It was on this day a year ago that Ex-Hurricane Katia slammed Scottish shores producing damaging 70-80 mph winds and huge swells. A year on and we’ve another once-tropical cyclone set to impact our lives here in the Northern UK.

For many days now, the charts have shown once Hurricane Leslie, taking the recurve path after slamming eastern Canada with the orientation of the rather strong Atlantic jet stream taking it towards Iceland. This system became extra-tropical before even reaching Newfoundland due to a mix of warm and cold air, cold water temperatures and greatly increased upper level winds. This system, now fully transitioned from warm to cold core develops fronts and becomes driven by baroclinic properties rather than the heat of the ocean. Leslie’s remnant now is now undergoing a secondary deepening process as it reaches the latitude near to the southern tip of Greenland where here, brutally cold air enters the circulation on the north side while warm, humid air flows north from the central Atlantic into the south side of the circulation, this helps drop central pressure which in turn intensifies the storm and often, lows will deepen once their positioned to the southeast of Greenland where greater thermal contrast interacts, fuelling the intensity.

The models have been persistent in tracking Leslie’s remnant low across or just off the south shore of Iceland and heads due east or ESE, with the centre of the system always remaining well north of Scotland.

What could mean stronger winds across a large part of Scotland with gusts likely to top 50 mph for many, even across inland areas with higher gusts on the coast and mountain tops is due to the contrast between the deep low and a strong upper ridge of high pressure not that far to the south. The combination of a 1028mb high SW of the UK and a deep sub-970 mb low not that far to the north means the pressure gradient is tight and so winds blow harder. Had that ridge not been as strong or as close then we likely wouldn’t have seen much in the way of wind except for the far northern mainland and isles.

While I don’t expect the winds to be as strong as what Katia produced last year, I do think we could widely see winds sustained at 20-30, gusting to 45-65 mph across most areas including the Central Lowlands and the main population belt. Some higher, more exposed spots in Ayrshire, Lanarkshire and Stirlingshire could see some gusts nearer 70 mph as well as on exposed coastal areas such as Girvan, Ayr and Prestwick.

The higher parts of the Central Highlands, NW Highlands, Western and Northern Isles should see strongest sustained winds ranging 30-45 mph, gusting to 70-80 mph. The higher ridges and some exposed coasts could see gusts beyond 90 mph. Cairngorm for example should see gusts top 100 mph.

It appears the ridge stands strong to the south through the Friday-Sunday period and with more lows riding the jet between Iceland and Scotland, winds look to stay strong out of a westerly direction for the next several days.

So, it’s worth noting that not only will tomorrow into Friday be windy but we could be in for a sustained period of perhaps 72 hours or more of strong west winds.

Tags: ex-hurricane leslie hits scotland, leslie remnants hitting scotland