Posted by Dr. Eddy Graham on 15 May 2015, 2:29 PM
So you think May's weather can't get any worse, can you?
Well, sorry, have I got news for you... a frigid blast of cold Canadian air (direct from the Davis Strait between western Greenland and Labrador) is expected to impact the Highlands and Islands Saturday-Monday. Expect frequent rain/hail showers with blustery squalls from Saturday afternoon onwards - some sleet is even possible at times, with snow on the highest hills.
n.b. See 2nd image below - sea surface temperatures in the North Atlantic are considerably below normal at present. The negative anomalies are some of the lowest on the globe with respect to the rest of the world at present.
Posted by Dr. Eddy Graham on 11 May 2015, 4:49 PM
Monday 11 May 2015
A rare hook echo was apparent in the Lewis radar scan of this morning's torrential rain (see below). This is BAD NEWS meteorologically speaking, and rather unusual for a maritime location of British Isles in May.
Hook echoes (the curvilinear feature on the rainfall radar image, over Lewis and Harris) indicate rotation in a storm clouds, yielding possible severe thunderstorms, hail, flooding rains and possibly even tornadoes (when the hook is well developed).
A very bright infra-red image (see next image) also indicates powerful convection to the tropopause.
Spring and summer, oh summer, have you deserted us?
Eddy, Stornoway, 11 May 2015, 17h.
Posted by Dr. Eddy Graham on 10 May 2015, 11:01 PM
With another soaking near-inch of rainfall (20mm) in Stornoway on Sunday 10 May 2015, many folk are rightly beginning to ask "Where is Spring?" (let alone summer!).
There's no definite answer to this, other than saying no prolonged respite from either the unseasonal cold, nor recurrent rain, appears likely over the coming week. Certainly sea temperatures in the North Atlantic ocean are considerably below normal at present (see map below) - but there is no straightforward link between weather conditions in the Hebrides and the above.
So we will have to wait and see what summer brings - let's just hope it won't be another 1816, aka 'The Year Without a Summer'.
N.B. From NASA: Two nice satellite images of line convection over the Isles, Fri & Sat 8/9 May 2015:
And the current sea temperature anomalies - blue means cold!
Posted by Dr. Eddy Graham on 05 May 2015, 5:19 PM
There's still no sign of a lengthy pause or calming-down of the weather situation, with respect to the latest St. Kilda swim attempt.
Presently, a 36-hr window that was previously forecast from early Friday 8th - Sat 9th May now seems to be closing-in slightly (with a N/NE swell of 1-2 metres remaining). However, a new window starting around 00h Sunday 10th May may be opening (see NOAA WWIII chart below for Sun 00h - green means a mean wave height of 5ft or greater)
E. Sty. 5.5.2015
Posted by Dr. Eddy Graham on 01 May 2015, 10:19 PM
With a min temp of -1.3degC this morning in Stornoway town, it was the 2nd coldest night of the 'winter' period 2014-2015. At Lews Castle meadows (Alt nam Brog, a frost hollow site), the min temp was an incredible -4.3C, just short of the lowest on record for May in Stornoway, which is -4.4C set in 1938.
Meanwhile, Tulloch Bridge in Lochaber on the mainland went down to -5.6C.
Today (daytime), despite strong sunshine all day, the air temperature reached only +8.2C in Stornoway town (a value more akin to March).
Eddie, Stornoway, 1st May 2015
Posted by Dr. Eddy Graham on 28 April 2015, 10:16 PM
Update to Outlook:
The good news is that it's going to become much milder by the end of the coming weekend. The lovely spring sunshine will continue Friday and Saturday too, as breezes swing into the east.
A period of strong cold easterly winds is likely early on and during the day of Sunday. Some rain is likely too (snow on hills), but hopefully showery in nature. The good news is that it will become much, much warmer by Monday, though with the increased risk of heavy, blustery showers breaking out.
In closer detail, a slack flow will prevail till Friday or so, followed by a strengthening easterly flow later. There is disagreement between the met models on how soon the east wind picks up, moves in our direction, and then how soon it dissipates.
As for the St. Kilda swim hopefuls, the NOAA Wavewatch-3 model has swells less than 1m (deep blue) in the inner Minches for midday Friday, increasing by midday Saturday (see images, Fri 12h, Sat 12h).
Sat 12h (below):
Thereafter, larger swells are likely stretching into next week, as active lows swing up from the southwest.
