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Terms
Used by Blackwell Storm Spotters
by Mick Phillips - 10/27/11
Terms used by the Blackwell Storm Spotters
At this time Blackwell has
storm spotters who are out there watching for severe weather to provide advanced warning of severe storms
approaching our community. We are unpaid volunteers, and do it as a service for the residents of
Blackwell. We are also a key component of the “Severe Weather Operations Department” (S.W.O.D.) of the
City of Blackwell.
On May 3, 1999 Oklahoma County
had 90 confirmed tornados starting in 1950. Until that time Kay County had the highest
number of confirmed tornados with 85. This was due to dedicated storm spotters in Kay County.
The night after the 1955
Blackwell Tornado, Blackwell had storm spotters in the field. There has been a storm spotter program in Blackwell
since that time.
We are “Storm Spotters” not
“storm chasers” as you may see on television. Storm chasers like the thrill of seeing tornados
and storms. They travel many miles away from their community to take pictures or video of storms. However, “Storm
Spotters” are dedicated volenteers who will warn the citizens of possible impacts of a severe storm moving toward
their community. In addition, Blackwell storm spotters attend meteorological classes, training
and attend many severe weather seminars throughout their lifetime to keep up to date with advancing
technology.
A lot of people listen to us on
their scanners. We want the community to know what we are doing and encourage everyone to listen
to us on their scanners on 155.235 Mhz. All scanners will pickup this
frequency. Some of the spotters are on the local Amateur radio repeater on 145.310 Mhz when we
need to communicate at a greater distance than our public safety frequency will let us
talk.
I have been told there is some
confusion in the terminology the spotters use. I hope I can explain some of the terminology that
you will hear the spotters saying on their radios.
The National Weather Service
and the Blackwell storm spotters use the following terms. The list is in alphabetical order, and will help you
understand what we are seeing in the storms.
Back-building Thunderstorm - A
thunderstorm in which new development takes place on the upwind side (usually the west or southwest side), such
that the storm seems to remain stationary or propagate in a backward direction.
Beaver’s Tail - A particular type of
inflow band with a relatively broad flat appearance suggestive of a beaver tail. It is attached to a supercell’s
general updraft.
Bow Echo - A radar echo which is
linear but bent outward in a bow shape. Damaging straight-line winds often occur near the center
of a bow echo. The July 4, 2005 storm was straight winds from a bow echo
storm.
Cold-air Funnel - A funnel cloud or
(rarely) a small relatively weak tornado that can develop from a small shower, or thunderstorm when the air aloft
is unusually cold. They are much less violent than other types of tornadoes.
Collar Cloud - A generally circular
ring of cloud that may be observed on rare occasions surrounding the upper part of a Wall
Cloud.
Condensation Funnel - A funnel-shaped
cloud associated with rotation, and consisting of condensed water droplets. This is some times
seen before the tornado touches ground, or you will see a Debris Cloud on the
ground.
Debris Cloud - A rotating cloud of
dust, or debris near, or on the ground, often appearing beneath a Condensation Funnel, and
surrounding the base of a tornado.
Downburst - A strong downdraft
resulting in a outward burst of damaging winds on or near the ground. Downburst can produce
damage similar to a strong tornado. You really do not have any warning of a downburst, but are
possible from any storm.
E.O.C.- That’s short for Emergency
Operations Center. This is located in the Blackwell City Hall. Before, during
and after severe weather moves thru the Blackwell area, The Severe Weather Operations Dept. will operate from this
center. This center contains TV’s, ham radios, radios for emergency traffic to other cities,
counties and the State of Kansas and Oklahoma. This center is where radar imagery is viewed and
analyzed by trained weather radar operators. The E.O.C. is also a location where city officials could meet incase a
severe weather event impacted the City of Blackwell. It could be said that the E.O.C. is the
“nerve center of Blackwell during severe weather operations.”
Funnel Cloud - A condensation funnel
extending from the base of a thunderstorm associated with a rotating column of air that is not in contact
with the ground. This is not a tornado until it touches the ground.
Gustnado - This is a slang that is
used to describe dust whirls that are seen in fields that are caused be updrafts, and
downdrafts. They are not tornados.
Gust Front - The leading edge of gusty
surface winds from thunderstorm downdrafts sometimes associated with a Shelf Cloud or Roll
Cloud.
Ground Flashes - Power lines flashes
seen from a distance mean there is very strong winds, or a tornado blowing the wires together, or blowing them
down. At night this gives the spotters a very good indication that there is something going on
in that area.
Inflow - This is the warm moist air
being drawn into the storm. This air moves into the rain free base of the storm usually on the
southwest part of the storm.
Landspout - A tornado that does not
arise from an organized storm rotation, and therefore is not associated with a wall cloud.
Mesocyclone - A region of rotation,
typically around 2 to 6 miles in diameter, and often found in the right rear flank of a supercell
storm. The circulation of a mesocyclone covers an area much larger than a tornado that may
develop within it. You will hear the Blackwell spotters call this a MESO, and it does not mean
there is a tornado in the storm.
Microburst - A small concentrated
downburst of air affecting an area less than about 2.5 miles across. Most microbursts are rather
short-lived.
Multi-vortex tornado - A tornado in
which two or more condensation funnels, or debris clouds are present at the same time, often rotating about a
common center or each other. Multi-vortex tornados can be especially
damaging. The Blackwell 1955 tornado was a multi-vortex tornado that had smaller funnels
rotating around the main tornado.
