The Influences of the North Atlantic Subtropical High and the African Easterly Jet on Hurricane Tracks During Strong and Weak Seasons

• Main Author: Messier, Hannah
• Format: Text
• Language: unknown
• Published: Iowa State University Digital Repository 2018
• Subjects: Meteorology; Nash; North Atlantic
• Online Access: https://lib.dr.iastate.edu/mteor_stheses/40; https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1044&context=mteor_stheses

The summertime behavior of the North Atlantic Subtropical High (NASH), African Easterly Jet (AEJ), and the Saharan Air Layer (SAL) can provide clues about key physical aspects of a particular hurricane season. More accurate tropical weather forecasts are imperative to those living in coastal areas around the United States to prevent loss of life and property. This study aims to decipher NASH, AEJ, and SAL and discover how they vary between a strong (10 or more hurricanes developed) and a weak (5 or fewer hurricanes developed) hurricane season. This study was accomplished by looking at two strong seasons (2005 and 2017) and two weak seasons (1997 and 2009). Then 850 mb heights were plotted for every 10 days during a season to understand how NASH progressed throughout the season. NASH was also averaged over each season. The strong and weak years were also combined and averaged over to compare the strong and weak seasons. It was discovered that looking at NASH over an entire season was not a good indicator of hurricane trajectories over an entire season. However, hurricanes followed NASH’s anticyclonic flow at the time that it propagated through the Atlantic. In addition, NASH was significantly stronger in the eastern United States and the northern Atlantic during strong years compared to weak years. The AEJ was centered to the south (north) during strong (weak) years. Results also revealed that the AEJ was weaker (stronger) during strong (weak) years. SAL also lasted longer and spread further into the Atlantic during weak years compared to strong years. The significance of this finding was verified using a statistical significance test. Therefore, meteorologists can use NASH’s and the AEJ’s position and reach, to determine the number of hurricanes in a season as well as where these storms will propagate.