 |
Place weather marks in the slots on the table and see what happens on the monitor. Try different options. Which combination gives the most difficult road conditions for traffic? |
You are 2-3 times more likely to meet with an accident in snowy or rainy weather than in dry road conditions. Slushy weather increases the risk to 6-8 and icy weather to 10-30 times. Especially quick changes in weather increase the risk of accidents.
Weather forecasts help road users and maintenance to prepare for changes in road conditions. They are based on a computer model that can combine a large amount of weather observations into one forecast.
Weather forecasts have become more accurate due to the forecast models and the larger calculation capacity of computers. In 2005 the accuracy of the Finnish Meteorological Institute’s average temperature forecast for one day was 87,1 %. The forecast for two days had an accuracy of 80,2 %. Probability of precipitation in the forecast for one day was 85,3 % and 81,7 % in the forecast for two days.
Co-operation
partner:
Finnish
Meteorological Institute
VARO service
The new VARO (WATCH OUT) service, maintained by the Finnish Meteorological Institute and the Finnish Road Enterprise (www.varopalvelu.fi), gives voice message warnings about changing road conditions such as unexpected slippery roads, violent thundershowers or snow storms. When approaching a dangerous or particularly slippery spot, the driver receives a beeping message in his/her mobile phone. The service uses GPS localisation in the car’s navigator. It is also possible to ask for a weather and road condition forecast for your route beforehand.
Road condition model and its different classes of warnings
|
Class |
Road conditions |
|
|
|
|
0 |
Nothing to warn about |
|
1 |
Road surface covered with hoarfrost |
|
2 |
Road surface partly icy |
|
3 |
Road surface icy |
|
|
|
|
0 |
Nothing to warn about |
|
1 |
Road surface changing, soon covered with hoarfrost |
|
2 |
Road surface changing, becoming partly icy |
|
3 |
Road surface becoming icy |
|
4 |
Slippery because of frost (cold road surface with some snow) |
|
5 |
Index of road conditions deteriorating fast |
|
6 |
Rain on cold road surface (below 0 degrees) |
|
7 |
Raining sleet on partly frosty road surface |
|
8 |
Raining sleet on frosty road surface |
|
9 |
Rain on partly frosty road surface |
|
10 |
Rain on frosty road surface |
Drivers’ opinion: influence of difficult road conditions
|
Road conditions |
Lorry drivers |
Bus drivers |
||||||
|
Places |
Places |
Place 1 |
unnecessary |
Places |
Places |
Place 1 |
unnecessary |
|
|
Snow |
0 % |
39 % |
0 % |
6 % |
20 % |
60 % |
0 % |
40 % |
|
Sleet |
17 % |
44 % |
0 % |
6 % |
0 % |
60 % |
0 % |
20 % |
|
Icy rain |
89 % |
0 % |
61 % |
0 % |
100 % |
0 % |
0 % |
0 % |
|
Black ice |
89 % |
6 % |
22 % |
6 % |
80 % |
20 % |
80 % |
0 % |
|
Frost |
78 % |
11 % |
17 % |
6 % |
80 % |
0 % |
0 % |
0 % |
|
Hoarfrost |
6 % |
67 % |
0 % |
17 % |
0 % |
60 % |
0 % |
20 % |
|
Mist |
17 % |
61 % |
0 % |
6 % |
0 % |
80 % |
0 % |
20 % |
|
Rain |
6 % |
89 % |
0 % |
22 % |
20 % |
60 % |
20 % |
20 % |
A new weather forecast model tries to cover even city districts
The Finnish Meteorological Institute is testing a prototype of
the new AROME weather forecast model.
It depicts weather on the scale of city districts.
The new fine grid model is expected to be useful in the future in
predicting violent weather conditions such as heavy rains and
thunder storms. Due to its good ability of distinction, the model
also describes the changing winds of coastal and lakeside areas
better than current models. Better wind forecasts help to make more
accurate air quality predictions and to be prepared for accident
situations in which dangerous substances can spread. Accurate wind
forecasts are useful for waterborne traffic as well.
During test phase, the distance
between the model’s calculation points or the so called grid
distance is 2,5 km but it’s possible to use a smaller grid
distance if needed. The testing of this system at the Finnish
Meteorological Institute is part of a development project in which
the system’s new possibilities are being surveyed.
This will become standard
procedure within the Institute.
The weather forecast model
simulates currents and weather conditions in the atmosphere. With
the help of this model it’s possible to imitate the
atmosphere’s activity as well as evaluate how weather
phenomena develop. The model functions in a three-dimensional grid.
It calculates future weather situations based on the laws of
physics and the weather observations marked on the grid. The
physical description of weather conditions is state-of-the-art, and
the thick grid helps to make accurate local forecasts.
The development of the AROME-model began in 2002 at Meteo-France
(MF). The Finnish Meteorological Institute, as member of the
HIRLAM-A research programme, started co-operation with the large
European model community lead by MF in 2004. Also the Meteorological institutes of Sweden,
Denmark, Spain and Hungary have been active in this
co-operation.
The Finnish Meteorological Institute is one of three institutes
that use AROME on a daily basis at the moment. The model is a
prototype and its development will take several years.
Lisätietoja
Erikoistutkija Carl Fortelius
puh. (09) 1929 4130 tai 050 525 1394
carl.fortelius
fmi.fi
Tutkija Sami Niemelä
puh. (09) 1929 4172
Updated 8.1.2007/KT
