A lone supercell thunderstorm moved along Highway 18 in northwest Iowa late this morning. This storm produced golf ball sized hail east of Hartley Iowa, with reports of baseball and softball sized hail in Spencer Iowa.
A loop of the radar reflectivity images from 1036 am to 1119 am. Note the "spike" extending east-southeast from the storm cell at times (single image from 1054 am on the right). This feature is known as a three-body scatter spike (TBSS), and indicates the potential for very large hail.
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A simplistic description of a TBSS once provided on a NWS Birmingham webpage explains:
"In brief, simple terms, this is caused by the radar beam hitting the wet hail, scattering to the ground below, then scattering back upward, and finally being scattered once again by the hail aloft. The 3 scatterings illustrate the triple reflection, thus the term 'three-body scatter spike'. "
Basically, the energy that has 'bounced around' as described above, is received back at the radar later than the energy reflected directly back from the storm. The increased time causes the radar to think this energy is coming from a target that is farther away from the radar, thus the reflectivity extending farther beyond the actual storm.
These pictures were sent to us by Curtis Dean of Spencer Iowa:
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Pictures courtesy of Stacey Robinson of Spencer Iowa:
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And these photos were sent in by Rory and Jenn Schuster:
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Here is the preliminary summary of Storm Reports received by the NWS Sioux Falls office for the entire day on Friday, 21 May 2004:
PRELIMINARY LOCAL STORM REPORT ... SUMMARY
NATIONAL WEATHER SERVICE SIOUX FALLS SD
730 PM CDT TUE MAY 25 2004
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION...ST.. ...SOURCE....
..REMARKS..