Sea temperatures are also running 1 to 2degC below normal in mid-Atlantic at present (see below):
Eddie, Stornoway, Tues 28/4/2015
Posted by Dr. Eddy Graham on 24 April 2015, 11:46 PM
On the night of the Stornoway Hurricane (8-9 January 2015), I inadvertently left a camera running for 5 minutes on a window-sill in my home at the height of the storm. No visual imagery was recorded (the screen was simply black due to the pitch during the storm) but I realised recently that the audio file might prove valuable.
You can hear part of it at http://youtu.be/8iCHNxmC944 (with the visual backdrop of a few photos - but the sound itself is actually best listened to without the imagery).
Bear in mind that this recording was made using a small camera indoors, located some distance from double-glazed windows.
Eddy, Stornoway, 24 April 2015
Posted by Dr. Eddy Graham on 24 April 2015, 2:25 PM
Yes, it's true - winter is about to make a brief return during this coming weekend, with raw northerly breezes bringing flurries of sleet, hail and snow at times (especially Sunday), and hard frosts by night - beware all gardeners and plant growers!
Posted by Dr. Eddy Graham on 22 April 2015, 2:07 PM
I spotted the following new island in the Minch (NE of Broadbay) this afternoon (Wed 22 April 2015) at 1:40pm. At first, I thought it to be a spectacular superior mirage of Sulisker (a rocky island some 100km distant to north). Later, I noticed it to be moving, so I think now it is rather an unidentified floating object (UFO) linked to the current NATO joint warrior exercise taking place, possibly the warship USS Vicksburg (stretched vertically by the superior mirage)
Posted by Dr. Eddy Graham on 19 April 2015, 10:01 PM
With almost 40 hours of sunshine over the three days (Fri 17th, Sat 18th & Sun 19th April), there was more sun than during the entire months of December 2014 or January 2015 during the past winter!
Eddy says expect more of the same tomorrow (Mon 20th April), but the threatened low cloud, dullness and drizzle is expected to return Tues/Wed.
Posted by Dr. Eddy Graham on 16 April 2015, 9:10 AM
So far this April, the weather has been swinging wildly between spells of warm spring sunshine and sudden blasts of cold wind from the north-west, accompanied by hail and snow on several days. Eddy says this is nothing out of the ordinary for the time of year - April weather is notoriously fickle (changeable) and is a direct consequence of the cool ocean, a relatively dry atmosphere and an increasingly strong Sun.
The outlook for the coming few days is for more settled weather than of recent, as a large area of high pressure is predicted to build over Northern Scotland by the coming weekend. Although it is likely to be dry with light winds, don’t expect a heatwave - indeed it will remain quite cool (especially at night) with banks of low-cloud and fog threatening to spoil the sunshine at times. As winds slowly veer into the east by Saturday/Sunday however, increased amounts of sunshine may develop.
Eddy, Stornoway, 15 April 2015
Posted by Dr. Eddy Graham on 13 April 2015, 9:08 PM
Blue skies, fresh spring breezes, and a beautiful Scottish landscape all make for ideal conditions to create time-lapse animations.
Clouds, when animated at higher velocity, often reveal hitherto hidden features, such as oscillating and breaking waves. Similarly, waves on the ocean or a loch surface resonate at higher frequencies, but these too can be captured precisely to reveal surprising new characteristics. Even people, when moving about, can look curiously familiar to ants, or bees, in their perambulations.
Here's a selection of some of Eddie's favourite spring and summer-time time-lapse movies:
- The grey man of Ben Macdhui and Loch Morlich (Scotland)
- The Dance of the MV Loch Portain (Caledonian MacBrayne ferry)
- Angry, eddying clouds above Marsco and Sligeachan, Isle of Skye
- The European Union Berlaymont building (Brussels): People, flags, clouds, reflections
- The 'Tablecloth' over Table Mountain, Cape Town, South Africa
Eddy, Stornoway, April 2015
Posted by Dr. Eddy Graham on 10 April 2015, 8:49 PM
Sometimes during fine stable weather over Scotland (especially with an airflow from the south or south-west, but ahead of a warm front), a special type of weather and cloud system known as a 'hydraulic jump' develops - such occurred today, Friday 10th April 2015.
Firstly though, a wee graphic to aid understanding - air flowing over mountains and hills is forced to descend rapidly in their lee (as it is stable and therefore tends to try and 'recover' its previous position quickly). In consequence, another wave propogates vertically upwards a short distance to the lee, amplifying as it travels upwards - this is known as a hydraulic jump. It often leads to saturation - usually seen as cirrocumulus lenticularis clouds.
We can see these clouds today, in the following very high resolution NASA MODIS Terra satellite image (below) - cirrus clouds can be seen over Lochs (Lewis, in the lee of the Clisham - thick enough even to cast a shadow), Lochs Shieldaig and Torridon (in the lee of the Skye Cuillin), and more generally over Wester Ross (in lee of many peaks). Tiny hydraulic jumps can even be seen over the Little Minch (to the lee of Benbecula, and possibly Beinn Mhor/Hecla on South Uist!)
