Edward Graham's Journal RSS
Below please find a few spectacular NASA Terra satellite images of NW Highlands and Islands, Scotland, during the recent fine spell of weather:
NASA Terra channels 3, 6 and 7: Ice clouds show up as orange or pink, water as black and land as emerald green (11 October)
NASA Terra channels 7, 2 and 1: Ice clouds show up as cyan blue, water clouds as white, open water as black and land as lush green (10 October).
NASA Terra Visible and Infra-Red channels: As close to as we see them with our own eyes (if we were in space) - 5 October.
@eddy_weather, Stornoway, October 2016
The United Arab Emirates (UAE) of the Middle East present one of the strangest of juxtapositions of climate, land and people on Earth today. Despite having one of the hottest, driest and most inhospitable climates on Earth (air temperatures regularly surpass +50degC during the summer season), the region today boasts two of the most extraordinarily wealthy, ultra-modern and glittering cities found on Earth: Dubai and Abu Dhabi.
Eddy-Weather recently had the good fortune to visit the latter of these two cities (Abu Dhabi). He also spent some time observing the unique weather systems of the region.
The primary reason why the weather is so hot in the UAE is because it lies on the eastern fringe of the world's greatest sandy desert, the Rub' Al Khali of the Arabian Peninsula. At a latitude of only 24degN, the Sun remains very strong all year-round (and is directly overhead in the zenith during the summer season). The UAE also lies exactlly under the influence of the global descending arm of the Hadley Cell circulation, the Earth's most powerful air circulation system. Furthermore, lying beside one of warmest seas on the planet (the Persian Gulf), the weather can get extremely humid as ocean temperatures frequently reach well above +30degC. Here are some photos:
View across Abu Dhabi to the southwest. Note the hazy blue skies - the restriction in visibility is due to a combination of fine desert dust and anthropogenic aerosols, some of which are likely to be hygroscopic at high relative humidity.
The Abu Dhabi National Oil Company (ADNOC) headquarters and Etihad towers (location of the Fast and Furious Tom Cruise Hollywood movie), in downtown Abu Dhabi.
Eddie on the Marina seafront.
2nd wonder of the modern world: The Sheikh Zayed Grand Mosque
The Dusit Thani hotel (515ft high): "A little town in heaven"
The thermodynamic upper air plot (tephigram) shows conditions typically of the region, with two separate inversions at 920mb and 600mb above Abu Dhabi, with a surface air temperature of +33degC. Very dry air lies above both inversions.
@eddy_weather, October 2016
Intense bursts of rain caused by a 'Narrow Rain Band' (NRB) were captured by the Lews Castle Micro-Rain Radar in Stornoway this morning, Tues 27 Sep 2016. Having only been recognised as unique and distinct meteorological features in their own right in the past decade or so, these bands of rain comprise of heavy downpours only a few kilometres wide, but can stretch for tens to hundreds of kilometres in length. They may cause considerable disruption, as they are sudden, squally events, and are often accompanied by severe wind gusts and torrential bursts of rain, lasting all for a few minutes.
As this morning's Stornoway radar images show (above), NRBs are shallow features, originating from turbulence in warm low-level clouds. Note that there are at least 2 x separate NRBs in the plot above - the final one at 0745UTC (08h45 local time) was hardly more than 1,000m deep.
@eddy_weather, Stornoway, 27 Sep 2016
The remains of two separate tropical storms (#Karl #Lisa), currently just short of hurricane status, are heading towards our Scottish & Hebridean shores. But please don't panic; although they do add a bit of "oomph" or "turbo-boost" to our regular low pressure systems, hurricane force winds are generally *rare by the time such systems reach us. Instead, expect a regular spell of 'fiadhaich' (wild and wet) weather.
* Occasionally these storms reach full hurricane force status in Autumn e.g. Debbie on 16/9/1961. But on average, it is during December, January and February that we suffer the most severe gales.
@eddy_weather Stornoway 23 Sep 2016
Following the overwhelming success of the inaugural pilot project last year (2015-16), #NameOurStorms is being rolled out again for the coming winter by the UK Met Office and Met Eireann (the Irish National Met Service). Naming storms saves lives - because people (including who control the infrastructures that protect us) are made more aware of the danger posed by such storms, allowing preventative and adaptive measures to be put in place against potential damage and loss.
