Posted by Dr. Eddy Graham on 18 November 2015, 2:51 PM
With 850hPa temperatures likely to dip to -9degC (minus nine) early on Saturday 21 November (and with a 1000 to 500hPa thickness of 520dam), snow is likely to fall and lie (inland, away from onshore coasts) during the latter part of Friday (20 Nov) and early Saturday (21 Nov). The snow will accompanied by a strong, bitter, northerly wind,
I don't expect it to last long, however - a thaw will arrive quickly by Sunday (22 Nov). It is also unlikely to lie for long near the windward coasts (as sea temperatures will be nearly 10degC warmer than the air).
There will be a risk of "thunder snow" too (hail and snow with lightning).
Oh boy, it's a tricky one.. (especially after largely escaping the wrath of #Abigail and I have no wish to 'cry wolf'), but...
It's looking possible that there will be a short but potentially violent spell of winds, lasting perhaps 3-4hours at their worst, tomorrow Monday 16 November, especially across the northern Hebrides i.e. Lewis, Harris.
However, no met model is perfect - and it's of interest that the models have not been performing well at T+24 hours recently.
Nevertheless, the GFS met model has violent storm force 11 winds (65mph+ mean) off St. Kilda at midday, spreading east across Lewis during the early afternoon, but weakening slightly to 50-55mph mean (severe gale 9 or storm force 10) around 3pm on the eastside of Lewis- see charts below:
Abigail came at night - and the warning was later downgraded from amber to yellow. The difficulty tomorrow (Monday) is that it will come during daytime.
If winds do reach in excess of 70-75mph+ (there's still some uncertainty), I recommend everyone staying indoors (school-children too, should they be at school) until the winds abate - the worst thing one can do is to evacuate a building during the height of a storm!
Posted by Dr. Eddy Graham on 13 November 2015, 4:33 PM
Although a potentially potent storm, the Western and Northern Isles together with NW Scotland were spared the worst from storm #Abigail.
Maximum windspeeds as measured across the region were as follows:
Stornoway Airport: 73mph South Uist: 84mph Sule Skerry 79mph Bealach na Ba (above Applecross): 98mph Lerwick 81mph
The storm did bring very heavy rain for several hours on Thursday, resulting in spot-flooding around Stornoway town. Abigail has also ushered in much colder air today (Friday) with squally showers of hail and sleet likely to continue, with the first winter snows likely to lie on the hills.
The weather outlook remains mostly unsettled and cool for the coming week, though it won't be quite as stormy.
Above, the picture shows the Abigail moving in across Stornoway on Thursday, as seen by the Stornoway rain radar.
Posted by Dr. Eddy Graham on 12 November 2015, 4:27 PM
She's a lady alright - storm #Abigail is already making her presence felt across Ireland and Scotland. Here's the final synopsis and prognosis from Eddy:
An extremely active cold front (with embedded thunder) cleared Stornoway at 3:30pm - there's a comparative lull at the moment. But don't be lulled into a false sense of security though, as winds will pick up again later this evening and tonight. The strongest winds are likely over the westside of Lewis, up towards the Butt of Lewis.
GFS has maximum windspeeds of 65mph (Violent Storm Force 11) off the Butt of Lewis / Sulisker and North Rona at midnight. But onshore (e.g. Stornoway), 50mph mean windspeeds are more likely (Severe Gale 9 or Storm Force 10).
Sting Jet/CCB: The region with the strongest winds is known as the sting jet and cold conveyer belt- look for the rapidly evaporating Scorpion's Tail-shaped cloud as it heads towards the Isles - you can see the animated satellite images at: http://en.sat24.com/en/eu?type=infraPolair
Lots of lightning too - but most of it has been going into Ireland and SW Scotland, so far:
Posted by Dr. Eddy Graham on 10 November 2015, 12:28 PM
The Met Office have issued the first high wind warning of the season for this Thursday and Friday for most of Northern and Western Scotland. As part of a new scheme for 2015-16, the storm has been named Abigail by forecasters at Met Eireann and the Met Office. Winds are expected to reach over 70mph, possibly touching 80mph in the strongest gusts. Winds of these speeds are dangerous when outdoors - please stay safely indoors when conditions deteriorate.
