Water vapour of the atmosphere gave on Thursday the 17th March 2005 a fatal surprise to three drivers causing 3 mass pile-ups in which 70 person were injured and 300 cars wrecked. Strong winds cleaned roads from snow but a hard and slippery ice layer formed on their surface which motorists observed too late in hurry to work. Supercooled water dashed to windscreen only after the crashes already occurred.
Weather radars indicated only moderate snowfall on that tragic morning and it should not have been that dangerous as the temperature was -7 Celsius and thus well below zero. The weather radars detect atmospheric water vapour only after drops of water or snow drops begin forming and so the warning comes too late from them.
There already existed a geodetic network of GPS reference stations that serves the Virtual Real-Time Kinematic (VRS) land-surveys of the Geotrim company. The Southern Finland was already covered and the propagation delays caused by the water vapour were continuously removed from the received GPS signals.
One can now ask with a good hindsight why our national weather service did not make use of this information on the water vapour that insidiously penetrated on the busy entrance ways of Helsinki.
What actions are being taken by the authorities that motorists must not drive to work next winter under this kind of a threat?
