Notify net control of your location and the current weather conditions (or No Traffic). Report, again, whenever your weather conditions change.

Initiate reports of severe weather conditions as follows:

Report hail occurrences when the hailstones are Pea size (1/4”) or larger (refer to Spotter Quick Reference Guide for details)
Report wind gusts when their speed exceeds 50 miles per hour (see Wind Specifics below)
Report tornadoes and funnel clouds. If a funnel cloud reaches more than half of the way to the ground, report it as a tornado

Report pre-tornadic phenomena such as rotating wall clouds
Report rainfall exceeding an inch per hour or resulting flash flooding
Report any storm damage

When reporting, cover the following points:

SOURCE:

Identify yourself; call sign, name and whether you are a trained spotter.

TIME:

This is the time you observed the event. Use 12 hour format such as 8:07 AM, 6:36 PM. Report to the nearest minute.

LOCATION:

This is the exact location of the event. Use street names or highway numbers, which can be referenced on a map. Give the city or town and the county

CONDITION:

If the severe weather situation that is taking place is ...

a tornado or funnel-cloud, report speed and direction of travel
a wall cloud, report existence of rotation, speed and direction of travel and the length of time you have observed
hail, report size using size descriptors in your spotter guide in the case of wind, report speed and direction and if speed was measured or estimated
heavy rain, the amount of rain over what period and if it was measured or estimated
flooding, the current extent of the flooding.
causing any physical damage

SUMMER	WINTER
Tornadoes – Speed and direction	Snowfall rates greater than 3" every 6 hours
Funnel Clouds - Be sure of your observations!	White Out or Fog Conditions
Wall Clouds- Rotating? Be sure of your observations!	Poor Road Conditions
Damage- Large grove of trees downed, power lines, windows blown out, major roof/building, vehicles blown over, heavy damage	Wind Gusts greater than 50 MPH
High Winds 50 MPH or greater. Report highest gust. Indicate estimate or actual measurement	Tree, Power Line, or Ice Damage
Hail 1/4 Inch or larger. Report largest stones. Indicate estimate or actual measurement	Unexpected or Significant Events
Flooding - Major Structural Damage/Evacuations, River Banks Broken, Water Out of Bank, Roads, Bridges or Railroads washed out.
Visibility - When less than 1/2 mile from rain or blowing dirt
Rainfall - 1/4 inch in 15 minutes, 1 inch per hour. Rain gage reports should include start time.

Wind Specifics

Measured or Estimated

One way to get an idea of wind speed is to estimate the average length of a downed branch or limb.

Rule of Thumb Example: You witness a 25 foot branch or limb down on your property, however, most of the other branches are just 10 to 12 feet. Chances are the 25-foot branch was weak and just fell in the wind. Take the 12 footers as your average. If you add the length to 40 and you have the estimated wind, 52-MPH. Report 50 MPH

Rule of Thumb Example: You have had strong thunderstorm winds and many branches and limbs are down. Several limbs of 30-foot length are observed along with an array of 20-foot sections. Since the 20 footers seem to dominate, take the 20 and add to 40 and you have estimated winds, 60 MPH. Report 60 MPH

"This is (your call)...Estimated wind speed of 60 MPH" observed at Route 83 and 75^th Street, in Willowbrook at 4:06 PM," or: "(your call)... MEASURED wind gust of 72 MPH at......"

Note: All references to trees are for trees with foliage. Significantly higher winds may be required to cause similar damage to trees without foliage. Very wet soil conditions may allow weaker winds (30-57 Mph) to uproot trees. Storm spotters are not expected to be structural engineers and you can not judge wind speed strictly by damage alone. The quality of construction techniques and materials used greatly affect the end result.

All wind speed reports should be qualified, that is they are either an estimate of speed or an actual Measurement of speed. You never want to report something like: "winds are very strong, boy, its really getting bad."

If wind speed direction is requested, remember the direction is from which way the winds are blowing. Don’t judge surface wind direction, by cloud movement because upper level wind fields often move at different directions than do the surface (ground level) wind.

