Monthly mean values of temperature from both hydrographic and XBT casts are used to compute isotherm displacements at weather station November (30N, 140W) and at six 2-degree squares between Hawaii and the weather station. A composite spectrum computed from all the isotherms in the six 2-degree squares shows significantly higher potential energy in the frequency range below the theoretical cut-off frequency (corresponding period about five months) for baroclinic Rossby waves....