Model: Global weather forecast model from the "Japan Meteorological Agency" Update: 5:30 GMT und 18:30 GMT Greenwich Mean Time: 12:00 GMT = 13:00 BST Variable: Precipitation Description: The precipitation map shows the modeled precipitation in mm over the entire North-Atlantic and European region. The precipitation areas are encircled by isohyets - lines with equal amounts of precipitation. However, modeling precipitation is still not very reliable. If you compare the modeled results with observed values you will realize that the model is nothing better than a first order approach. Yet this chart is of some use for forecasters. Note: Based on international convention meteorologists use the metric system. 100 mm of precipitation is equivalent to roughly 4 inches.