NWS completes hail report: Mount Pulaski wins for biggest

[August 24, 2011]  A vigorous upper-level disturbance tracked across central Illinois during the afternoon of Aug. 13, triggering scattered strong to severe thunderstorms. The National Weather Service in Lincoln received numerous reports of hail between 2 p.m. and 6 p.m., mainly along and north of a line from Jacksonville to Danville.

The largest hail fell across southern Logan County at around 4:30 p.m., when a weather observer from Mount Pulaski noted tennis ball-sized stones (2.5-inch diameter) at his location. Several cars suffered damage due to the hail. Other large hail was noted across portions of Morgan County, where golf ball-sized stones (1.75-inch diameter) created significant crop damage near the town of Pisgah, and across southern Peoria County, where pingpong ball-sized hail (1.5-inch diameter) caused car and shingle damage just north of Mapleton.

Cold air aloft created a moderately unstable environment characterized by convective available potential energy values of 1,500 to 2,500 joules per kilogram. In addition, a weather balloon launched by the NWS in Lincoln at 6 p.m. indicated a relatively low freezing level of around 12,500 feet, as well as steep low-level lapse rates. These conditions allowed the thunderstorms that formed across the area to develop strong updrafts capable of supporting large hail.

See list of the Aug. 13 hail reports below.

[Text from National Weather Service report]

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Preliminary local storm report summary

National Weather Service, Lincoln
7:22 p.m. Aug. 13

Time	Hail size	Place	Source
2:05 p.m.	1 inch	2 mi. S of Bartonville, Peoria County	Emergency manager
2:49 p.m.	1 inch	Pekin, Tazewell County	Emergency manager
2:51 p.m.	0.75 inch	Pekin, Tazewell County	Emergency manager
3 p.m.	1 inch	Pekin, Tazewell County	Trained spotter
3:01 p.m.	0.88 inch	4 mi. SE of Pekin, Tazewell County	Emergency manager
Reported halfway between Pekin and Tremont.
3:06 p.m.	0.75 inch	2 mi. SW of Pekin, Tazewell County	Emergency manager
Dime-size hail at Powerton power station.
3:09 p.m.	1.5 inch	1 mi. N of Mapleton, Peoria County	Trained spotter
Hail lasted about 2-3 minutes. Four cars damaged and several houses with shingle damage from hail.
3:13 p.m.	0.75 inch	5 mi. SE of Morton, Tazewell County	Emergency manager
3:16 p.m.	0.75 inch	3 mi. S of Morton,  Tazewell County	Emergency manager
Dime-size hail at Interstate 155 and Birchwood.
3:20 p.m.	1 inch	Pekin, Tazewell County	Emergency manager
3:37 p.m.	0.75 inch	3 mi. SE of Morton, Tazewell County	Trained spotter
Hail lasted for 2 minutes.
3:42 p.m.	1 inch	5 mi. SE of Morton, Tazewell County	Emergency manager
Quarter-size hail at the corner of Allentown Road and Herberger.
3:43 p.m.	1 inch	2 mi. S of Philadelphia,  Cass County	Mesonet SWOP report.
3:50 p.m.	1.25 inch	1 mi. NW of Jacksonville, Morgan County	CoCoRaHS
Pea-size to half dollar-sized hail.
3:53 p.m.	0.75 inch	Armington, Tazewell County	Emergency manager
Hail at corner of Monroe Street and Armington Road.
3:55 p.m.	1.75 inch (est.)	6 mi. NW of Franklin, Morgan County	Mesonet
Significant crop damage to a bean field near the town of Pisgah.
4:08 p.m.	0.75 inch	2 mi. E of Bloomington, McLean County	NWS employee
Penny-sized hail with estimated 40 mph wind gust.
4:08 p.m.	0.88 inch	2 mi. W of Springfield, Sangamon County	Trained spotter
Penny- to nickel-sized hail on the west side of Springfield.
4:25 p.m.	0.88 inch	1 mi. SW of Loami, Sangamon County	Emergency manager
4:30 p.m.	0.75 inch	Clinton, DeWitt	Emergency manager
4:34 p.m.	1.25 inch	Mount Pulaski, Logan County	Co-op observer
4:37 p.m.	2 inch (est.)	Mount Pulaski, Logan County	Co-op observer
4:38 p.m.	2.5 inch	Mount Pulaski, Logan County	Co-op observer
Several cars damaged in town, and bean fields southwest of town also damaged.
4:42 p.m.	1.5 inch	Elkhart, Logan County	Emergency manager
4:45 p.m.	1.25 inch	3 mi. SE of Auburn, Sangamon County	Emergency manager
4:50 p.m.	0.75 inch	Divernon, Sangamon County	Law enforcement
5:02 p.m.	1.5 inch	Latham, Logan County	Emergency manager
5:30 p.m.	0.75 inch	1 mi. N of Chatham, Sangamon County	CoCoRaHS

(Hail sizes listed above are measured figures unless otherwise noted.)

Hail diameter	Description
1/4 inch	Pea
1/2 inch	Plain M&M
3/4 inch	Penny
7/8 inch	Nickel
1 inch (severe)	Quarter
1 1/4 inch	Half dollar
1 1/2 inch	Walnut, pingpong ball
1 3/4 inch	Golf ball
2 inch	Hen egg, lime
2 1/2 inch	Tennis ball
2 3/4 inch	Baseball
3 inch	Teacup, large apple
4 inch	Grapefruit
4 1/2 inch	Softball
4 3/4 - 5 inch	Computer CD-DVD

[From National Weather Service report]