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Sachse R.A.C.E.S.

THE STORM SPOTTER'S CHECKLIST

National Weather Service
Fort Worth/Dallas, TX

www.weather.gov/fortworth

REPORTING TIPS...

SAFETY TIPS... NIGHT SPOTTING TIPS... SEVERE STORM CHARACTERISTICS...
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ARE STRONG UPDRAFTS PRESENT?
Thick, cumuliform anvil
Large, persistent overshooting top
Hard, cauliflower texture to updraft tower
Moderate to strong inflow winds
Warm, moist air blowing into storm
Rain-free base
Inflow bands
Rising suc clouds (possibly)
Wall cloud
ARE STRONG DOWNDRAFTS PRESENT?
Is a shelf cloud present?
Is there a rain or dust foot?
Is there an intense rain area that quickly reaches ground?
Are the winds blowing away from the storm?
IS THE STORM ROTATING?
Do you see striations?
Do you see mid-level cloud bands?
Bell- or barrel-shaped (flared out) updraft tower?
Beaver tail
Rotating wall cloud
ARE YOU SEEING A "LOOK-ALIKE"?
Scud (not attached to the cloud base, likely not roating).
Precipitation shaft (likely not rotating, often has a fuzzy or stringy appearance).
Smoke/Steam column (originates from a stationary point likely not rotating)
"Gustnado" (not associated with updraft, not attached to the cloud base)
IS THE TORNADO THREAT INCREASING?
Large, circular updraft base
Increasing spin in wall cloud and colud base
Strong, increasing inflow
Rapid vertical motions near wall cloud
Clear slot (rear flank downdraft) formation
Precipitation burst behind wall coud or a curtain of precipitation around wall cloud
Tornado forms in minutes or, more likely, outflow undercuts wall coud and updraft

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WALL CLOUDS vs. SHELF CLOUDS...
WALL CLUDS
  • suggest updraft
  • slope upward away from the precipitation
  • maintain their position with respec to the precipitation
  • form under a smooth, flat updraft base
SHELF CLOUDS
  • suggest downdraft
  • slope downward away from the precipitation
  • visibly move away from the precipitation area
  • have a ragged, choppy appearance to their bases
TORNADOES vs. DOWNBURSTS...
TORNADOES
  • Narrow, well defined path
  • Convergence in damage pattern
  • Evidence of vertical rotation
  • Return flow signatre on left side of damage track
DOWNBURSTS
  • Broad, diffuse path (especially with small events)
  • Divergence in damage pattern
  • No rotation, or eyewitness accounts of horizontal rotation
WIND SPEED ESTIMATION
25-31 mph
Large branches in motion, wistling heard in telephone wires
32-38 mph
Whole trees in motion; inconvenience felt walking againt the wind
39-54 mph
Twigs break off of trees; difficulty walking against the wind
55-72 mph
Damage to chimneys, TV antennai, and light storage buildings; breaks large tree limbs; pushes over shallow rooted trees
73-112 mph
Peels shingles/sheeting off roofs; windows broken; mobile homes pushed or overturned; moveing cars pushed off of road
113-157
Roofs torn off of houses; vehicles picked up and thrown
SUGGESTED REPORTING CRITERIA
URGENT (tornado, flash flooding)
  • Tornado
  • Funnel cloud
  • Low-level rotation signatures
  • Flash flooding
HIGH (non-tornadic supercell)
  • Hail golf ball size or larger
  • Winds 65 mph or stronger
  • Strong updraft signatures
MEDIUM (near or above severe t-storm criteria)
  • Hail ½ inch to golf ball size
  • Winds 45 to 65 mph
  • Other significant cloud formations
  • Localized flooding
LOW
  • Hail smaller than ½ inch
  • Winds less than 45 mph
  • Heavy rain, no flooding impacts
HAIL SIZE ESTIMATION
1/4"Pea 1 3/4"Golf Ball
1/2"M&M (Plain) 2"Hen egg
3/4"Penny 2 1/2"Tennis Ball
7/8"Nickel 2 3/4"Baseball
1"Quarter 3"Tea Cup
1 1/4"Half Dollar 4"Grapefruit
1 1/2"Ping Pong Ball 4 1/2"Softball

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