MEDIUM-SCALE TRAVELING WAVES OVER THE NORTH-ATLANTIC

An analysis is made, with the aid of ECMWF operational data, of medium -scale, eastward-traveling waves in the mid-latitude upper troposphere over the north Atlantic area asa counterpart of the similar analysis of Sate et al. (1993) for the medium-scale waves over Japan. It is sho wn that the waves dominate in wintertime (January and February of 1990 ) over the north Atlantic centered around 50 degrees N, with the typic al wavelength of 2400 km, a period of 33 hours, and hence an eastward phase velocity of about 20 m s(-1). In view of their vertical structur e and relationship to the background zonal flow, it is concluded that the wave character obtained in this analysis is the same in essence as that shown by Sate ct al. (1993).