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Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Oct 31, 21:12
by Eddy Graham
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.

Eddie Graham, Stornoway

Re: Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Oct 31, 21:38
by David Lee
Not quite a record here after last year's 22.4C, but yesterday evening saw a good night-time föhn with the temperature rising as the southeasterly kicked in during the evening. This is now the season when many of my high temperatures occur overnight (as explained at the AGM) and this time it peaked at 19.0C around 310100, so I suppose technically the max was on the 30th anyway.

I do have a graph of a mini data-logger pass along the A55 and that showed a max of 19.5C which is not surprising as my station is about 40m above the road near here. I was going to put it on here, but it wouldn't copy over.

David Lee

Re: Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Oct 31, 22:36
by Stephen Burt
An overcast start to the day here, but low St deck broke between 1100 and 1200 to give unbroken warm sunshine all afternoon. The screen maximum was a very creditable 17.7 °C, 4.6 degC above the 1981-2010 daily average maximum for 31 October, but a long way below the 21.6 °C recorded on the same date last year.

With very light winds, low-angle solar heating of the Stevenson screen was very evident; the aspirated temperature was often 2 degC below the screen during the early afternoon, and the aspirated maximum was 'only' 16.2 °C, 1.5 degC cooler than the Stevenson screen (a modern Metspec/Met Office plastic screen).

As a reminder of how fickle the weather can be at this time of year, at the end of October in 2008 we had one morning (29th) with a 2 cm snow cover, while on 29/30th in 2000 we had a severe overnight gale and 58 mm of rain!


Re: Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Nov 01, 16:13
by Chris Richards
So near and yet so far! Here, in the NW of Wirral we've been under low cloud for much of the day, yet just across the Dee estuary to the west, sat pics show virtually cloudless skies over the Welsh mainland!
It was a clear dawn period, here, but fog and patchy low cloud rolled in from the SE over breakfast time. gradually blotting out the low sun. It tried to break up lunchtime, but in the past hour it's thickened up and visibility dropped to 1km or so. Temperature only 13 deg C. Just heard a BBC news report of the warmest Nov day on record of 22.3 deg C in W Wales!
There is an (unseasonal?) 1000-500 hPa thickness value of 564dm on Met O fax f/c chart for today over W Europe. I had to look twice! Is this a record thickness reading so far north for 1st Nov?

Chris Richards
West Kirby

Re: Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Nov 01, 20:07
by greg_gruner
Apparently 22.4 recorded at Trawscoed in Wales - a new UK November record.

A very different story here in the SE, max of 11.0C in Farnborough. Fog and then low cloud persisted all day; the fog is thickening again now (9.5C now and 97% RH).

Re: Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Nov 01, 22:13
by Eddy Graham
The November record for Stornoway is 16.3C from 1898 - currently (as of 9:45pm Sunday 1/11) it's blowing a strong S force 6, air temp 13.0C with starry skies.

Mind you, I do remember a similar very mild Halloween/1st Nov, was it in 1982 or 1980? (I shall check my diaries - there were Saharan dust deposits if I recall correctly).

Meanwhile, David - I regret missing your talk on the North Wales A55 traverses at the recent AGM, though I read the account in the Bulletin. On the other side of the Irish Sea, southside county Dublin occasionally enjoys similar foehn conditions (as do many other locations in the British Isles), being directly in the lee of the Wicklow mountains (although they are not quite as high as Snowdonia). As a youth I was very interested in these unique weather conditions, and during my undergraduate project in 1992, I fastened a small stevenson screen to the roof of my mother's car (whilst she peaceably drove around!). Inside it I put a precision thermometer (which I had got on loan from Prof. John Sweeney of Maynooth Uni), and it had a readout in the car. As long as the car was moving at greater than ~15mph, the radiation error was kept within manageable limits. I was then able to draw isotherm maps for specific times - attached please see the air temperature distribution around southside Dublin on 28/6/1992. A clear zone of (probable compressional) warming can be seen, occupying no more than a few kilometres. There was some approximation in the drawing of the isotherms (I had to interpolate increases/decreases of air temperature in areas, though they were generally not large). Also it was difficult to isolate foehn-caused warming from 'regular' inland warmth/cooler coasts, but the same lee-pattern kept appearing. Often years later, when flying over Anglesey en route from Dublin to Heathrow I would glance down at beautiful ac. lenticularis over North Wales.
tn_28JUN1~1.JPG (74.36 KiB) Viewed 1690 times

p.s. This map was made long before the days of Surfer, Photoshop and alike!
sincerely, EG

Re: Warmest Halloween (31st October) on record in Stornoway

PostPosted: 2015 Nov 02, 18:16
by David Lee

Wow! What a great story and resulting map. I too find the influence of topography fascinating and there must be many COL stations that are subject to large or small enhancements of temperature. it's such a pity that local variations are not highlighted enough on public broadcasts.

Your survey has set me thinking and I will certainly do more runs along the A55 this winter to see how the high temp 'peak' slips east and west depending on the gradient wind direction. I'll also do some on radiation nights to try and pick out the cold drains. Last night (only glancing at the car thermometer as I drove along) there was a sharp drop west of Junction 15 as the drain from my valley came north. This wasn't the case further east at Penmaenmawr.

In reply to Chris's query about 564 thickness for the time of year, I recall in my early forecasting days a closed 564 line over the southwest of the UK in a very intense anticyclone in the first week in December, probably sometime in the 1970's or early 80's. Then the inversion was well off the surface and there was just a widespread sheet of Sc.

Now two monthly records gone in one year!

David Lee