Model: GFS (Global Forecast System) Global Model from the "National Centers for Environmental Prediction" (NCEP) Update: 4 times per day, from 3:30, 09:30, 15:30 und 21:30 GMT Greenwich Mean Time: 12:00 GMT = 13:00 BST Parameter: Precipitation across the Pacific in mm (or litres per square metres) Description: The precipitation map - updated every 6 hours - shows the modeled precipitation in mm over Australia and New Zealand. 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.