. - Steve Horstmeyer's Severe Weather Primer Part 11- Hail
This is the final post of my 11 part series on severe weather.
***** This is a re-posting of Part 11 of my Severe Weather Primer. At the beginning I have added photos from the large hail that fell in the FOX19 NOW viewing area the evening of October 19, 2016. *****
Hail: Southeast Indiana October 19, 2016
So here is how the biggest hailstone record book stands at of this writing, April 8, 2016:
Heaviest Hailstone: 2.25 pounds, Gopalganj District, Bangladesh, 14 April 1986.
Largest Diameter: 7.9 inches, Vivian, South Dakota, 23 July, 2010.
It would be another 2200 years before the next big step in explaining how growing clouds worked when James Pollard Espy wrote about temperature decrease of rising air in the 1840s.
Aristotle rejected the ideas of Anaxagoras because, he reasoned, that if hail formed high in the cloud it would be found on mountain tops and hail was not found there. Aristotle considered heat and cold to be opposites and in conflict. In warm months because there was so much heat cold air was "squeezed" into small intense concentrations that would freeze the hail. Like most other phenomena in the atmosphere Aristotle was wrong about hail too.
Today we know how hail forms and clues to the process are visible in the image below.
- 1. The layers tell us this hailstone grew by a process where water (frozen and solid) was added incrementally.
- 2. The clear vs. milky ice tell us there are two ways ice is added. Milky white ice, called rime ice, is added through direct deposition from vapor in air colder than freezing. The clear ice is added as a layer of liquid water in warmer regions of the cloud then freezes in colder air.
- 3. The distinct center tells us there was an original object new ice was added to. This is called the hail embryo and can be a small hailstone, an insect, graupel or other object.
- 4. The spikes were probably made of water flowing across the surface of the stone following air flow around the stone as it fell. It seems likely the spikes formed in the up direction as the water was pushed around the falling stone.