Articles | Volume 16, issue 13
Atmos. Chem. Phys., 16, 8511–8519, 2016
https://doi.org/10.5194/acp-16-8511-2016
Atmos. Chem. Phys., 16, 8511–8519, 2016
https://doi.org/10.5194/acp-16-8511-2016

Research article 13 Jul 2016

Research article | 13 Jul 2016

Why did the storm ex-Gaston (2010) fail to redevelop during the PREDICT experiment?

Thomas M. Freismuth1, Blake Rutherford2, Mark A. Boothe1, and Michael T. Montgomery1 Thomas M. Freismuth et al.
  • 1Naval Postgraduate School, Monterey, CA, USA
  • 2Northwest Research Associates, Redmond, WA, USA

Abstract. An analysis is presented of the failed re-development of ex-Gaston during the 2010 PREDICT field campaign based on the European Centre for Medium Range Weather Forecast (ECMWF) analyses. We analyze the dynamics and kinematics of ex-Gaston to investigate the role of dry, environmental air in the failed redevelopment. The flow topology defined by the calculation of particle trajectories shows that ex-Gaston's pouch was vulnerable to dry, environmental air on all days of observations. As early as 12:00 UTC 2 September 2010, a dry layer at and above 600 hPa results in a decrease in the vertical mass flux and vertical relative vorticity. These findings support the hypothesis that entrained, dry air near 600 hPa thwarted convective updraughts and vertical mass flux, which in turn led to a reduction in vorticity and a compromised pouch at these middle levels. A compromised pouch allows further intrusion of dry air and quenching of subsequent convection, therefore hindering vorticity amplification through vortex tube stretching. This study supports recent work investigating the role of dry air in moist convection during tropical cyclogenesis.

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Numerical model analyses are used to investigate the role of dry, environmental air in the failed redevelopment of a tropical cyclone (ex-Gaston, 2010). As early as 12:00 UTC 2 September 2010, a dry layer at and above 600 hPa results in a decrease in the vertical mass flux and vertical, relative vorticity. The intrusion of dry air led to a reduction in vorticity and a compromised pouch at these middle levels. This study supports work looking at the role of dry air in moist convection.
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