A few brief comments on High Sea levels that have been recorded on the East Anglian and Essex Coast, with Flood Alerts issued for a number of days in a row for Essex, Suffolk and Norfolk. The chart below from the British Oceanography Data Centre shows the Observed High Water levels comprised of tide heights and small surge levels for Lowestoft for the dates of 17th-23rd August.
Elevated sea levels saw two different sea states, with noticeable high sea levels, but low wave heights over the period of Tuesday 20th and Wednesday 21st August. With higher wave levels beginning to show on the evening of Thursday 22nd going into Friday 23rd August, Both Sea states pose challenges, as high volumes of water can inundate coastal locations, like the Mersea Strood, which has been frequently underwater in recent days. Additionally, estuary islands like the RSPB nature reserve at Havergate Island, have seen the island cut in half, due to a surge into spillways designed to absorb brief floods of sea water. Video courtesy of RSPB volunteer Steve Everett.
Higher sea levels occurred at a time of Spring Tides alongside a Supermoon. However, two particular storms, the remnants of Ex-Hurricane Ernesto and the 12th named storm of the season, Storm Lillian hit the UK particularly hard. The chart below shows the Ex-Hurricane Ernesto to the west of the UK, on Tuesday 20th of August.
According to the Met Office, a weather pattern moving into Wednesday and Thursday saw the Jet Stream absorb a weather system which shifted onto the cold side of Jet Stream. It was suggested this could rotate into a more dynamic feature into the early hours of Friday 23rd August. This system could have developed into Storm Lillian.
From sea state measures like the Shipping Forecast and monitoring data, from Felixstowe in Suffolk and Happisburgh in Norfolk, it seems Storm Lillian was a much more intense powerful storm. Particularly as it moved into the North Sea during the morning of Friday 23rd of August, before clearing into Scandinavia. The map below shows areas of the UK, subject to 8-11 Gale Force winds for the period of 10:00 am on Thursday 22nd August-10:00 am Friday 23rd August 2024.
The video from the Met Office below explains about the arrival of Storm Lillian, and shows the storm moving into the North Sea, and around 1 minute in the video shows wind speeds over the northern North Sea of around 60-70 gusts per hour.
Data from National Coastal Monitoring list the Surface Pressure Measures and wind speeds for Felixstowe and Happisburgh for Friday 23rd August 2024. For both areas, the deepest measures of Low Pressure occurred in the early hours of Friday 23rd August. At Happisburgh, Low Pressure (LP) dipped to 999 mb at 1:10 am with wind gust speeds of 18.1 Knotts. LP fell further to 995 mb at 04:30 am with wind gust speeds of 26. 8 knotts. Eventually returning to 999 mb at 09:40 am with wind gust speeds at 28.6 knotts. At 07:20 am, with LP at 995 mb, wind gusts speeds reached 32.7 knotts.
At Felixstowe, the period of Low Pressure was briefer, with LP falling to 999 mb at 02:00 am with wind gusts speeds of 25.1 knotts. LP dipped further to 997 mb at 03:50 am with wind speed gusts of 37.3 knotts. Eventually returning to 999 mb at 08:50 am with wind speed gusts of 41.3 knotts. Wind gusts reached their maximum at 06:00 am, measuring 41.9 knotts, with LP at 997. Data courtesy of the National Network of Regional Coastal Monitoring Programmes of England
Interestingly, the areas that saw the most noticeable, albeit small surges on Friday 23rd of August were Harwich and Sheerness, measuring stations both placed in the Southern North Sea, just down the coast from Felixstowe. Data recorded by the British Oceanography Centre.
Chart for Sheerness.
Chart for Harwich
Discussion of the intensity of a storm can be useful as it enables a consideration of the force likely to be transmitted to the body and surface of the sea. This in turn relates to the ability of High Wave Sea states to shift large amounts of sediment. Agitated sea states can also contain more force, which can cause more damage and be harder to contain. However, during the week of 19th-24th of August 2024, it has been the Total Water Level that has been a significant problem to manage.
Previous discussions on AlteredCoast, have considered whether it is the big storm events or incremental erosion episodes that can be more destructive. But events over the last week have shown the vulnerability and the volatility of the interface between land and sea. Open as it is to the rise and fall of the ocean and the winds whipped up by storms that swell the sea
alteredcoast 