mm falling on 23 rain days.  This amount represents  a mere 50% of the expected rainfall for this time of year.

A slow moving high pressure system over the UK brought a rest bite from the wind and we experienced several days of calm, almost windless days between 17th– 22nd. Clearer skies during this period also brought the first ground frost on the 20th.

The predominant wind direction was NW, a substantial factor in the below average temperatures. The average wind speed was 7.2mph with the highest gust being 38mph on the 30th. The wind run was 5381.4 miles.

The sun shone for a total of 83.8 hours during October. There were 24 days when the sun shone for more than 30 minutes, the suniest being the 14th  with a total of 6.7 hours.

September 2012 – Weather Summary

September will be remembered for the wind. Continuing this years trend of records being broken every month, the highest ever daily wind run and highest daily average wind speed was recorded during this month.

Throughout September, the wind was the predominant feature, there being only one day when the highest wind gust did not exceed 20 mph. The record for the highest daily wind run was broken twice during the month with 587.2 miles being recorded on 25th. This day also broke the record for  the highest daily average wind speed which was recorded at 27.9 mph. Despite all this, September’s wind run of 9093.8 miles nor the average windspeed of 12.7 mph did not exceed  that of November 2011 (9383.4 miles & 13.0 mph) and there were no gale days. The predominant wind direction was WSW and the highest wind gust for the month was 54 mph also recorded on 25th.

September also continued the trend of below average rainfall with only 62.8mm falling on a total of 24 rain days. This is some 35.8mm (circa 30%) below the 10 year average.

Average temperatures were slightly below the norm with a mean of 11.6°C. The highest temperature was 16.5°C on the 2nd and the lowest falling to 1.8°C on 20th.

The total hours of sunshine for September was 75.5 hours with the sun shinning for more than 0.5 hours on 22 days.

 

Another Windy Day!

Published September 26, 2012

September is proving to be a month noted for the wind with the highest wind run being recorded for the second time.

With the record being broken on the 13th of this month, stood for just 12 days,  being superceeded today (26th) with a wind run of 587.2 miles.

The average wind speed for the day was 27.9mph with the highest gust being recorded at 54mph

 

The Windiest Day

Published September 14, 2012

The 13th September 2012 was the windiest day to be recorded at this station with a  windrun of 516.6 miles for the 24 hour period ending today (14th September) at 0900GMT, beating the previous record by 0.9 miles.

Despite the winds only peaking at 48mph during the early evening, steady Force 5 to 7 winds during the day which then persisted overnight accounted for the high windrun.

 

August 2012 – Weather Summary

Published September 1, 2012

August was in many ways “back to normal” with a return to a southerly airstream  and its accompanying moisture and seasonal winds. Despite this, August still managed to continue the record breaking sequence, being the month with the highest average temperatures and highest minimum temperature ever recorded at this station.

Average temperatures for the month were slightly higher than the 10 year average (1 min) at 14.5°C which in itself is a record for this station. There was also new records for the highest monthly mean minimum and monthly mean maximum temperatures, these being 11.5°C and 17.6°C respectively. The record for the highest minimum temperature was also broken with a temperature of 15.1°C being recorded on the 12th. There were 5 days when the temperature exceeded 20°C.

With the return of southerly winds, rainfall was higher than previous months with 94.0 mm falling on 19 rain days. Unlike previous months, this is a return to something like the expected monthly average for August, it still falling short of that average by 1.4mm. Although only slight, statistically it still means that for this year, every month has had below average rainfall.

The dominant wind direction was SSW bringing with it more blustery conditions, especially towards the end of the month. The highest gust was recorded at 44 mph on the 25th with a monthly average wind speed of 8.5 mph. The wind run was 6320.1 miles, which exceeded last Augusts total by some 1300 miles

With the installation of our solar radiation censor, we are now able to measure hours of sunshine, this being the first full month. A total of 120.4 hours of sunshine were recorded and there were 25 days when the sun shone for more than 0.5 hours, the maximum being 14.1 hours on the 3rd.

 

Temperature record!

Published August 13, 2012

A new record was achieved overnight – the highest minimum temperature we have recorded since our records began in December 2010.

The temperature did not drop below 15.1′C for our weather day yesterday (the 24 hours from 9am 12th August to 9am 13th August)

Highest minimum temperature record

 

*New Weather Statistics pages*

Published August 9, 2012

One of the endless fascinations of collecting weather data is being able to look back over the records when asking questions like “what was it like this time last year?” and “what was the driest month last year or since we started?”.

We particularly liked the look of the pages by Murry Conarroe of Wildwood Weather who has made available scripts for producing colourful summaries from the data extracted from Cumulus (the weather software that we use) and the Saratoga Weather AJAX/PHP template set that we use for our website.

