Insights from Nowcasting and Mesoscale Research Working Group Projects of the World Weather Research Programme

Insights from Forecast Demonstration Projects and Research Development Projects, training workshops, and symposia, conducted between 2000 and 2024 are summarized. The projects were organized by the Nowcasting and Mesoscale Research Working Group of the World Weather Research Programme of the World Meteorological Organization. The objective was to advance, promote, and build capacity in nowcasting and very short-range forecasting. The projects were associated with the Olympic Games, emergency management, and aviation services. They brought international experts together to work in a collaborative fashion. Extensive interaction with end users and decision-makers expanded and extended the scope of services from traditional weather hazards (heavy rain, wind, hail, lightning) to include specific user needs (e.g., visibility in complex terrain or airport runways, periods of calm winds or light rain, heat stress). Substantial progress has been made in many areas including advanced radar nowcasting algorithms, stochastic nowcasts, kilometric and hectometric numerical weather prediction models, blending of observations and models, and multimodel systems. Verification was a key and valuable component of the projects quantifying the results. Also, the types of services have expanded to include both summer and winter services, complex terrain and urban environments, air transport, air quality, hydrology, and health. Insights are presented in all aspects of nowcasting and very short-range forecasting from end-user decision-making, critical role of the forecaster, forecast systems (models, heuristics, observations), to science and knowledge gaps. Significance Statement The goal of nowcasting and very short-range forecasting is to provide predictions with lead times of 0–2 and 0–6 h, respectively, and with sufficient skill to issue reliable warnings for weather hazards. It has been an elusive goal. In the past 25 years, the scope has expanded from summer thunderstorm warnings to winter, aviation, air quality, hydrology, and health applications. Led by the World Meteorological Organization’s Nowcasting and Mesoscale Research Working Group, considerable progress has been made through leveraging international expertise, forecast and research projects at the Olympics, engagement with emergency management agencies, training workshops, and symposia. This paper summarizes and discusses the insights, lessons learned, and challenges.