0110 AM HAIL ELLSWORTH 43.52N 96.02W
05/21/2004 0.88 INCH NOBLES MN LAW ENFORCEMENT
0131 AM HAIL WORTHINGTON 43.63N 95.60W
05/21/2004 1.00 INCH NOBLES MN TRAINED SPOTTER
0132 AM HAIL 5 SE REMSEN 42.76N 95.90W
05/21/2004 0.88 INCH PLYMOUTH IA PUBLIC
0135 AM HAIL 4 SSW MARCUS 42.77N 95.84W
05/21/2004 0.88 INCH CHEROKEE IA PUBLIC
0255 AM HAIL OCHEYEDAN 43.42N 95.54W
05/21/2004 1.00 INCH OSCEOLA IA TRAINED SPOTTER
0300 AM HAIL 2 NW LAKE PARK 43.47N 95.35W
05/21/2004 0.75 INCH DICKINSON IA PUBLIC
0306 AM HAIL HARRIS 43.45N 95.43W
05/21/2004 1.00 INCH OSCEOLA IA BROADCAST MEDIA
0923 AM HAIL 5 SE ROCK VALLEY 43.15N 96.23W
05/21/2004 0.75 INCH SIOUX IA TRAINED SPOTTER
1029 AM HAIL 1 E HARTLEY 43.18N 95.46W
05/21/2004 0.88 INCH O'BRIEN IA TRAINED SPOTTER
1029 AM HAIL HARTLEY 43.18N 95.48W
05/21/2004 0.88 INCH O'BRIEN IA TRAINED SPOTTER
1036 AM HAIL 4 E HARTLEY 43.18N 95.40W
05/21/2004 1.75 INCH O'BRIEN IA CO-OP OBSERVER
1040 AM HAIL 1 NW EVERLY 43.17N 95.34W
05/21/2004 1.75 INCH CLAY IA BROADCAST MEDIA
1051 AM HAIL 5 W SPENCER 43.15N 95.25W
05/21/2004 1.75 INCH CLAY IA BROADCAST MEDIA
1100 AM HAIL SPENCER 43.15N 95.15W
05/21/2004 2.50 INCH CLAY IA TRAINED SPOTTER
1105 AM HAIL SPENCER 43.15N 95.15W
05/21/2004 4.25 INCH CLAY IA BROADCAST MEDIA
FELL ON THE WEST SIDE OF TOWN
1106 AM HAIL SPENCER 43.15N 95.15W
05/21/2004 2.75 INCH CLAY IA BROADCAST MEDIA
FELL ON THE SOUTH SIDE OF TOWN
1115 AM HAIL DICKENS 43.13N 95.02W
05/21/2004 1.75 INCH CLAY IA BROADCAST MEDIA
0350 PM HAIL SMITHLAND 42.23N 95.93W
05/21/2004 0.75 INCH WOODBURY IA PUBLIC
0411 PM HAIL 7 NE REMSEN 42.88N 95.88W
05/21/2004 1.75 INCH PLYMOUTH IA PUBLIC
0414 PM HAIL 5 NNW MARCUS 42.89N 95.85W
05/21/2004 1.50 INCH CHEROKEE IA PUBLIC
QUARTER TO PING PONG BALL SIZE MIXED
0425 PM HAIL 6 WSW PAULLINA 42.95N 95.80W
05/21/2004 1.00 INCH O'BRIEN IA TRAINED SPOTTER
0436 PM HAIL 6 E WASHTA 42.58N 95.60W
05/21/2004 0.88 INCH CHEROKEE IA PUBLIC
0436 PM HAIL 3 N HOLSTEIN 42.53N 95.54W
05/21/2004 0.75 INCH IDA IA PUBLIC
0450 PM HAIL AURELIA 42.71N 95.44W
05/21/2004 1.00 INCH CHEROKEE IA TRAINED SPOTTER
0455 PM HAIL DICKENS 43.13N 95.02W
05/21/2004 0.75 INCH CLAY IA BROADCAST MEDIA
0457 PM HAIL 1 N SUTHERLAND 42.99N 95.50W
05/21/2004 1.75 INCH O'BRIEN IA BROADCAST MEDIA
0500 PM HAIL 4 S HARTLEY 43.12N 95.48W
05/21/2004 1.50 INCH O'BRIEN IA PUBLIC
0517 PM HAIL 1 SE ROYAL 43.05N 95.27W
05/21/2004 1.75 INCH CLAY IA PUBLIC
0519 PM HAIL 2 E ROYAL 43.06N 95.24W
05/21/2004 2.75 INCH CLAY IA TRAINED SPOTTER
0519 PM HAIL 5 S SPENCER 43.07N 95.15W
05/21/2004 4.25 INCH CLAY IA BROADCAST MEDIA
0525 PM HAIL 5 NNE CHEROKEE 42.82N 95.51W
05/21/2004 1.00 INCH CHEROKEE IA TRAINED SPOTTER
0527 PM HAIL 7 SW LINN GROVE 42.82N 95.34W
05/21/2004 1.00 INCH BUENA VISTA IA PUBLIC
MOSTLY 1/2 TO 3/4 INCH HAIL
0530 PM HAIL 7 SE SPENCER 43.07N 95.05W
05/21/2004 1.50 INCH CLAY IA PUBLIC
0550 PM HAIL 5 W WEBB 42.95N 95.11W
05/21/2004 0.75 INCH CLAY IA PUBLIC
0625 PM HAIL 5 NE GILLETT GROVE 43.07N 94.97W
05/21/2004 0.75 INCH CLAY IA PUBLIC
0814 PM HAIL 4 NW ELK POINT 42.72N 96.74W
05/21/2004 1.00 INCH UNION SD AMATEUR RADIO
0818 PM HAIL 6 N ELK POINT 42.77N 96.68W
05/21/2004 0.88 INCH UNION SD TRAINED SPOTTER
