Impact of radar retrieval winds on data assimilation and forecast of a mesoscale convective storm using Non-Hydrostatic Model

A variational wind retrieval algorithm is applied to weather radar data to obtain 3-dimensonal wind for investigating mesoscale features and dynamics on the development of a severe convective storm affecting Hong Kong on 28 July 2010. Between 14 and 18 HKT on that day, there were more than 100 mm of rainfall and 4000 lightning strikes over the territory. The retrieved 3-dimensional wind vectors are ingested in the 3DVAR system of a Non-Hydrostatic Model (NHM) as additional observation data. To resolve the storm structure and cloud microphysical process, NHM is configured with a horizontal resolution of 2 km to study the impact of the retrieved wind vectors in model analysis and simulation of the convective storm. Positive impacts are found on resolving the wind flow over low to mid-tropospheric levels in the initial condition of NHM, that enhances shear line signature in the lower troposphere and southwesterly flow on mid-troposphere associated with the passage of a short-wave trough. This results in improvements to the model simulation on the structure and movement of the convective storm, though the timing of its passage over Hong Kong lags behind the actual situation by a couple of hours. Real-time application of the radar retrieved wind data in the NHM analysis and forecast will also be discussed in the paper.