The lunch starts at 12:00, and the talk will start around 12:20.

NB: Wednesday BigInsight Lunches are open to staff and students from any of the BigInsight partners, including UiO, but not to others.

Speaker: Nina Schuhen, from the Norwegian Computer Center

Location: Spiseriet at Norsk Regnesentral.

Title: Rapid Adjustment of Weather Forecast Trajectories

Abstract: In weather forecasting, accuracy is hard to achieve due to the chaotic nature of the earth’s atmosphere. Numerical weather prediction (NWP) uses sophisticated dynamical models to simulate and predict future states of the atmosphere, thanks to some of the most powerful super computers in the world. Still, they are far from perfect. Statistical post-processing strives to improve weather forecasts by looking at the past performance of the weather models and removing biases and false trends. The skill of a typical numerical weather forecast decreases over time, so that forecasts from more recent model runs are generally considered to give more accurate predictions. Some post-processing techniques make use of older model runs through time lagging or blending, but with very little relevance, as the newer model runs are preferred.

At the same time, technological advances mean that observations become available in very short time frames and in increasing amounts. A new method, Rapid Adjustment of Forecast Trajectories (RAFT), works in combination with traditional statistical post-processing techniques and uses short-term observations to improve older forecast runs. As a result, older forecasts match or even surpass the skill of the forecasts from the newest model run. Relying on the inherent correlation structure of the forecast errors between lead times, RAFT updates the tail of a forecast trajectory, while the first part verifies. The adaptive regression approach takes into account changes in predictability and local patterns, while being computationally efficient.