Dayton SKYWARN Spotter's Reference Material To Be Used During Severe Weather Spotting

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What to Report to Dayton SKYWARN During Severe Weather

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The National Weather Service (NWS) has the responsibility of organizing and instructing Amateurs to participate in their Skywarn program. Dayton Skywarn will assist NWS during the Amateur portion of the class, within the Dayton Skywarn's counties of responsibilities. (Wilmington NWS Website is

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Estimating Hail Size

Pea Size = 1/4"

Quarter Size = 1"

Marble Size = 1/2"

Golf Ball Size = 1 3/4"

Nickle Size = 3/4"

Baseball Size = 2 3/4"
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Spotters Rules and Clues

Estimating Wind Speed

1. Always have a safe place nearby to protect yourself from wind or hail.      Calm          Smoke rises vertically.
2. Cars are safe places in case of lightning, but not in the case of tornadoes.   1 - 3 MPH     Direction of wind shown by smoke drift but not by wind vane.
3. Moving Water is very powerful, it only takes a slight current to push our car off the road. Do not drive a vehicle through roads covered by moving water.   4 - 7 MPH     Ordinary wind vain moved by wind.
4. Large hail often falls just in advance of a tornado, especially large tornadoes.   8 - 12 MPH    Leaves and small twigs in motion, light flags extended.
5. Tornadoes generally moves toward the north-east at 25 to 35 MPH when associated with fronts and squall lines.   13 - 18 MPH  Dust raised, loose paper raised, small branches move.
6. Ground speeds of a tornado can exceed 70 MPH. Go to a substantial building instead of trying to out run an approaching tornado.   19 - 24 MPH  Small leafy trees sway, crested wavelets form on lakes and ponds.
  25 - 31 MPH  Large branches in motion, whistling in telephone wires or link fences.
7. The first gust of wind to reach you from a thunderstorm is frequently the strongest.
  32 - 38 MPH  Whole trees in motion, inconvenience in walking against wind.
8. A rain-free base denotes the storms up-draft area. A place to watch closely.
  39 - 46 MPH  Twigs and small branches break off trees, impedes progress walking.
9. Wall clouds form from the rain-free base often 15 to 20 minutes before a tornado occurs.
  47 - 54 MPH  Slight structural damage, chimneys have bricks loosened and shingles blown off roof.
10. Watch Wall clouds closely for 1 to 2 minutes to determine if there is any rotation.
  55 - 63 MPH  Trees up-rooted, widespread structural damage, mainly roofs
11. Look carefully, Spotters may not be able to see a tornado due to it being wrapped in a curtain of rain.
  64 - 72 MPH  Damage to structures major and widespread. Roofs and window damage.
12. Over-shooting tops are an indicator of very strong storms.
  73 - 112 MPH Peels surface off of roofs, windows broken, moving autos pushed off of road, some mobile homes overturned.