NAME:
KEY
Call sign (if applicable):
2010 South Plains Storm Spotting Team Test
As usual this test is used to measure
the skill and knowledge level of the team members and is used to help
determine areas to stress during training. The questions mostly
come from either the Advanced Spotters Field Guide or the
Glossary. A few may be more based on situations to see how you
will respond. . If you don’t know the answers then concentrate on
that material when you review your information this season.
Do your best and good luck.
1. If we have moisture at the lower to mid levels of the
atmosphere and a source of lift available to cause updrafts to form,
what other basic ingredient is required to get thunderstorm development?
Instability, so that updrafts will
continue upward
2. The amount of vertical wind shear in the storm’s
environment is critical in determining what type of storm will form.
Vertical wind shear is defined as a change in wind ___speed
or __direction__
with height.
3. Why does a mid-level capping inversion of moderate
strength, when the conditions for thunderstorm development are present,
make severe thunderstorms somewhat more likely?
It prevents weak storms from forming,
“saving up” the atmospheric instability. Only the strongest
updrafts will be able to break the cap and continue to develop.
They can take advantage of the high instability (when present) and with
little competition from other nearby storms can possibly develop into
severe storms.
4. If you position closer than 2 miles from a
developing tornado without a quick safe road choice available, what
major danger might you face?
If the tornado increases in size and moves in your direction you may
quickly be in the area of tornadic winds without being able to
escape. Also you may find yourself being hit by very large hail.
5. If you happen to be outside your vehicle or other
protective shelter, what warning signs may indicate that you are in
imminent danger from a lighting strike?
Feeling your hair rise up due to static build up, buzzing heard from
your antenna or other metal components on the exterior of your vehicle
and of course nearby lightning strikes. If you are near or
under any portion of the thunderstorm’s clouds, then you are in range.
6. A squall line (multicell line storm) has
developed across our area bringing several reports of golf ball sized
hail and embedded areas of rotation or tornadoes. The NWS informs
the spotters that a bow echo is forming in the section of the line
approaching your position. What, besides the previously mentioned
threats should you be expecting?
Very strong downburst (straight-line) winds, these cause the area of
the line to bulge forward in to the bow shape.
7. While tornadoes are possible with just about any
thunderstorm, which specific type of the four main types is not only
the most organized, but usually the most likely to produce a strong or
violent tornado?
The supercell, due to the extremely strong updraft, with rotation, that
is usually found with a supercell.
8. What is the normal term for the rotating updraft
present in the type of thunderstorm in the previous question?
Technically, it’s a term for the radar indication of the rotation
though there are visual clues that this may be present in an updraft?
A mesocyclone, denoted by the term “meso” in team communications, often
visually indicated by striations on the main updraft tower, a mid-level
cloud band, or with some storms, a smooth flat inflow band known as a
“beaver’s tail” especially with high precipitation supercells.
9. Mobile spotters generally try to position to
watch what area of a thunderstorm?
The UDI, or updraft-downdraft interface, where the two are close
together, severe weather tends to occur near the UDI in mature
cells. This often marks the strongest areas of updraft and
downdraft. Very large hail will tend to fall near this area.
10. A vortex of dust forming along the gust front, and not
associated with a thunderstorm updraft is called what?
A gustnado, or gust front tornado
11. Rainfall from a thunderstorm that evaporates before reaching
the ground, called virga, can lead to what potentially severe event?
A downburst, most commonly a dry
microburst, or dry macroburst depending on the area affected when it
reaches the ground. Blowing dust under an area of virga can
indicate one is occurring.
Thunderstorms
start forming in the western part of our operations area. The
team is activated with requests to position members to observe the
storms as they strengthen. The Weather Service is expecting
severe storms and associated warnings to begin shortly. A Severe
Thunderstorm Watch has been issued for the western and central South
Plains and the southern Panhandle area.
Atmospheric
conditions are favorable for rapid development of severe weather, and
are expected to remain so for several hours. This is the
situation for the following questions.
12. You move to a position about 5 miles southeast of a
thunderstorm. The storm appears rather complex. There is an
anvil cloud extending to the east and northeast, with a smaller anvil
cloud formed just above the western part of the larger anvil.
There appear to be 3 or 4 updraft sections behind the anvil.
There appears to be moderate rain failing beneath the dissipating cells
in the forward portion of the storm.
What type of storm are you likely watching?
A mulicell cluster storm
13. You continue to observe the storm, moving along with it as
necessary. What area is most likely to experience severe weather,
i.e. which updraft, or the updraft in what stage of development?
The updraft that is in the mature
stage, with both updraft and downdraft present, severe weather tends to
occur near the UDI in mature cells.
14. As the storm continues, you notice the rear-most updraft
begin to grow much stronger than its predecessors. The area on
its rear flank begins to take on a stair step appearance, rather than
moving to become new sequential main updrafts. The storm may be
evolving into what different type of storm?
A supercell, with a developing
flanking line
15. Besides the one clue just given, what visual clues would you
look for to confirm your observation of the change in the nature of the
storm?
Look for striations on the updraft
tower, a mid-level cloud band, a thick cumuliform anvil, vertical storm
tower, crisp cumuliform appearance of the tower, domination of the
local area, suppressing other nearby storms.
The National
Weather Service upgrades the Severe Thunderstorm Watch to a Tornado
watch and includes the remainder of the county warning area. The
situation is now more favorable for tornado development.
16. As the storm continues to strengthen, part of the anvil,
thick and cumuliform in appearance, begins to stream upwind to the
west-southwest. What is this feature called?
A back-sheared anvil, that shows the
updraft is strong enough to force air upwind against the prevailing
upper level winds.