WIND SPEED ESTIMATES BASED ON DAMAGE
WIND SPEED	OBSERVATIONS
30-44 MPH	Trees in motion. Light-weight loose objects (e.g., lawn furniture) tossed or toppled.
45-57 MPH	Large trees bend, twigs and small limbs break and a few larger dead or weak branches may break. Old/weak structures (e.g., sheds, barns) may sustain minor damage (roofs, doors). Buildings partially under construction maybe damaged. A few loose shingles removed from houses. Carports may be uplifted, minor cosmetic damage to mobile homes and pool lanai cages.
58-74 MPH	Large limbs break, shallow rooted trees broken/uprooted. Semi-trucks overturned. More significant damage to old/weak structures. Shingles, awnings removed from houses, damage to chimneys and antennas; mobile homes, carports incur minor structural damage; large billboard signs may be toppled.
75-89 MPH	Widespread damage to trees with trees broken/uprooted. Mobile homes may incur more significant structural damage; be pushed off foundations or overturned. Roofs 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	Many large trees broken or uprooted. Mobile homes severely damaged; moderate roof damage to homes. Roofs partially peeled off homes and buildings. Moving automobiles pushed off dry roads; barns, sheds demolished.

Hail Specifics

Thunderstorm hail is not normally a direct threat to life, but hail stones are one of the more costly severe weather elements in its damage to crops, roofs, livestock, automobiles and other outdoor objects. There are several requirements for a storm to be classified as severe. The hail requirement is 3/4 inch stones or larger.

Roughly 20% of all severe weather events involve hail. Serious hail storms (with hailstones 1.5 inches or larger in diameter) are not common in Illinois and rarely is a person injured or killed by large hail in any event. The peak hail season in this area is April through August, although hail has been reported with thunderstorms in every month of the year.

Marble size hail?..... Since marbles come in different sizes, this report would require a clarification. A better approach would be a hail conversion chart and ruler (or calipers) with the spotter and at the relaying station.

Serious spotters should obtain a ruler or calipers for measurement accuracy, making measurements only when it safe to do so. Typically the largest or most common sized hailstones are reported. For odd shaped stones measure along the stones longest axis. If a stone measures 2x3 inches, report it as 3 inches. 2x4 inches, report it as 4 inches. etc. If the hail covers the ground in sufficient quantities and depth, report that as well. If you observe real-time hail damage occurring, report it immediately, along with injuries or other significant damage.

Most people tend to over estimate hailstone sizes, and this condition is worse when spotting at night. When making estimates keep in mind that as the distance between you and the stone increases, your accuracy decreases!

Numerical hail reports (estimated or measured) assist radar operators to more precisely adjust the radar's hail detecting software programs for more accurate forecasts regarding hail producing storms.

ALL reports should be qualified as either "measured" or "estimated" in inches.

Hail Size and Common Comparisons

Common Name	Diameter
BB size	0.10 inch
Pea	0.25 inch
Mothball, small marble, peanut M&M	0.50 inch
Penny or Dime, large marble, Milk Dud	0.75 inch
Nickel	0.88 inch
Quarter	1.00 inch
Kennedy Half-Dollar	1.25 inches
Ping Pong ball	1.50 inches
Golf ball	1.75 inches
Hen Egg	2.00 inches
Tennis ball	2.50 inches
Baseball or Orange	2.75 inches
Hockey Puck	3.00 inches
Grapefruit	4.00 inches
Softball or larger	4.50 inches

Spotter Quick Reference Guides

Definitions: www.crh.noaa.gov/images/mkx/pdf/spotters/sptr-definitions.pdf

Diagrams: www.crh.noaa.gov/images/mkx/pdf/spotters/sptr-diagrams.pdf

Hail Specifics

Spotter Quick Reference Guides

Website design by WR9U/CFI, Inc.

Copyright © 2008 WR9U & CFI, Inc.