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256 Cards in this Set

  • Front
  • Back
What is electromagnetism?
Magnetism developed by an electrical current passing through a wire coiled around a metal bar that induces
a magnetic field.
If electromagnetic waves were visible and moving, describe what pattern they would have?
Like a series of sine waves.
What is the effect of wavelength on attenuation?
A short wavelength is scattered and blocked by heavy precipitation and thus is attenuated more than a long
wavelength.
How are frequency and wavelength related?
Inversely, because wave speed is constant.
What does the attenuation of radar waves depend on?
The wavelength of the emitted waves and the size and composition of the particles encountered.
Explain why absorbed energy that is later re-radiated back to the antenna is not recognized.
Energy is absorbed and reradiated at a different wavelength. For the WSR–88D, with a wavelength of
approximately 10 cm, absorption by precipitation particles is very small.
Name two ways to measure pulse length.
In units of time it takes the radar to send one pulse (expressed in microseconds) or in units of distance
(horizontal) from the front edge to the back edge of the pulse (expressed in meters).
What does the amount of energy transmitted by the radar depend on?
The duration or length of the pulse.
Define pulse repetition frequency (PRF).
The rate at which the pulses are transmitted in a unit of time.
What is the effect of pulse length and PRF on radar range?
Pulse length affects the minimum range of the set, because the transmitter must be shut off by the time the
reflected signal returns. Pulse repetition frequency affects the maximum range. The signal must have time
to return to the set before the next pulse is transmitted.
Match the radar term in Column B with its description in Column A.
Column A Column B
____ (1) Measured from the leading edge to the back
edge of the pulse.
____ (2) The rate at which pulses are transmitted.
____ (3) The period of waiting for a returned pulse.
____ (4) Is limited by how often pulses are broadcast.
____ (5) Occurs when energy is received from an old pulse
after transmission of the next pulse.
a. Pulse length.
b. Range folding.
c. Listening time.
d. Maximum unambiguous
range.
e. Pulse repetition frequency
(PRF).
(1) a.
(2) e.
(3) c.
(4) d.
(5) b.
What happens if an antenna moves at too great an angle between pulses?
The number of pulses returned per target will be too low, and some regions may not be probed for targets.
Explain range folding.
Range folding occurs when energy is received from an old pulse after transmission of the next pulse.
Where can the maximum power density of the radar beam be found?
Along the centerline of the beam.
What occurs when a target occupies only a small portion of the beam, thus hiding or altering the
true characteristics of the target during display?
Partial beam filling.
Explain the term “below beam effects.”
Missed targets below the beam.
What is beam blockage the result of?
The radar beam striking large obstructions near the antenna site.
How far should two targets be separated, in order to be displayed as separate targets?
By more than one beam width.
What is the ability of the radar to distinguish between two targets at the same direction but at
different ranges called?
Range resolution.
How does the cone of silence affect the viewing of meteorological targets that move into it?
Meteorological targets appear to weaken and disappear as they move into the cone of silence.
Normally, what does the radar beam do with respect to height as it moves away from the antenna?
Increases.
List the two types of anomalous propagation (AP) and briefly describe the atmospheric conditions
that cause each to occur.
Superrefraction—which occurs when warm, dry air overlies cool, moist air, as in an inversion. The result is
that the radar beam bends below its normal path. Subrefraction—occurs when water vapor content
increases and temperature decreases with height. The result is that the radar beam travels above its normal
path.
When the radar beam is being refracted below its normal path, what is this process called?
Superrefraction.
What is the straightening of the radar beam upward called?
Subrefraction.
What effect does superrefraction have on the displayed echo heights on the radar?
Displayed echo heights are overestimated.
What effect does subrefraction have on the displayed echo height on the radar?
Displayed echo heights are underestimated
List five assumptions that the basic radar equation makes?
