The life cycles of short baroclinic waves are investigated with the in
tention of completing a simple classification of nonlinear equilibrati
on scenarios. Shea waves become important in moist environments as lat
ent heating reduces the scale of maximum baroclinic instability. Long-
wave life cycles (wavenumber 6) were previously found to depend on det
ails of the low-level momentum fluxes established during the earliest
stages of development. These fluxes also serve as a focal point for th
e present study. For a realistic, zonally symmetric jet on the sphere,
the normal mode life cycle of a short wave (wavenumber 8) under both
dry and moist conditions is described. Latent heating intensifies the
low pressure system and frontal zones but does not alter the broader d
etails of the life cycle. The normal modes have predominantly equatorw
ard momentum fluxes, in contrast to the mainly poleward momentum fluxe
s of long waves. The short waves are more meridionally confined. The e
quatorward momentum fluxes direct the waves toward cyclonic breaking.
The feedback with the zonal mean wind, the so-called barotropic govern
or, is less effective than in the standard long-wave life cycle, which
ends in anticyclonic breaking. However, in contrast to long-wave life
cycles that are ''engineered'' to produce equatorward momentum fluxes
, relatively little potential vorticity and surface temperature anomal
y roil up into isolated vortices. Therefore, the short wave undergoes
protracted barotropic decay leading to complete zonalization. Short wa
ves also have a brief period of baroclinic decay due to cold advection
over the surface cyclones. Eliassen-Palm cross sections for the short
-wave life cycles show the usual combination of upward and meridional
propagation of wave activity. However, the meridional propagation is m
ainly toward the pole and there is a consequent zonal-mean deceleratio
n at high latitudes. These details are included in the proposed classi
fication of equilibration scenarios.