"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:

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:

TYPE OF EVENT
WHEN TO CALL
NWS WARNING CRITERIA/
ADDITIONAL INFORMATION
TORNADO

Always Call - ALSO CALL 911

Tornado Warning Issued.
Look for debris on the ground
FUNNEL CLOUD/
WALL CLOUD

Always Call

Look for organized, persistent, sustained rotation

HAIL

Call if Half-inch size or larger**

Severe Thunderstorm Warning Issued:
1 inch diameter or larger. Always report the largest size hailstone

WIND GUSTS

Call if 50 mph or higher

Severe Thunderstorm Warning Issued:
Sustained 40 mph. Gusts to 58 mph or greater. Specify estimate or measurement

HEAVY RAIN/
FLOODING
1.0" rain/hr or greater for urban areas.
1.5" rain/hr or greater for rural areas.
Also Call 911 for flooding.

Flash Flood Warning issued: Flooding that impacts roads, homes or businesses.

STORM DAMAGE Always Call

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 Or any other significant damage


**Quarter size hail (1.00 inch) is considered as severe weather hail.
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.

If you are unsure whether to report or not to report, GO AHEAD AND REPORT IT.


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