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
Posted by Dr. Eddy Graham on 23 February 2015, 5:28 PM
It's been one of the wettest weeks of the winter so far, with a waterlogging 84.5mm (3.32in) of rain falling in Stornoway from Sunday 15th to Sunday 22nd inclusive.
More very unsettled weather is likely this week, with heavy rain, gales, hail, sleet, thunder and possibly a storm too later in the week.
Winter - GO AWAY!
Posted by Dr. Eddy Graham on 20 February 2015, 1:57 PM
The unsettled, changeable and generally mixed bag of wintry weather will continue for coming weekend and into next week.
At some stage we'll experience nearly every type of weather - brief snowfalls followed by the risk of ice, heavy rain, southerly gales on Sunday morning, and even a risk of some coastal flooding where the onshore wind and low pressure coincide with the high Spring tides.
Eddy, Stornoway, Fri 20 Feb 2015, 2pm
P.S. The very large snowflakes (estimated width of 4-5cm) seen in Stornoway on the morning of Sat 21st Feb are not particularly rare or unusual. The air temperature at the time was +0.5degC, ideal for the formation of such big, wet flakes (actually, such large snowflakes are conglomerations of many smaller flakes together - they stick together better when slightly melted).
Posted by Dr. Eddy Graham on 12 February 2015, 5:07 PM
There's a total solar eclipse expected on 20 March next, with the area of totality passing close to NW Scotland and the Hebrides (see map below). Approximately 95% of the Sun will be covered by the moon. And if you can sail to the Faroes, well it''ll be a full eclipse there...
Here's the predicted path (courtesy NASA):
If you want a Smartphone App for the eclipse, try this: http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2015Mar20Tgoogle.html
Eddie, Stornoway, Feb 2015
Posted by Dr. Eddy Graham on 06 February 2015, 8:19 PM
After battle and repeated battle this winter, the weather has finally quietened down, thanks to a very welcome and huge area of high pressure which has anchored itself near Ireland at present - and looks like remaining there for several days yet. With a central pressure of perhaps as high as 1047hPa (millbars), it could be highest 'high' since 1992 (I will need to check the records to confirm this).
High pressure areas are huge blobs of warm, sinking air, so the upward motions of air necessary for steady rain will be largely absent over the coming few days. Some smirs of drizzle are still likely in the wind across the Isles and northwestern slopes, but they won't amount to much - and with the air coming in from the west over warm seas, it will stay rather mild for the time of year.
N.B. Have a look at this lovely satellite picture taken this afternoon (credit: NASA/GSFC) which shows a hole in the cloud layer over the southern half of Scotland, revealing much snow still lying across the Highlands (snow and ice is shown in cyan-blue):
Posted by Dr. Eddy Graham on 27 January 2015, 12:49 PM
Further update on Monday 2/2/2015: Heavy rain moving into the Westside tonight (Mon night), rapidly turning to heavy thick snow over the moors, and possibly and the east of the Isles, including Stornoway later. Several inches of fresh snow are likely in places, although the strong to gale-force (and bitter) northerly wind may blow some of it away! Even deeper snow is likely on the high ground of the mainland, Skye and Lochaber.
Update on Saturday 31/1/2015: There remains a high risk of further snow (especially tonight Saturday into Sunday morning, and again on Tuesday). The bitterly cold northerly wind will remain, though it will ease down from the current gale force 8 over the next 24-48hrs (mas gust was 57mph this morning). There are signs of a slight improvement from Wednesday onwards (milder conditions).
Yes, it's gonna snow tomorrow (Wed), expect the snow to arrive during the mid-morning. It will come in periodic squalls with hail and high winds, and there is a risk of thunder and lightning again. Severe temporary blizzards are possible over the moors by evening, as temperatures drop to freezing or below.
The snow will lie on Thursday, but later some milder air (incorporated around the top of the 'low') will arrive from the north, with a slight thaw, giving rise to the risk of much ice by Friday, Saturday and Sunday.
