Colloquium Archive

Wednesday, September 9th
Physics & Astronomy Department Afternoon Tea

4:00pm
Tome Hall 2nd Floor Lounge Area

Thursday, November 12th
Lydia Spychalla, Graduate Student
Penn State University
"How does a large hailstone grow? Untangling hail growth pathways in severe storms"

Hail is the most damaging severe storm hazard in the United States. Accurate hail prediction and forecasting is important for the protection of life and property and helps prepare communities for potential hail risk. High-quality hail forecasts require a good understanding of the hail growth processes and storm conditions that produce large hail. However, robust hail science is constrained by hail observing limitations. Most hail goes unobserved after falling far from roads and populations centers, and observed hailstones often melt substantially on the ground before being measured. Growing hailstones are practically impossible to observe because of the danger of flying into severe storms. To combat these observational limitations, hail trajectory models have been developed to simulate the growth and fall of hailstones that cannot be reliably observed in the real world. Hail trajectory models have identified multiple unique pathways to large hail growth in supercell storms. These hail growth pathways are explored in a high-resolution storm simulation, and the contribution of three pathways to bulk hail production is analyzed: The classical pathway produces the majority of small hailstones; the anti-cyclonic pathway produces fewer, but larger hailstones; and a two-stage pathway produces extremely rare, but extremely large hailstones. In a second simulation, the giant (D > 10 cm) hail trajectories are explored, revealing the storm features responsible for opening and closing a left-turning hail growth pathway that produces giant hail.

Noon
Tome 115
Lunch provided