Nowcasts

Nowcasts are short-term weather forecasts focused on the immediate future, typically covering up to six hours ahead with high spatial and temporal resolution. The term emphasizes rapid updates as new observations become available, allowing forecasters to track evolving weather trends in near real time.

In meteorology, nowcasting relies on real-time observations such as radar, satellite imagery, and surface sensors. Techniques include extrapolation of observed precipitation (persistence and motion tracking), storm-cell tracking, and object-based methods. These are often combined with rapid, high-resolution numerical models and statistical or machine learning approaches to improve short-term predictions of precipitation and severe weather.

Nowcasts are widely used by weather services, aviation, maritime operations, agriculture, and emergency management to issue short-term warnings for hazards like thunderstorms, heavy rainfall, lightning, or hail. Their strengths include a high update frequency and relatively accurate forecasts for the immediate term. Limitations arise from rapid changes in storm intensity and structure, gaps or errors in the observational data, and the fact that forecast skill generally decreases beyond several hours.

In economics and finance, nowcasting refers to methods that estimate the current state of the economy using timely, high-frequency data when official statistics are not yet available. These uses are distinct from weather nowcasting but share the goal of producing timely, near-term estimates to inform decisions and policy.