IMPROVING THE NOWCAST OF MESOSCALE CONVECTIVE SYSTEMS IN FORTRACC

Renato Galante Negri and Luiz Augusto Toledo Machado¹

¹ Instituto Nacional de Pesquisas Espaciais / Centro de Previsão de Tempo e Estudos Climáticos -  INPE/CPTEC

ABSTRACT

Winds estimated from an successive satellite image sequence has been widely used in numerical weather prediction models in the last decades. This wind data is known by many names, being Atmospheric Motion Vectors (AMV) a common one. The AMV are used, generally, to describe the large scale flows in data assimilation schemes for numerical prediction models (NWP). In the last years, with the regional NWP being configured at higher scales (10 to 1 km), AMV at higher spatial resolution will be probably necessary.
Recently, an new wind estimative technique has been developed at CPTEC/INPE, aiming to extract high resolution wind fields at deep convective cloud tops. This technique is based in the use of infrared channel combinations to identify different cloud structures (like thin cirrus, overshooting zones, etc) to be isolated and tracked. By this approach, the wind at the convective cells scale can be extracted from the large scale flow where the mesoscale convective cluster is inserted.
Using these high resolution AMV estimated from brightness temperature differences (Negri et al., 2014) is possible identify areas of a deep convective cluster which will intensify or dissipate. This can be done using the wind divergence calculated from these high resolution AMVs.
An algorithm for tracking and forecasting radiative and morphological characteristics of mesoscale convective systems through their entire life cycles using geostationary satellite thermal channel information (11 µm), called ForTraCC, was developed at CPTEC/INPE and is keep operationally since early 2000's. The ForTraCC can be used as a scientific tool, to extract many informations about the life cycle of the convective systems as well as a nowcasting tool.
This work evaluates the use of the BTD-AMV developed at CPTEC/INPE to improve the forecast of the mesoscale convective systems life cycle done by ForTraCC for nowcasting purposes.