Why
does hail form and how does hail form?
GRAPEFRUIT SIZED
Monday, April 5th 2004 SEVERE WEATHER STATEMENT NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX 640 PM CDT MON APR 5
2004 ...
AT 620 PM CDT... A SPOTTER REPORTED
GRAPEFRUIT SIZED HAIL
Aggregate hailstone. Large hailstone with smaller stones visible. Ruler shows radius of
this remarkable hail stone. Diameter is approximately 6 inches - the size of a
grapefruit.
Credit: NOAA Photo Library, NOAA Central Library
How does large hail form or why does hail form?
People may not be used to seeing hail at their
summerhouses, but
during a thunderstorm hail can be a very common thing in some areas.
Hail is formed from updrafts within
thunderstorms
as it pushes rain high into the cloud where very cold air freezes
it. Once frozen it starts to fall but gets caught in another strong updraft where it
gathers more moisture on its way back up making it larger. If the updrafts are strong
enough they will continue this process for long periods of time allowing the hail to
accumulate more moisture and more moisture. In a severe thunderstorm downdrafts may act
like a wedge and increase the intensity of the updraft. Updrafts can get so strong
they even intrude into the stable stratosphere. When updrafts are this strong it
becomes possible to suspend large hail for long periods of time further adding moisture to
the hail, sometimes building it to incredible sizes. Updraft winds can be from 100 to 120
miles per hour when producing baseball and larger size hail.
 Watch this
movie of hail forming in an thunderstorm. It gives you a good idea of where it will fall
in relationship to where the tornado will drop in a severe storm.
|
When large hail falls with strong winds, it can become a deadly projectile. Ranchers
across America tell stories about hail storms that had killed their cattle because they
were trapped in an open field during a thunderstorm. Scientists commissioned by the
National Geographic television channel studying the remains of 200 people buried in
Himalayas dating from the 9th century found that Giant hail apparently killed them.
According to the Guinness Book of World Records, the heaviest hailstones on record
weighed up to 2.2lb and killed 92 people in Bangladesh in 1986. |
|
Hailstone size |
Size |
Updraft Speed |
| in. |
mph |
| bb |
< 1/4 |
< 24 |
| pea |
1/4 |
24 |
| marble |
1/2 |
35 |
| dime |
7/10 |
38 |
| penny |
3/4 |
40 |
| nickel |
7/8 |
46 |
| quarter |
1 |
49 |
| half dollar |
1 1/4 |
54 |
| walnut |
1 1/2 |
60 |
| golf ball |
1 3/4 |
64 |
| hen egg |
2 |
69 |
| tennis ball |
2 1/2 |
77 |
| baseball |
2 3/4 |
81 |
| tea cup |
3 |
84 |
| grapefruit |
4 |
98 |
| softball |
4 1/2 |
103 |
|
