Thermodynamic Contribution to Vortex Alignment and Rapid Intensification of Hurricane Sally (2020)

As a part of the Tropical Cyclone Rapid Intensification Project (TCRI), observations were made of the rapid intensification of Hurricane Sally (2020) as it passed over the Gulf of Mexico. High-altitude dropsondes and radar observations from NOAA’s Gulfstream IV, radar observations from WP-3D aircraf...

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Bibliographic Details
Published in:Monthly weather review 2023-04, Vol.151 (4), p.931-951
Main Authors: Stone, Željka, Alvey, G. R., Dunion, J. P., Fischer, M. S., Raymond, D. J., Rogers, R. F., Sentić, S., Zawislak, J.
Format: Article
Language:English
Subjects:
Aircraft
Alignment
Altitude
Amplification
Convective instability
Cyclones
Dropsondes
Dynamic stability
Entropy
Environmental conditions
Equilibrium
Fluctuations
High altitude
High-altitude environments
Humidity
Hurricanes
Hypotheses
Lightning
Lightning strikes
Mass
Mass flux
Precipitation
Radar
Radar data
Radar imaging
Radar networks
Relative humidity
Satellite data
Satellite imagery
Satellites
Saturation
Simulation
Temperature
Thermodynamics
Time series
Tropical cyclones
Variables
Vertical shear
Vortices
Vorticity
Wind
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Summary:As a part of the Tropical Cyclone Rapid Intensification Project (TCRI), observations were made of the rapid intensification of Hurricane Sally (2020) as it passed over the Gulf of Mexico. High-altitude dropsondes and radar observations from NOAA’s Gulfstream IV, radar observations from WP-3D aircraft, the WSR-88D ground radar network, satellite images, and satellite-detected lightning strikes are used to apply recently developed theoretical knowledge about tropical cyclone intensification. As observed in many other tropical cyclones, strong, bottom-heavy vertical mass flux profiles are correlated with low (but positive) values of low- to midlevel moist convective instability along with high column relative humidity. Such mass flux profiles produce rapid spinup at low levels and the environmental conditions giving rise to them are associated with an intense midlevel vortex. This low-level spinup underneath the midlevel vortex results in the vertical alignment of the vortex column, which is a key step in the rapid intensification process. In the case of Sally, the spinup of the low-level vortex resulted from vorticity stretching, while the spinup of the midlevel vortex at 6 km resulted from vorticity tilting produced by the interaction of convective ascent with moderate vertical shear.
ISSN:0027-0644
1520-0493
DOI:10.1175/MWR-D-22-0201.1