Using the GOES sounder to nearcast severe convection

A relatively simple nearcasting model has been developed that assimilates full resolution information from the 18-channel GOES sounder and generates 1-6 hour nearcasts of atmospheric stability indices. Products generated by the nearcast model have shown skill at identifying rapidly developing, convective destabilization up to 6 hours in advance. The system fills the 1-6 hour information gap which exists between radar nowcasts and longer-range numerical forecasts. Nearcasting systems must be able to detect and retain extreme variations in the atmosphere (especially moisture fields) and incorporate large volumes of high-resolution asynoptic data while remaining computationally efficient. Our nearcasting system uses a Lagrangian approach to optimize the impact and retention of information provided by GOES sounder. It uses hourly, full resolution (10-12 km) multi-layer retrieved parameters from the GOES sounder. Results enhance current operational NWP forecasts by successfully capturing and retaining details (maxima, minima and extreme gradients) critical to the development of convective instability several hours in advance, even after subsequent IR satellite observations become cloud contaminated.