Vertical Circulation and Release of Kinetic Energy during the Development of Hurricane Hazel into an Extratropical Storm

The thermal structure of the atmosphere over the eastern and central parts of the U. S. on October 15, 1954, when the tropical hurricane “Hazel” entered the American continent and rapidly was transformed into an extratropical cyclone of great intensity, is analyzed by the aid of upper air charts and vertical cross sections. The field of divergence and vertical velocity is determined from the horizontal wind field at different levels for the synoptic time October 15, 1500 GCT, and the results are used for computing the precipitation in the region of strongest ascent of the warm and moist air of the tropical disturbance and for a determination of the release of kinetic energy in the whole region due to vertical solenoidal circulations associated with the general sinking of the cold polar air masses and the simultaneous ascent of the warm tropical air masses. The production of kinetic energy is also computed directly from the work done by the horizontal pressure forces in the same area. Both methods give a production of kinetic energy of about 19 × 10¹⁰ kilojoules or 19 × 10²⁰ ergs per second over an area 366 × 10⁴ km² large. Only a small part of the energy released is again dissipated due to friction in the same area, whereas the essential part is exported outwards from the source region, thus furnishing the surrounding atmosphere with large amounts of kinetic energy.

In the last section some general conclusions are made concerning the budget of kinetic energy in the whole Northern Hemisphere, considering the net effect of the disturbances in the westerlies, the mean meridional circulations, the mean meridional flux of kinetic energy and the frictional dissipation.