Dr. Eddy Graham's Hebridean Weather Blog

by Dr. Eddy Graham

Edward Graham's Journal (Details)

Hebridean Summer Weather

Posted by Dr. Eddy Graham on 24 May 2016, 3:16 PM

'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).

Hebrides

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!

Enjoy! 

@eddy_weather

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Hook echo (possibly tornadic) in Nairn, Sat 21 May

Posted by Dr. Eddy Graham on 24 May 2016, 1:47 PM

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.

Radar echoes

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.

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Sun burnt and thunder struck!

Posted by Dr. Eddy Graham on 23 May 2016, 10:47 PM

In a slack cyclonic synoptic (atmospheric pressure gradient) flow between April and September, surprisingly sharp contrasts in air density can arise over short distances, even in the Hebrides (due to uneven heating of the land and ocean surfaces by strong morning sunshine). Sea breezes quickly develop, and where they meet (often near mountain peaks), powerful convection is often set off.

This is what happened yesterday, Sunday 22 May 2016 - when a very powerful convegence line developed over Barra, Beinn Mhor and Hecla (South Uist), then Eabhal (North Uist), during the morning, leading to large cumulus and cumulonimbus clouds (see photo).

Benbecula and North Uist skyscape

These clouds moved steadily northeast with the upper steering flow towards Harris and Lewis in the afternoon, developing further all the time - eventually leading to a powerful thunderstorm -whilst the west coasts of the Isles remained bathed in glorious sunshine an warmth.

A later NASA satellite picture of the southern Hebrides clearly shows the sunny coastlines, with cloud streets rapidly developing into anvil tops (red/orange) downwind to the northeast.

NASA Terra 367

The weather conditions were well predicted by Eddie on Facebook last Friday morning- see which stated: 

Eddy Weather here: Everyone's asking me / demanding me to get the sunshine back!

Well - there will be some warm sunshine for some this weekend -though generally the weather will remain very mixed, with heavy (even torrential) showers at times (with a risk of thunder too), particularly inland and away from the coasts (e.g. nearer the centre of the islands).

So in detail - probably nowhere staying dry for more than 24hrs: Some decent sunshine in Point, Westside fringe, south Harris, machair coasts of Uists, Barra and Benbecula - but heavy downpours (especially inland N Harris, Clisham, central Lewis including Stornoway, inland parts of the Uists). The exact positioning of the showers and sunshine will depend on sea-breezes and other wind effects.

@eddy_weather
Eddy-Weather: Met & Climate Tweets by Dr. Eddie Graham

 

 

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Pancake clouds

Posted by Dr. Eddy Graham on 15 May 2016, 9:44 PM

The eminent and highly perceptive Prof. Richard Scorer (1919-2011) used to describe these clouds as "pancakes" (for that is how they look from above when viewed by satellite, and that is how that spread out in the sky - like 'pancakes in a pan').

Closed cell edge

Speaking in the strictest meteorological vernacular, however, they are a form of stratocumulus, caused by the the spreading out of a shallow anvil (incus) of a cumulus congestus, or a ragged cumulus fractus (scud) turret. Reaching an inversion level quite low down in the troposphere (often caused by an anticyclonic inversion), the cloud material spreads out sideways (rather than upwards) to occupy most of the visible sky, except for small areas along the leading edges of the 'pancake', which descend in an evaporative fashion.

Thus, today's photograph (above), taken in Stornoway town at 19h50, shows the evaporative 'silver blue lining' edge of a dark 'pancake' contrasting strongly with more stable air to the right. Accessory cloud features such as mammatus are often present under the pancake, though they bring hardly more than a few light drops of rain at most. 

These cloud formations are also known as "closed cell convection" - for that is what they are: Cells made by convection, and closed in by clouds.

Very occasionally, the cumulus turret sets off a gravity wave, which can propogate is radial fashion from the centre of the cloud out to the edge, giving a 'flying saucer mothership' appearance, but this is unusual.

Finally - this is how they look from space (today's NASA Terra 367 image) - on the left, see I told you, pancakes!

NASA Terra shows closed cell convection to west of Scotland today 

@eddy_weather, Stornoway, 15 May 2016

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Abair bhlàth! Highland heatwave hits

Posted by Dr. Eddy Graham on 10 May 2016, 9:43 AM

Abair bhlàth! 25-26C tro na Gàidhealtachd agus nan Eilean an-diugh!

