DTN's High Ice Water Forecasts

High altitude aircraft sometimes encounter ice crystals that can dangerously disrupt jet engine and sensor functions. Ice crystal encounters are difficult to avoid because of their poor radar reflectivity characteristics. Therefore forecasts and nowcasts are very valuable to aircraft operators. DTN recently added high ice water content (HIWC) forecasts to their suite of aviation products. Because cloud ice reduces supercooled liquid water, DTN has been computing ice crystal forecasts for years as a component of its lower altitude icing forecasts. One of the unique aspects of DTN’s icing forecasts is its ability to forecast both liquid and ice water content in convective storms. Since dangerous HIWC occurs near convective storm cores, HIWC forecasts are created by simply extending upward these lower altitude forecasts. We will review DTN’s icing forecast methodology and show how we make HIWC forecasts. We then validate these with HIWC observations taken in three different research campaigns in the tropics. Retrospective HIWC forecast values typically are within the expected observational range. The problems with these forecasts are location errors of these weakly forced convective storms which will plague tropical forecasts for the foreseeable future. To better help aircraft avoid HIWC, DTN is developing nowcast capability similar to its one for convective turbulence.