Northwestward-Propagating Wave Patterns over the Tropical Western North Pacific during Summer

Abstract The possible relationship between northwestward-propagating wave disturbances and tropical cyclones over the tropical western North Pacific during summer is studied using data assimilated by the navy's global model during May–September 1989–91. A multiple-set canonical correlation (MCC) analysis is applied to the 850-hPa meridional (v) component over a core domain covering the western Pacific. The analysis seeks the maximal geometrically averaged correlation between 12 consecutive twice-daily fields. Two MCC components, with a 90° phase difference and comparable variances that combine to nearly one-third of the total variance, describe the northwestward-propagating pattern with a period near 8–9 days. Upstream of this steady northwestward-propagating pattern there is a weaker, westward propagation along 5°N that may be traced back to 170°E. The surface pressure cell advancing east of the Philippines is consistent with low-level winds for a circulation in gradient wind balance. It has a zonal wave...