Genesis and persistence of Hurricane Nadine (2012) provides multiple opportunities for in situ sampling by unmanned aircraft

The genesis of Hurricane Nadine (2012) in the tropical East Atlantic was preceded by the merger of three previously identified pouches associated with easterly waves emerging from West Africa. The merger occurred in two stages, with the pairing of two comparable waves in the moist southern storm track, followed by a lop-sided entrainment of a third wave, and coincidentally, the entrainment of cyclonic vorticity originating in the dry northern storm track. The combined anomaly approached the central Atlantic as one entity, but according to analyzed vorticity fields, merger on the day of genesis was not yet complete in the mid-troposphere. Following genesis, Nadine underwent a period of intensification, weakening, and re-intensification, lasting altogether nearly a month, becoming one of the longest lived Atlantic hurricanes. Fortuitously, Nadine provided a suitable target for multiple flights of the unmanned Global Hawk during the first year of the ongoing NASA HS3 airborne field campaign. The results of airborne sampling, meteorological analyses, and geostationary imagery document various stages of development and intensity variation. These stages include (i) an initial interaction with the Saharan Air Layer prior to genesis, and (ii) some unusual interactions with the Dynamic Tropopause following re-intensification, with downstream effects subsequently, including a pair of weather disturbances in western Europe. The atypical longevity of Nadine and her ability to resist extratropical transition in the latter stage was due largely to the parity of Nadine's middle tropospheric intensity, on the one hand, and the relatively weak DT anomalies, on the other hand. Re-intensification of Nadine occurred despite a secular cooling trend of SST in this region. Data throughout the storm lifecycle are analyzed in a pseudo-Lagrangian coordinate system derived from a translating stream function in the wave-relative frame, with horizontal translation velocity chosen to optimize agreement with the observed Lagrangian coherent structure associated with Nadine. Bulk measures of circulation, horizontal deformation, and Lagrangian Okubo-Weiss parameter are documented for this event, which will be included in the suite of pouch products available for use in future hurricane seasons.