Senior forecaster, Royal Netherlands Meteorological Institute (KNMI) - Netherlands
Forecasting severe weather and issuing significant warnings about severe weather phenomena to the common public is one of the main tasks of the Meteorological Office in the Netherlands. The main events in the warning criteria concentrate on heavy thunderstorms in the summerseason, high winds in autumn/winter and on snow and ice-phenomena in the cold period. The regular KNMI-observationnetwork consists of 40 synoptic stations, partly manned, partly automatic wind/temperature masts. For climatological purposes about 300 people gather precipitation-data, once a day.
Especially in situations with severe weather, the above mentioned synoptic network is many times unable to detect small-scale destructive weatherphenomena shortly after development. Radar and satellite-data are useful tools to keep the meteorologist informed as fast as possible but still these tools are not "the eyes on the site itself".
A small but fierce tornado struck the northern Veluwe-area on July 17th 1987. Greenhouses and some homes were demolished. Miraculously no people were injured. Before KNMI was able to detect the exact phenomenon a private survey had to be carried out. Eyewitness reports afterwards gave hard evidence that a tornado had struck the area. In the days ahead a detailed pattern of damage through a narrow 25 km long corridor has been found. This damage-survey raised my attention for severe weather phenomena and funnelclouds in particular.
In 1996, together with a colleague, I visited the NSSL in Norman Oklahoma, invited by Senior forecaster Mike Branick.
Branick showed that close co-operation between meteorologists and severe-weather spotters is contributing to detect severe weather phenomena, as large hail or tornado's, close after their development.
Back in the Netherlands I proposed to stimulate such a voluntary severe-weather-observation network too. In 1997 it started. At this moment 110 observers contribute to inform the forecasters in the weather-room with their information. All reports are received by e-mail. The plans for the near future allow forecasters to inform the spotters by SMS-alertmessages. In great detail destructive weather phenomena in the Netherlands could be monitored than online which enables us (KNMI) to issue severe weather warnings in time and with more detail.
Damage survey of the July 17th 1987 tornado over the Veluwe-area in the Netherlands, containing (20-25 sheets):
• Images of the damaged buildings, woods etc.
• Maps with detailed tree-fall patterns along the 25 km long swath of the tornado.
• Additional meteorological maps, satellitepictures and radar-images.
The voluntary severe weather-observation network in the Netherlands, containing (10-15 sheets)
• Map with all voluntary observers-locations.
• The communication-system.
• Examples of incoming messages (reports) and outgoing warnings.