  This work examines the breakup of a single drop of various low viscosity
fluids as it deforms in the presence of continuous horizontal air jet. Such a
fragmentation typically occurs after the bulk liquid has disintegrated upon
exiting the atomizer and is in the form of an ensemble of drops which undergo
further breakup. The drop deformation and its eventual disintegration is
important in evaluating the efficacy of a particular industrial process, be it
combustion in automobile engines or pesticide spraying in agricultural
applications. The interplay between competing influences of surface tension and
aerodynamic disruptive forces is represented by the Weber number, $We$, and
Ohnesorge number, $Oh$, and used to describe the breakup morphology. The
breakup pattern considered in our study corresponds to that of a bag attached
to a toroidal ring which occurs from $12 < We < 16$. We aim to address several
issues connected with this breakup process and their dependence on $We$ and
$Oh$ which have been hitherto unexplored. The $We$ boundary at which breakup
begins is theoretically determined and the expression obtained, $We = 12(1 +
2/3Oh^2)$, is found to match well with experimental data available in
literature. An exponential growth in the radial extent of the deformed drop and
the streamline dimension of the bag is predicted by a theoretical model and
confirmed by experimental findings. These quantities are observed to strongly
depend on $We$. However, their dependence on $Oh$ is weak.
