Tuesday, 19 April 2016
Plaza Grand Ballroom (The Condado Hilton Plaza)
A recurving tropical cyclone (TC) can disturb the extratropical flow resulting in amplification of downstream Rossby waves and a degradation of medium-range forecast skill. These features have been demonstrated previously through case study analysis (e.g., Grams et al., 2011, QJRMS) and in a North Pacific climatology (Achambault et al., 2013, MWR). This paper presents a climatology of recurving TCs and the associated extratropical response in the North Atlantic using ECMWF operational analysis. The overarching objective of this investigation is to determine not only whether the extratropical jet is disturbed, but also by what mechanisms is the disturbance achieved. Is the disturbance accomplished by a local disturbance to the jet or by a modification to the potential vorticity gradient across a broad section of the jet? Preliminary analysis reveals that, on average, the Rossby wave pattern is amplified for several days following TC recurvature. The amplification is significantly correlated to the TC minimum pressure as well as to the spatial phasing between the recurving TC and the nearest pre-existing trough in the extratropical flow. Specifically, TCs with lower minimum pressure and/or recurving on the downstream side of a pre-existing trough resulted in the largest amplification of the Rossby wave pattern. Significant correlation to Rossby wave amplitude was not found for TC wind speed, latitude of recurvature, or month of year.
- Indicates paper has been withdrawn from meeting
- Submission entered in competition