  Transient luminous events (TLEs) is the collective name given to mesospheric
electrical breakdown phenomena occurring in conjunction with strong lightning
discharges in tropospheric thunderstorms. They include elves, sprites, haloes
and jets, and are characterized by short lived optical emissions, mostly of red
(665 nm) and blue (337 nm) wavelengths. Sprites are caused by the brief
quasi-electrostatic field induced in the mesosphere, mostly after the removal
of the upper positive charge of the thundercloud by a +CG, and they have been
recorded above most of the lightning activity centers on Earth. In wintertime,
there are just a few areas where lightning occurs, and of those, sprites have
been observed over the Sea of Japan, the British Channel, and the Mediterranean
Sea. Unlike their summer counterparts, winter thunderstorms tend to have weaker
updrafts and as a result, reduced vertical dimensions and compact charge
structures, whose positive and negative centers are located at lower altitudes.
These storms are often susceptible to significant wind shear and as a result
may exhibit a tilted dipole charge structure and a lateral offset of the upper
positive charge relative to the main negative charge. We present results of
numerical simulations using a three-dimensional explicit formulation of the
mesospheric electrostatic electrical field following a lightning discharge from
a typical mid-latitude winter thunderstorm exhibiting tilt due to wind shear
and evaluate the regions of possible sprite inception. Our results show, as
numerous observations suggest, that sprites can be shifted a large distance
from the location of the parent +CG in the direction of the shear and will
occur over a larger region compared with non-sheared storms.