For example, up to the mid-1990s it was common for a winter wind storm with a maximum gust of between 90 and 100mph to cause the loss of 5 to 10 or more lives across the British and Irish Isles. Today, despite the increasing severity and frequency of winter storms over recent years, the number of injuries and deaths has plummeted due to better awareness.
Here are this year's names: Some really popular ones are included this year: #Ewan #Malcolm #Oisin #Conor #Angus, though I'm perhaps less keen on #Doris (storm in a teacup?) and #Wilbert!
Final word of warning: There is an unfortunate over-abundance of unqualifed individuals proclaiming meteorological advice and expertise on the web today (e.g. Facebook 'weather' sites, Old Moore's Almanac, Exacta Weather). Many of these are operated by unqualified individuals, with little, if any, training or belief in the science of meteorology. I strongly recommend that you take these with a pinch of salt. Certainly, do not make any safety decisions based on their forecasts - use official sites only!
Tip: Accredited individuals will usually have the initials RMet, CMet or FRMetS (or an equivalent qualification) after their name (in the same way that accredited trades persons have e.g. CEng, FRCS after their name). Reputable organisations are usually easily identified as having a long track record of providing met information to service providers.
20 Sep 2016, Stornoway @eddy_weather, FRMetS!
The Lews Castle College Stornoway precipitation radar captured a textbook example of a warm front passing over the Hebrides today (Sunday 11 Sep 2016). See the following plot (explanation below):
Top left (Fall Velocity): Raindrops fall faster than snowflakes. Hence, the level at which the fall velocity changes rapidly (today 1600m, rising to 2700m after passage of the warm front) indicates the melting height of precipitation particles within the atmosphere. As a warm front brings warmer air, so the melting level rises - as seen towards the right of the image.
Top right (Raw reflectivity): This is raw signal sent back to the radar. It is useful for detecting the type of precipitation (e.g. hailstones, snow or rain). Today it's rain at the surface I'm afraid.
Bottom left (Rainfall rate): This is how much rain is falling on the ground in mm/hr. We have rates typical of the Hebrides this afternoon, about 2mm/hr.
Bottom right( Doppler mode): This is super snazzy information tells us which way the precipitation particles are moving, up, down, left or right, etc..
Tweets from the LE RADAR can be seen every 15 minutes on Twitter at: https://twitter.com/lewscastleradar and on Facebook at: https://www.facebook.com/eddyweather/. The radar is a powerful tool for research into precipitation at the University of the Highlands and Islands.
@eddy_weather Stornoway (11 Sep 2016)
Hurricane season reaches a peak in September over the Caribbean and western Tropical Atlantic Ocean, as this is the warmest time of the year in this region. When the met conditions are right (which they will be over the next few days), the Coriolis force directs warm, moist plumes of this tropical air north-eastwards across the North Atlantic Ocean towards the British Isles. This usually results in heavy rain, and strong, sometimes damaging gales* for the western Atlantic "Arc" seaboards of Scotland and Ireland.
As of today (Wed), the met models are currently forecasting gales on Thursday 8 Sep, Friday 9 Sep, with possibly a severe gale later Sunday 11 Sep (keep on eye on the forecasts for updates). Winds could reach over 60mph during the worst gales. Heavy rain is also expected. Here are the current GFS forecasts of mean windspeed (gusts up to 50% stronger) for Thurs 09hz Fri 18z and Sun 18z.
Why so windy? Current sea surface temperatures are 'off the wall' across most of the northern Pacific and Atlantic oceans (see chart from NOAA ESRL) - and since mid-latitude depressions take most of their energy from the contrast in temperatures along the polar front, it's no surprise it's getting stormy.
*The strongest winds ever recorded in Ireland occurred on 19 September 1961 during the passage of ex-hurricane Debbie with max gusts of 120mph.
@eddy_weather, Stornoway, 7 Sep 2016
We all know well that mountains influence the weather, and in Scotland even more so than elsewhere... However, today (6 Sep 2016), we were treated to a much more benign, indeed beautiful reminder, of how the Highlands hills act in harmony with nature – that is, in concertina with the mountains, the atmosphere resonates just like a musical guitar or violin string – with the evidence portrayed in the clouds.
We can see clear evidence of this resonance today in the forms of stratocumulus lenticularis and undulatus clouds on today’s NASA Terra satellite image, where the clouds take the shape of classic herring-bones (or lee waves), as seen across most of central, southern and western Scotland.
Close inspection of the distance between each cloud crest reveals a wavelength of approximately 10km in southern Scotland, and 12km in the far northwest.
