Probabilistic forecasting for weather prediction

Date and Time: 
Monday 2018 Apr 2nd
CG Auditorium
Luca Delle Monache

Probabilistic forecasts provide a distribution of the potential future states of the atmosphere. There are two main methods to generate probabilistic forecasts: one is to run multiple model realizations or multiple models with initial perturbations, and the second is to use analogs. The Analog Ensemble (AnEn) algorithm discussed in this presentation generates probabilistic predictions using a single deterministic NWP, a set of past forecast predictions, and their corresponding observations. The AnEn technique compensates for the model bias by taking past errors into account. The main assumption is that if similar past forecasts can be found, the model error can be estimated. Specifically, the AnEn seeks to estimate the probability distribution of the observed future value of the predictand variable given a model prediction, which can be represented as p(y ~ f) where, at a given time and location, y is the unknown observed future value of the predictand variable and f the values of the predictors from the deterministic model prediction at the same location and over a time window centered over the same time. Advantages of the AnEn including the use of higher resolution forecasts and no need for initial condition perturbations, running multiple model instances, or post processing requirements. The AnEn is able to capture the flow-dependent error characteristics and show superior skill in predicting rare events when compared to state-of-the-art post processing methods. This presentation will provide an overview of probabilistic forecasting with specific emphasis on the AnEn technique as one means of generating an ensemble prediction.

Speaker Description: 

Luca Delle Monache is the Deputy Director of the National Security Applications Program at NCAR. Dr. Delle Monache has research interests in applied mathematics, atmospheric chemistry, meteorology, probabilistic forecasting, applied research, and interdisciplinary research.

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