Recent updates and extensions to a steady-state two-dimensional linear
ized model of global-scale atmospheric waves have facilitated improved
calculations of the subset of those waves which are subharmonics of a
solar day and propagate with the apparent motion of the sun. The mode
l improvements are briefly described and some updated predictions of t
he migrating solar diurnal component are highlighted. The latter repre
sent the first numerical modeling effort to examine the seasonal varia
bility of the migrating diurnal harmonic as it propagates into the mes
osphere and lower thermosphere.