Comparison of Wave Packets associated with Extratropical 1 Transition and Winter Cyclones

5 Developing wave packets associated with the extratropical transition (ET) of tropical cy6 clones and winter cyclones in the Western North Pacific (WNP) and Atlantic basins are 7 diagnosed observationally by compositing reanalysis data over a 32 year period. While the 8 development of winter cyclones amplifies a weaker wave packet moving through the mid9 latitude storm track, there is no indication of an upstream disturbance during ET; thus, 10 on average, the wave packet is generated by the ET process. In the WNP, ET and winter 11 cyclone wave packets have comparable group velocity and amplitude relative to climatology, 12 whereas ET wave packets have relatively longer wavelength and near-zero group velocity 13 during the ET process; ET events also have a detectable signal further downstream. Wave 14 packets associated with winter cyclones in the Atlantic basin have greater amplitude and 15 have a detectable signal further downstream relative to those associated with ET. Near the 16 surface, winter cyclones are characterized by larger meridional heat fluxes relative to ET. 17 WNP ET cyclones are characterized by larger meridional moisture flux convergence and 18 thus latent heat release relative to their winter counterparts, while Atlantic basin ET and 19 winter cyclones have similar moisture flux convergence. This result suggests that the wave 20 packets associated with ET cyclones are related to diabatic processes and could explain why 21 the amplitude of Atlantic basin ET wave packets are smaller than winter cyclones. Finally, 22 the greater baroclinicity during winter does not seem to influence the downstream packet 23 amplitude in either basin. 24