Structural changes of a tropical cyclone (TC) during extratropical transition (ET) cause high impact weather. One of the primary goals of the THORPEX-Pacific Asian Regional Campaign (T-PARC) in 2008 was to obtain insights into the various physical processes that account for these structural changes. During this campaign one of the major typhoons in the West Pacific in 2008 -Typhoon Sinlaku- was investigated from tropical cyclogenesis until ET.
As Sinlaku approached the midlatitude baroclinic zone a strong convective system developed in the vicinity of the transitioning typhoon. Research flights with the NRL-P3 and the USAF-C130 aircrafts captured unique observations of the detailed structure of this convective event during ET using the Dual-Doppler-Radar ELDORA and dropsondes. The observational data are assimilated with the recently developed Spline Analysis at Mesoscale Utilizing Radar and Aircraft Instrumentation (SAMURAI) software tool at 4 km horizontal resolution. The obtained SAMURAI analysis enables us to identify deep convection, a stratiform region, warm- and cold frontal structures, and a dry intrusion in the vicinity of the transitioning TC. Q-vector diagnostics indicate that forced ascent in a potentially unstable environment triggers the deep convection.
Strong potential vorticity production by latent heat release within the deep convection leads to a deformation of Sinlaku's wind field and presumably favors the cyclone's decay. Finally, a validation of the ECMWF operational analysis against the SAMURAI analysis identifies remarkable differences with respect to the representation of the convective event.
Structural characteristics of Typhoon Sinlaku (2008) during its extratropical transition: an observational study