Overnight 12-13 Sept the first of the UK/Ireland named storms of the 2016/2017 season crossed the British Isles. Storm Aileen brought strong winds of up to 112 km/h (70 mph).
22 October 2020
12 September 2017
By Ian Mills (Ian Mills Training)
The animation of Metesat-10 Airmass RGB images shows the storm forming south of Iceland at the beginning of the sequence and moving west across the UK and Ireland and into the North Sea by 12:00 UTC on the 13th (Figure 1).
The sequence is dominated by a large low to the west of 'Storm Aileen'. However, Aileen forms ahead of a trough. This trough can be seen at the start of the sequence to the south of the large low, before it moves quickly east to engage with an area of cloud to the north of the jet stream (marked by the fast moving white cloud running from Newfoundland to Ireland).
Aileen forms a circulation out in the Atlantic, but it is not obvious until the low crosses Ireland and moves into the North Sea.
On the animation of Metesat-10 Water Vapour imagery the jet stream can be clearly seen swinging round the southern side of the large low and driving the developing storm quickly eastwards.
As the storm moves east, towards the western coastline of the British Isles, the cloud tops become whiter as they cross Scotland and move eastwards into the North Sea as the storm develops rapidly.
At 20:15 UTC on 12 September the ASCAT winds and the AVHRR IR image show strong winds affecting the southwest of the British Isles. Large areas of winds around 35 knots (65 km/h) can be seen south of Ireland, with a marked veer in direction to the west of Ireland as the trough passes.
Figure 3 is the ECMWF analysis on 13 September at 12:00 UTC, which shows the position and relates fairly well to the ASCAT winds at 09:30 UTC.
The ASCAT winds show strong winds on the north and south flanks of the depression (40–45 knots/74–83 km/h on the south side). These strong winds caused cross wind issues at Amsterdam's Schiphol Airport , because their runways are oriented north-south.
The image of ASCAT winds overlaid on the AVHRR IR imagery (Figure 4) shows the circulation of the cloud around the low and the associated strong winds of 35 to 45 knots (65–83 km/h) along the coast of the Netherlands and northern Germany.
A second image at 09:48 UTC on the 13th (Figure 5) again shows the strong winds on the southern side of the low and, by this time, fresh to strong north-westerly winds are becoming established in the cold unstable air to the west of the British Isles.
Heavy showers in this air stream affected the British Isles on the 13th.
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