With just a little adjustment for our own particular set-up the pages were up and running in just a short time. For each of Temperature, Rain, Wind and Wind Run there are three different summaries available – Daily Detail – Monthly Summary – Seasonal Summary. See the pages here: http://www.southuist-weather.info/wxtempdetail.php

As we only started our weather records here in mid-December 2010 i have omitted that part-month from the displays. The summaries are updated automatically on a daily basis just after the end of our weather day which is 9am GMT/UTC

The new pages available

The amazing thing, to me, in this ever more commercial world is that these were all freely available! The templates and scripts from Saratoga Weather are available to download from: http://saratoga-weather.org/wxtemplates/install.php and work with the following weather software: Cumulus, Weather Display, WeatherLink and others. Again the scripts from Murry were provided free, downloadable from:  http://weather.wildwoodnaturist.com/downloadsCVW.php  and the most excellent Cumulus software, constantly being improved by it’s creator Steve in Sanday, Orkney, that our weather station is connected to is available to download for free from: http://sandaysoft.com/downloads 

What else can we say but “thanks guys for your many hours developing these things, it’s much appreciated!”

Measuring Sunshine – Not Such an Easy Task!

Published August 2, 2012

As with all these things, nothing is ever quite so simple as it first appears. When attempting to measure sunshine, like all things you should always ask the question “what are you measuring and how are you measuring it?”

“Current solar radiation” (technically known as “Global Solar Radiation”) is a measure of the intensity of the sun’s radiation reaching a horizontal surface, in this case, our sensor. This irradiance includes both the direct component from the sun and the reflected component from the rest of the sky. The solar radiation reading gives a measure of the amount of solar radiation hitting the sensor at any given time, expressed in Watts / sq.m (W/m²).

That’s the easy bit! Now we have to convert that into sunshine. As in all scientific measurements, there are standards. In this case there are 2, Bright Sunshine and Sunshine,  and both are commonplace.

First, Bright Sunshine as it is the simplest to understand,  the definition being :-

Bright sunshine is considered to be occurring when the solar radiation level exceeds 100 W/m².

From this we can easily work out how many hours of Bright Sunshine occur daily from the readings obtained. The problem is that even on the dullest of days there is still a likelihood that some Bright Sunshinewill be recorded as the threshold of 100 W/m² is quite low, and it stretches the imagination to the limits to consider this to be “sunny”.

Then there is Sunshine and this is not so straight forward. Sunshine is based on a complex algorithm know as the Ryan-Stolzenbach formula. This is a mathematical algorithm that calculates the theoretical maximum solar radiation throughout the day on a day by day basis. Once integrated into the software, it is further modified to calculate the theoretical value for your exact location based upon longitude and latitude.Sunshine will then occur when the solar radiation reading equals or exceeds 75% of that theoretical value.

As ever, the theory is easy to understand but the practicalities of measuring then come into play. Setting the sunshine threshold to 75% – no problem. Next step is to keep the readings from the sensor within the boundaries of the theoretical maximum and near the maximum on bright, clear days.  But differences occur due to atmospheric conditions. In city locations there is less penetration of the suns rays due to pollution etc., while here in the Western Isles there is very little in the way of pollution, so the suns strength, and hence the readings obtained will be different. In software this compensation is achieved by adjusting the “transmission factor” of the atmosphere. Even then, just waiting for that clear, bright sunny day can take a while and the constant anguish over whether the readings are correct leads to the continual “adjustment” of the settings.  All these things takes their toll.

Then there is the wee problem of dawn and dusk. Even when the sun is shining, the radiation levels will be low at these times.  Equally, the algorithm may calculate a value of “zero” while there is still some light which will result in some sunshine being recorded. To compensate for this, there is a minimum threshold which can be set, under which no sunshine will be recorded.  So, if this is set to zero or a very low value, sunshine will be recorded for up to 2 hours a day even though it will be almost dark. Conversely set too high and some sunshine will be lost. Striking a balance is proving a little tricky!

In conclusion Bright Sunshine is the simplest and would give the most consistent results across all stations, although the results would be almost meaningless in terms of what most people would consider to be sunshine. The Sunshine measurement is more scientific and would give better results, but there are several arbitrary settings that could influence consistency between stations. This is probably why the data we provide to other weather agencies such as the Met Office is provided in its raw form i.e.,  Watts/sq m. They can then do their own calculations.

Even so,  it still begs the question “what are they measuring and how are they measuring it?”

As for us, we shall record both, but display only Sunshine. We are still endeavouring to calibrate the algorithm and adjust the thresholds, so this is very much “work in progress”. As to how well we do, you will be able to make up your own minds once we are able to display the graphs showing the theoretical and actual solar radiation measurements in the next release of software.

July 2012 – Weather Summary

Published August 1, 2012

After the recent run of record breaking months, it was back to normality of a kind in July.

Most noticeable once again was the rainfall, 17 rain days producing just 36.8mm with 11.6mm of that falling in the last 12 hours of the month. Without that downpour, July would have been the driest month on record, but was still 22.7mm below the 10 year mean.  This continues the trend of every month this year being below the 10 year average.

The average temperature (1 min mean) for July was 13.0’C, slightly lower than the average of 13.9’C despite there being 3 days over 20’C. This is a rare enough event in itself, the only other days to exceed 20’C  on record being 5 in May 2012.

