Pukyong Orographic Nowcasting (PKON) and its verification

Radar-based nowcasting widely performs for short term weather forecasting for 1–3 hour by using the extrapolation. In this time period, it is possible to forecast of high-impact weather events such as flood-producing precipitation, hail, and snow with reasonable accuracy. The period of nowcasting may be extended up to 6 hour but the accuracy decreases gradually with increase in the duration of prediction. In recent years, the radar based nowcasting blending with high-resolution NWP is gaining popularity. One of the reasons is that the convection resolving models performed better in terms of convective initiation with parameterized convection. However, short-term forecasting near mountainous area still remains a challenge in current nowcasting technique (Mandapaka et al. 2011).

The PuKyong Orographic Nowcasting (PKON) specifically developed for orographic precipitation. PKON included the orographic precipitation-producing mechanisms such as wind direction, speed, mixing ratio of water vapor, and directional terrain slope gradient. The dynamic aspects depend on the upstream characteristics of the flow and on the terrain configuration, which together determined from high-resolution NWP (Cloud-Resolving Storm Simulator; CReSS) model using a predefined temporal weighting function. PKON validated the severe thunderstorm (i.e., bow echo) which developed on 17 July 2012 over the Jeju Island, Korea. The results represented an improvement of orographic enhancement (or dissipation) over Mt. Halla. It could be seen that PKON forecast showed bow-shaped precipitation over the ocean.