The particles are small, homogeneous spheres whose diameters are much smaller than the radar’s
wavelength (Rayleigh scattering). The particles are spread uniformly throughout the contributing region
(sample volume). Precipitation throughout the sample volume is the same (all rain or all snow—no mixed
precipitation). The main lobe of the antenna beam pattern is adequately described by mathematical notation.
Attenuation and multiple scattering are negligible.
The reflectivity measurement received for each sample volume is simply a measurement of what?
Power, expressed in watts.
The strength of a thunderstorm return increases from 49dBZ to 52dBZ. By how much has the
strength increased?
100 percent.
How does the use of the decibel system, to compare returned radar energy, allow increases or
decreases to be expressed?
Logarithmically.
What is the best resolution for base reflectivity product and how are the sample bins averaged?
The.54nm reflectivity product. Average of four successive.13nm bins
Describe how the 1.1nm base reflectivity product is displayed.
Displays the highest of every two.54nm bins
Describe how the 2.2nm base reflectivity data is displayed.
Displays the highest of four.54nm bins
What is the maximum degrees of phase shift in electromagnetic energy that can be related to a
correct velocity?
179 degrees or less than 180 degrees.
If radar energy strikes a stationary target, what kind of phase shift is experienced?
The electromagnetic energy experiences no phase shift.
If a target moving toward the radar causes the energy to be backscattered, will it be at a higher or
lower frequency?
Higher.
What is the Doppler shift?
The change in position of the backscattered wave as the radar interprets it to be moving is called the
Doppler shift.
What is meant by the term radar coherency?
It is when a radar produces a pulse at the same frequency as the preceding ones and can remember the
specific frequency to determine the frequency shift, and therefore, the radial velocity.
The ability of the radar to compare the frequency of each new pulse with that of the preceding
pulse is known as what?
Pulsed-pair processing.
By convention, how are velocities toward the radar expressed?
Negative values.
206 q2
By convention, how are velocities away from the radar expressed?
Positive values.
207 q1
Define unambiguous velocity.
The limit to the speeds the WSR–88D can measure without error.
In radar terms, what are the speeds that exceed the maximum unambiguous velocity called?
Aliased velocities.
At how many degrees of phase shift do velocities become ambiguous?
Greater than or equal to 180°.
What limits velocity detection?
The wavelength of the radar.
How does increasing the PRF affect the chances of aliasing?
Increasing the PRF increases the Nyquist co-interval.
Define Doppler dilemma.
It is the tradeoff where an increase in PRF increases the maximum unambiguous velocity but decreases the
maximum unambiguous range.
What is the Doppler dilemma a compromise between?
The maximum range and the maximum velocity.
A PRF of 4,000 pulses per second results in what kind of velocity detection and range?
Since 4,000 pulses per second is a high PRF, velocity detection will be high, but the range will be very
short.
What is the square of the standard deviation of the distribution known as?
Variance.
206 q2
By convention, how are velocities away from the radar expressed?
Positive values.
207 q1
Define unambiguous velocity.
The limit to the speeds the WSR–88D can measure without error.
In radar terms, what are the speeds that exceed the maximum unambiguous velocity called?
Aliased velocities.
At how many degrees of phase shift do velocities become ambiguous?
Greater than or equal to 180°.
What limits velocity detection?
The wavelength of the radar.
How does increasing the PRF affect the chances of aliasing?
Increasing the PRF increases the Nyquist co-interval.
Define Doppler dilemma.
It is the tradeoff where an increase in PRF increases the maximum unambiguous velocity but decreases the
maximum unambiguous range.
What is the Doppler dilemma a compromise between?
The maximum range and the maximum velocity.
A PRF of 4,000 pulses per second results in what kind of velocity detection and range?
Since 4,000 pulses per second is a high PRF, velocity detection will be high, but the range will be very
short.
What is the square of the standard deviation of the distribution known as?
Variance.
The sample volume represents the smallest amount of the atmosphere that can be instantaneously
sampled by the radar. Why is this?
209 q2
The energy returned from particles separated by less than the sample volume’s dimensions will be averaged
together as a single return.
