RESUME / ABSTRACT  


Sous-système de prévisions immédiates Scribe, Version 1.0: Premiers résultats des vérifications objectives

Scribe Nowcasting sub-system -Version 1.0: First objective verification results

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C. Landry, R. Parent, J.-F. Deschênes, A. Giguère, G. Hardy and R. Verret

Division du développement CMC






The SCRIBE Weather Forecast Product Expert System is now capable of ingesting the latest observations and nowcasting model data to update in real time the Scribe weather elements. This sub-system has been developed to minimize the necessary manual adjustments done by the forecaster to merge the current weather conditions with the forecast.

Version 1.0 of the Scribe Nowcasting is currently using surface observations, North American radar mosaic data and lighting data from the Lighting Detection Network. These observations are used to feed short term forecast models. A statistical model called "PubTools" uses the surface observations to forecast the probabilities of occurrences of weather elements. The observed radar reflectivities are projected during the next 6 hours with a vector motion calculated from observed imageries 20 minutes apart. Finally, an algorithm has been developed at CMC to predict the probabilities of thunderstorm occurrences based on the forecast position of the lightning clusters. All these observed and forecast data are processed by a rules base system to determine the best sequence of weather elements representing the current observation and short term tendencies.

The first 6 to 9 hours of the Scribe weather elements will thus be influenced by the nowcasting data. Depending on the weather conditions and on how well the model handles these conditions, significant changes can be done to the regular Scribe weather elements. To assess whether these changes contribute to improve the first hours of the forecast or not, objective verifications was perforemed. For some weather elements preliminary results show that in the first 6 hours of the forecast the Probablily of Detection has increased and the related False Alarm Ratio has decreased. Other verification scores also indicate an improvement of the short term forecast performance.