Reporting Severe Weather
Spotters provide an invaluable service to their communities and to the National Weather Service.
Spotter reports help your community by assisting local public safety officials in making critical decisions to protect lives – when to sound sirens, activate safety plans, etc
Spotter reports also help the NWS in the warning process. Your report becomes part of the warning decision making process, and is combined with radar data and other information and used by NWS forecasters to decide whether or not to:
- Issue a new warning
- Cancel an existing warning
- Continue a warning
- Issue a warning for the next county
- Change the warning type (from severe thunderstorm to tornado, for example)
For your reports to be the most useful, they should be as detailed, accurate and timely as possible. Use the guidelines below to help you make your report:
The Importance of Coordination
Spotter networks usually work best when a central location (an EOC or warning point, for example) collects reports from the local spotter network, then relays a consolidated report to the National Weather Service. This reduces duplicate reports and makes the system flow smoothly.
In this type of network, communication between the spotter and the control point must be clear to avoid misinterpretation. As a report is relayed through multiple sources, the chances for error being introduced into the chain grow.
Look at this example:
ORIGINAL SPOTTER REPORT at 730 PM:
“I am 3 miles north of Mayberry on Highway 78. I see a tornado about 5 miles to my northwest. It looks to be moving east along Highway 412”
Spotter report is relayed to another station, who relays it to the county warning point, who relays it to the NWS.
REPORT AS RECEIVED BY NWS at 740 PM:
“There is a tornado in Mayberry”
Obviously, the report the NWS received is not accurate – the location and the time are incorrect.
WHAT TO REPORT
Weather Events
Although reporting criteria may vary slightly depending on the spotter network and local needs, these are the events the National Weather Service would like to know about as soon as possible:
| TORNADO |
|
|
| FUNNEL CLOUD |
|
Organized, persistent, sustained rotation
|
| WALL CLOUD |
|
Organized, persistent, sustained rotation
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| HAIL |
Dime size or larger
|
Report the largest size hailstone
|
| WIND GUSTS |
58 mph or higher
|
Specify estimate or measurement
|
| FLOODING |
|
Flooding that impacts roads, homes or businesses.
|
| STORM DAMAGE |
|
Damage to structures (roof, siding, windows, etc)
Damage to vehicles (from hail or wind)
Trees or large limbs down
Power/telephone poles or lines down
Damage to farm equipment, machinery, etc
|
Again, reports should provide as much detail as possible to describe the where, when, how, etc of the event.
Some commonly used hail sizes
| Pea |
.25 inch |
Golf Ball |
1.75 inch |
| Half-inch |
.50 inch |
Hen Egg |
2.00 inch |
| Dime |
.75 inch |
Tennis Ball |
2.50 inch |
| Nickel |
.88 inch |
Baseball |
2.75 inch |
| Quarter |
1.00 inch |
Tea Cup |
3.00 inch |
| Half Dollar |
1.25 inch |
Grapefruit |
4.00 inch |
| Ping Pong Ball |
1.50 inch |
Softball |
4.50 inch |
General Guidelines for Estimating Wind Speeds
| 30-44 mph (26-39 kt) |
Whole trees in motion. Inconvenient walking into the wind. Light-weight loose objects (e.g., lawn furniture) tossed or toppled. |
| 45-57 mph (39-49 kt) |
Large trees bend; twigs, small limbs break and a few larger dead or weak branches may break. Old/weak structures (e.g., sheds, barns) may sustain minor damage (roof, doors). Buildings partially under construction may be damaged. A few loose shingles removed from houses. |
| 58-74 mph (50-64 kt) |
Large limbs break; shallow rooted trees pushed over. Semi-trucks overturned. More significant damage to old/weak structures. Shingles, awnings removed from houses; damage to chimneys and antennas. |
| 75-89 mph (65-77 kt) |
Widespread damage to trees with large limbs down or trees broken/uprooted. Mobile homes may be pushed off foundation or overturned. Roof may be partially peeled off industrial/commercial/ warehouse buildings. Some minor roof damage to homes. Weak structures (e.g., farm buildings, airplane hangars) may be severely damaged. |
| 90+ mph (78+ kt) |
Many large trees broken and uprooted. Mobile homes damaged. Roofs partially peeled off homes and buildings. Moving automobiles pushed off the road. Barns, sheds demolished. |
HOW TO REPORT
Your severe weather report should be detailed but concise, and should address the following questions:
WHAT did you see?
WHERE did you see it?
Report the location/approximate location of the event. Be sure to distinguish clearly between where you are and where the event is thought to be happening (“I’m 5 miles north of Mayberry. The tornado looks to be about 5 miles to my northwest”).
WHEN did you see it?
Be sure that reports that are relayed through multiple sources carry the time of the event, NOT the report time.
Any other details that are important - How long did it last? Direction of travel? Was there damage? etc.
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