The effect of convective momentum transport on tropical cyclones in the Canadian numerical weather prediction system

A significant update to the package of physical parameterizations used in the Canadian operational numerical weather prediction models has recently (summer 2019) been implemented (global and regional prediction systems) . While the primary objective of this implementation was to improve the global energy and hydrological budgets, significant improvements were also obtained in forecast performance, in particular in the Tropics. Furthermore, a dramatic reduction in spurious tropical cyclones was also demonstrated. This reduction was shown to result from the introduction of a parameterization of convective momentum transport (CMT) by the deep convection scheme. Results will be presented based on series of 80 5day forecasts covering the period from June to November 2018. This presentation will describe the different formulations for CMT that were tested, and propose an analysis of the mechanisms by which CMT eliminates the spurious tropical cyclones.