Which of the diagrams best shows a precipitation echo with large particles and high internal
shear?
Figure C, since large particles reflect more power back to the radar there will be more area under the curve.
What is most likely occurring when you observe low base reflectivity values with high spectrum
width values?
Early stages of convective development
What is most likely the most likely cause of uniform spectrum width values with isolated areas of
higher values?
Stratiform precipitation with embedded convection
Match the WSR–88D components/functions in column B with its function in column A. Items in
column B may be used more than once or not at all.
Column A Column B
____ (1) VCP 31 and 32.
____ (2) Separates the analog signal into the three digital base
moments.
____ (3) Controls the degree of clutter filtering.
____ (4) Connects the RRRAT to the RPG.
____ (5) Has a peak output of one megawatt.
____ (6) Could be hardwired, fiber optics, or microwave line-ofsight.
____ (7) Combines near zero velocities and small spectrum width
to distinguish targets.
____ (8) Employs variable PRFs.
____ (9) VCP 11 and 21.
____ (10) Connects the PUP to the RPG.
a. Wideband.
b. Narrowband.
c. Signal processor.
d. Transmitter.
e. Clutter filtering.
f. RRRAT.
g. Data thresholding.
h. Scan strategies.
i. Precipitation mode.
j. Clear-air mode.
(1) h.
(2) c.
(3) f.
(4) b.
(5) d.
(6) a.
(7) e.
(8) f.
(9) g.
(10) b.
Name the six basic subcomponents that make up the RDA.
The antenna, pedestal, radome, transmitter, receiver, and signal processor.
What determines the elevation steps used by the RDA’s antenna?
The particular volume coverage pattern (VCP) being used.
Why would the height of the radome be different for each RDA location?
The height depends on the location of the RDA to any nearby obstructions.
Describe the signal processor’s main job.
It takes the raw analog data from the receiver and processes it into a digital base data.
The WSR–88D combines what two features during the clutter filtering process to distinguish
between unwanted clutter and meteorological targets?
A near zero Doppler velocity and small spectral dispersion.
Explain the process the RDA employs that can eliminate most range folding problems.
212 q2
It uses the target ranges found from the low PRF to properly place the velocity and spectrum width data
gathered at high PRFs.
Why is VCP 11 the best scan strategy during the presence of severe thunderstorms close to the
RDA?
It slices a storm more times, providing detailed storm data.
The clear air mode contains two VCPs—VCP 31 and VCP 32. Both scan five elevations in ten
minutes. What is the difference between the two?
VCP 31 uses a longer pulse and a lower PRF to allow more power per pulse, resulting in increased
sensitivity. VCP 32 uses a shorter pulse and a higher PRF to increase the Nyquist co-interval, therefore
increasing the velocity resolution of the sample.
What RPG storage device can store up to three months or over 600 megabytes of product data?
Optical discs.
Where is the control of the RPG executed?
The RDA/RPG remote access terminal (RRRAT).
Name two functions used by the RRRAT to interface with the RPG.
An applications function and an RPG system control function.
What are the different types of base data the RPG receives from the RDA via wideband
communications link?
Reflectivity, radial velocity, and spectrum width.
Identify the method the RPG uses to dealias velocity data before using it in meteorological
algorithms.
The Eilts dealiasing technique.
____ (1) Hail.
____ (2) Shear.
____ (3) Storm segment.
____ (4) Precipitation adjustment.
____ (5) Velocity azimuth display (VAD).
____ (6) Tornadic detection (TDA).
____ (7) Severe weather probability (SWP).
a. VIL and SWP.
b. Storm analysis.
c. Clear air analysis.
d. Kinematic analysis.
e. Precipitation processing.
(1) b.
(2) d.
(3) b.
(4) e.
(5) c.
(6) d.
(7) a.
One-time product requests have the second highest priority in the RPG. What task has the highest
priority?
The task(s) generated by an automated alert.
What hardware makes up the PUP workstation?
The makeup of PUP workstation is two 19-inch color graphic displays, an applications terminal and system
console, a graphic tablet and puck, and a printer.
