Publication Date

Fall 2020

Degree Type


Degree Name

Master of Science (MS)


Meteorology and Climate Science


Sen Chiao


Atlantic, dry air, hurricane, reanalysis data, storm track, tropical cyclone

Subject Areas



This study aims to understand how often dry air occurs or co-exists with a tropical cyclone (TC) and to what degree dry air will affect the way the TC proceeds. Four tropical cyclones of 2015 were chosen: Hurricane Fred, Hurricane Danny, Tropical Storm (TS) Grace and Tropical Depression (TD) 9 as their formation and tracks were located within the eastern Atlantic Ocean region. Relative humidity (RH) from MERRA-2 and NCEP-FNL datasets were compared within 3 days of the highest storm status and looking forward 3 days on the storm path. Results at 700 hPa suggested that dry air (≤30% RH) tended to precede TCs regardless of final intensity status. Hurricane Danny showed dry air transpiring earlier by at least 2 days before hurricane status was declared. Dry air occurred closer to the time point observed but further down the future storm path for TD9 and TS Grace. For Hurricane Fred, dry air was more frequently observed closer to the actual time point and physical location on the storm path compared to Hurricane Danny. Results from this study may help to provide early warning guidance on TC formation and tracks.