Significant progress has been made in the identification and forecasting of dangerous icing conditions following the crash of American Eagle Flight 4184 near Roselawn, Indiana in 1994. Widespread understanding of synoptic and mesoscale conditions surrounding icing events are now known, and the advent of microphysics-based research has aided in the understanding of icing on the scale of droplets. Operational forecasts of glaze icing are now produced by several entities.
A few gaps remain in icing forecasting, however. Previous studies have noted that unexpected severity in icing can be found in locations where the expected droplet type is under forecast, often in the presence of rapid advection of moisture on both horizontal and vertical planes. Recent research has suggested that water droplets can hold a residence time in the atmosphere of up to a few days and be carried hundreds of miles. This realization has profound implications for icing forecasting. Most icing forecasts are limited in their ability to represent droplet transportation into a region, and the operationalization of three-dimensional moisture advection remains limited as well.
This paper will use the publicly available NOAA HYSPLIT model to explore the parcel trajectories of air masses associated with significant icing impacts, including aviation incidents known to have been influenced by icing, as well as selected moderate, severe, and extreme icing reports. Common themes and unique events will be studied alike, and the aim for this research is to provide suggestions and possible supplemental forecast material to aid aviation forecasters.
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