State the two major functions of the applications terminal.
Give commands to the PUP through the alphanumeric keyboard and view the alphanumeric displays on the
cathode-ray tube (CRT).
What does the system console provide?
Access to the PUP’s display processor and operating software.
State the primary interface between you and the PUP.
The graphic tablet.
Describe a routine product set list.
It is a list of product types and associated parameters that tells the associated RPG what products to send
routinely and repeatedly over the dedicated communication line.
A principal user having access to WSR–88D products through dial-in capabilities only best
defines what user?
A nonassociated user.
A WSR–88D CONUS site providing data via a dedicated or dial-in telephone link to a nearby
NWS Warning and Forecast Office (WFO) best defines what type of site?
A supplemental site.
Briefly describe two ways to select products from the PUP database.
Graphics tablet and puck OR the applications terminal.
Which menus on the applications terminal are used for product selection?
The display and status menus.
What does a list of thirty-one separate products sent to the RPG for delivery to the PUP best
define?
A routine product set (RPS).
When the weather mode changes, what happens to the current RPS list?
The current RPS list defaults to adaptation RPS list A or B.
Your associated RPG has just changed from clear-air to precipitation mode. Where do you find
the active RPS list?
On default RPS list A in the adaptation menu.
You should define your adaptation RPS list according to what?
Specific weather situations.
Who or what defines alert-paired products?
The associated RPG’s unit radar committee.
Name the different groups of alert thresholds.
The grid group, the volume group, and the forecast group.
Of all the alert categories within the volume alert group, which ones are not storm-based?
VAD and max one hour precipitation.
Of the three alert groups, which one is storm-oriented and requires a complete volume scan?
The forecast group.
How many threshold values for the mesocyclone (MESO) alert category are available to the PUP
operator?
Three.
Describe a user alert message (UAM) and what information is contained in that message?
The UAM is a brief message to the user defining the phenomena triggering an alert. The UAM contains the
location, type, and severity of the weather event and, if appropriate, storm speed and direction of
movement.
When the WSR–88D issues an alert to your PUP, what should you do?
Interrogate the products further to determine the validity of the alert.
217 7
Processing of alerts takes place where, while establishing alert areas is done where?
Processing takes place at the RPG, while the alert areas are established at the PUP.
What WSR–88D major components have archive capability?
The RDA, the RPG, and the PUP.
Explain the primary use of Archive Level I.
Maintenance activities such as testing the signal processors.
What is the media storage device for Archive Level II?
12-inch optical discs.
Which archive level uses a CDROM optical disc that has a storage capacity of about three
months of data or over 600 megabytes?
Archive Level III.
All PUPs are equipped with what archive level recording device?
Archive Level IV.
Briefly describe the term open system.
Using vendor-independent equipment instead of exclusive computer equipment designed for only one
purpose.
What type of computers does OPUP use?
Common, off-the-shelf computer systems.
What is the purpose of the GUI?
Allows radar users to view and manipulate radar information without having to use the puck and tablet or
the applications terminal used in the legacy PUP.
Do the legacy PUP and the OPUP functions differ? Explain why or why not.
OWSs may connect to 17 different RDAs while Weather flights can only view data from their own RDA.
Do the legacy PUP and the OPUP functions differ? Explain why or why not.
No. Functions are the same—only the capabilities differ.
A hook echo radar signature is actually what?
Precipitation wrapped around the vortex.
Where is a hook echo usually located in relation to the parent storm?
In the right rear quadrant of the parent storm with respect to its motion.
In what level of the storm should the radar operator look for a hook?
The mid-levels of a storm.
The WSR–88D’s 10cm wavelength makes finding embedded thunderstorms in stratiform
precipitation easier by reducing what atmospheric problem?
Attenuation.
How does the melting level appear on WSR–88D single-slice reflectivity products?
A ring or partial ring of enhanced reflectivity.
What factors may prevent detection of the melting level on WSR–88D reflectivity products?