Strong dry, descending winds were indeed recorded - gusting 37mph at Stornoway Airport at 4pm, with a very low relative humidity (for the west of Scotland) of 59%. In Stornoway town, air temperatures reached +15degC for the 2nd time this week.
Eddy, Stornoway, 10 April 2015
Posted by Dr. Eddy Graham on 05 April 2015, 9:10 PM
Today (Sunday 5th April 2015) was the warmest day of the year so far, with a sizzling +15.5degC measured in Stornoway town during the afternoon, some +6C above the normal for early April.
On the mainland it was even warmer with 20.0degC measured at both Strathallan and Leuchars, and 20.7degC at Aboyne in rural Aberdeenshire!
Statistically speaking, April is the most fickle month of the year (i.e. it has the most rapid changes from warm to cold and vice versa) - this is enabled by a relatively dry atmosphere (compared to the rest of the year), cool seas, and an increasingly strong sun.
Today, the coolest areas were those coastal areas prone to sea-fog, which lapped onto some western and northern coasts (see satellite pic below), and temperatures reached no higher than +9.0degC on Tiree and only +7.9degC on Fair Isle. In contrast, most of the (dry) Highlands reached 18-21degC.
Focusing in on the specific meteorology of the Hebrides today, the fog layer was very shallow in depth and was blocked by even the smallest of hills. Thus, in a series of photographs taken today from the Lews Castle Grounds, Stornoway (below), show:
- The shallow haar flowing along the Minch (with the peaks of Beinn Mhor Coigach and other mainland mountains rising up beyond it)
- The fog also tried to rise up the Clisham in Harris, but failed - instead flowing through the mountain passes and quickly evaporated in doing so.
- Finally a 'lee wake' of St Kilda is noted in today's satellite image of the fog layer, streaming many miles upwind (see red arrow) - (fog moving up the Minch from the south indicated by green arrow). There are also some rare ship's trails in the fog layer too, see if you can spot them!
Eddy, Stornoway, 5 April 2015
Posted by Dr. Eddy Graham on 03 April 2015, 10:28 PM
The trend towards very wet weather over recent months continues in Stornoway - with March 2015 proving to be one of the wettest Marches in at least 25 years, and possibly the 4th/5th wettest on record.
A closer looks at the stats for the latter part of winter also reveals that from 16th Feb-7th March (inclusive) 226.4mm of rain fell in Stornoway town. Futhermore, during the 48-hr period on 6th/7th, 49.6mm of precipitation fell - making It was at least the 2nd wettest 48-hr period in March in the Stornoway area since 1931.
In addition, before 2013 the absolute daily max for March in Stornoway was only 28.3mm. Last year (2014), 32.2mm fell on the 15th. On 6th March this year (2015), another 30.3mm fell again!
Weather Stats /Summary for Stornoway Town (March 2015):
Mean max: 8.7C
Highest Max: 11.1C on 7th
Lowest Max: 3.0C on 2nd
Mean min: 2.3C
Highest Min: 7.5C on 7th
Lowest Min: -0.6C on 18th, 25th
Diff from average: +0.5C (1873-2010), -0.1C (SYY, 1981-2010)
Precip: 197.8mm (170% / 217%)
Wettest day: 30.3mm on 6th
Lowest grass: -4.2C (25th)
Large Hail: 0
Snow Fall 11
Snow Lying 4
Grass Frosts 19
Air Frosts 5
Eddy, Stornoway, 3 April 2015
Posted by Dr. Eddy Graham on 02 April 2015, 12:10 AM
There's nothing particularly unusual about snow falling in late March or early April - it happens most years. However, after the never-ending winter that we've just had, one does wonder when (indeed, if) any settled, warm and sunny spring weather may arrive.
I made this movie of winter clouds scurrying across the face of the Ben Macdhui in the Cairngorm Mountains last week - watch out for his disappearance. then reappearance within slanting crespecular rays.
Total exposure time was just short of 1 hour, 1 foto taken every 2 secs = 1747 total frames, speeded up to 25 frames/sec = time velocity of reality X 50 (i.e. frequency = 50 hertz)
Eddy, Stornoway, April 2015
Posted by Dr. Eddy Graham on 24 March 2015, 9:46 AM
The recent return to rather chilly late March / early Spring weather will continue for the coming week. There'll be plenty rain (with sleet and fresh spring snow over the mountains) or showers, but there'll still be some nice bright sunshine and blue skies in-between the showers. There are risks of gales from Friday onwards. So, all-in-all, rather typical Hebridean March weather!