Outflow Boundary- As large
thunderstorms start to fall apart they sometimes send out a area of cool moist air. This front
is very much like a cool front and new storms can develop from them.
Overshooting Top - A dome-like
protrusion above a thunderstorm anvil, representing a very strong updraft, therefore a higher potential for severe
weather.
Rain-free base- A dark, horizontal
cloud base with no visible precipitation beneath it. It typically marks the location of the
thunderstorm updraft. Tornados may develop from the wall clouds attached to the rain-free base,
or from the rain-free base itself- especially when the rain-free base is on the south, or southwest side of the
main precipitation area.
Rear Flank Downdraft (or RFD)- A
region of dry air subsiding on the backside of and wrapping around a MESO attached to the rain-free
base. Sometimes very high winds from the RFD will occur.
Right Mover (or making a 90 degree)- A
thunderstorm that moves appreciably to the right, relative to the main steering winds and other nearby
thunderstorms. Right movers are typically associated with a high potential for severe
weather.
Roll Cloud - A low horizontal
tub-shaped cloud associated with a thunderstorm, or gust front. Roll clouds are completely
detached from the thunderstorm base, or other cloud feature. Roll clouds usually appear to be
rolling about a horizontal axis, but should not be confused with a funnel cloud.
Rope Funnel- A narrow often contorted
condensation funnel usually associated with the decaying stage of a tornado. Some tornados will
start out small and rope looking then grows into a full tornado.
Scud Clouds - Small ragged low cloud
fragments that are unattached to a larger cloud base. Such clouds generally are associated with
cool moist air, such as thunderstorm outflow.
Shear - Variation in wind speed and/or
direction over a short distance. Shear usually refers to vertical wind shear, or in
height. This means that winds may be blowing from different directions and speeds at different
heights in the storm. This can cause the storm to start to rotate.
Shelf Cloud - A low horizontal
wedge-shaped cloud associated with a thunderstorm. Unlike the Roll Cloud the shelf cloud is
attached to the base of the parent cloud above it. Rising cloud motion often can be seen in the
leading part of the shelf cloud, while the underside often appears turbulent, boiling, and
wind-torn.
Squall Line - A solid or nearly solid
line or band of active thunderstorms.
Supercell Thunderstorm - A
thunderstorm with a persistent rotation updraft. Supercells are rare, but are responsible for a
remarkably high percentage of severe weather events especially tornadoes, extremely large hail, and damaging
straight-line winds.
Tail Cloud - A horizontal tail-shaped
cloud (not a funnel cloud) at low levels extending from the precipitation region of a thunderstorm toward a Wall
Cloud.
Tilted storm - A thunderstorm which is
not purely vertical, but instead exhibits a slanted, or tilted character. Tilted storms usually
tend to last longer than none tilted storm, and have favorable conditions for severe storm
development.
Towering Cumulus (towers going up)- A
large cloud with great vertical development, usually with a cauliflower-like appearance, but lacking the
characteristic anvil look at the top of the cloud.
TVS (Tornadic Vortex Signature)- This
is only seen on Doppler radar showing intense concentrated rotation-more so than a MESO. The
existence of a TVS strongly increases the probability of a tornado Occurrence, but does not guarantee it. A TVS is
not a visually observable feature. When the spotters are told that radar shows a TVS it gives us
a place to look for the formation of a tornado, but does not mean that one is there, or going to be there
later.
VIL (Vertically-Integrated Liquid
Water)- This is just a term that tells use how much water there is in a storm. It helps
use in determining its potential severity, especially terms of maximum hail size.
Wall Cloud (lowering)- A localized
persistent, often abrupt lowering from a rain-free base. Wall clouds can range from a fraction
of a mile up to nearly five miles in diameter, and normally are found on the south or southwest (inflow) side of
the thunderstorm. When seen from within several miles, many wall clouds exhibit rapid upward
motion, and cyclonic rotation. However, not all wall clouds rotate. Rotating
wall clouds usually develop before strong or violent tornadoes, by anywhere from a few minutes up to nearly an
hour. Not all rotating wall clouds produce a tornado.
There are many other terms used by the National Weather Service,
and sometimes by the storm spotters. These are the terms you will hear most
often.
When its time to take cover, the Severe Weather Operations Dept.
will alert you by sounding Blackwell’s Tornado Sirens. If you are inside you may not hear them unless you are close
to a sirens location. In addition, you can watch Channel 65 from Get Real Cable, which
keeps up to date with radar on what is going on with the storms & their possible impact on the City of
Blackwell.
You can also stay informed by subscribing to
Nixle. If you can receive text on your cell phone and you subscribe to a texting plan, you can
get the latest severe weather information for Blackwell. Nixle is free!
When you listen to the scanner, you
will hear different storm spotters units referred to by numbers. For example, you may hear,
“E.O.C. to 1509.” The “15” represents a Blackwell storm spotter.
Blackwell storm spotters are known as “1500” units. If it was “1402” the “14” represents a
Braman storm spotter. Braman storm spotters are known as“1400 units” The last 2 numbers, is the storm spotter’s
individual unit number.
The number prefixes you hear on
the radio are as follows:
1100 Kay County spotters; 1200 Tonkawa
spotters; 1400 Braman spotters; 1500 Blackwell spotters; 1600 Newkirk spotters; 1700 Ponca City spotters, and 1800
Kaw Indian Nation spotters.
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