1 Paper submitted to the Public Weather Service Customer Group ‘Recommendations for improvements in MET Office Ice predictions’

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Introduction

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This document reviews the current status of MET Office ice predictions and makes four recommendations for improvements. These improvements involve the publication of data that the MET Office generates but does not currently provide to the public in its forecasts. A principle behind the proposals is that the information should be communicated in simple direct terms. The full forecasts should be available on mobile phones.

 

The proposals have been put together with the help of Audax (UK) and Cycling UK. Cycling UK was previously known as the CTC. Cycling UK endorsed this document by email on 22 April 2016

 

The proposals have been specifically produced to help cyclists make better informed decisions about when to cycle in winter conditions. The overall aim is to encourage more cyclists to cycle during the winter period as they will have better knowledge of the conditions. And the risk of injury should be significantly reduced as cyclists will be able to make better decisions about riding if ice is a risk. This approach supports the Government policy to expand cycling.

 

Some of the limitations of the current MET forecasts are recognised in the recent MET Office blog http://www.cyclinguk.org/blog/metoffice/ice-time-ride-reading-signs. This blog also makes the point that ‘cycling on ice can often result in physical injury’.

 

Whilst the proposals are aimed at cyclists they are hoped to be valuable to all other road users. As an example, motorcyclists have similar issues to cyclists and should benefit as would car drivers on ungritted roads. Pedestrians should also be helped, such as the more elderly for whom a fall on ice can easily lead to bones being broken.

 

Current status of MET Office ice predictions. 

 

          A written area forecast is produced daily covering each of the MET Office areas of the country such as South West England. Ice is usually covered with a general statement that such as 'ice is forecast in Dorset and Wiltshire'. It is not usual for   specific times to be given when the ice is expected to form or to clear. 

 

          The MET Office produces hourly weather predictions 36 hours ahead for 7500 locations. These forecast are made for weather conditions such as rain, visibility, UV levels, wind and  cloud. Ice is not included in these forecasts.

 

          The MET office also produces UK wide weather maps showing conditions such as temperature contours at 5 degree  intervals, rain locations indicating the intensity of rain by colour, pollen count and surface pressure. Ice is not included in these forecasts. These weather maps are not available on mobile phones.

 

         

 When (air)  temperatures are low ( even below zero) the MET Office does not usually forecast ice if there is no precipitation forecast e.g. a forecast of minus 3 degrees for Grampian on 30 March 2016. This is understandable on dry roads but where there is water run-off from fields or field springs running onto and across roads unforecasted ice can be encountered. For example, on an organised event around Bristol on Sunday 3 April this year, there were around 10 locations where water was running down or across the road mostly from field springs.

 

When ice meets the MET Office criteria for ‘Severe Weather’ it is forecast as part of the Severe Weather Warning Service. However traction controlled cars with a crumple zone are included in the same group of users as cyclists. As a result ice is often not forecast unless it would meet the much higher risk threshold for cars.

 

Gardeners do receive specific forecasts for grass frost. Cyclists need their equivalent i.e. road temperature but it is not provided.

 

Even when precipitation is forecast when sustained air temperatures have been below zero ice is not always forecast e.g. at 9 am on 25 April 2016 the weather map centred on Dalwhinnie in the Highlands showed many areas where, at 11am, the  air temperatures had not risen above zero. Rain and snow was forecast for these areas but there was no prediction for ice.

 

Local Authorities who are responsible for gritting major roads usually receive their ice related weather information in two principle parts from the weather prediction contractors. In simple terms, the first part predicts ice when it comes about directly from weather conditions e.g. rain/snow falling on a frozen surface. For the second part they receive road temperature information. If road temperatures are close to zero they grit the roads in the areas where, with local knowledge, there is water seepage onto the road.

 

       Implications of current forecasting

 

 

        In order to allow cyclists to make informed decisions on cycling in winter they need reliable comprehensive information  on the forecast for ice in terms of the area affected and the times when ice is expected to form and clear that covers the route which they plan to ride. This information is not available. As a result cyclists may either take a more cautious approach than they otherwise would or vice versa.

 

Those taking a more cautious approach are missing out on being able to cycle. Alternatively cyclists may encounter ice when they do not expect it.

 

As a substitute for a comprehensive forecast of ice many cyclists just use the temperature forecasts as a rule of thumb which can be very misleading. They do not realise that these are air temperatures which are a poor indicator of the formation risk for ice.

 

       Potential improvements

 

       The MET Office generates all the information required by cyclists but does not publish it. It predicts 36 hours ahead the spread of ice on an hourly basis which it could present as a country-wide  map showing when ice is expected to form and when it is expected to clear (this is a necessary input into the Severe Weather Service). Road temperatures can be many degrees lower than the 'temperatures' appearing in the MET forecasts which are air temperatures. Road temperatures should also be predicted on an hourly basis.

 

The forecasting of road temperatures could be a variation of the current method of forecasting grass frost for gardeners. The MET Office records through its weather stations air temperatures, grass temperatures and ground temperatures. The later use a standard solid block sunk into the ground. This data can be used in the assessment of road temperatures for cyclists.

 

Cyclists are not generally aware that they can often encounter ice when the MET Office does not forecast ice. This occurs because it is not usual for the MET Office to forecast ice when road temperatures are below zero but the source of the water is from seepage from fields for example. In these cases cyclists will be assisted greatly if they could predict ice in the same way as the gritting departments of local authorities do in this situation; i.e.  receive road temperature maps and, using their local knowledge of water seepage, assess whether or not they are likely to encounter ice.

 

       If the above information is provided to cyclists in the regular weather forecasts on mobile phones they could make their own informed decision about winter travel. The information can be provided as maps of ice spread and individual hourly predictions for each of the 7500 locations that the MET Office currently produce forecasts for. The road temperature information will be valuable to those who travel through country roads where water runs onto and across roads from water-run-off and field springs; especially as the MET Office normally only predicts ice when precipitation is forecast.

 

Summary of Specific Recommendations

 

In order to establish cost effective improvements in forecasting it is necessary for discussions to take place on the following recommendations. The final solution may not be exactly as proposed below but if discussions take place then there is a good chance that significant improvements can be made.

 

 

a)MET Office to explain when they specifically predict ice and when ice may still be encountered but it is not forecast by the MET Office i.e. the MET Office usually only predicts ice when the water that freezes comes directly from the weather on the day and not, for example, from water seepage onto the roads

 

        b) Hourly predictions of areas affected by ice are shown as maps. These could be similar to the current temperature maps. Full information to be provided on mobile phones as well though other media.

 

        c) The start times and finish times of ice are shown for each of the 7500 locations for which forecasts are produced, similar to the way in which rain is forecast. Information to be provided on mobile phones.

 

        d) Hourly predictions of road temperatures to be shown as maps. Information to be provided on mobile phones. This will be used by cyclists when the MET Office does not forecast ice even though road temperatures are below zero (see (a) above) Cyclists will then use their local knowledge of water seepage across roads to decide whether or not to ride.

 

e) Ice predictions are included in the criteria that the MET Office use for measuring their predictions against actual outcomes.

 

Issue 1 25 April 2016

 

Issue 2 21 June 2016