Recent Glazed Ice Event in Stornoway - Photos

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Recent Glazed Ice Event in Stornoway - Photos

Postby Eddy Graham » 2014 Dec 31, 15:20

Again I bring you a report of some unusual weather conditions recently in Stornoway town - which you won't have seen in the Stornoway Airport (03026) Synop report (as it is yards from the sea)... but for the third time in the past 6 years of living in Stornoway, we have had a severe glazed ice episode (resulting from rain showers freezing on the surface)... it seems this recent incident was quite widespread across parts of N & W Scotland .

Interestingly the air temperature hardly fell much below freezing during the event, only briefly on the nights of 25th/26th and 28th/29th (see daily data below), although grass mins were consistently below zero each night. It was noted that all ice accretions were on open surfaces with a high sky-view factors (e.g. all paved surfaces, pavements, roads, short grass) and none on trees or shrubs or sides of objects. All standing water froze solid (ice thicknesses of several centimetres were noted in places), indicating a possibly strong 'ice-bulb' evaporative cooling and freezing effect throughout the period.

The event started on the night of 25th/26th, when afternoon rain showers froze quickly in the coming night. On the following night (26th/27th) a little fine graupel and light snow fell too, freezing into the ice soon after and gave it a slightly white sheen, thankfully adding some traction too! - see photo below).
tn_2014-12-28 11.27.22.jpg
tn_2014-12-28 11.27.22.jpg (47.93 KiB) Viewed 521 times


The 'worst' morning was possibly the 28th, when further rain showers added to the glaze (on a journey across the Island on the following day, it seemed these showers had fallen mostly as snow a few miles away from the coast). A hoar frost, followed by rapid thaw on the 29th gave renewed slippiness.

In this next photo, salt and grit has been added to the road, grinding the ice up into a white powder - but the undisturbed glaze can be seen on the footpath to the right:
tn_2014-12-29 10.26.22.jpg
tn_2014-12-29 10.26.22.jpg (44.6 KiB) Viewed 521 times

Here are the corresponding values for maxes, mins, grass mins and rainfall for the following morning observations:
26 Dec:
Max: 6.1
Min: -0.5
Grass: -3.1
Rain: 1.9mm

27 Dec:
Max: +2.6
Min: +0.2
Grass: -2.5
Rain: 4.4mm (some snow, graupel contained in this total, trace depth)

28 Dec:
Max: 3.8
Min: 0.2
Grass: -2.1
Rain: 2.1mm

29 Dec
Max: 4.6
Min: -0.7
Grass: -3.9
Rain: trace

30 Dec
Max: 10.1
Min: 3.5
Grass -1.2
Rain: 0.7mm

Note the relatively 'high' maxes on 27th and 28th (thrown back from following mornings) - but no thawing occurred, presumably due to low RH and 'ice-bulb' effect as already mentioned.

Eddie Graham
Stornoway
Eddie Graham
Stornoway, Na h-Eileanan an Iar (Outer Hebrides), Scotland.

Stornoway town COL station, 20 AMSL, local records back to 1873.
Hebridean Weather Blog: http://bit.ly/1IFAPJa
Twitter Weather Feed: https://twitter.com/eddy_weather
Eddy Graham
 
Posts: 82
Joined: 2012 Jul 18, 17:09
Location: Stornoway, Scotland

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