Eddy, Stornoway, 24 March 2015
Posted by Dr. Eddy Graham on 20 March 2015, 2:53 PM
A high resolution sensor, recording the air temperature every 10 seconds in Stornoway this morning, reveals a drop in air temperature of 1degC over the course of the Eclipse (see below, arrow).
This data will be submitted to the National Eclipse Weather Experiment (NewEx).
Full Report - The Eclipse in Stornoway:
There were more breaks in the cloud layer than predicted by various models at T+24 (which had indicated a uniform 8 okta low layer). From 06h30 to 09h30 it was predominately 4-7 okta stratocumulus /stratus undulatus with some wave activity apparent. Just after eclipse maximum ~9h30, more general showery 7-8 okta stratocumulus praecip. conditions rolled in from the west bringing showers (just 'smirs' of drizzle / a high density of very fine raindrops giving the broad rainbows, total precip to 9am on 21st was only 0.8mm).
There was a noticeable rise in wind from WF3-4 (before eclipse maximum) to WNW/NW F4-5 (afterwards). From 11-12h onwards, the sun came out again in an open cell cloud structure, with the light showers dying out in the afternoon. With 98% occultation of the Sun in Stornoway, it grew quite dark (though perhaps not as dark as one might expect given a 98% loss of solar radiation, and the darkest period lasted only 2-3 minutes); cars had to put their headlights on, and it certainly felt chiller.
It was quite encouraging to see most people outdoors; most workers stopped their jobs and came outside to line the streets; school-children were also given free time to go outside.
I had three separate dataloggers running in Stornoway, at two different locations. Firstly, here at home in Stornoway town (I am on the summit of a slight hill, SW aspect):
(a) High resolution PRT record every 10 secs (see below): The key thing noticeable here is the delay of the development of the convective boundary layer until 11h00! (identifiable by the sudden increase in high-frequency temp fluctuations).
(b) The same Stornoway town site, Conrad Electronics Temp/RH logger every 1-min (below), red=temperature, green=dewpoint:
(c) A frost hollow site in a small glen near Lews Castle to the west of Stornoway (Gleann nam Brog), also Conrad Electronics Temp/RH logger every 1-min (green=relative humidity; red=air temperature, blue=dewpoint)
Stornoway Town (PRT): -1.0degC drop in temp, 10-15min lag behind eclipse peak
Stornoway Town (Conrad logger): -0.7degC drop, 10-20 min lag
Gleann na Brog (Conrad logger): -1.6degC drop, 10-20min lag
I was expecting a larger drop at the frost hollow site (which was confirmed). Analysis of the satellite animation for British Isles didn't show any obvious or apparent change in the cloud structure, it just looked like a fairly typical WNW flow in early spring. Nor were there any discernible air fluctuations.
Eddie Graham, Stornoway, Scotland
Posted by Dr. Eddy Graham on 20 March 2015, 11:26 AM
Eerie, wasn't it? Did you notice the darkness, with more direct 'polarised' light and enhanced shadows? Did the birds stop singing?
And I'm delighted that the mostly pessimistic weather forecasts were proved wrong, with enough breaks in the cloud forming to see the Eclipse!
I have my own eclipse story - after delivering a pre-Eclipse lecture at the Nicolson Secondary School to 300 pupils 8:50-9:15am, I rushed back through Stornoway town on my bicycle, making my way up to Lews Castle College. All the way through town, people were lining the streets outdoors, glancing up towards the sky, it was quite surreal.
Here's a couple of photos and animations:
Photos (above) by Gareth Davies.
Photo (above) by John Smith (UHI, Stornoway).
And an animation of this morning's satellite images showing the Eclipse pass across NW Europe (below):
Eddie, Stornoway, 20 March 2015
Posted by Dr. Eddy Graham on 15 March 2015, 10:37 PM
Posted by Dr. Eddy Graham on 15 March 2015, 10:31 PM
Talk-about "Jekyll and Hyde" weather!
But to put the recent rains in context: In 27-days (16 Feb to 14 March inclusive), I recorded 267.3mm at my station in Stornoway town In the same 27-day period, Stornoway Airport recorded 206mm.
I have only once recorded a higher total within 1 month (Dec 2013). At Stornoway Airport (based on Met Office monthly data), only the month of March 1990 equals such a value (206mm). For February, only the Februaries of 1990,1997 and 1998 exceed 206mm (in a record back to 1873).