0837 PM HAIL SUTHERLAND 42.97N 95.50W
05/21/2004 0.88 INCH O'BRIEN IA TRAINED SPOTTER
0845 PM HAIL 6 W MERRILL 42.72N 96.37W
05/21/2004 0.75 INCH PLYMOUTH IA AMATEUR RADIO
0852 PM HAIL 4 WSW ROSSIE 42.99N 95.26W
05/21/2004 0.88 INCH CLAY IA PUBLIC
0901 PM HAIL 4 W MERRILL 42.72N 96.33W
05/21/2004 2.75 INCH PLYMOUTH IA EMERGENCY MNGR
0904 PM HAIL 7 SW ROCK VALLEY 43.13N 96.40W
05/21/2004 1.00 INCH SIOUX IA PUBLIC
0910 PM HAIL LE MARS 42.79N 96.17W
05/21/2004 0.75 INCH PLYMOUTH IA EMERGENCY MNGR
0920 PM TORNADO 7 E YANKTON 42.89N 97.25W
05/21/2004 YANKTON SD EMERGENCY MNGR
0928 PM HAIL 2 W GILLETT GROVE 43.02N 95.07W
05/21/2004 0.75 INCH CLAY IA TRAINED SPOTTER
0932 PM HAIL GAYVILLE 42.89N 97.17W
05/21/2004 1.75 INCH YANKTON SD TRAINED SPOTTER
0933 PM HAIL 3 SW MECKLING 42.81N 97.11W
05/21/2004 1.75 INCH CLAY SD TRAINED SPOTTER
0945 PM HAIL 2 E CALUMET 42.94N 95.51W
05/21/2004 0.88 INCH O'BRIEN IA PUBLIC
0945 PM HAIL 4 SE WAKONDA 42.97N 97.05W
05/21/2004 1.00 INCH CLAY SD AMATEUR RADIO
0950 PM HAIL CHEROKEE 42.75N 95.55W
05/21/2004 0.88 INCH CHEROKEE IA CO-OP OBSERVER
1000 PM HAIL VERMILLION 42.78N 96.93W
05/21/2004 1.00 INCH CLAY SD AMATEUR RADIO
1000 PM TSTM WND DMG 2 SW HOMER 42.32N 96.49W
05/21/2004 DAKOTA NE PUBLIC
3 INCH DIAMETER TREE LIMBS DOWN.
1003 PM HAIL 9 NW ELK POINT 42.77N 96.81W
05/21/2004 1.00 INCH UNION SD PUBLIC
1005 PM HAIL 6 W LINN GROVE 42.89N 95.36W
05/21/2004 0.75 INCH BUENA VISTA IA PUBLIC
1007 PM FLASH FLOOD LE MARS 42.79N 96.17W
05/21/2004 PLYMOUTH IA AMATEUR RADIO
WATER COVERING HIGHWAY 3 AT LE MARS.
1015 PM TSTM WND DMG 2 NW SALIX 42.31N 96.29W
05/21/2004 WOODBURY IA PUBLIC
3 INCH DIAMETER TREE LIMBS DOWN.
1032 PM HAIL 5 N CENTERVILLE 43.19N 96.96W
05/21/2004 1.75 INCH TURNER SD TRAINED SPOTTER
1035 PM HAIL 5 E GILLETT GROVE 43.02N 94.94W
05/21/2004 1.75 INCH CLAY IA PUBLIC
1037 PM HAIL 7 WNW BERESFORD 43.12N 96.91W
05/21/2004 1.00 INCH LINCOLN SD TRAINED SPOTTER
1040 PM HAIL 2 E MARATHON 42.86N 94.94W
05/21/2004 0.75 INCH BUENA VISTA IA PUBLIC
1041 PM FLASH FLOOD GILLETT GROVE 43.02N 95.04W
05/21/2004 CLAY IA AMATEUR RADIO
4 TO 5 INCHES OF WATER COVERING THE ROADS AT GILLETT
GROVE.
1110 PM HAIL HOLSTEIN 42.49N 95.54W
05/21/2004 1.00 INCH IDA IA PUBLIC
1110 PM HAIL HOLSTEIN 42.49N 95.54W
05/21/2004 0.75 INCH IDA IA PUBLIC
1120 PM HAIL 3 NE DANBURY 42.27N 95.68W
05/21/2004 0.75 INCH WOODBURY IA PUBLIC
1124 PM HAIL 1 S WILMONT 43.75N 95.83W
05/21/2004 0.75 INCH NOBLES MN TRAINED SPOTTER
1125 PM HAIL 1 E TEA 43.45N 96.82W
05/21/2004 1.00 INCH LINCOLN SD AMATEUR RADIO
1125 PM HAIL HARRISBURG 43.43N 96.70W
05/21/2004 1.00 INCH LINCOLN SD AMATEUR RADIO
1130 PM HAIL 4 S IONA 43.91N 95.79W
05/21/2004 0.75 INCH MURRAY MN PUBLIC
1133 PM HAIL 3 S IONA 43.91N 95.79W
05/21/2004 1.00 INCH MURRAY MN PUBLIC
1137 PM HAIL 7 ENE WAKEFIELD 42.31N 96.74W
05/21/2004 1.75 INCH DIXON NE LAW ENFORCEMENT
1140 PM HAIL 7 ENE WAKEFIELD 42.31N 96.74W
05/21/2004 0.88 INCH DIXON NE PUBLIC
1142 PM HAIL 7 WSW HOMER 42.28N 96.62W
05/21/2004 1.75 INCH DAKOTA NE PUBLIC
1200 AM HAIL 8 S MOVILLE 42.37N 96.07W
05/22/2004 0.88 INCH WOODBURY IA PUBLIC
&&
COMPLETE SUMMARY OF EVENTS FROM FRIDAY 5/21/04
$$
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