And now for the Atmospheric Physics bit:
Using basic met data, the Brunt-Vaisala Frequency (N) equation can also be used to determine the wavelength of the clouds. N is calculated as follows, where g = gravity (9.8ms-1), θ is the average air temperature (Kelvin) and dθ/dz is the rate of drop of temperature with height (Km-1):
Using data from today’s regular atmospheric radio-soundings at Valentia (Ireland) and Lerwick, Shetland (see http://weather.uwyo.edu/upperair/sounding.html), θ was ~280K and dθ/dz was approximately 12K in the lowest 3,000m of the atmosphere. Infra-red thermal satellite images also confirmed that cloud top temperatures were relatively warm, between +5 and +8degC, with a strong series of inversions between the surface and 700hPa. Mean windspeeds were about 25ms-1 (50 knots) across the profiles.
Using these values, the Brunt Vaisala frequency (N) works out to 0.01183 s-1.
As the period of oscillation (τ) of the harmonic is = 2π/N, so τ = 2π/0.01183 = 530 seconds (or about 8 minutes). This means it takes 8 minutes for the wind to blow from one wave crest to the next.
This result can be confirmed using the standard formula V = λf (Velocity = Wavelength x Frequency), using V = 25ms-1 (average windspeed from the soundings) and Wavelength λ = 12km (12,000m) as observed in the satellite images.
V = λf
25/12,000 = f = 0.0020833 s-1 or 1/0.0020833 = 480 seconds (also 8 minutes!)
And this is what was seen from the ground in Dingwall, on the night before (during the same harmonic event) - photo courtesy Andrea Goddard:
@eddy_weather, Stornoway, 6 September 2016
Seall dè a chì mi anns a 'mhadainn an-diugh!
Yes, it's the now infamous "Trans-ocean winner" (sic) oil rig which ran aground on the west side of the isle of Lewis during gales on the 6-7 August last. It is now being towed into the safer haven of Broad Bay, Stornoway - where it will await final departure by next month. This is the view from my loft office centred in Stornoway town.
From a meteorological point-of-view the summer gale of 6-7 August was particularly interesting, not because of its absolute severity (max gusts were typically up to 60mph, a fairly frequent occurrence in the Outer Hebrides), but because there was a persistent dryness associated with the westerly gale during the daytime on Sunday 7 August. This is unusual, as most gales bring abundant rain or frequent showers.
A clue as to why this may have occurred is contained in the data recorded by SEPA volcanic emissions network station, based at Lews Castle College, University of the Highlands and Islands, Stornoway. For a period of 48hrs, there were elevated readings of PM10 and PM2.5 (fine particulate matter) in the air (see chart below), despite it having origins over the clean Atlantic ocean. At the same time, considerably reduced visibilities were observed across the Isles. @Eddy_weather makes the conclusion that this was caused by copious volumes of fine salt (NaCl) particles, made airborne after bubbles burst during the breaking of ocean waves. NaCl is a well known CCN (cloud condensation nuclei) and hence, they could feasibly have influenced the rain-bearing dynamics of the weather system during that period.
See broad low-frequency peaks centred around 7 August below:
This whole event highlights many vulnerabilities in the current offshore industry, among them being:
- Need for more accurate local weather forecasts, particularly of meso-scale meteorological features
- Dissemination of said information
- Usage of said information, by people who are trained to understand it
Luckily, no-one was injured in this episode, nor was their any major environmental damage, but it may not be the case next time!
@eddy_weather, Stornoway, 24 August 2016
Well, it was a bit like Samuel Beckett's Waiting for Godot, not?
Certainly, up until last week, it felt like summer was never going to arrive! Indeed, the weather actually got worse as summer progressed. But finally upon finally, a late Indian as summer has come to the rescue, albeit with the caveat that the summer school holidays end this week accompanied by the perennial back-to-work grudge (as always happens).
Mind you, I remember that Godot never did arrive in Beckett's play! So really the metaphor is better used against 2015 - our infamous "year without a summer".
So enjoy it while it lasts - and apart from a few blips, it may last a while yet!