17. A large bulging dome of cloud material pushes up above the
anvil, above the strongest part of the updraft tower. What is
this feature called?
An overshooting top, which is a sign
of an updraft strong enough to push moisture above the anvil area where
most of the air has spread out and condensed.
18. A lowered area develops below the rain free base of the
updraft. What characteristics would you look for to see if it is
a wall cloud rather than a shelf cloud?
It usually suggests inflow into the
updraft, not outflow moving away from the precipitation. Look to see if
holds position relative to the precip, rather than moves away. It
may slope upward away from the precipitation as it draws in moist air
from the precip area, not downward and away from the precipitation.
19. If it is a wall cloud, what four characteristics would lead
you to believe it is a “tornadic wall cloud,” or one considered more
likely to have a tornado develop?
One of the main things we’re out
looking for!!!!!
The wall cloud will be persistent,
even if it changes shape, lasting 10 to 20 minutes or more before the
tornado forms.
It will not only rotate, but the
rotation will be persistent, sometimes very visible and violent before
a tornado develops.
Strong inflow winds will blow in
toward the wall cloud from the east or southeast, usually surface winds
of 25 to 35 mph are observed near the tornadic wall cloud. A
tornado that formed near Dimmit on May 5, 2002 prior to the tornado
that struck Happy, Texas was warned on first when an approximately 70
mph wind from the southeast was measured by the Texas Tech University
mesonet station in Dimmit, moving directly at a radar detected
mesocyclone.
Finally, the wall cloud will exhibit
evidence of rapid vertical motion. Small cloud elements in or near the
wall cloud quickly will rise up into the rain-free base.
Remember that not all tornado
producing wall clouds will show this behavior and not all tornadoes
form from wall clouds. However, a wall cloud showing these
characteristics needs to be observed carefully, and reported for its
high potential for a tornado to form!
20. The storm develops a definite wall cloud, then a
funnel. The funnel dissipates after the warm moist inflow to the
wall cloud area is cut off by outflow wrapping around the rear of the
storm. Where will you look for possible wall cloud re-development?
The rule of thumb is to watch the area
around 3 miles (2 to 5 miles to be safe) to the northeast, east or
southeast of the “occluded” mesocyclone area for a new one to
develop. Remember 2 things! One, you may have the new area
developing right over your head, even if you were properly positioned
for the first wall cloud/funnel and at a “safe” distance for observing
it, and two, the new mesocyclone may not only form but might produce a
tornado before the old one dissipates! Always keep a watch above
your head and keep ready to use your planned “escape” route.
21. What is the usual term for the air wrapping around the rear
of updraft/wall cloud that cuts off the inflow occluding the rotation
area?
Rear flank downdraft or RFD, it is
often visible as a “clear slot” or “bright slot” just to the rear
(southwest) of the wall cloud. You may experience a sudden strong
to damaging wind strike your location from the west or northwest when
this downdraft wraps around the mesocyclone area. The RFD and the
tornado may reach the ground within minutes of each other. It you
detect a RFD then keep careful observation of the wall cloud area.
22. As the storm continues to cycle, it approaches a boundary
left over from previous thunderstorms. Do you think that this
could increase or decrease the potential for further severe weather
from this storm?
While either is possible, you need to
watch out for the storm to use the boundary to act as an additional
lifting mechanism and potential source of moisture increasing severe
and tornado potential. On April 29, 2009 a primarily outflow
dominant storm system approached a boundary north of Lockney and
Floydada. It began producing tornadoes as it moved along the
boundary, producing several as it crossed Floyd and Motley counties.
23. You observe a wall cloud beneath the storm you’ve been
observing. It exhibits strong rotation. Scud clouds are
forming under the rotation area and being quickly drawn up into the
wall cloud. You start to see an area of rotating dust or debris
forming under the rotating wall cloud. How will you report this
phenomenon?
When in doubt describe exactly what
you are seeing. In this case, with a strongly rotating wall
cloud, signs of vertical motion and a possible debris cloud under it, a
tornado or at least a developing tornado is probably the correct call.
24. The storm begins to produce massive amounts of precipitation,
almost completely encircling the updraft area and the wall cloud.
What problems do you face in trying to observe the wall cloud area?
The storm is likely transitioning to a
high precipitation supercell. The area of rain will limit both
the available light to see the wall cloud area and you will likely be
limited to a narrow angle of view to see into the storm to view the
wall cloud area. The mesocyclone is often displaced to the
southeast portion of the storm. With the heavy rain wrapping
nearly all the way around you have to get into a position that is
likely in the path of the mesocylone area and the heavy rain in order
to see into the storm to the desired area. It may not even be
possible to see a wall cloud from an area outside of the
precipitation. Trying to move into a “better” position may leave
you open to heavy rain, large hail or a tornado appearing suddenly in
front of you.
25. The storm continues to be severe and show strong, deep
rotation on radar as the sun sets and the light fades. In the
absence of daylight, assuming you can see the proper area of the storm,
what will you look for to try to visually confirm a radar indicated
tornado?
If precipitation doesn’t block your
view to the proper part of the storm, i.e. the mesocyclone area, then
watch for power flashes occurring without associated lightning strikes
or strong straight-line winds. These may be power lines and
transformers being destroyed by a tornado. In addition, use
lightning flashes to look for a funnel or tornado. Not seeing a
funnel or tornado with a lightning strike is not proof that one isn’t
there. If the stroke is between you and the funnel or tornado you
probably won’t see it well enough to confirm it. It will take a
strike on the far side of the tornado or funnel that backlights the
tornado or funnel to visually confirm it. Remember to keep a
larger safety distance from the action area of the storm at night as it
may be hard to determine the exact distance and the speed or motion of
the storm features.
