Development of Satellite-based Significant Convection Nowcasting Product in Support of Air Traffic Flow Management in Hong Kong

During the months from April to October, convective weather quite often develops in the South China Sea impacting on flight operations in the Hong Kong Flight Information Region (HKFIR). With significant growth of air traffic, it is important that the Air Traffic Control (ATC) in Hong Kong are brought to the attention of the presence and movement of convective weather within or approaching the HKFIR to allow sufficient lead time to implement flight control and flow measures. The Hong Kong Observatory (HKO) has been developing and enhancing significant convection tailor-made forecast products and services in close coordination with the ATC in Hong Kong since June 2010.

The objective guidance products for assisting forecasters in the formulation of significant convection forecast for the next 12 hours with a focus of the first 6 hours in support of the air traffic flow management are generated from numerical model outputs. Forecasters will adjust the model-based forecast product based on radar and satellite imageries for the first few hours if necessary. Noting that the forecasting skills of the objective guidance for the forecast range of 2-4 hours during which radar-based nowcasting skill normally drops significantly, with a view to alleviating this problem, additional forecast guidance was developed by applying optical flow nowcasting technique to satellite deep convection product.

This paper describes the satellite-based significant convection nowcasting system on trial in HKO. Preliminary verification results using September 2010 data showed that the performance score for 2-3 hour forecast was on a par with the first hour forecast of radar-based nowcasting system with a threat score of about 0.3.