Too few clouds present at the melting level, a disruption of the melting level by some form of turbulence or
convection, and heavy precipitation that may saturate the display.
Below what measurement of dBZs are most returns considered non-precipitable?
18dBZs.
A backward S-shaped velocity pattern suggests what type of advection is occurring?
Cold-air advection.
What is most likely occurring when a base velocity product displays a rapid change in velocity
values over a very short distance with a directional change?
A frontal boundary.
The radar is to the south of a velocity pattern with inbound velocities on the left side and
outbound velocities on the right side as you look at the pattern. There is a Doppler zero velocity
line, oriented north-to-south, separating the inbound and outbound velocities. What does this
pattern suggest?
221 3
Rotation.
The radar is to the north of a velocity pattern with a Doppler zero line oriented west-to-east. On
the north side of the zero line, closest to the radar, there are inbound velocities. On the south side
of the zero line, farthest from the radar, there are outbound velocities. What does this pattern
suggest?
Divergence.
What is the best WSR–88D product to use to identify veering winds with height?
Base velocity.
What does the spectrum width product provide a display of?
The variance of motions within the mean radial velocity field.
What can the spectrum width product be used for?
It is used with other products for estimating turbulence associated with thunderstorms, frontal boundaries,
and clear air. It is also used to show the validity of mean radial velocity estimates and gives a first look at
possible convective development.
Within a sample volume, what does the WSR–88D sense?
A combination of different particle motions.
The maximum returned power is usually at what frequency?
The frequency of the backscattered energy from the largest meteorological targets.
In a geographical area where turbulence is suspected, what type of spectrum width values would
you expect?
Comparatively higher values.
What can the spectrum width product identify to aid in forecasting icing?
The increased variance in particle velocities.
For which product can the spectrum width product be used as a data reliability check?
Mean radial velocity.
What is the best use for the CR product?
To get the overall “total” picture of what is happening in the atmosphere.
How can the CR product be displayed?
By itself or as a background for overlays.
From how many elevations does the CR product provide the WSR–88D user with a composite of
reflectivity?
The entire volume scan.
At one geographical location, you have three elevation slices with reflectivity values of 35dBZ,
40dBZ, and 25dBZ. What reflectivity value will be displayed for that location on a composite
reflectivity product?
40dBZ.
What do reflectivity values displayed on a CR product represent?
The maximum reflectivity in the entire volume scan.
Why can volumetric overlays be used with the CR product?
Because it is a volumetric product.
List three limitations of the CR product.
Many of the typical horizontal plane signatures that do not exhibit high reflectivities are not visible on the
CR product (e.g., hook echo). Other features may also be disguised on the CR product. If you detect a
classical feature on CR, investigate it further by using base reflectivity. Altitude information about the 3-D
structure of reflectivity is lost. Since CR is made up of information that comes from the base reflectivity
products, many of the same situations that affect the quality of reflectivity data also cause problems with
CR. (Any three limitations will suffice)
What is the major difference between the composite reflectivity and layered composite
reflectivity maximum product?
The CR product is produced by using the entire volume scan, which makes it difficult to determine the
approximate altitude of a particular reflectivity value. The LRM uses three layers—low, mid, and high—in
the production of the product. This allows you to look at maximum reflectivities for a specific section of the
storm.
In how many data levels is the LRM product available?
8
What are the data thresholds for the LRM product?
From 5 to 57 dBZ.
What is the height range of the low layer for the LRM product?
224-4
Surface to 24,000 feet.
Describe a use of the LRM product.
In providing the operator a quick look at significant reflectivity values for a specified layer. The LRM is an
excellent way of tracking the intensity trends of convection.
Name some limitations of the LRM product.
The LRM uses only three elevation angles that fall within the altitude of the layer specified; is adversely
affected at distant ranges from the radar where the layer may only encompass one or two elevation slices.
At close ranges, mid and high layer altitude products are ineffective due to the cone of silence. Signatures
such as hook echoes, BWERs, and WERs may not be detectable because of the LRM’s use of several
elevation slices.
