NSSL’s Warn-on-Forecast Probabilistic Intense Rainfall Guidance at WPC’s Met Watch Desk during Summer of 2019

The NOAA National Severe Storms Laboratory’s Warn-on-Forecast program is developing and testing an on-demand, regional, frequently-cycled, convective-scale ensemble analysis and prediction system. The goal is to provide NWS forecasters with a more continuous flow of probabilistic model guidance for the 0–6 h timeframe that will enable earlier and more accurate communication of hazardous weather threats. Once transitioned to NWS operations, the WoF System (WoFS) will likely play a critical role in filling the forecast guidance gap between the watch and warning temporal and spatial scales of the evolving weather threat from individual convective storms. Since 2017, the experimental WoFS has been evaluated within NOAA testbed experiments. The feedback from the evaluations are used to enhance and improve all aspects of the experimental system.

In addition to examining the applications of WoFS guidance during controlled settings in the NOAA testbed environment, the “concepts of operations” of WoFS was explored for the first time during the summer of 2019 in collaboration with NOAA/NWS Weather Prediction Center (WPC). The Met Watch desk at WPC directed the domain location and forecast start time of WoFS, which was driven by a slight risk or higher in Day 1 Excessive Rainfall Outlook. Both traditional and object-based post-processing, visualization, and verification products from the 0–6 h WoFS ensemble were evaluated by Met Watch desk forecasters and several WFOs (e.g. Norman OK, Topeka KS, and Baltimore/Washington offices). In particular, evaluations reflected on how forecasters used these products to make decisions regarding the issuance of Mesoscale Precipitation Discussions, advisories, watches, and warning products. This naturalistic approach gave insights into what the WoFS work flow would likely look like in NWS operations. Results from the experiments will be presented at the annual meeting.