Posted by Dr. Eddy Graham on 10 November 2015, 12:24 PM
The Stornoway Micro-Rain radar spectacularily captured a heavy rainfall event early on 9 November 2015.
Between 03h15 and 04h30 hours, a torrential downpour occurred (identifiable by the region of bright pink colours in the image below). The time/vertical plot clearly shows the 'bright band' echo region (where snowflakes begin to melt, giving enhanced reflections), and it rose from about 700m in height at the start of the rainfall event to 1300m at its end (i.e. the frontal feature brought in warmer air).
Posted by Dr. Eddy Graham on 31 October 2015, 9:17 PM
Today brought the highest day max on record for 31st October in the Stornoway region, with 15.6C recorded at my site in Stornoway town. Nearby Stornoway Airport also recorded 15.6C. These are highest maxima for this date in the Stornoway area since computerised daily records begin in 1930.The previous day record was 15.2C in 2011.
Amazingly, the highest temperatures were recorded at normally the coldest time of day, 06h04 this morning, during the passage of a narrow warm sector. Foehn conditions are not usually extreme in Stornoway (when compared to say Inverness, south Dublin or North Wales), but do occur sometimes to the lee of the Harris hills with maximum amplitudes of 1-2degC generally.
At Aultbea on the nearby mainland (and closer to higher mountains), the high today was 17.2C.
Posted by Dr. Eddy Graham on 26 October 2015, 2:59 PM
On Monday 26 October, there were some lovely examples of mountain lee wave clouds over Stornoway and the Hebrides (see images below). These clouds are similar to waves on the surface of the sea, and are caused by regular vertical oscillations in the horizontal airflow, with mountains causing the initial disturbance.
Posted by Dr. Eddy Graham on 17 October 2015, 9:20 PM
It was another gloriously fine day today (Saturday 17 October), with Mother Nature making amends (well, at least partly) for the disastrous non-summer of 2015.
However, not everywhere was fine all of the time - as from about 12 noon to 3pm, locally dense cloud 'streets' (long parallel lines of cloud) developed over south-east Harris, emanating principally from two singular points - the Shiant islands, and east Harris (over an unpopulated region, near the peak of Uisinis, 371m). Locally conditions were overcast and foggy, in stark contrast to the glorious sunshine elsewhere around the island. You can see two rows of streets clearly here in today's satellite image:
This is how they looked from the ground, looking upwind from Reinigeadal (contrasted with the blue sky inland to the west):
And the low-cloud as it impacted upon Toddun (528m), now hidden in the mist:
Without a very high resolution (and plausible) met model, it is not possible to say exactly what caused this instability - but the alignment of breezes from the north-east suggest that local airflow convergence in the Minch / east of the Harris hills probably contributed, as may have residual moisture from an evaporating cloud deck entering the Minch via Cape Wrath to the north (as the satellite image shows).
Posted by Dr. Eddy Graham on 15 October 2015, 10:55 PM
The following two images may be of interest to those meteorologically-minded:
1) A photograph I took of a cloud street to the lee of Porto Santo (Madeira) whilst on an airplane recently:
2) The same cloud street as seen by the MODIS Terra sensor (VIS & IR channels combined) that same afternoon:
Due to the shallow trade-wind inversion to the east of the Azores high, the steep volcanic islands of Madeira and the Canary Islands frequently obstruct the otherwise smooth flow of moist surface air from the north/north-west. This maritime layer is usually capped at low-levels (~1,000m) by a very strong quasi-permanent temperature and humidity inversion, caused by the descending arm of the Azores high / Hadley Cell - skies are usually clear above 1000m. The blocking of the shallow maritime layer often yields beautiful and intricate patterns in the stratocumulus clouds downwind of the islands, such as Von Karman vortices, etc.. on this occasion we have a lovely bow-shape of cloud, with a single cloud street directly in lee of the island (presumably where pressure is lower and thus convergence is greater).