Heatwave 

NASA Terra image 9/5/2016

What a stunner - here are the highest temperatures for Monday 9 May 2016 -the warmest spell in May since 2012:

Stornoway town: 19.7C

Stornoway Airp: 19.5C

Lusa, Isle of Skye: 26.7C

Aultbea, Wester Ross: 25.5C

South Uist: 23.0C

Benbecula: 25.2C (possibly a new record for May for the site)

Kinlochewe: 26C

The Scottish May record remains 30.7C at Inverailort during the 2012 heatwave. Achnagart (Kintail) reached 29.4C during this spell too.

@eddy_weather

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Heatwave? Well, certainly A LOT warmer

Posted by Dr. Eddy Graham on 04 May 2016, 10:37 PM

Heatwave

Due to persistent lower-than-average sea surface temperatures in the North Atlantic Ocean, the highest temperature during the whole of April in Stornoway was a mere 11.4degC, colder than the highest in either January or March of this year!

Yet all of this is to change from this Sunday (8th May) onwards as winds switch from the prevailing cool northerlies and westerlies of recent, to a much, much warmer easterly, coming straight off a rapidly warming continent.

To watch out for? Pressure will decrease quickly over the mainland from Tuesday onwards, so widespread thunderstorms are likely inland by mid-week. Haar is often a problem too on onshore coasts during early heatwaves.

@eddy_weather

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Coldest night of winter in Stornoway - on April 28th!

Posted by Dr. Eddy Graham on 29 April 2016, 10:18 PM

Severe spring frost

In a past 12-month period that has seen the meteorological seasons practically reversed, the recent abnormally cold late April weather has brought heavy snow, large hail, severe frost and bitter winds across Scotland.

Amazingly, Stornoway town actually reported its coldest night of the 'winter' on 28 April 2016, with -2.9degC (grass min of -5.4degC) recorded at the Met-Office spec station in the town centre. The -2.9degC value is lower than any recorded during the normal winter period of December, January and February (or indeed March) - the next coldest night was 27 Feb with -2.3degC.

Drier soils, lighter winds, cooler sea temperatures and more frequent northerly airflows in late winter usually mean the lowest night-time air temperatures are often reserved for late January or February in the Hebrides - but it is highly unusual to have the absolute lowest so late in the season on 28 April, a mere 8 weeks from midsummer.

It is noted with interest that 2015 also saw very low air temperatures as late as 1st May (-4.5C at Lews Castle meadows, the 2nd lowest value of that year). 

All this follows on from some remarkably topsy-turvy variation in seasonal weather over the past 12 months (2015 was the worst summer in least a century in western and northern Scotland; Scotland also experienced the astonishingly record wet December 2015).

@eddy_weather

 

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Celestial Landscapes: Art, clouds and science

Posted by Dr. Eddy Graham on 14 April 2016, 11:02 AM

Come and see @eddy_weather in action at the Inverness Science Festival on 29 April next!

UHI

WHEN? Friday, 29 April 2016 from 17:30 to 19:00

WHERE? University of the Highlands and Islands STEM hub - 1 Inverness Campus Beechwood Campus, Inverness IV2 5NA, United Kingdom - View Map

Abstract:

Clouds cover 40-50% of the earth’s surface at any one time – yet, how often do we get the chance to pause from our busy schedules and look-up to fully appreciate the beauty and spectacle of our ever-changing celestial landscape? In this lecture, Dr. Eddie Graham (FRMetS), will show, with the aid of photographs and time-lapse animations, how an initial aesthetic appreciation of clouds can quickly translate into a enhanced understanding of the meteorology and science behind clouds, by simply ‘looking at them from both sides’.

This event is part of the Inverrness Science Festival and will take place at the University of the Highlands and Islands STEM hub, Room 51 in the building behind Inverness Campus.

 

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Glorious summer ahead as scientists find way "to stop rain"

Posted by Dr. Eddy Graham on 01 April 2016, 6:56 AM

A new scientific breakthrough in cloud physics means this summer "could be the best yet" over the UK, reports @eddy_weather.

Line convection over Lewis and Harris

Project FAIR-LOOP-l, a consortium which has revolutionised a new cloud-seeding technology, announced this morning that they will be using their fleet of new airplanes, currently based in western Scotland and Ireland, to seed the clouds from above on a daily basis during the coming summer. Their operation will make the clouds "rain-out" all their precipitation before reaching the UK, thus ensuring sunny skies and a "barbeque summer" for all.

