Dr. Eddy Graham's Hebridean Weather Blog

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Maritime Arctic Airmass Views from Stornoway

Spectacular maritime arctic skies during the recent cold snap in Stornoway (by Eddy):

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Varied hues of Cumulus mediocris radiatus, with congestus.

Translation: Small heaped clouds, wider than taller, in a line; with a few taller than wider versions.

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The remains of a cumulonimbus anvil, but the cumulonimbus tower is no more! Cirrus spissatus virga cumulonimbogenitus.

Translation: Horse's hair (ice) cloud, thick with falling snowflake streaks (virga), formed earlier by a cumulonimbus shower cloud.

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Arcus, ahead of an approaching cumulonimbus squall.

Translation: A threatening arched line of cloud racing out from a thunderstorm.

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Cumulonimbus incus capillatus (white cloud in background).

Translation: A raining large heap of a cloud, possibly with thunder, with a flat-top shaped like an anvil, producing ice-cloud like horse's hair.

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A powerful single cumulus congestus thermal (white) rises under the shadow of an enormous cumulonimbus incus anvil (dark left).

Translation: A heap of cloud, taller than wider.

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And a severe hoar frost (air temperature -4.6degC) at 08h00 on 18 November, Stornoway Golf course. The grass min temperature was -6.7degC in Stornoway town.

@eddy_weather, Stornoway, November 2016.

November chill? A diagnosis and prognosis by Dr. Eddy

There's been some speculation that the coming winter will be a cold and snowy one. Certainly the past fortnight (up to 20 November) has been rather chilly across Scotland, with early severe frosts and heavy snow falling on the mountains. So what's the prognosis for the rest of the winter? 

Every winter brings snow, especially in Scotland! And humans have enjoyed speculating (not just on the weather) since time immemorial. And after two or three mild and stormy winters on the trot, it's not that difficult to predict a change in our weather fortunes!

At the same time, however, recent advances in atmospheric science mean that there are some guides to the general state of the hemispheric* weather pattern for perhaps a few to several weeks' ahead in time.

Let's start by looking at today's global weather pattern (courtesy of the University of Maine - see map below). This shows the current air temperature anomaly. There's an intense pink swath across Siberia and central Asia where it is record cold at the moment - but it is equally hot over most of the Arctic Ocean (where there has been unprecedented reduction in Arctic sea ice). A wee smidgen of blue over Scotland and Ireland confirms our current cold snap, but overall the British Isles occupy only a tiny part of the global picture. 

weather image

Today's air temperature pattern arises due to aforementioned 'Arctic amplification' due to sea-ice loss (Serreze et al. 2006), and very unusual stratospheric dynamics. Let's now consider the latter i.e. the stratosphere, which is the region of the atmosphere between 15 and 40km in altitude above our heads.

Stratospheric conditions are sometimes known to 'teleconnect' down to the surface, over the course of several weeks following an event such as a Sudden Stratospheric Warming (Mitchell et al. 2013). Today, NOAA's 50 millbar (~20km) air temperature plot shows clear signs of a polar vortex breakdown (see plot below). In 'normal' circumstances, there should be a circumpolar 'low' surrounded by a 'high'; instead we have a shift of the 'low' south to mid-Atlantic with a 'high' in the Bering strait - current forecasts indicate that this pattern is unlikely to change for at least the next 2 weeks.

weather image

Finally, winter storms in the North Atlantic region take their energy from the contrast in sea surface temperature between the Poles and the Tropics. They also gain energy from the condensation of water vapour evaporated from over the oceans. Here's the current sea surface temperature anomaly from NOAA Earth System Research Laboratory. There remains a cold pool ('the big blue blob'; Josey et al. 2016) in the middle of the North Atlantic, surrounded by warmer water on all sides, much the same as it was in 2015 (when a very stormy and record wet winter ensued). 

weather image

So all-in-all, a dodgy stratosphere, a very dodgy Arctic, and a stubborn big blue blob!

Conclusion: I'd say that we'll continue the cool and variable start to the winter (remainder of November, early December), but there always the chance of severe storms and gales returning, especially during the second half of winter (if the Arctic and stratosphere return to more 'normal' conditions).

@eddy_weather, Stornoway, 20 November 2016

* The Rossby waves, usually at wavenumber 6 or 7

References:

Josey, S., Grist, J., Duchez, A., Frajka-Williams, E., Hirschi, J., Marsh, R. and Sinha, B., 2016, April. Causes and Consequences of Exceptional North Atlantic Heat Loss in Recent Winters. In EGU General Assembly Conference Abstracts (Vol. 18, p. 4562).

Mitchell, D.M., Gray, L.J., Anstey, J., Baldwin, M.P. and Charlton-Perez, A.J., 2013. The influence of stratospheric vortex displacements and splits on surface climate. Journal of Climate, 26(8), pp.2668-2682.

Serreze, M.C. and Francis, J.A., 2006. The Arctic amplification debate. Climatic Change, 76(3-4), pp.241-264.

 

Big Minch 'Danglers' and Sunny Uist and Barra 'on the Lea'

Meso (and micro) scale meteorological effects gradually more become enhanced (i.e. less dominated by the synoptic airflow) when skies clear (allowing greater radiation fluxes) and winds slacken (reducing convective and advective heat transfer).

