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Storm Viewing Ques
Upper-Level
Features
Anvil - As the equilibrium level is reached, the air and cloud
material spreads out and the anvil is formed. If the anvil is
thick, smooth-edged and puffy like the lower part of the storm, then the
storm probably has a strong updraft and is a good candidate to produce
severe weather. Also, if the anvil is streaming away from the
storm in one particular direction, then the storm will be well
ventilated by strong upper winds.
Overshooting Top - the storm
has a vigorous updraft. Persistent (more than 10 minutes)
overshooting tops indicate updraft strong enough to produce severe
weather.
Mid-Level Features
Most of
the mid-level features are associated with the storm's main updraft
tower. If the clouds in the updraft tower are sharply outlined
with a distinct cauliflower appearance, then the storm has a strong
updraft which may produce severe weather.
Flanking Line
- thunderstorms with good storm-scale organization typically have a
series of smaller cloud towers to the south or southwest of the main
storm tower. These smaller towers usually have a stair-step
appearance as they build towards the main tower.
Striations
- are streaks of cloud material that give the storm tower a "corkscrew"
or "Barber pole" appearance and strongly suggest rotation.
Mid-Level
Cloud Band - a ring of cloud material about halfway up the updraft
tower encircling the tower like ring around a planet. This is
another sign of possible rotation.
As a storm
grows in size and intensity, it will begin to dominate its local
environment. If cumulus clouds and other storms of interest
dissipate, it may be a sign that the storm is taking control of the
local area.
Lower-Level Features
Rain-Free
Base - the flat, smooth cloud base beneath the main storm tower from
which or no precipitation falls. The rain-free base is usually to
the rear (south or southwest) of the precipitation area. This
marks the area of INFLOW.
Inflow
Bands - ragged bands of cumulus clouds that extend from the main
storm tower to the southeast or south and suggest the gathering of
low-level air from several miles away.
Tail Cloud
(Beaver's Tail) - a smooth, flat cloud band that extends from the
eastern edge of the rain-free base into the rain-base.
Wall
Clouds (Accessory Cloud)
-
Suggests inflow/updraft
-
Attached to rain-free cloud base
-
Maintains position with respect to rain
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May contain a tail cloud that slopes upward from precipitation into
storm
Shelf Clouds
(Accessory Cloud)
-
Suggests downdraft/outflow
-
Leading edge of gust front, moving away from rain
-
Slopes downward away from the precipitation area
-
Often associated with a squall line
Funnel Clouds Vs Tail
Clouds
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Funnel clouds rotate, usually rapidly, extending downward from the
cloud base
-
As opposed to scud clouds, funnel clouds typically have laminar or
smooth appearance
-
Funnel clouds are located near the updraft, usually vertical and
several orders of magnitude smaller than parent wall cloud
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Tail clouds (Beaver's Tail) are often horizontal and funnel-like, but do not
rotate; they should not be confused with actual funnel clouds for
these reasons. Beaver's clouds extent from the updraft tower
into the rain0free base.
Clear Slot
-
A local region of
clearing skies or reduced cloud cover, indicating an intrusion of
drier air; often seen as a bright area with higher cloud bases on
the west or southwest side of a wall cloud. A clear slot is
believed to be a visual indication of a rear flank downdraft (RFD)
and RFD may contribute to the formation of tornadoes.
Optimal Spotter
Viewing Angle
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Wall clouds and tornadoes are typically on the right or front side
of storm with respect to their movement. This makes knowledge of
storm motion important!
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The safest and best viewing angle is with the storm moving to your
right as you look at it (Right Hand Rule)
-
Viewing on the left or rear flank of the storm or with the storm
moving to your left, often results in poor viewing with the line of
sight obscured by rain and/or hail
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