Analysis of operational model forecast trends in extratropical transition storm structure

The cyclone structure life-cycle of tropical cyclones (TC) undergoing extratropical transition (ET) in the North Atlantic is discussed. An inspection of AVN analysis and forecast fields suggests that model representation of cyclone structure is impacted both by model biases and by bogus vortex insertion. The AVN appears to systematically overdevelop the lower tropospheric warm core of TC before ET. For cyclones undergoing ET, the inclusion of a synthetic vortex delays the transition of the cyclone's warm core structure to cold core and thus plays a role in the evolution of ET.