It’s been a fascinating summer so far. From cool and at times wet, to record summer heat followed by a record summer storm. Warmth looks set to return in a more modified fashion soon.
Back on 12th July, 2025 Scotland was in the midst of a heatwave which set all-time records across the Highlands.
On 4th August the same region was breaking low pressure and wind speed records for August!
August wind gust records were equaled in Scotland and Northern Ireland along with Highland and Orkney’s lowest August pressure since 1992.
Severe disruption to road, rail, air and ferry travel along with over 53k properties loosing power. Some are yet to be restored days following the storm due to severe damage in remote areas of the North.
The feature which became Storm Floris started out over the Southeast US and was pulled into a strengthening jet exiting North America. Containing Subtropical warmth and humidity, this seemingly innocuous feature helped increase the thermal gradient over the North Atlantic, further strengthening an already strong jet stream.
Riding a rare 180-200mph summer-time jet stream, the system crossed from warm to cold side by entering the right entrance and departing the left exit region of the jet core. This allowed rapid cyclogenesis to occur, enhancing ‘lift’ and with a dip on jet, tightening of the circulation which further lowers pressure and speed of ascending air.
Pressure fell by 28mb within 24 hours, meaning Storm Floris underwent ‘rapid cyclogenesis’, a very rare summer occurrence.
Unfortunately for the UK, particularly Scotland, the storm ‘peaked’ in intensity as it crossed Northern Scotland.
Prior to the storm’s peak, a frontal fracture occurred (cold front detaches) allowing a bent back warm front to wrap around system’s core. (known as a Shapiro Keyser type cyclone) This tends to aid more rapid descent of air from mid levels down to the surface.
There was visible satellite imagery suggesting the formation of a sting jet on the tip of the cloud hook though this has not been confirmed.
Winds were found on the south/southwest flank of the circulation core as is often the case but stronger than usual (75+mph) due to that downward transfer of wind energy. These systems only occur every few years during autumn and winter but in summer, this is an extremely rare event.
One contributing factor to fueling such a system at this time of year may have been the unusually warm SST’s and gradient.
The above in combination of the winter-strength jet stream and all ingredients coming together perfectly.
While peak gusts occurred early afternoon on the 4th, the lowest pressure was observed mid/late afternoon at around 976mb over Caithness and Orkney. According to Dan Holley of the Met Office this is the lowest August pressure for Highland and Orkney since 1992.
Selection of Sites Which Set New August Wind Records!
133 mph Cairngorm (previous 115 mph)
109 mph Cairnwell Summit (previous 79 mph)
105 mph Aonach Mor (previous 92 mph)
82 mph Wick (previous 59 mph)
79 mph South Uist Range (previous 58 mph)
78 mph Tain (previous (62 mph)
74 mph Loch Glascarnoch (previous 70 mph)
All sites which recorded a new August wind gust record.
Storm Floris will go down as one of the UK’s strongest August’s storms. It was the 6th named August system since the Met Office began naming storms back in 2015 and the first name in the 2024-25 season since Eowyn back in January.
How Unusual Was Storm Floris As A Summer Storm?
Excerpt from the Met Office
Named storms across the UK in the summer months are not particularly unusual, with examples
including storm Lilian in August 2024, storms Antoni and Betty in August 2023, storm Evert in July
2021, storms Ellen and Francis in August 2020 and storm Hector in June 2018. However, what
made Floris unusual was the strength of the strongest winds. More than 30 stations across the
network recorded gust speeds of 50Kt (58mph) or higher, with 13 reaching 60Kt (69mph) or
higher. While this would not be unusual in the winter months, this number of stations in the
summer months makes this one of the most severe summer wind storms to affect the UK in
observational records – although not unprecedented.
The charts below count the number of UK stations recording gusts >= 50Kt (58mph) and 60Kt
(69mph) during summer wind storms, based on wind observations from the 1970s until present.
The varying number of stations in the network makes direct comparisons difficult, but in terms of
severity storm Floris was overall comparable with storm Hector in June 2018, with overall gust
counts slightly lower than 25 July 1988.
According to Sryan Bruen, the closest August comparison to Storm Floris may be a strong (though further north) system which swept across the top of Scotland back on 24th August 2005 with pressure in the mid 960s and generating gusts of 101 mph at North Rona.
FEATURED IMAGE CREDIT: NASA WORLDWIDE
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