Meanwhile, here's today's NASA Terra satellite image from 700km above our heads:
Updates of daily temperature highs can be seen on Eddie's twitter feed at: https://twitter.com/eddy_weather
Eddie, Stornoway, 10 August 2016
A funnel cloud was spotted off the coast of South Uist (Outer Hebrides, Scotland) by Eddie at 17h50 on 9 August last. Here are a few photographs:
A zoom into the funnel, contrast enhanced. Photos copyright @eddy_weather
Funnel clouds rotate and descend from the ambient cloud base, having the appearance of an incipient tornado - but in this case there was was no evidence of the whirlwind touching the sea surface at any time to form a waterspout. In addition, tornadoes are rare phenomena in the British Isles, and are never as severe as those experienced on the Great Plains of the USA. The sighting of one off Uist is unusual still, however.
Interestingly, meteorological conditions were not conducive towards strong convection nor funnel clouds on this day - sea-level air pressure was high at 1025.6hPa at the time of observation and there was negative vorticity. Even so, satellite images reveal a sliver of deep convection forming above on the leading edge of warm frontal cirrus shield. A heavy shower and gust front passed by minutes later,
@eddy_weather, Stornoway, 13 August 2016
It's rare for a "westerly" summer to revert back to easterlies during early August - and July this year was overwhelmingly westerly (with a record 30 our of 31 rainy days in Stornoway). So I'm afraid that this augers poorly concerning the weather, at least for the next few days.
So expect more lashings of rain and showers, with a risk of hail at times too. Winds will reach gale force on Sunday, especially on the westside of Lewis and Harris, and down through the Uists and Barra. There's an equal chance that north Lewis might miss the worst of the gale, for a few hours anyway, as the eye of the low tracks across the Butt towards Sulisker in the middle of the day - it all depends on the exact track of the weather system.
Is an August gale unusual? No. Is it inconvenient? Yes (and there's a lot more stuff to blow about in summertime).
The Silver Lining? Westerly summers along the Celtic fringe often blow themselves out by September/October, so don't give up on us having a fine Indian summer yet... there are plenty of precedents of such in recent memory (e.g. 1985, 1986).
@eddy_weather, Stornoway, 4 August 2016
Abair mìos fliuch 's mi-shoilleir!
What (another) appalling month of weather for Stornoway during July 2016, writes @eddy_weather
Although there are still a few hours of the month to go (climatologically speaking, July does not end until 09h on 1st August), July 2016 will end up in the record books as yet another DIRE month weatherwise. Here are some of the monthly statistics:
- Total precipitation: 145mm (5.7 inches), some 200% of normal and the 3rd wettest in a 144-year record from 1873 to 2016 for the Stornoway area. This is considerably worse than in last year's washout of 2015 (see chart below)
- It rained on 30 out of the 31 days - again, worse than in 2015, and a new record.
- It was also the 4th dullest July (lack of sunshine) in an 88-year record from 1929 to 2016 in the town (see 2nd chart)
- However, it wasn't especially cold -> The average air temperature was close on average at 13.2degC, which although is below the warming trend of recent years, was still some +0.8degC above its counterpart's value in 2015 (see final chart)
@eddy_weather, Stornoway, 31 July 2016
July 2016 has now surpassed last year's (2015) "washout" total of 123.1mm. with 125.1mm (4.93') of rain having fallen in Stornoway town up to 09h00 this morning, 22 July 2016, reports @eddy_weather.
Over the past 48 hours (20-22 July), two separate cloudbursts over the town have added an enormous and near-flooding total of 50.0mm (1.97') to the monthly total, and there appears to be so sign of the rain easing during the final third of the month yet to pass.
However, July 2016 is proving to be much warmer than its 2015 counterpart, with the mean temperature almost +1degC higher this year when compared to that of July 2015. In addition, May and June 2016 were both significantly warmer and drier than their 2015 counterparts.
@eddy_weather, Stornoway, 22 July 2016
Last night's (19 / 20 July) thunderstorm, as well as bringing torrential rain and spectacular displays of lightning, also caused a rare atmospheric pressure wave (a sudden jump of air pressure) of more than 2 millibars to Stornoway. The pressure wave was recorded using high precision met equipment at the Stornoway town weather station, operated by Dr. Eddie Graham (@eddy_weather). The jump can be seen in the following trace indicated by the red arrow (it occurred at 5:25am). The sharp pressure jump is also coincident with a sudden veer of wind from E/NE to SW/W (i.e. a cyclonic veer), and also an intense burst of rain (possible microburst).
A convenient visual metaphor which describes the physical manifestation of such a wave might be like "throwing a huge rock into a pond, and having the resultant waves surge over the perimeter of the shoreline" (the thunderstorm is the rock, the atmosphere is the water) says Eddie.
