Stratospheric zonal wind and temperature oscillations observed in a 30 day time series of four times per day radiosonde data taken as part of Nauru99 show a strong negative quadrature relationship at periods of 9.5 days and 5 days. The 9.5-day waves have vertical wavelength of about 4.5 km, and are deduced to be Kelvin waves of zonal wave number 2; the 5-day waves have vertical wavelengths in the range of 3--4.5 km, and are deduced to be Kelvin waves of zonal wavenumber 4. Vertical momentum fluxes associated with the 9.5- and 5-day modes are estimated to be 1¿10-4 m2s-2 and 2¿10-4 m2s-2, respectively, in the 20--25 km altitude range where the mean zonal flow is characteristic of the westerly phase of the quasi-biennial oscillation (QBO). These are an order of magnitude smaller than momentum fluxes associated with traditional wavenumber 1 Kelvin waves analyzed in the easterly phase of the QBO. ¿ 2001 American Geophysical Union