Dr. Matt Jeglum
National Weather Service
Abstract: Advances in computing power, data storage, and scientific understanding have expanded the quantity of forecast guidance beyond the capability of human forecasters to comprehend it. The National Blend of Models (NBM) is designed to objectively synthesize this guidance so the forecaster can focus on assessing and communicating high-impact weather events. In conjunction with NBM development, National Weather Service (NWS) forecast operations are shifting from a largely deterministic paradigm to one where the NWS leverages calibrated probabilistic data to increase the skill and lead time of the forecasts it provides to its partners and the public.
In its current state, the NBM assimilates over 160 individual model inputs into a comprehensive database of surface weather elements out to 264 hours lead time. The most advanced post-processing methods in the NBM are used to produce QPF and probability of precipitation. Quantile mapping, along with several minor steps, is used to calibrate and downscale the multimodel ensemble QPF guidance. The 2.5 km resolution Unrestricted Mesoscale Analysis (URMA) precipitation analysis is used to populate the observed cumulative distribution functions (CDFs) and "supplemental locations" with similar analyzed CDFs are utilized to expand the forecast CDFs at a given point.
Verification of the current operational NBM QPF has shown it to be superior to forecasts from both NWS Weather Forecast Offices and the NWS Weather Prediction Center in the Western United States. Case studies have also shown that NBM QPF performance has been competitive with or better than other guidance, including the GFS and HRRR, for high-impact atmospheric river events.
The NBM will only reach its highest potential as a collaborative project between the NWS, NOAA labs, and academia. As a result, outside assessment of and development for the NBM will be beneficial.
Biography: Matt Jeglum received his B.S. in Atmospheric Science from the University of Washington and M.S. and PhD degrees in Atmospheric Science from the University of Utah. He spent two years as an operational forecaster between graduate degrees. His graduate work focused on cyclones and cyclogenesis in the Intermountain West as well as mesoscale wind flows in complex terrain. Matt participated in a number of field projects in his graduate career, in part due to a love of the outdoors. Matt's initial interest in meteorology came from his fascination with snowstorms and the need to know when his local ski hill would receive fresh powder. Matt has been a research meteorologist at the Western Region Headquarters of the National Weather Service in Salt Lake City for 3 years, where he very much enjoys his job and his proximity to world-class backcountry skiing.