A model-based diagnostic study of the development and maintenance mechanism of two polar lows

Abstract

The life cycles of two polar lows in the Norwegian Sea have been studied. Both lows were observed, analysed and forecast by the Norwegian mesoscale model system. The system is run operationally 4 times a day and provides high spatial and temporal resolution data for diagnostics in addition to daily forecasts. Both lows start developing as upper level vorticity maxima approach low-level baroclinic zones. One of the lows decays after the initial baroclinic intensification phase, while the other develops further. This second phase, the maintenance phase, seems to be related to organized convection. The possibility for air-sea interaction instability is discussed. The role of the underlying surface in creating conditions favourable for polar low developments is addressed as is the predictability of these mesoscale cyclones.