Using Precipitation Type Weather Reports to Assess Select Operational Numerical Weather Prediction Models for Terminal Area Icing Weather Information for Nextgen (TAIWIN)

Providing highly resolved and timely forecasts of freezing precipitation and cloud properties related to icing conditions in terminal areas is a high-priority goal for the Terminal Area Icing Weather Information for NextGen (TAIWIN) project funded by the Federal Aviation Administration (FAA).  To achieve this goal, evaluation of select operational models with high spatial and temporal resolution [i.e., High-Resolution Rapid Refresh (HRRR) and North American Mesoscale contiguous U.S. nest (NAMnest) models] was conducted to identify strengths and potential shortcomings or weaknesses in the models in terms of TAIWIN-relevant fields. In this regard, daily operational output initialized at 00 and 12 UTC from the HRRR and NAMnest were acquired for forecasts out to 15 hours during the winter season of January – March 2016. The temporal resolution of the forecasts was hourly for both operational models; spatially, the horizontal grid spacing for the HRRR was ~3 km, while the NAMnest was ~4 km.

Evaluation of the HRRR and NAMnest mixing ratio values for rain, freezing rain, and snow at the surface and categorical surface precipitation type diagnostic output of rain, freezing rain, snow, and ice pellets was conducted. Gridded model output fields were assessed through a comparison with the Multi-radar/Multi-sensor (MRMS) gridded observation dataset. In addition, precipitation type observations from aviation routine weather reports (METAR) and Meteorological Phenomena Identification Near the Ground (mPING) were used for point comparisons. Objective model verification statistics were generated using the Model Evaluation Tools (MET) software package. Along with the presentation of season-long statistics for each operational model, a case study from a large winter storm that impacted the eastern U.S. on 22-24 January 2016 will be discussed.

This research is in response to requirements and funding by the Federal Aviation Administration (FAA). The views expressed are those of the authors and do not necessarily represent the official policy or position of the FAA.