The expected change in weather will be especially welcome in the Scottish Highlands says FAIR-LOOP project manager Dare H. Tweedy, as last summer (2015) was a washout - "the worst in nearly 200 years".

It's a "win-win" situation adds Tweedy because "since the weather will be drier there'll be far fewer midgies too, so that's an added bonus". A severe drought for the whole of the UK is unlikely however, as the cloud-seeding planes will only be in operation during the daytime (due to current EU working-time and health-and-safety legislation) and so "some rain is still likely at night-time" according to Tweedy.

FAIR-POOL says it has funding for exactly one year only due to UK government austerity measures and spending cutbacks on research. Pending success, interested parties with a view to expanding the project for perennial summer weather are asked to DM @eddy_weather on Twitter for further information.

@eddy_weather

1 April 2016

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Excellent examples of line convection

Posted by Dr. Eddy Graham on 31 March 2016, 5:37 PM

Line convection is a bit like 'strip-the-willow line dancing' - it's a narrow line, but it's very exciting, energetic and goes on forever!

Yesterday and today (31 March 2016), due to the slack cyclonic synoptic airflow upon us, and together with the strong post-Equinoctial sunshine, meso-scale conditions were ideal for the formation of morning sea-breezes followed by powerful inland convection.

Yesterday saw a narrow convection band lined North-South over the Uists (see image). Today, it was the same thing over Lewis and Harris (see 2nd and 3rd images), although there was enough upper streamflow to force the latter line east into the Minch by 5pm. Glorious sunshine, followed by heavy showers occurred in both cases.

Uists white cloud line convection

Line convection over Lewis and Harris

Line convection over Lewis and Harris

@eddy_weather

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Happy St. Patrick's Day

Posted by Dr. Eddy Graham on 17 March 2016, 5:51 PM

What stunning St. Patrick's Day weather for Stornoway!

Green island

Apparently the island has turned green too! (NASA MODIS Terra satellite image), as it emerged today from the haar surrounding most Scottish coasts today.

Altogether over past four consecutive days, we've had nearly 35 hours of sunshine (about 80% of the maximum possible), with air temperatures rising up into the teens (High of +13.5C in Stornoway town on St. Patrick's Day, low of +0.7C on the crisp frosty mornings, -3.1C on the grass).

Alas, the glorious weather ain't to last, as the breeze has now turned onshore and the haar and low cloud will likely be dominant over coming days, though some breaks are possible.

@eddy_weather

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There's 7% extra weight on your heid today!

Posted by Dr. Eddy Graham on 15 March 2016, 3:31 PM

We live at the bottom of an ocean of air, known as the 'atmosphere'. So, in much the same way as if we dived to the bottom of the sea, the total weight of air above our heads causes a compressive force on our bodies at sea-level -> this force is air pressure. In physical terms, this is simply measured as the mass of air over every metre, per second every second (or even more simply, newtons per square metre). 

Today, the Ides of March (15th), we have an enormous high pressure zone sitting over Scotland (see chart) with a super-tremendous central pressure of 1040hPa. In simpler terms, that's the same as 10,400 kg (over 10 tonnes) of air acting over each metre per second, every second.

Frosty grass Frosty grass

During the past winter, air pressure was often below 970hPa during the frequent storms that battered our coasts and country. When understood as kilograms per metre over time, this means that the force acting on our heads today (i.e. weight of air acting on our heads) is some 7% greater than during the past winter!

However, unless you are super-sensitive, I doubt that you can feel a tangible 7% more compressed today!

@eddy_weather, Stornoway, 15 March 2016

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Hint of spring ahead next week...

Posted by Dr. Eddy Graham on 10 March 2016, 6:21 PM

The mornings may still be frosty, and the grass still yellow with few, if any, shoots of green... but there's a (slight) hint that Spring may be just around the corner...

Frosty grass

At the moment, the met models are indicating much milder weather for all of Scotland over this weekend, but with plenty of rain along the west coast and through the Highlands. However, from Tuesday onwards, pressure will rise again from the east - hopefully bringing glorious skies and warm air, with the air temperature reaching into the teens degC... let's wait and see!

N.B. Fine weather in spring always brings the risk of haar too, so don't get too excited yet!

