The 13th Paralympic Winter Games are set to begin officially in PyeongChang on March 9th, and the mountainous Olympic venues in eastern South Korea have had no shortage of snow in the last week. Three major winter storms have affected the Korean Peninsula since 28 February 2018, helping to recharge the snowpack for the Paralympic Winter Games. Figure 1 shows 24-hour simulated snowfall totals from SPoRT’s real-time NASA Unified-Weather Research and Forecasting (NU-WRF) model for the three recent snowstorms on 28 February, 4 March, and 7-8 March. SPoRT is continuing to generate 24-hour forecasts of NU-WRF model runs, updated four times per day as part of the research field campaign known as the International Collaborative Experiments for PyeongChang 2018 Olympic and Paralympic Winter Games (ICE-POP).
The Korea Meteorological Administration’s surface analysis on 0300 UTC 28 February shows a potent low pressure approaching the Korean Peninsula from the southwest (Fig. 2), which eventually intensified to less than 970 mb near northern Japan the next day. A picture taken of the NASA Precipitation Imaging Package after the 28 February storm (Fig. 3) shows the substantial snowpack resulting from the ~40 cm (~16 inch) snowfall that occurred at the research station labeled “DGRWC” in the NU-WRF simulated snowfall plots of Figure 1.
Perhaps the most interesting of the three events is the latest storm from 7-8 March. The NU-WRF model simulated composite radar reflectivity at 30-minute intervals (Fig. 4) shows a shield of moderate to heavy synoptic precipitation associated with the low pressure tracking to the south of the Olympic venues. As the precipitation shield pulls away after ~0600 UTC 8 March, surface winds increase from a northeasterly direction over the Sea of Japan and push residual moisture inland against the mountains oriented parallel to the coastline. This leads to a prolonged band of shallow, but moderately intense snowfall in the mountains as the moist onshore flow is forced upward by the topography. Consequently, snowfall amounts are enhanced along the east coast of the Korean Peninsula. Finally, the evolution from deep synoptically-driven snowfall to the shallower forced uplift snowfall is captured nicely by NU-WRF time-height cross sections at the various Olympic venues. Figure 5 shows one of these time-height sections at the Alpensia site (location labeled in Fig. 1 panels), depicting the deep snowfall mixing ratios until ~0600 UTC 8 March, followed by a transition to much shallower, episodic snowfall for the remainder of the time period through 1800 UTC 8 March.