A Glance at the Relationship between Multi-Radar/Multi-Sensor (MRMS) Rotation Tracks and National Weather Service (NWS) Tornado Warnings

Several Multi-Radar/Multi-Sensor (MRMS) products became operational in National Weather Service Weather Forecast Offices (WFOs) in September 2015. MRMS products are able to give forecasters a broader picture by blending data from multiple radars into one product. Specifically, the Azimuthal Shear and its associated Rotation Tracks products blend azimuthal shear from nearby radars at both low (0-2 km) and mid (3-6 km) levels, giving a unique look at storms’ rotation. The 60-minute Low-Level Rotation Tracks product has shown some utility for identifying low-level mesocyclones, and some tornadoes, in the operational warning environment. However, little research has been conducted to provide guidance to forecasters on the use of these products in warning decision-making. This study will take a first, small step at accomplishing this task. A number of tornado-warned events archived by the Warning Decision Training Division (WDTD) Weather Event Simulator (WES) II since MRMS became operational will be analyzed. The start times of the tornado warnings will be compared with the magnitude of the origin of the Rotation Tracks.  Preliminary conclusions will be drawn as to what categorical magnitude of Rotation Track value corresponds with the issuance of a tornado warning. If time permits, final warning expiration for individual tornadoes will also be compared to the Rotation Tracks values.