@eddy_weather

Stornoway, 10 March 2016

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Muirneag, Beinn Bharabhais with dustings of snow

Posted by Dr. Eddy Graham on 27 February 2016, 9:59 PM

Glorious clear skies today (27 Feb 2016) reveal dustings of snow still lying on Muirneag and Beinn Bharabhais (Isle of Lewis), as seen by the NASA Terra satellite sensor. Further south, the snow-capped hills of Harris and Uig stand out like icebergs against the faded winter landscape shades.

Stornoway snow

N.B. Last night was the coldest night of the winter in Stornoway town so far, with -2.3degC measured at 06 UTC. Possibly even colder tonight.

@eddy_weather

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Sneachd 's Grian ann an Steornabhagh

Posted by Dr. Eddy Graham on 24 February 2016, 2:54 PM

Bha e uabhasach breagha ann an Steornabhagh an-diugh - Seall na dealbhan!

Stornoway snow

Stornoway snow

Stornoway snow

Stornoway snow

Thuit 2cm sneachd tron oidche 's tron an mhadainn. Bha an temperature as isle -1.1C, agus bha -4.9C air an talamh.

@eddy_weather 

27 An Gearran 2016

 

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NASA Terra images snow extent

Posted by Dr. Eddy Graham on 18 February 2016, 2:54 PM

One of the most useful and versatile satellite sensors in operation today is surely NASA MODIS Terra. Using a combination of visible and infra-red radiometer detectors, the various channels can be combined in a way to identify and distinguish almost any type of surface from space - including snow.

In the images from today (Thursday 18 Feb 2016), thanks to clear skies over most of Eastern Scotland, we can see the snow extent as cyan (channels 7, 2 and 1) and mauve (channels 3, 6 and 7).

Black Frost Black Frost

Yesterday (17 Feb) we could also clearly distinguish the peaks of Toddun, Beinn Mhor na Hearadh and Beinn Mhor, Uibhist a' Dheas, on the 7-2-1 image for the Western Isles (see below)/

Black Frost

@eddy_weather

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Beware of the Black Frost!

Posted by Dr. Eddy Graham on 13 February 2016, 9:53 PM

There has been a very welcome switch to 'easterly' weather over the past few days across the Hebrides - with low relative humidities permitting an excellent clarity to the atmosphere.

However, one of the risks of such low humidity means the wet-bulb depression is enhanced (evaporation is enhanced), and in such conditions an ice-bulb effect can be observed (see chart).

Black Frost

The result is an invisible 'black' frost - this occurs when the ground and objects freeze, but there is no trace of a visible 'hoar' frost (normally caused by humidities reaching 100%, which isn't the case at present across the Isles). With low relative humidities, this can happen even with air temperatures well above freezing (e.g. +2, +3degC)!!

So you have be warned - beware of the black frost!


Postscript (14 Feb 2016): Today I realise that I may have confused some folk with the graph above. Here's a hopefully better pic i.e. If the air temperatures is +2.5C and relative humidity is 60%, and a wet surface (e.g. grass, ground) evaporates to the drier air above, it actually cools right down to -0.0C (and thus could freeze as a 'black' frost, with no visible 'hoar' frost). The drier the air, the greater the potential cooling! (just as we've had recently):

Black Frost

@eddy_weather

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Nacreous clouds: A beautiful spectacle or a terrible beauty?

Posted by Dr. Eddy Graham on 05 February 2016, 12:58 PM

One of the most widespread displays of nacreous clouds ever witnessed in the British Isles took place recently over 1-2 February 2016. In some places (such as Dublin, Ireland), there is no recorded evidence of any previous occurrence, right back to the 19th century, at least (Dixon 1953).

Most of central and southern Scotland, northern England (including Manchester and Leeds) and eastern Ireland witnessed the clouds over an unprecedented length of time. In Dublin, the clouds apparently remained in the sky for nearly 48hrs (again a very unusual duration). A few example photographs are shown below (courtesy Garry Quinn photography and Kieran Commins, Met Eireann).

nacreous clouds

By gquinnphotography.com

nacreous clouds

By gquinnphotography.com

The clouds were coincident with an moderately-intense ozone hole of 200-250 DU (Dobson Units) over north-west Europe (normal ozone is about ~360 DU) - lower values have been documented in the past, for example 165 DU in November 1999 (Graham 2002). This is to be expected in this case, for ozone is responsible for heating of the stratosphere - and so a lack of it usually means a colder stratospheric air temperature. If cold enough (below -80 to -85degC), nacreous clouds (also known as 'Mother-of-Pearl' or 'PSC: Polar Stratospheric Clouds') can form.

nacreous clouds

By Kieran Commins (Met Eireann)

The clouds involved in this display were generally considered to be Type 2 PSC, and so not directly involved in ozone depletion. However, it is possible that some Type 1 PSCs may have been present too (they deplete ozone at a rate of about 1% per day). Some photographs of suspect PSC Type 1 clouds were taken early on 3 February (please ask author if interested). 

