A Targeted Operational Aircraft Reconnaissance Program Strategy for Improved Prediction of Atmospheric Rivers and Winter Storms

A new aircraft observing strategy is proposed for obtaining much-needed atmospheric dropsonde observations for developing winter weather systems in the Central and Eastern Pacific (CPAC and EPAC) adjacent to the U.S. West Coast as well as ‘Bomb Cyclones’ along the U.S. East Coast. The observing strategy involves new and improved dropsonde targeting strategies from high-level aircraft reconnaissance flights over CPAC and EPAC winter weather events, potentially impacting U.S. West and East Coast locations, including Atmospheric River and precursor ‘Bomb Cyclone’ events. Flights in advance of coastal landfall over CPAC and EPAC are envisioned that target regions of enhanced model uncertainty diagnosed using operational global ensemble forecast models. Data from these flights would be for the purpose of reducing model uncertainty in the prediction of developing systems that may impact Hawaii, Alaska and the U.S. West and East Coasts. Secondarily, data from these flights would play a role in improving longer range, down-stream forecasting of severe weather impacts over the CONUS region during the winter season. This operational project involves the combined use of 1) a new global model core, 2) improved model physics, 3) improved Data Assimilation methodology, 4) a new dropsonde system employing state of the art instrumentation and data transmission technology and, most importantly, 5) the use of an emerging new dropsonde targeting technique defining regions of enhanced operational ensemble model uncertainty which, in total, will help insure the successful implementation of this new plan.

The Atmospheric River Reconnaissance program for 2019 (ARR-2019) was conducted in February 2019 as an initial test of certain components of this plan. It was a joint effort of the Scripps Center for Western Weather and Water Extremes (CW3E), NOAA Environmental Modeling Center (EMC) and the Air Force Reserve Command 53rd Weather Reconnaissance Squadron (AFRC/ 53rd WRS). The Naval Research Laboratory, NCAR/EOL and University at Albany also partnered in providing ensemble model-based targeting strategies for dropsonde deployments, and the new dropsonde technology as well. Initial analysis of AR features such as the low-level Integrated Moisture Transport (IMT) and mid and upper features such as the polar low, and associated polar and subtropical jet-streak features were intercepted and sampled in the rapidly evolving environment 24-48 hours prior to AR impact along the U.S. West Coast for 7 different cases. East Coast targets were not sampled in this test program. However, tentative plans to sample East Coast precursor AR features prior to forecasted ‘Bomb Cyclones’ as well as ‘Bomb Cyclone’ reconnaissance are planned for 2020, along with a continuation of CPAC and EPAC targeted flights prior to landfalling West Coast AR systems in the Feb-Mar time frame.