On the Structure of Hurricanes in the Upper Troposphere and Lower Stratosphere1

A synoptic study of a number of hurricanes at the time of landfall is described with particular reference to the thermal and wind structure in the upper troposphere and lower stratosphere. It is shown that the low pressure core of the mature hurricane, before recurvature, extends not only throughout the troposphere but sometimes protrudes into the lower stratosphere up to about 27 km., the upper limit of this investigation. The upper core is found to be cold above 15 km. with temperatures occasionally 8°–10° C. below normal at the tropopause Level. A peripheral ridge and a peripheral jet in the upper troposphere are described, and the possible role of these features, as well as of the cold core, in the hurricane mechanism is discussed. It is suggested that the cold core may be caused by forced ascent above the well-known warm core of the hurricane. It is also shown that a hurricane which has recurved and become embedded in the extratropical westerlies may not have an upper cold core and its structure closely corresponds to the classical model. Tentative schematic models of the distribution of temperature and height anomalies are indicated in the case of a mature hurricane before recurvature.