Data for the Stornoway town weather station can be accessed online at: https://www.wunderground.com/personal-weather-station/dashboard?ID=ISTORNOW2#history
Tens of thousands of lightning strikes were recorded across the British Isles during the night, with a peak discharge rate of 9,000 strikes per hour at 8 o'clock this morning, mostly in Scotland. The map below (courtesy of the Icelandic Met Service) shows the location of the hits (frankly, the whole of Scotland is covered by strikes!).
Meanwhile, the Stornoway rain radar at Lews Castle College recorded intense bursts of rain from 2:00-4:00am, and again from 5:30-6:30am (this latter downpour caused the pressure surge).- see the plot below. The pink colours show where raindrops maxed out in size on the droplet scale (i.e. they were the largest possible size) and also, they fell at the maximum possible velocity from a height of nearly 3,000 metres.
More information: @eddy_weather, 20 July 2016, Stornoway
Today was the warmest day in Stornoway town since 23 August last year, with a high temperature of +22.0degC reached at 5pm - see photograph of the mercury at its peak below (plus a nice photo of this morning's skies across Stornowy - altocumulus lacunosus floccus with virga, and a hint of altocumulus lenticularis undulatus too):
As seen from space, the Isles show up fine with lots of wispy aircraft contrails (condensation trails), but the Hebridean beaches were sparkling in the sunshine too.
Tonight, powerful thunderstorms have popped up NW of Ireland / SW of Barra and risk bringing a firework display in the night, more especially for the Southern Isles and mainland.
@eddy_weather, 19 July 2016
Noctilucent clouds are the highest type, forming in the mesosphere at an altitude of 80km or more. At this great height, the average air pressure is a mere 1/1000th of that at the Earth's surface.
Until recently, scientists did not know the exact cause of these clouds. NASA confirmed in 2015, however, that their likely origin is water vapour (ice) contained in meteorites arriving from space. They are very distinctive and beautiful clouds, having a tenous blue and luminous appearance (see photo above).
Due to their great height, noctilucent (meaning 'night-shining') clouds remain in direct sunlight (and thus shining) over latitudes 50 to 70degN, from May through to July. Over recent summers (2012-2015) we have seen a profusion of these clouds, but so far during summer 2016, the displays have been much less frequent and less pronounced.
Photo: 0033UTC, Stornoway, 6 July 2016 by @eddy_weather,
As part of the new Scottish Volcanic Ash Emissions Network, the Scottish Environmental Protection Agency (SEPA) have recently installed a new air quality sensing station at Lews Castle College, University of the Highlands and Islands, Stornoway, Scotland.
The sensors are capable of measuring sulphur dioxide (a main constituent of volcanic gas) and very fine particulates in the air down to a size of 10 and 2.5 microns diameter (about 1/50 the width of a human hair). The new Stornoway site is one of four national sites across Scotland, and it will act as a first-alarm site in the case of an eruption of an Icelandic volcano.
Live data, streamed directly from the sensors can be accessed and downloaded online at: http://apps.sepa.org.uk/volcanicemissionsnetwork/Dashboard.aspx?id=Lewis
@eddy_weather Stornoway, 3 July 2016
The vote to leave to the European Union is an unmitigated disaster for research and education at the University of the Highlands and Islands, and a catastrophe for Scottish Science, writes Eddy Weather.
The decision is likely to have significant ramifications for the further development and the enhancement of the economy of the region, as much of the initial funding that was been put in place to create the idea of the University came from EU structural funds.
Large collaborative research projects, such as Horizon 2020 and Inter-Reg which had the potential of injecting £many millions into the economy (and much, much more in spin-offs - each £pound invested has been shown to create £7 or £8), will now have to be abandoned, making the region a poorer place.
Many staff (such as Eddy himself) were brought to the Highlands and Islands by EU funding grants. Many new buildings, roads, small business start-up grants (e.g. Leader) on which the Highlands and Islands economy is vitally dependent, will now cease. The new Geography degree was largely developed with University Educational Development Unit's EU funds, it was hoped others (e.g. Geology) would follow suit.
Focussing in on the Isles themselves, there are countless regional projects that have only become manifest through EU funds: For example, the new Stornoway Airport, new double-track roads, causeways/bridges and community projects.It is very unlikely that such projects could have been funded by either (i) Scotland alone (for it doesn't have such monies available), nor (ii) UK Westminster (for it does not adhere to the EU fairness principle of 'subsidiarity'.