Further snow showers, accompanied by strong northerly gales are likely by Saturday/Sunday, blizzards are again possible.
Eddy, Stornoway, Tues 27/1/2015
Posted by Dr. Eddy Graham on 21 January 2015, 12:57 PM
It is reported that a gust of 82.9m/sec (185mph) was recorded during the recent 'hurricane' at the MOD radar site on St. Kilda, at an altitude of 350 metres (on the summit of the 2nd highest hill of the island archipelago). If accepted, this speed would represent a new max wind record for a high altitude site in Scotland (and in the UK as well) - the current record is 173mph from Cairngorm summit on 20 March 1986.I am told that the anemometer has been taken down for testing and calibration before/if any official statement is made. The island staff themselves had to be evacuated by Coastguard helicopter at 3p.m. on the day after the storm.
Posted by Dr. Eddy Graham on 17 January 2015, 9:29 PM
The lowest temperatures since December 2010 are set to occur in the Scottish Highlands over the coming 48-72hrs: Temperatures could dip to as low as -15degC in some sheltered glens.
A snowy NW Highlands and Minch on Monday 19th January 2015 (NASA Terra).
It won't be nearly as cold over the Isles, though severe frosts are still expected, with overnight lows of -4 to -7degC commonplace.
Recognise this island? Why, it's Lewis and Harris of course, as seen by NASA's MODIS satellite sensor flying overhead today The snow-free Westside of Lewis stands out plainly, but most of Harris and east Lewis (except northern Point) are covered in thick snow (the second infra-red image shows the whole of the Scottish Highlands, snow is cyan-blue in colour).
Posted by Dr. Eddy Graham on 14 January 2015, 10:21 AM
A quick update on the weather folks (as of Wed 14/1/2015, 10am): The wind will pick up quickly to a gale from the southeast this (Wed) evening, bringing heavy rain and a thaw (but no storms as bad as last week). Tomorrow, the thaw continues during the day with rain showers. The wind will die completely for a while, only to return as a severe gale from the NW by evening with the snow returning also by Friday. Outlook for weekend: Very cold and further snow, risk down to below -10C in some places!
Snow lying at the Stornoway Town Weather Station (toppled during the recent hurricane).
Posted by Dr. Eddy Graham on 09 January 2015, 3:45 PM
Posted by Dr. Eddy Graham on 08 January 2015, 10:17 PM
Update 10:50am Fri 9 Jan 2015: Friends and family are safe. If I could sum the storm up in a word, it would be the noise - 'the sheer roar like a huge angry monster or animal, unleashed upon us down from the heavens'.
There is debris around the streets of Stornoway, and dozens of hundred-year old beech trees in the Castle Grounds have been blown down. Photos to follow.
Update 3:20am Fri 9 Jan 2015: Well, if you live in Stornoway, you don't need me to tell you - we officially had a hurricane force 12 (mean windspeed 79mph, gusting 113mph) between 1-2am. That is easily Category 1 Hurricane on the Saffir-Simpson scale.
In meteorology, a 'sting jet' is a relatively small region (50-100km wide) of extremely strong winds that hooks around the south side of a rapidly deepening low pressure system. Associated with them is a characteristic hook-shaped cloud (as seen in satellite images), which looks similar to the stinging tail of a scorpion, hence the term "sting jet".
Tonight, as the violent storm approaches, we can see the formation of the cloud hook, from which the sting jet may develop, in the infra-red satellite image (sat24,com) for 21h30 (below):
We are also seeing a huge number of thunderstorms across Uist and Barra this evening as well (Icelandic Met Service)
Sting jets are thought to have responsible for some of the most infamous storms in recent and distant meteorological memory, such as the October 1987 hurricane in SE England, and the 2005 hurricane in the Hebrides.
Stay safely indoors until the storm passes!
