Recurving tropical cyclones and downstream impacts as revealed by singular vectors

The impact of recurving tropical cyclones on mid-latitude predictability is examined using singular vector (SV) diagnostics. The leading SVs provide the fastest growing perturbations (in a tangent linear sense) to a given forecast trajectory. For this particular application, SVs are constrained to provide the initial perturbations to which the tropical cyclones are most sensitive, as well as providing the initial perturbations to which the down-stream mid-latitude flow is most sensitive. This allows for an investigation of the interactions between the tropical cyclone and the mid-latitude flow both before and after extratropical transition. SVs are calculated about the Navy Operational Global Atmospheric Prediction System (NOGAPS) operational forecasts for several cases of interest. Preliminary results indicate heightened midlatitude forecast sensitivity that propagates downstream from the extratropical transition region, with significant case-to-case variability. Detailed analysis of the SV sensitivity patterns associated with different storms will be presented. Implications for adaptive observing and ensemble design will be discussed.