2100 UTC Sunday 23 July to 2100 UTC Wednesday 26 July 2017
Issued by the Met Office, on behalf of the Maritime and Coastguard Agency, at 212020 UTC
On Sunday evening a complex area of low pressure, with various minor centres possibly developing over the UK and mainly covering southern waters of the Cullercoats area. A centre of low pressure is expected to be centred near Dogger 1009. This low is then likely to slowly move eastwards with a centre near Denmark 1006 by midday Monday, with a ridge extending northwards just west of the UK. By midday Tuesday little change is expected with the ridge of high pressure expected near the west coast of Wales and Scotland. The ridge is then expected to cross the North Sea during Wednesday morning with a low developing near Northern Ireland 1006 by midday. No gales are currently expected to affect waters in the Cullercoats area through the forecast period, but winds may be strong at times, especially during Monday and Tuesday
On Sunday evening an anticyclone centred 400 miles west of Trafalgar 1030 is expected to be slow moving with a ridge of high pressure extending northwards as an area of low pressure becomes centred near Denmark 1006 by midday Monday. By midday Tuesday a broad ridge of high pressure is expected to extend eastwards across Fitzroy and Biscay. During the course of Wednesday a low is expected to develop near Northern Ireland 1006 by midday, and by evening an anticyclone is likely to become centred near Shannon 1018. Winds are likely to be strong on Sunday night across most waters of the Niton area, and there is a small risk of gales affecting Biscay for a time in the early hours of the morning on Monday. During the early hours of Tuesday morning there is a risk of further gales across southern waters of Fitzroy
On Sunday evening an area of high pressure is expected to persist across northwestern and far western waters of Portpatrick, and during Monday morning move eastwards to cover most waters by early afternoon. An anticyclone may become centred Southeast Iceland 1024 by the same time. Current indications are then for pressure to fall and this will allow frontal troughs to affect the far west on Tuesday morning. Overnight and into Wednesday morning an area of low pressure is then expected to develop on the trough extending eastwards across Northern Ireland 1006 by midday. No gales are currently expected in the area through this forecast period. Winds may increase to become strong at times, more especially on Sunday night and through much of Monday across some eastern waters. There is also a risk of gales across Rockall and Malin during Wednesday
Extended outlook overview
The extended outlooks are issued once a day, at 2300 GMT and cover the next 3 to 5 days.
For the extend outlooks the waters surrounding the British Isles are divided into three areas; Cullercoats, Portpatrick and Niton. These three areas reflect the coverage areas of the UK's Navtex transmitters, which overlap in some areas.
The extended outlook forecast contains details of the likelihood of gales or storms, a general synopsis and a general forecast for the area of coverage of each Navtex transmitter.
In the UK, the Maritime & Coastguard Agency (MCA) is responsible for the provision of Maritime Safety Information (MSI) to ships at sea, which includes the broadcast of warnings and forecasts. The Met Office initiates warnings and prepares routine forecasts for dissemination on behalf of the MCA.
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