The dominant wind direction once again had a northerly element, it being  NNW, but this was the same as July 2011. The highest gust was measured at 39mph and the average wind speed was 8.1mph, slightly calmer than last July. The wind run was 6006.2 miles.

As an aside, the Eden Winter Snow Index  (EDWI) for the year 2011/12 ended on 31st June.  The EWSI snow year runs from 1st July to 31st June and measures the amount of snow during that year. The EWSI is calculated by adding together the snow depth in centimetres for all days with snow-lying at 0900 GMT.

The Snow Index for  2011/12 at Askernish was 4.

Weather Station Upgrade – Solar Radiation Sensor Added

Published July 30, 2012

The weather station has now been upgraded to include a solar radiation sensor. This will allow the measurement of, amongst other things, evapotranspiration and hours of sunshine.

At present, the current value of solar radiation is all that can be displayed on the home page as a measurement in Watts/sq meter until our software is upgraded to a build which is currently undergoing  Beta testing but due for release shortly.

Until then, we have developed a  “sunshine” page in the main menu.  This shows in tabular form evapotranspiration for the current day, the hours of sunshine today so far, the total hours of sunshine for the previous day and the current theoretical solar radiation value. This table is updated every 10 minutes.

The dial shows the “real time” value of solar radiation being measured at the station. If you hover the mouse over the dial, it will show a current theoretical solar radiation value, the “real time” solar radiation and a percentage value.

The percentage value is by how much the real time solar radiation exceeds or falls short of the theoretical value. For the “geeks” amongst us, this is important as the calculation as to when the sun is shining or not is deemed to be when the real time value exceeds 75% of the current theoretical value.

For the uninitiated, evapotranspiration  is a term used to describe the sum of evaporation and plant transpiration from the Earth’s land surface to the atmosphere, ie how quickly the land surface is drying. This is used mainly for agricultural and irrigation purposes.

I hope the explanation helps but it will be easier to display when the new software build becomes available.

June 2012 – Weather Summary

Published July 1, 2012

June continued the recent trend of becoming a “record breaker”, with the lowest wind speed and wind run ever recorded at this staion.

The month continued where April  and May left off,  in a northerly airstream which brought brighter, clearer, drier weather if a little cooler than is usual for this time of year. This continued until the 24th when the wind swung southerly  for 6 days and with it came moist air resulting in the majority of this months rain fall along with low cloud and mist. The month ended with the winds returning to the north once again.

Rain fall for the month was 42.8mm which is still 20.9mm below the 10 year mean for June and this years rainfall is now 162.2mm below the average for the year to date.  Temperatures were unspectacular with the average temperature (1 min mean) reaching 11.7’C, comparable with June 2011 but still 0.8’C below the 10 year mean.

The dominant wind direction was NE with an average wind speed of 6.5mph and a wind run of 4660.7 miles, making this month the calmest since records began.

May 2012 – Weather Summary

Published June 1, 2012

Despite the dominant wind direction again being NNE, May will be remembered for it’s sunshine, below average rain fall and a spell of record breaking high temperatures.

The month began with a chill northerly wind but dry and sunny with an overnight low of -0.6’C on the 6th.  Under clear skies, temperatures were slow to rise, that is until the 22nd when they began to increase rapidly resulting in 5 consecutive days over 20’C. The highest temperature reached was 27.2’C on the 25th, a record for this station. As the previous record high had only been 19.8’C set on 30th July 2011, all other high temperature related records were also broken. (see previous posting – Record Highs).  This late spell of warm weather also raised the average temperature (1 min mean) for the month to 10.4’C  which is the 10 year mean for May.

May was also noted for it’s clear skies resulting in copious amounts of sunshine, sometimes 17 hours a day and below average rainfall. The total rainfall for the month was 29.6mm which is 38.9mm below the 10 year average. This means that the total rain fall to date for 2012 is 272.6mm, 141.2mm below the 10 year average for January to May.

Compared to May 2011, this month could not be more different, it having 28 rain days compared with 11 this, which resulted in 147.2mm of rain falling.

The predominant wind direction was again NNE. Winds were a little lighter than last year with the average wind speed being 8.3mph and a total wind run of 6194.5 miles.

March 2012 – Weather Summary

Of all the months, it is March that is showing the most deviation from the 10 year norm (2000 – 2010), a trend continuing on from last year.

Most pronounced was the months rainfall with only 19 rain days producing 32.8mm of rain, 10.4 mm of this falling in 1 day. This is a full 48.4mm below the 10 year average! The month ended with no measurable rain recorded on 11 consecutive days, an all time record in itself at our station and set to continue into April.

The temperature was also higher than the 10 year norm by 1.8′C, the mean temperature (1 minute) being 8.6′C. Although there was 1 air frost, the mean minimum was also 1.2′C higher than last year.

Wind and wind direction was as expected with the monthly average wind speed being 10.2mph, the predominant wind direction being SW. The wind run was 7568.7 miles, slightly up on last year.