This is also one reason why the high volcanic peaks of the Canary islands are highly sought after as a destination for astronomical observation.
Posted by Dr. Eddy Graham on 09 October 2015, 8:42 PM
Without wanting to cherry-pick the data too much, a final study of the summer 2015 weather during May, June and July (using the original scheme devised by Poulter, 1962) reveals it was by far the worst ever recorded in Stornoway - by a considerable margin (see graph below)
I have chosen May, June, July (in contrast to June, July and August), as these have the longest daily lengths, and May is normally considered to be a 'summer' in the Celtic fringes of Ireland and Scotland - O mo chreach, oh dear indeed!
Eddie Graham, Stornoway, 9/10/2015
Poulter, R. M. (1962). The next few summers in London. Weather, 17(8), 253-255.
Posted by Dr. Eddy Graham on 25 September 2015, 5:43 PM
The good news is that high pressure is building again over this coming weekend (26-27 Sep), bringing settled and drier weather. It's not certain yet how much sunshine we'll get (indeed it will be dull and breezy with drizzle at times around the coasts and hills during early Saturday and again on Sunday), but hopefully from Monday onwards there will be some nice spells of warm, late Indian summer weather - temperatures could reach 18degC on the Isles, and over 20degC inland over the Highlandse.g. Inverness region. It will be breezy at times too, especially in the Minch with a strong southerly breeze at times, but no gales.
Posted by Dr. Eddy Graham on 20 September 2015, 10:33 PM
I've been down in sunny Dundee for the past 2 days, taking part in the BBC Tour 'Make it Digital' tour - in an attempt to try and improve digital literacy among school-children. I was helping to man the BBC Weather and Royal Meteorological Society's tent, where we had many interactive weather attractions for young and old.
Weather and the meteorological sciences make use of vast amounts of digital/computing resources, hence their inclusion in the tour.
Here's our set-up location, in City Square Dundee, right beside the beautiful Caird Hall (below):
The weather tent was just on the left (below):
View across City Square:
Oh boy, what's this? A Dalek! (Dr. Who has a tent across the square! - see below):
Yours truly in his BBC Weather T-shirt
Now, back to the weather -some lovely 'eyebrow' wave crests of sc. lenticularis over Inverness
Posted by Dr. Eddy Graham on 08 September 2015, 9:14 PM
At long last it seems the weather has settled down, bringing us an "Indian Summer" - this term is often used to describe a spell of fine weather late in the year, usually anytime from late August to early November.
NASA MODIS Satellite Image of a sunny Minch, Lewis, Harris and NW Highlands, but a dull and misty Inverness (9 Sep)
The NASA Terra satellite sensor passed over Scotland this morning (8 Sep) and revealed the Highlands and Isles emerging from a persistent (but gradually evaporating) deck of cloud and fog. This is what it saw - Can you pick out each glen and loch in the West Highlands?
Posted by Dr. Eddy Graham on 29 August 2015, 10:25 PM
Recently I visited the longest remaining glacier in Europe, the 'Aletsch' (Switzerland), during the peak of the intense continental heatwave of summer 2015. Presently, the glacier is 23km long, but like the vast majority of glaciers worldwide, the lower reaches of the Aletsch are melting quickly due to global warming. Intense summer heatwaves such as 2015 are highly detrimental to the survival of glaciers (during the 2003 heatwave, the Aletsch was observed to be receding at 1 metre per day, and about 50m per year on average over recent years) See below for a range of geomorphological photographs.
