BBC Shipping and Inshore Waters Forecasts

About this page

Introduction

For many sailors and the general public, the UK Shipping Forecast is the “flagship” with which we have a love-hate relationship. It is often criticised for its “accuracy” or lack of it without any thought as to how accuracy is defined for a forecast:- –

1. Covering a 24 hour period,
2. Describing weather over a 1M square mile area,
3. Written in no more than 330 words including the preamble and gale warning summary. This is to fit in the BBC allocated 3-minute time slot.

Background to the BBC Shipping Forecast

The first forecasts for shipping were issued in 1874 but routine forecasts on BBC Long wave, now Radio 4, began on the in 1924. These have continued ever since, apart from during war-time. However, with the increasing use of the internet there must be doubt about how much longer they will be seen as necessary.

Broadcast times and length of broadcast are compromises between providinderg useful information and the BBC losing listeners as people switch to othe channels.

Forecasts for 31 Sea Areas are broadcast in a fixed order starting from Viking, between Norway and the Shetland Isles, clockwise round to Southeast Iceland, because of the time limit, areas are usually grouped. The order of information for each area is fixed order of Wind, Sea state, Weather, Visibility so that thos words can be omitted. As in this example.

At 0048 and 0520, the BBC allow more time enabling the addition of reports from coastal stations; a long list at 0048 and a short list at 0520.

Approximate time scales for the production of the basic shipping forecasts are shown in the following table:

NOTE These timings will probably have changed a little but the table will still give some idea of the timescales involved.

In addition to the predictions from the computer models, the forecasters have more recent data from the British Isles, the near Continent, data buoys, oil rigs, light vessels and islands. These are all used to fine tune the model output and are scrutinised as carefully as time allows, particularly with regard to the need for gale warnings.

Inshore Waters Forecasts

Forecasts for Inshore or Coastal Areas can be a liitle more sepecific as they only cover, for example, 12 miles out to sea for UK waters and 20 miles for French areas. Again, the format is fixed. Although there is not quite such a tight word limit, forecasts have to be read out by Coastguards. A typical forecast looks like this:

These are brpadcast once a day on BBC Radio 4 in thr 0520 slot and eight times daily on VHF by the Coastguard, with updated texts every 6 hours.

Why are forecasts sometimes so vague?

First and foremost, t the weather itself is so indefinite; it is a truism to say that the weather does not know itself to within one Beaufort force. On Channel or North Sea crossings, for example, we can experience variability in the wind about which the forecaster knows very little. As an example, a westerly F4 up the Channel will occur with a 4 hPa difference in pressure between the south coast of England and northern France, say 1000 hPa over Southampton and 1004 over St Malo. A force 5 would occur with 999 hPa over Southampton - a pressure difference of 0.1% - and 1004 over St Malo. Relatively small errors in a forecast can make all he difference between a nice force 4, an exciting force 5/6 and a nail biting force 7/8 with gusts to 9!

Secondly, marine forecasts cover large sea areas some with complicated stretches of coast. The wind can vary from force 3 outside the Dart to force 6 off Bolt Head, in about 15 miles and 3 hours. Imagine the length and complexity of the forecast if all such detail was included for even 12 hours ahead from "Lands End to Lyme Regis including the Isles of Scilly".

It does not help anyone if the forecaster tries to be more definite than he really can be. The forecaster does not like using such words as "perhaps", "possibly", "locally" but it is all too often necessary if he is to convey the possibilities in a sensible manner, achievable in a script that is not so long that it becomes meaningless.

Another truism is that there is nothing really definite in the forecast except for the date. Even the date is subject to a certain amount of theological discussion!

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Finally!

There are various sources of GMDSS weather information available around the UK and Western Europe. These come originally from the various National Met Services and are free at the point of delivery. Most other forecasts will be entirely automated. By and large these will be very similar to the GNDSS product but will be less reliable as indicators of bad weather – wind strength and visibility etc,

Good luck and fair winds. If not fair winds then the least that I can wish you is foul weather well forecast.

'A version of this page was originally published in Cruising'', the quarterly magazine of the Cruising Association. mhome

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