We will now have to deal with the lack of freedom of movement, and lack of attraction of talented individuals to the region, which will further diminish our standards of living and broad-mindedness. This is an appalling shame for Scotland, a country which prides itself on the highest standards of education and research,
@eddy_weather, 24 June 2016
Good news! Together with a team of about 30 cyclists, @eddy_weather has completed the annual charity cycle from the Butt of Lewis to the Isle of Barra.
The cycle was completed in record time, with strong tailwinds meaning high average speeds throughout the 3-day event. At one stage, the going was so fast that the 20-mile stretch from Sgoil Lionacleit (Benbecula) to the Borrowdale Hotel (Dalabrog, South Uist) was completed in just less than 1 hour!
The weather en route was much as forecast; strong northerly winds on all three days, with rain on Wed, clearing to glorious sunshine by Friday. There was a rogue heavy, soaking shower on Thurs on the approach to Benbecula, however!
There is still time to sponsor me - all donations welcome! https://www.justgiving.com/fundraising/CE-Graham
All eyes are on the annual Butt to Barra charity cycle from the Butt of Lewis to Isle of Barra, from 15-17 June this week. Here's Eddie's specially-prepared weather forecast for the event:
Wednesday: I'm afraid it gonna be cold, chilly, windy and damp start at the Butt! But the strong wind will be at our tails, and we should make record speed down to Barvas, and then onto Leurbost and Scaladale.
Precipitation: Light rain, smir showers, drizzle, cloudy.
Wind: NE windy Force 5-6
Temperature: Cool, 9-11C (good for cycling!)
Still cool and somewhat cloudy to start, but dry with clear and sunny spells breaking through after we cross the Clisham. Again, we should profit from a gusty tailwind. Watch the speedos going down the Clisham!
Precipitation: None or trace
Wind: N /NE Force 4, breezy
Temperature: 9-13C, cool but nice in sunshine
Another dry and fine day with some lovely sunshine.
Wind: North, Force 3-4, light to moderate breeze
Temperature: Cool, but feeling warm in Sun. 10-14C
No precipitation, fine.
Yes, it's true - Dr. Eddy will be hopping onto his bike later this week to cycle 175 miles along the spine of the Outer Hebrides, from the most northerly tip (Butt of Lewis) to its southern extremity (Isle of Barra).
Please sponsor his cycle adventure here: https://www.justgiving.com/fundraising/CE-Graham - Thank you! I will be posting regular updates on Twitter at: https://twitter.com/eddy_weather - please follow my progress!
Meanwhile here's a much fresher looking Eddie when I joined the Trans-Canadian C3 Cycle Crusade in the North American heatwave of 2001 long ago... the journey still continues..
On the warmest day of the year in many places (Stornoway town 20.0C, 24-25C inland), a powerful multi-celled storm developed over the North Harris and Uig hills, peaking at 2:30pm during the afternoon. Radar echoes maxed out at the highest possible value (greater than 120mm/hr) indicating torrential rainfall and/or large hail (see image below - dark blue and white colours indicate the location of the most extreme conditions):
First-hand reports from Breascleit confirmed the occurrence of a tremendous thunderstorm - although it weakened quickly as it spread north in the following 20 minutes.
The storm missed Stornoway but heavy showers were later picked up by the Stornoway Rain Radar operated at Lews Castle College, University of the Highlands and Islands (see image below).
'S seo an t-Samhradh - it looks like summer is finally here in the Hebrides. With offshore easterly winds likely to remain all week, skies should remain largely sunny and clear, and it will turn warmer too by the end of the week (17-18degC or higher).
The only fly-in-the-ointment is possibly tomorrow (Wed) and Sunday, when some cloud may affect Lewis (due to the north -east wind), but not certain yet by any means.
Update 29/5: It looks like the fine weather is set to remain for another week - though perhaps not quite as sunny as last week, with the cool north-east wind returning from Monday - but potentially much warmer by next weekend, maybe even surpassing 20degC!
A brief but violent storm squall passed through Nairn last Saturday, 21 May 2016. Sadly, one person died at Findhorn during the disruption. The radar echo (below) clearly shows an intense echo approaching the town from the west at 13h00. The echoes have maxed out at the highest possible reflection (dBz), suggesting either giant hail, or a debris cloud from a tornado. The hook echo clearly indicates rotation of some sort.
Please see http://www.gurnnurn.com/2016/05/wee-storm-rocks-nairn.html for more local information.
@eddy_weather conclusion: A suspect tornado, or a violent squall with significant rotation and windshear.