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19

Jan

Making Sense Of The Shipping Forecast

Written by Alex under Weather Station Reviews, Weather Stations | No Comments ""

If you’re not a trawlerman or the skipper of a car ferry travelling to the continent you’ve probably heard the shipping forecast and wondered what on earth this pleasant sounding yet nonsensical droning means. If you had a desk top weather station then the information regarding your local area would be right in front of you, but that might not be very practical in the Roaring Forties!

Bad Weather Ahead

The seas around the British Isles are divided up into 31 separate sea areas and twenty four hour forecasts are broadcast at 11pm, 5am, 11am and 5pm. The forecast contains warnings of gales, storms and rain as well as visibility and wind direction and force. However, if you don’t know what you’re listening to the information may seem to be confusing at the very least.

For example the meteorologist may say:

“Cromarty, Forth, Tyne. Storm force 10 veering northwesterly, decreasing gale force 9 imminent. Northwest 7 to severe gale 9 decreasing 5 or 6 backing southwest 4 or 5 later. Rough or very rough becoming moderate or rough. Squally showers then fair. Good occasionally poor at first.”

The first part relates to shipping areas where ferries, container ships, fisherman and also aircraft might be, the forecast names them as they appear in a clockwise direction around the British Isles so Cromarty, Forth, Tyne describes a sea area stretching from John O’Groats down the eastern coast of Scotland past the border into England down as far as the southern side of the Tyne estuary. The next part is a storm or gale warning, the numbers are wind speeds based on the Beaufort scale where zero means a flat sea and, inland, smoke would rise directly upwards up to twelve which would be a hurricane, waves would be above fourteen metres, inland trees would be blown over, windows break and structures such as sheds and mobile homes are damaged along with objects being thrown about. Veering means a change in the wind’s direction, veering means that the wind will be changing clockwise as it turns, if it were to change anticlockwise it would be described as ‘backing.’ When winds are above force 8 they are also given their name for emphasis, hence “severe gale 9 decreasing 5 or 6.”

The next portion describes the sea conditions, in this case there is a storm so, as you would expect, conditions are rough, precipitation is also given, although there are high winds are expected not a great deal of rain is so we have “squally showers or fair” not withstanding the fact that the wind will be blowing a great deal of spray. The final section is visibility. If (excluding spray) visibility is expected to be more than 5 nautical miles (9.3km) it is defined as good, moderate describes visibility between 2 and 5 nautical miles, poor there visibility stretches from a kilometre to 2 nautical miles down to fog where visibility is less than one kilometre.

 


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