Examining Asymmetric Precipitation Processes and Vertical Wind Shear in Typhoon Nesat (2017)
Open Access
- Author:
- Tenembaum, Katriella
- Graduate Program:
- Meteorology and Atmospheric Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 05, 2023
- Committee Members:
- Anthony Carl Didlake, Jr., Thesis Advisor/Co-Advisor
Yunji Zhang, Committee Member
David Stensrud, Program Head/Chair
Kelly Lombardo, Committee Member - Keywords:
- Tropical Cyclone
vertical wind shear
precipitation
Nesat 2017 - Abstract:
- Tropical cyclones (TCs) can produce heavy precipitation which can be difficult to predict. Asymmetric structures in TCs are prominent features, and understanding how these asymmetric precipitation patterns can form and vary is critical for forecasting TC rainfall. This study analyzes the characteristics and variability of precipitation asymmetries in TCs of different intensities using an ensemble model run of Typhoon Nesat (2017) that was run in preparation for the NSF PRECIP field campaign. Given that a TC’s precipitation is affected by the environmental deep-layer vertical wind shear, further study of the effects of vertical wind shear on TC precipitation will be helpful in further elucidating the interactions between the asymmetry and the important precipitation forcing mechanisms. This work analyzes the processes and variability of shear/precipitation interactions in ensemble members that are divided into three groups of storm intensity. It is found that more intense storms tend to have lower shear magnitude and more precipitation before landfall and vice versa. While rain rates tended to be similar, the increase in precipitation before landfall is due to variations in the track trajectory as a result of the stronger storm intensities. In the eyewall the precipitation maxima tends to be left of shear, and for the rainbands it tends to be right of shear. This is due to the tilt of the vortex leading to potential temperature and potential vorticity anomalies leading to increased updrafts. Composites of the ensemble were examined and they support the previous conclusions and prior research.