Alert archive / Illinois / Severe Thunderstorm Warnings in 1987
Severe Thunderstorm Warning 1, NWS Quad Cities, IA
NWS Quad Cities, IA issued this severe thunderstorm warning at May 20, 1987, 5:10 PM CDT for Henry County, Mercer County, Rock Island County, Illinois. It was in force for 50 min. 2 reports came from inside the area while it was in force.
The area
The counties it named, with what was reported inside it.
The facts
- Issued
- May 20, 1987, 5:10 PM CDT (22:10 UTC)
- Expired
- May 20, 1987, 6:00 PM CDT
- In force
- 50 min
- Issued by
- NWS Quad Cities, IA
- Area
- Whole counties
Counties Henry County, IL, Mercer County, IL, Rock Island County, IL
The radar
The WSR-88D network and its archive begin in 1991, so there is no radar volume for this alert.
What was reported inside it
| Time | Report | Where | Remark |
|---|---|---|---|
| May 20, 5:20 PM CDT | Thunderstorm Wind 70 | Henry, IL | |
| May 20, 6:00 PM CDT | Thunderstorm Wind 70 | Rock Island, IL |
NCEI Storm Data entries that began inside the alert's area while it was in force. Before 2003 the local storm report archive is thin, so this is the record of what happened rather than what was phoned in. Storm Data before 1996 records only tornadoes, thunderstorm wind and hail.
The nearest sounding before it
Peoria Regional, IL (KPIA), launched 12:00Z, 10.2 hours before the alert went out and 105 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.
- Mixed-layer CAPE
- 1840 J/kg
- Mixed-layer CIN
- -73 J/kg
- Mixed-layer LCL
- 690 m above ground
- 0-6 km bulk shear
- 30 kt
- 0-1 km storm-relative helicity
- 56 m²/s²
- 0-3 km storm-relative helicity
- 65 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 2.8
The text
The text of this product is not in the archive. The NWS text archive before 2002 is incomplete.
What forecasters said that day
The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
In the hours before
Special weather statement, May 20, 2:00 PM CDT, 3 hours 10 minutes before
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MOLINE IL 159 PM CDT WED MAY 20 1987 ...STRONG THUNDERSTORMS DEVELOPING RAPIDLY IN SOUTHEAST IOWA... AT 155 PM CDT...NUMEROUS THUNDERSTORMS..SOME STRONG..WERE OVER SOUTHEAST IOWA BOUNDED BY A LINE FROM MT PLEASANT TO BURLINGTON TO KEOKUK TO MT PLEASANT. ANOTHER CLUSTER OF THUNDERSTORMS WAS NEAR COLUMBUS JUNCTION IOWA ABOUT 40 MILES WESTSOUTHWEST OF THE QUAD CITIES. SOME OF THESE STORMS MAY BE ACCOMPANIED BY BRIEF HEAVY RAIN.. STRONG WIND GUSTS AND POSSIBLE SMALL HAIL. MOVEMENT WAS TO NORTHNORTHEAST ABOUT 25 MPH. WIGGINS
Special weather statement, May 20, 4:15 PM CDT, 55 minutes before
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MOLINE IL 415 PM CDT WED MAY 20 1987 AT 410 PM CDT A CLUSTER OF STRONG THUNDERSTORMS WAS BETWEEN MUSCATINE AND DURANT IN EASTERN IOWA..OR ABOUT 20 MILES WEST OF THE QUAD CITIES. THESE STORMS ARE LIKELY TO PRODUCE HEAVY DOWNPOURS..HAIL..STRONG WINDS AND FREQUENT DANGEROUS LIGHTNING AS THEY MOVE TO THE NORTHNORTHEAST ABOUT 30 MPH. ANOTHER STRONG THUNDERSTORM WAS NEAR MORNING SUN IOWA ABOUT 50 PMILES SOUTHWEST OF THE QUAD CITIES. THESE STORMS WERE PART OF A LARGER AREA OF SHOWERS AND THUNDERSTORMS THAT COVERED MOST OF SOUTHEAST IOWA AND A SMALL SECTION OF WESTERN ILLINOIS. MOVEMENT WAS TO THE NORTH ABOUT 30 MPH. WIGGINS
The office that day
Everything else NWS Quad Cities, IA issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 20, 3:24 PM CDT | Tornado Warning | DVN | Cedar, Muscatine | 21 min |
| May 20, 5:10 PM CDT | Severe Thunderstorm Warning | DVN | Scott | 50 min |
Nearby
Severe Thunderstorm Warnings in Illinois, 1987Every severe thunderstorm warning in 1987
Sources
The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; verification from NCEI's Storm Data; the sounding from the Mesonet's radiosonde archive.