How is the LRM APR different from the standard LRM product?
An algorithm is used to remove reflectivity readings from ground targets.
Describe the omit all region used by the LRM APR algorithm.
It is defined as the portion of the atmosphere within 45km of the RDA and below 1km in altitude. The
algorithm discards all reflectivity returns from this region, thereby deleting them from the product display.
Describe the accept if region used by the LRM APR algorithm.
It is defined as the portion of the atmosphere within 103km of the RDA, on the 0.5° elevation slice and
below 3km in altitude, and not within the omit all region. A target in this region is accepted for inclusion in
the product if its velocity is > 1.0m/s and its spectrum width is > 0.5m/s.
Describe the reject if region used by the LRM APR algorithm.
It is defined as the portion of the atmosphere within 203km of the RDA and below 5° in elevation. The
region does not include any of the omit all and accept if regions. A reflectivity return is rejected by the
algorithm if its velocity is < 1.0 m/s and its spectrum width is < 0.5m/s.
What are the altitude settings for the LRM APR product?
Surface to 24,000ft.
Name some of the limitations of the LRM APR product.
The algorithm works best if traditional clutter filtering is applied before the algorithm begins processing
data. The algorithm assumes all reflectivity returns below 1km in altitude and with 45km of the RDA to be
clutter. This could result in valid meteorological data being removed. Current parameters may not be the
optimum settings and further testing may be needed to enhance the algorithms processing.
How many data levels does the VIL product display?
16
226-2
The VIL product is derived from what base product(s)?
The reflectivity product.
What is indicated by the values displayed on a VIL product?
How much water is in the storm.
VIL product values are in what units of measurement?
Kilograms per the mass squared (kg/m2).
Can the VIL product be useful for monitoring radar echo patterns for the beginnings of significant
convective development?
Yes
What are considered significant or high VIL values?
Significant or high VIL values vary according to geographical location, season, and weather system.
Besides the actual VIL values, what other detail(s) of the VIL product should you look for?
VIL patterns, trends, and gradients.
List two limitations for the VIL product.
Include any two of the following: VIL values change from seasonal variations, diurnal variations, and airmass
variations. A strongly tilted storm that may not have all of its vertical extent within the same stack of
grid boxes. An underestimation of the severity of a storm, due to its traveling through and even exiting the
stack of grid boxes. Factors that cause errors in reflectivity also cause errors with VIL.
What kind of VIL values do generally warm, moist air masses exhibit during severe weather
occurrences? What about cool, dry air masses under the same circumstances?
Higher values exist with warm, moist air masses during severe weather occurrences, while cool, dry air
masses generate lower values.
How is the SWP product displayed?
Independently or as an overlay.
What does the SWP product estimate the probability of?
That a particular storm cell will produce severe weather.
What data is used to calculate the values displayed on the SWP product?
VIL
What does the SWP product use to monitor SWP values?
A set of grid boxes.
How does the size of the SWP grid boxes compare to the VIL grid boxes?
The size of the SWP grid boxes is larger than the VIL grid boxes.
What can be said about SWP values if the VIL values are suspected to be unreliable?
The SWP values will most likely also be unreliable.
The echo tops product is based on data from what other product?
Base reflectivity.
What does the echo tops product use to compute echo top heights?
2.2 × 2.2nm grid boxes.
What is the ET product useful for?
It is useful as part of briefings prepared for aviation interests and the public. It can be used in defining
strong updraft regions or the presence of vertical tilt in a storm. Observation of collapsing echo tops can aid
in timing the onset of a severe weather event.
How does the echo tops product provide the heights of cloud tops?
By the return energy at more than a preset, adaptable threshold.
With the echo tops product, can a relationship be made between increasing and decreasing echo
tops and the strength of the updraft?
Yes, an increasing echo top is probably increasing in intensity while a decreasing thunderstorm echo top
could show a weakening storm. If the echo top collapses very quickly it may suggest a downburst occurring
on the surface.
