Tropical Storm, Mid-Latitude Cloud-Band Connections and the Autumnal Buildup of the Planetary Circulation

Abstract

Satellite photographs have revealed the occasional existence of broad and extensive cloud bands reaching from tropical storms northeastward into the westerlies of middle latitudes. Fourteen well-defined cases of such cloud connections from western North Pacific tropical storms in the autumns of 1967, 1968 and 1969 are examined with respect to the large-scale circulation. The composited data show that the 300-mb westerlies over the North Pacific increase for several days following the onset of the cloud-band connections. Hemispheric kinetic energy for the whole troposphere tends to increase in similar fashion. These associations suggest that the injection of heat and moisture from tropical cyclones into the middle latitudes plays a significant role in the autumnal buildup of the planetary-scale circulation.