Thus, regardless of the recent rains being split between 2 rainfall months (and which both will probably figure as "unremarkable" in the long-term stats), this was a highly unusual precipitation episode, but one that is becoming more common through recent decades.
I'll sum this up in two figures (using Stornoway Airport data only, based on daily Met Office records from 1931-2015)
Figure 1 (Above): 48-hr March precip totals over past 85 years; 7-8th March 2015 had 2nd highest amount
Figure 2 (above): 21-day running totals ending any day in Feb up to 14 March in any year: 2015 had the 3rd greatest amount (185mm), after 1990 and 1997. Note the increase in recent decades (esp. since the NW European 'step' change in climate ~1988) + the increase in variability (n.b. March 2013 actually had the LOWEST 21-day total in the record!). The X-axis is years from 1931 to 2015:
E. Graham, Stornoway Town, 15/3/2015
Posted by Dr. Eddy Graham on 13 March 2015, 2:21 PM
In total contrast to the dreadful weather of recent weeks, the coming weekend (Sat 14th/ Sun 15th) promise to be mostly dry, fine with some nice warm sunshine at times.
Shock, horror, I know, but that strange bright yellow object in the sky is called the Sun - and it's gearing up for the SOLAR ECLIPSE on Friday 20th.
Oh little brown Isle - Eilean Leodhais (Friday's satellite image)
Say 'hi' to the 'high' High! (1054hPa)
And a wee convergence line rounding the southern tip of Norway today:
Pressure was bouncing around like a yoyo during the recent storms & downpours:
Posted by Dr. Eddy Graham on 08 March 2015, 9:19 PM
UPDATE (Monday 9th March, 9:05am): See my twitter feed for all the latest updates https://twitter.com/eddy_weather . It presently looks likely to be worst over Barra / South Uist, indications of 80-85mph max gusts possible. Stongest winds will be from 6pm onwards this evening (Monday), peaking around 9pm.
-------------------------------------- (Sunday yest eve post follows)-----------------
More torrential rain, snow and severe gales are likely tomorrow, Monday 9th March. The gales will develop into at least a full storm (force 10) during the afternoon and evening, with gusts to 80mph (or more) possible. These are dangerous winds, which pose a risk of injury to persons and damage to property.
Just because we survived a hurricane does NOT mean it is NOT dangerous - please stay indoors everyone!
Details: The winds will pick up in the morning, reaching gale force by midday and severe gale force by afternoon, accompanies by heavy, sleet and snow (on hills). There may be a short lull during the afternoon (don't get fooled) after the cold front passes, before storm force 10 / violent storm force 11 winds belt in from the west sometime between 6pm and 9pm. Again, if winds lull (especially in North Lewis) for an hour or so, don't get fooled, as it'll be the 'eye' passing directly overhead. The worst should be over by midnight. I'm not expecting a hurricane, but they'll be dangerous and violent winds nonetheless.
The GFS model has winds peaking around 9pm over West Lewis and Benbecula at 65mph or so (mean speed), meaning gusts possible up to 90mph (see wind vectors below, and isotachs below again).
Ooch, she's already developing a nice hooked cloud indicative of a sting jet (Sun 8th March, 22h):
Posted by Dr. Eddy Graham on 01 March 2015, 10:40 PM
Unfortunately, there appears no sign yet of a break in the never-ending winter weather.
Warning of high winds (over 60mph) and heavy rain on Friday 6th March - please can all school-children be careful!
Whilst not quite as wet as last winter (2013-14), the present winter (Dec 2014 - Feb 2015) has been exceptional in many ways. An unbroken run of westerly winds has resulted in near continuous precipitation on most days, strong winds (not to mention the 'hurricane' of 9 January 2015), and frequent hail, sleet and snow showers.
The total number of thunder days for the winter (11 in total) is also record high.
Furthermore, the past fortnight (16 Feb to 1 March 2015, inclusive) has seen a waterlogging 149.7mm of rain (a full six inches), a near record quantity in such a short period.
E. Stornoway, 1/3/2015
Posted by Dr. Eddy Graham on 24 February 2015, 12:20 PM
A reminder of a truly rare, historic and memorable event: There will be total solar eclipse on 20 March 2015, with the region of totality brushing past the north-west coast of Lewis, some 230km offshore (see image).
In Stornoway itself, some 95% of the Sun will covered by the moon, with a maximum at 9:47am in the morning. The partial eclipse itself will last from 8:40 to about 10:45am. I estimate the likelihood of completely clear skies (based on long-term climate statistics) to be about 31% at Stornoway Airport
If anyone going by boat NW of Lewis? Or better still, by plane (fly above any clouds)? If so, tell me please!
Eddie, Stornoway, 24/2/2015