Evaluation of the Health-Impact Oriented Global Subseasonal Excessive Heat Outlook System during Summer of 2018

A health-impact oriented global subseasonal excessive heat outlook system (GSEHOS) has been developed at the University of Maryland. The GSEHOS provides experimental daily real-time forecasts for Week-2 and Week-3 since 20 May 2018 which inform outlooks that are disseminated bi-weekly to a global multi-disciplinary audience. The GSEHOS uses the 16-member ensemble forecast produced daily by NOAA’s Climate Forecast System to calculate thermal discomfort as formulated by the Excess Heat Factor (EHF). In the first part of this paper I discuss the EHF as measure of thermal discomfort, the post-processing of raw CFS forecast data, output produced by the GSEHOS, and verify forecasts of excessive heat events that occurred in the Northern Hemisphere during the summer of 2018. Dynamical downscaling of large scale tropospheric stationary modes through the boundary layer prior to the calculation of the probabilistic forecast information is the next step in health-impact oriented outlooks. This would allow for more precise forecasts in urban, coastal, and foehn wind prone areas, and during oppressive heat waves. Dynamical downscaling will require a choice of the set of boundary layer parameterizations that better fits the physics of extreme heat events. One of the avenues for guiding this choice was built by the S2S and SubX projects which allow to compare the behavior of forecast models during observed excessive heat events. In the last part of the paper I describe initial findings from such comparisons. The paper concludes with current research and development efforts, and remarks on the importance of interdisciplinary collaboration for developing the next generation operational health-impact oriented GSEHOS.