Eddie, Stornoway, 22h20 Thursday 8th January 2015
Posted by Dr. Eddy Graham on 07 January 2015, 10:46 AM
Folks, I don't want to dramatise this too much, but we're possibly looking at winds approaching near to, or even exceeding hurricane force early on Friday morning now... thus the storm is likely to be the strongest in the Hebrides since the 2005 'hurricane'.
Hurricane force is when winds exceed 63 knots (74mph) in average wind speed. Gusts typically exceed 100mph. These are structurally damaging, highly dangerous winds and pose a risk to life.
Please, stay safe and I advise everyone to stay indoors during the peak of the storm.
A further violent storm is possible Friday night/Saturday morning (but path and intensity of this is as yet uncertain)
Thunder and lightning are likely too going into Saturday, with snow falling as well (though that is likely to be the least of our worries!).
I'll be posting updates on my Twitter account regularly as long as the power lasts (https://twitter.com/eddy_weather)
Eddie, Stornoway, 7/1/2015
Posted by Dr. Eddy Graham on 06 January 2015, 11:49 AM
UPDATE 6/1/2015, 5:30pm: Some models are diminishing the Sat morning storm significantly - so it's not certain yet by any means.
We're looking at two possible violent storms in the coming days, at least one of which may reach the 'red' category of warning (the highest possible):
- On Thursday night / early Friday morning, a deep storm (<967hPa) with an associated sting jet is expected, with winds up to 90mph
- On Friday night / Saturday morning, a possibly more violent storm (938hPa) could clip N Lewis, with winds approaching 100mph
More later on Twitter... https://twitter.com/eddy_weather
Eddie, Stornoway, Tuesday 6/1/2015, 12 noon
Posted by Dr. Eddy Graham on 05 January 2015, 5:31 PM
Again, it's going to be a very unsettled week ahead (5th-9th Jan 2015), with severe gales likely on Wednesday and the risk of a major storm on Friday. Astronomical tides are high this week, so there could be problems (especially with the southerly gale up the Minch on Wednesday morning).
Hail, sleet, snow and thunderstorms could cause further problems on Thursday and again on Saturday.
The storm on Friday could possibly be quite violent, but its path is yet uncertain.
As always, I recommend you to please keep posted to my regular tweets on the weather as it develops on Twitter at: https://twitter.com/eddy_weather/with_replies
Eddy, Stornoway, Monday 5th Ja.
Posted by Dr. Eddy Graham on 02 January 2015, 12:02 PM
A exceptionally violent hailstorm swept through Stornoway this morning at 11:22am, bringing giant hailstones of over 1cm in diameter. Here are some pictures:
And a video of the storm as it passed through Kennedy Terrace:
And a screenshot of the 11h15 radar clearly shows the hailstorm as a highly reflective mesoscale feature (small area of white/blue colours inside the general orange/yellow/red rainfall reflections) heading east across the Pentland Road towards Stornoway (courtesy www.raintoday.co.uk)
Eddy, Stornoway, 12pm 2/1/2015
Posted by Dr. Eddy Graham on 29 December 2014, 3:18 PM
After the recent quiet, crisp, icy and wintry weather, the New Year is expected to usher in a period of renewed unsettledness, with heavy rain, gales, hail, sleet and squalls returning.
At the moment there is some uncertainty as to when the strongest winds will hit (as the weather systems themselves have yet to develop), but severe gales are likely to occur, especially in the days immediately after the New Year (1st-4th January). It will also turn much colder again by Friday, albeit briefly.
As always, I recommend you to please keep posted to my regular tweets on the weather as it develops on Twitter at: https://twitter.com/eddy_weather/with_replies
Eddy, Stornoway, 30th Dec 2014
Posted by Dr. Eddy Graham on 19 December 2014, 10:00 AM
Wishing everyone a peaceful Christmas 2014, festive season and New Year 2015
Scotland in the Snow (Christmas 2010) - NASA/MODIS/GSFC