Weather extremes of 2005; 13th-14th September- Flooding in NW Scotland

Following on from a thoroughly wet weekend across England and Wales, it was the turn of the far NW of Scotland to get a soaking at the start of the week. On the 12th, an anticyclone established itself across the British Isles. However, to the west, the remnants of tropical storms “Maria” and “Nate” were queuing up to bring some very wet weather to NW Scotland, Shetland, Orkney and later Scandinavia.

There were signs preceding the heavy rain indicative of ex-tropical storm remnants. These included the cloud type altocumulus floccus virga (see here) and indicate instability and large amounts of moisture in the mid-atmosphere.

The heavy rain commenced on the night of the 12th, and continued much unabated throughout the 13th at a fairly constant moderate/heavy intensity for some 36 hours. Between 16-17GMT on the 13th 15.6mm was recorded at Broadford on the Isle of Skye with some 127.6mm recorded in the 24h period to 10pm on the 13th.Highest totals are included in Table 1 below:

Table 1: Highest total rainfall obs from the 12/13th September 2005

Station	Total Rainfall (mm)
Skye/Lusa	130.6
Aultbea	81.6
South Uist Range	63.0
Stornoway	49.0
Lerwick	38.8

Synoptic analysis 20050913 at 00UTC.

http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20050913.gif

Synoptic analysis 20050914 at 00UTC.

http://www.met.fu-berlin.de/de/wetter/maps/Analyse_20050914.gif

There was some flooding affecting parts of Portree and Broadford on Skye as a result of the heavy rain. The steam train to Mallaig had to abandon its journey due to severe flooding at Glenfinnan, Highland, where the surrounding rivers had swollen and burst their banks. It was reported that the waters were as deep as car's windows for part of the day.

In fact, the depressions containing ex-tropical storms “Maria” and “Nate” caused further problems as they continued ENE across the Norwegian Sea. When moving across S Norway, the towering mountains forced the very moist and warm air to ascend, so increasing the amount of precipitation falling yet further. As a consequence, in Fana, Southern Bergen, nine people were injured and 1 killed after a mudslide took out several houses in the area. People were immediately evacuated after a state of disaster was declared. Overnight rainfall totals on the 13th/14th had brought over 100mm to the mountains and 50mm generally across a large part of Southern Norway.