The ozone layer is, of course, vital for life on Earth. Without it, we would suffer from harmful UV radiation, which causes skin cancer and damages crops. Northern Hemisphere ozone, although nowhere nearly as low as in the Antarctic, has shown some loss in recent decades.

Here's the Northern Hemisphere ozone distribution for 2 February, courtesy of NASA Ozone Arctic Watch (http://):

nacreous clouds

As stated by Hood and Manny (2002), such holes in the Northern Hemisphere are mostly caused by dynamics in the stratosphere, and the contribution from ozone depleting PSCs is minimal.

And here's the 30hPa air temperatures (about 24km, which was the height of the clouds during the November 1999 event, as shown by Graham [2002], courtesy of NOAA CPC (http://):

nacreous clouds

As you can see, there's a clear minimum of stratospheric air temperature below -80degC, located right over the UK/Ireland i.e. highly suitable conditions for PSC formation.

And finally, on Twitter on 2 Feb, I'd thought that I'd spotted the nacreous clouds themselves on NASA Terra Channels 7-2-1. It looks like there was a hydraulic jump generated by the very strong west wind (nearly 200kts at jetstream level) hitting the Wicklow mountain perpendicularly, side-on (see sat image below). Dörnbrack et al. (1999) state that the air temperature can drop significantly in stratospheric mountain wave crests (due to rapid uplift). In the case of 1-2 february, the air was likely cooled rapidly to saturation and a low-enough temperature for PSC formation (i.e. below -85degC).

However, closer analysis of MetOp imagery shows that this particular cloud had a cloud top temperature of only -30C to -40C. So alas, no PSC! (they are probably too thin optically to be seen on standard visible/infra-red satellite imagery, Graham 2002).

nacreous clouds nacreous clouds nacreous clouds 

(with thanks to Bernard Burton of http://www.woksat.info/ for this final image)

Conclusion: Whilst outstandingly beautiful, a more holistic view of these clouds could easily be 'Harbingers of Doom'. I think more research is needed on the exact causes of this outstanding display.

Appendix: Nacreous clouds (such as above) form in the lower stratosphere between 20-25km. Previous sightings near/around the British Isles include the following:

  • 16 Feb 1996: Northern England
  • 30 November 1999: Aberdeen and E Scotland
  • 19 January 2008: Belgium
  • 9 December 2012: Aberdeen and Isle of Harris
  • 1-2 February 2016: This event

i.e. Their incidence appears to be on the increase during recent decades, which is in line with global ozone depletion caused by human pollutants, but it may also be coincidence.

Websites on previous sightings:

@eddy_weather

Stornoway 5 February 2016

References:

Dixon, F.E. (1953). Weather in old Dublin. Dublin Historical Record13(3/4), pp.94-107.

Dörnbrack, A., Leutbecher, M., Kivi, R. and Kyrö, E. (1999). Mountain‐wave‐induced record low stratospheric temperatures above northern Scandinavia.Tellus A51(5), pp.951-963.

Graham, Eddie. "Nacreous clouds in November 1999 and record low ozone."Weather 57, no. 3 (2002): 107-109.

Hood, L.L. and Manney, G.L. (2002). Nacreous clouds. Weather57(10), pp.393-394.

 

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No @eddy_weather!

Posted by Dr. Eddy Graham on 31 January 2016, 3:54 PM

Alas, Eddie has come down the the lurgy recently, so I'm not issuing any weather news or updates at the mo, thank you @eddy_weather

Wild weather for Burns' week

Posted by Dr. Eddy Graham on 24 January 2016, 9:10 PM

It's Burns' Day tomorrow (Mon 25 Jan), and after some very pleasant but cold winter weather over the past two weeks, it's looking likely that we'll see a return to more seasonal winds, heavy rain and gales over the coming week - much as happened in the year of Burns' birth.

