Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Hemispheric Hail Shape 
Name: William
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A
Question:
We live in the Appalachian Mountains. After a bad storm, we found hail in the shape of hemispheres: round on one side and flat on the other. Why this shape?

Replies:
William,

The round side is the one that was facing the ground as the hail fell downwards in a fairly non-turbulent area of the cloud. The hailstone develops a preferential fall orientation as more ice accumulates on it, making the round side heavier and more aerodynamic than the other side. Therefore, that side continues to face downwards each time that the hailstone drops through the cloud, throughout its lifetime of being repeatedly carried aloft and dropped. Once the hailstone becomes too heavy to be lifted or the updrafts in the storm weaken, the hail falls to the ground with the rounded shape on the bottom and flat (or sometimes a scooped out bowl) shape on top.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory

Click here to return to the Weather Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory