The evolution of Hurricane Humberto (2001)

Abstract

The causes of intensity change in tropical cyclones have continued to be a major challenge for the meteorological community. A lack of sampling throughout the life cycle of a tropical cyclone has contributed to our lack of understanding. In September of 2001, NOAA and NASA marshaled their resources and deployed over 200 Global Positioning System dropwindsondes within a 300 km radius of Tropical Cyclone Humberto on 3 consecutive days in the Convection and Moisture Experiment. This dissertation presents the results of an observational study of the aforementioned storm, combining aircraft data with the Global Positioning System dropwindsondes, airborne expendable bathythermographs, lower fuselage, and tail radar. Kinematic and thermodynamic structures are examined in an attempt to better understand intensification processes for a high latitude storm traveling over a variable SST field, in a dry environment, and under increasing vertical wind shear. As Humberto is sampled as a tropical storm, the warm core develops from an area of subsidence on the trailing edge of an anvil. This warming acts to cap the boundary layer and allows for an increase in the energy content under the nascent eye. Throughout the experiment, thermodynamic and kinematic variables exhibit persistent relationships with the vertical wind shear vector. Vertical cross-sections of the warm core show that it has the highest temperature perturbation in the lower troposphere, contrary to past observations and theory. The present study investigates the evolution of an asymmetric system and the causes for the unusual warm core structures.