Today (Sunday 6 Nov 2016), we can see this in action across the British Isles: A strong northerly airflow has led to mesoscale convergence (meeting of air) over the Irish Sea, and a long narrow line of powerful convection (known as 'Pembrokeshire Dangler') has developed, extending more than 200km downstream into coastal Pembrokeshire and Cornwall. This is a common feature of the weather during northerly outbreaks (Mayes et al. 2013; Norris et al. 2013).

sat pic

Meanwhile, closer to home in NW Scotland, we can see a (reduced) similar effect in the Big Minch between NW Scotland and the Outer Hebrides. Showers have been funnelling down between the Harris and Skye hills all day, whilst inland Lewis has stayed dry. Further south, the Uists and Barra have been bathed in glorious sunshine, maintaining a 'clear slot' of sunny skies all the way to Donegal in Ireland ('Sunny Uist and Barra on the Lea').

sat pic

@eddy_weather, Stornoway, 6 Nov 2016

Images courtesy #NASA MODIS channels 367.

References: 

Mayes, J., 2013. Regional weather and climates of the British Isles–Part 5: Wales. Weather, 68(9), pp.227-232.

Norris, J., Vaughan, G. and Schultz, D.M., 2013. Snowbands over the English Channel and Irish Sea during cold‐air outbreaks. Quarterly Journal of the Royal Meteorological Society, 139(676), pp.1747-1761.

 

Best October in decades!

It's been the best October across NW Scotland and the Isles for decades.  Based on the long-term records for Stornoway, with a precipitation total of only 36.0mm (1.42in) it was the 2nd driest in 144 years of record keeping for the Isles (1873-2016) and the 4th sunniest since 1929 (87 years). See the graphs below by @eddy_weather.

graph

graph

Further information can be seen in a recent Met Office press release: http://www.metoffice.gov.uk/news/releases/2016/end-of-october-2016-stats

graph

Various views of NW Highlands and Islands during October fine spell

Below please find a few spectacular NASA Terra satellite images of NW Highlands and Islands, Scotland, during the recent fine spell of weather:

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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)

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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).

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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

Eddy goes East with Etihad

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:

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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.

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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.

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Eddie on the Marina seafront.

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2nd wonder of the modern world: The Sheikh Zayed Grand Mosque

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The Dusit Thani hotel (515ft high): "A little town in heaven"

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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 Narrow Rain Band passes through Stornoway 27/9/2016

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.

radar

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

 

Here come #Karl and #Lisa!

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.

radar  radar

* 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

New Storm Names for Winter Ahead Issued: And Beware of Bogus Weather Sites!

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

radar

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!

LE Radar detects strong (and wet) warm front

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):

radar

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)

Autumnal gales and rain on way for Hebrides

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.

Scotland ScotlandScotland

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.

Scotland

*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

Highland Clouds Revealed as Harmonic Oscillators

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.

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):

Equation

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!)

QED

And this is what was seen from the ground in Dingwall, on the night before (during the same harmonic event) - photo courtesy Andrea Goddard:

Scotland

@eddy_weather, Stornoway, 6 September 2016

Stricken Oil Rig now in Broad Bay, Stornoway

Seall dè a chì mi anns a 'mhadainn an-diugh!

Scotland Scotland

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:

Scotland

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

END

A late summer arrival like 'Waiting for Godot'...

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:

Scotland

Updates of daily temperature highs can be seen on Eddie's twitter feed at: https://twitter.com/eddy_weather

Eddie, Stornoway, 10 August 2016

Funnel cloud off South Uist, 9 August

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:

Tornado funnel

Enhanced funnel

Enhanced funnel

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 

 

Blustery and unsettled, summer gale Sunday

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! July 2016 is 4th dullest and 3rd wettest in Stornoway in 145 years! (but not cold)

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)

Rain, rain

    • 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)

Cloudy and dull

    • 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)

Average temperatures

@eddy_weather, Stornoway, 31 July 2016

END

 

July 2016 now wetter than "2015 washout" but warmer...

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.

Rain, rain

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

END

 

 

Severe thunderstorm causes pressure surge

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).

Met trace

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!).

Blitz

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.

MRR Lews

Regular tweets from the Lews Castle radar can be viewed at @lewscastleradar, with more information at: https://uhi-mahara.co.uk/view/view.php?id=24843

More information: @eddy_weather, 20 July 2016, Stornoway

END

 

 

Warmest Day of Year Brings Thunder Risk

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):

Mercury

 Sunny skies and wispy clouds

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.

Lewis and Harris

 Uists and Barra

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, Stornoway, 6 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.

Noctilucent clouds

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

New SEPA air quality and volcanic ash sensing station in Stornoway

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.

Hebrides

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

Leave vote is disaster for University and Scottish Science

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.

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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,

END

@eddy_weather, 24 June 2016

Eddy completes Butt to Barra Charity Cycle!

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.

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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

Thank you!

@eddy_weather

Dr. Eddy's Butt to Barra 2016 Weather Forecast!

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:

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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!)

Thursday:
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

Friday:
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.

For more info, please visit: https://www.facebook.com/Butt2Barra2016/. To sponsor Eddie, please go to: https://www.justgiving.com/fundraising/CE-Graham

@eddy_weather

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27 February 2014, 3:46 PM
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