This first pair of photographs shows the extent of the glacier tongue in 2008 (left) and its considerable retreat/dimunition by 2015 (right):
Here's a fuller view of the glacier, looking towards the Gross Wannenhorn, with its five mini corrie glaciers (background):
And next, as we descend to the glacier - newly exposed terrain below the tree-line reveals a glaciologist's paradise - we are walking on one of the old medial moraines here:
Looking back upslope across glacial smoothed rock, and some trees have established themselves in places:
Now, we're almost at glacier level (about 1900-2000 metres above sea level), and a small fen / bog area has developed in one of residual troughs / rock basins left behind by the glacier:
Recently exposed terrain on the south side of the glacier: Considerable rockfalls are adding detritus to the top surface of the glacier.
That's me (below) in the French foreign legion hat (a most useful protection against the searing mid-summer sunshine). We are at the edge of the glacier, where an ice-cave has formed due to melting water. It is lovely to drink!
Danny (age 9) surveys f the glacier snout.
by Dr. Eddy Graham, Stornoway, Scotland, August 2015
Posted by Dr. Eddy Graham on 23 August 2015, 10:44 PM
Today (Sunday 23rd August) was the warmest day of year so far. Highest temperatures recorded were as follows:
Stornoway Airport: 21.4C
Stornoway town 22.5C
Harris Quidnish: 22.0C
South Uist Range: 23.3C
Askernish, South Uist 24.7C
Lusa bridge, Isle of Skye: 25.5C
Amazingly and due to an 'inverted warm sector', it was much colder to the south of Scotland, with Dublin Casement in Ireland recording a high of only 14.1C today - see the upside down synoptic weather chart!
Posted by Dr. Eddy Graham on 18 August 2015, 12:52 PM
While north-west Europe and Scotland remained damp and frigid during much of the summer, most of the nearby continent saw an intense heatwave during July and early August - on a parallel (or even more intense) than the heatwaves of summer 2003 and July 2006.
Posted by Dr. Eddy Graham on 16 July 2015, 3:08 PM
There was a magnificent display of noctilucent clouds, coupled with a weak green aurora glow, last night (15/16th July 2015) in Stornoway and across the Hebrides. Noctilucent clouds are the highest known clouds, forming at a height of over 80km in the mesosphere. Because of their great height, they remain brightly lit by the Sun during the northern hemisphere summer. The clouds are very thin and tenous have a characteristic 'electric blue' colour. According to NASA, the water vapour required for their formation probably originates in meteorites.
Posted by Dr. Eddy Graham on 15 July 2015, 11:34 PM
Thursday:Good! A nice dry day again for the most part, with nice spells of sunshine breaking through by afternoon, but east breeze picking up by eve taking the edge off the temps. Late into Thurs night, heavy rain breaking out and fresh winds.
Friday:A spell of heavy rain will come through during the early hours I'm afraid, together with strong easterly winds. Clearing up then for a while by mid-morning/midday - but more showers breaking up by afternoon, risk heavy with thunder! - so wellies are a must!
Saturday: More rain and showers, but lighter in nature and clearing - drizzle, and feeling much colder as a fresh northerly wind picks up. Some brightness too though so not all bad!
Sunday & Next week: More of the same, more rain - sorry!
Posted by Dr. Eddy Graham on 30 June 2015, 8:59 PM
It is official, May and June 2015 together will go down in the met history books as two of the most awful months (of their namesakes) ever recorded in Stornoway.
Overall, the May+June 2015 period was the 2nd wettest on record since 1873 in Stornoway, the 4th dullest (lack of sunshine) and 10th coolest since 1900. Put altogether, these are by far the worst weather statistics for May & June combined since records began in Stornoway in the mid 1850s.
Graphically, we view these statistics are follows:
Temperature: But for a milder final five days of June, it would have been the 4th coldest June on record. Instead, it works out to be the coldest since 1987, and the 10th coolest May-June on record in Stornoway:
Sunshine-wise: Need I say anymore: There's an horrendous vitamin-D deficiency for all concerned (4th dullest on record) [BTW, the values for 2004 are missing due to a changeover of instrument at Stornoway Airport]:
And rainfall - mein Gottlieb Daimler! 2nd wettest on record, and if it pours again tonight (30th June), we'll break the record (as June rainfall-month officially ends at 09h00 on 1st July).