IJK 2004. Ivan, Jeanne, and Karl: The Trough Triumvirate

The evolution of a strong midlatitude trough and its relationship to three Atlantic hurricanes (2004) is examined with NOGAPS singular vectors and adjoint sensitivity analyses. The extratropical transition of Ivan over the mid-Atlantic US is identified as crucial to the development of a large cut-off low over the Canadian Maritimes. An equatorward extension of this trough dynamically interacted with the “looping” Hurricane Jeanne, aided in intensification, and nearly towed the system across the Atlantic. Similarly, Hurricane Karl rapidly recurved ahead of the trough, underwent a positive trough interaction and intensified before finally transitioning to an extratropical system.

Singular vector calculations based upon a 48-hour forecast error trajectory centered upon Jeanne and Karl each show large perturbation energy growth well away from each respective cyclone center. In conjunction with mesoscale model trajectory analysis, the SV perturbation growth areas match up well with potential vorticity advection directly impacting upon each tropical cyclone. Similarly, adjoint sensitivity to the forecast initial conditions shows strong dynamical signatures along the western periphery of the cut-off trough axis. The sensitivity of tropical cyclones to midlatitude influences is crucial to the forecast of looping tracks, trough interactions, and extratropical transitions.