Scotland's Greatest Bard - Robbie Burns

A severe gale is possible on Tuesday accompanied by heavy rain. More heavy rain and further gales will follow during the week, and it may turn much colder (with brief snow) at times later in the week.

Keep posted with me on Twitter at: @eddy_weather

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Snow extent across Scotland

Posted by Dr. Eddy Graham on 15 January 2016, 11:12 AM

Sneachd (gorm) tro na Crìochan na h-Alba 's an Gàidhealtachd an-de (as seen by the NASA Terra satellite) @eddy_weather

Scotland snow extent

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Never promise snow to children unless you are certain!

Posted by Dr. Eddy Graham on 10 January 2016, 11:07 PM

Recent weather updates on @eddy_weather

Lesson #1 in Forecast Meteorology:

Snow by Henryk Żychowski

Every year, in every country which has a winter, the forecasting pros (and not-so-pro) almost always stumble up at least once with one of the following errors:

Type 1:  You fail to forecast snow and it snows -> bad for you as your local council will be mad, but who cares, as the kids are delighted and it's a surprise snowfall, yippee!

Type 2: You forecast snow and it doesn't come -> worst case scenario as the council is still mad and your kids hate you too for months!

So what's it to be? Snow or no snow this week?

Update Tue 12/1/16: Probability of significant lying snow this week is reducing now; Wed pm is colder, but maybe Thurs milder. Then colder again Fri, let's see!

Original Post Sun 10/1/16: Currently, for Stornoway and the Hebrides, it's looking slightly possible that we may get some lying snow for a day or two between Wednesday and Friday of the coming week - but it won't last, it'll probably be gone by the weekend as mild southwesterlies will soon return. Of course the snow will come earlier on the Clisham - watch out for ice too!

P.S.. I note the astronomical tides are very high tonight and tomorrow. With a low air pressure of 970hPa tonight, the combined tide and surge could be +5.5m, so please watch out if you're near the coast at high tide.

@eddy_weather

 

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1st Anniversary of the Stornoway 'Hurricane''

Posted by Dr. Eddy Graham on 08 January 2016, 5:02 PM

Tonight, 8/9 January 2016 is the first anniversary of the Stornoway 'Hurricane', the most powerful storm to affect the British Isles for over 20 years. At its peak, winds reached hurricane force 12 during the night at Stornoway Airport, with a peak gust of 113mph - the strongest in the UK since the 1990s. It was about as severe as Hurricane Debbie of 16 September 1961.

Here's a remainder of some of the damage / synoptic chart that night:

Tonight is also the 176th anniversary of Ireland's greatest natural disaster, Oíche na Gaoithe Móire ('Night of the Big Wind') when hundreds died in a ferocious hurricane, the severity of which has hardly been equalled over the past 300-400 years. It strongly impacted Scotland too, with air pressure dropping to 931hPa in Shetland.

@eddy_weather

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Strong easterly winds promote good drying

Posted by Dr. Eddy Graham on 06 January 2016, 9:27 PM

The tale is told in the weather statistics:

  • The first six days of January 2016 have yielded a tiny total of 0.9mm (0.03in) of precipitation (rain) in Stornoway town
  • The final six days of December had... wait for it... 67.3mm (2.65in) of rain! (75 times more)

All because of a change in wind direction i.e. an offshore, easterly!

And although chilly, the lovely dry wind has meant some excellent drying conditions following seeming endless weeks of rain.

@eddy_weather, Stornoway, 6/1/2016

Attached files Attachments 1

washing.png (179KB) - Download

Stornoway 2015: Third Wettest Year at Airport Since 1930

Posted by Dr. Eddy Graham on 02 January 2016, 1:12 PM

Based on official Met Office data, the year of 2015 was the third wettest year on record in the vicinity of Stornoway Airport since 1930, with a total of 1494mm of rain falling. It ranks behind the two wettest years 1990 and 1999 which had totals of 1543 and 1547mm, respectively.

Incidentally, Stornoway town (a generally wetter location than the Airport) recorded 1680mm (66 inches) of rain during 2015.

The long-term trend in rainfall at Stornoway Airport (shown below) indicates an increase in variability and extreme high annual totals over the past 30-40 years.

Attached files Attachments 1

SYY-03026-Annual-Precip-1930-2015.png (26.2KB) - Download

 
 

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