Can the echo tops product be used to identify the beginning of embedded convective activity in a
stratiform cloud layer? Explain.
Yes, if a stratiform situation exists and convective clouds start to develop within the stratiform clouds, the
echo tops are usually detected before any indications on base reflectivity. As the updrafts develop and push
the tops of the cloud higher, these higher tops can be seen as mid-level echo tops on the ET product.
Do you ever use the echo tops product as the sole indicator of what is taking place in the
atmosphere?
No.
List the sources of data contamination for the echo tops product.
Side lobes, gaps in the volume coverage pattern, or if the true tops are above the highest elevation slice.
What occurs if the true echo top height exceeds the maximum elevation of the radar antenna?
The displayed echo top will be less than the actual top.
The HSR product is the foundation for what products?
Precipitation products
How do the HSR products assist forecasters?
In determining the accuracy of WSR–88D precipitation products.
What is the overall purpose of the HSR algorithm?
To search for low-level reflectivities (possibly precipitation) while eliminating ground clutter and
correcting for beam blockage.
Describe the terrain based hybrid scan.
The algorithm begins collecting data from the 0.5° slice unless it detects beam blockage. If detected, it
collects data from the slice above, the 1.5° slice. It follows this technique of moving up a level when beam
blockage occurs, to a maximum 3.4° in elevation.
Describe the tilt test.
The tilt test compares the areal coverage of echoes at 0.5° and 1.5° elevation slices. If a 75 percent (default
value) or greater reduction is found in the echoes at 0.5° slice as compared to the 1.5° slice, then the
algorithm assumes the echoes to be clutter and removes them from further processing.
What does the radar display when the tilt test determines echoes on the 0.5° elevation slice to be
clutter?
The message “LOWEST TILT UNUSED” will be displayed in the status and annotations area just above
the data levels in the product legend.
List some of the limitations of the HSR product.
The HSR product may display abrupt changes in reflectivity values at hybrid scan ranges. In some
instances, especially at RDAs located at higher elevations, it is possible the tilt test may eliminate valid
precipitation echoes during stratiform precipitation events.
List uses for STP product.
230-1
Include any two of the following: to give an estimate of total basin runoff due to a single storm, provide
rainfall data 24 hours a day, aid in the evaluation of flood reports, and provide a post storm analysis.
When does the STP reset?
If there has been no rainfall for more than one hour.
List the limitations of the STP product.
It has trouble with small-scale features and extended system outages during precipitation events,
compromise the data. Breaks in precipitation of more than one hour reset the system. Non-precipitation
reflectivity, such as clutter or anomalous propagation, may contaminate data. Also, the product does not
account for snow or frozen precipitation, bright bands, reflectivity gradients, or attenuation.
When is the STP product available?
From the first volume scan of detected rainfall.
What is the difference between the storm total, one hour and three hour precipitation products,
and the user selectable precipitation product?
The period of time the products use to accumulate precipitation amounts.
How many data levels is the USP product available in?
16.
What is the range of the USP product?
124nm
What accompanies the graphic product and provides the operator with the gage bias, the number
of hours used to build the product and whether or not a specific hour was used in the generation
of the product?
An attribute table
What is the maximum length of duration for which the USP product can be built?
24 hours.
List five uses of the USP product.
Monitoring precipitation for a specified time period, post storm analysis, estimation of basin run-off for a
specified time, estimation of basin saturation, and evaluation of flood reports.
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How many requests for the USP product, per volume scan, can the RPG satisfy?
Up to 10 requests per volume scan.
Through what technique does the mesocyclone algorithm locate a mesocyclone?
A pattern recognition technique.
The 2-D processor searches for cyclonic shear by identifying what?
Pattern vectors.
What are pattern vectors?
A series of azimuthally adjacent sample volumes having a continual decrease in Doppler velocities.
What processor has a task of building an attribute table for each identified vortex?
The 3-D processor.
What is the optimum effective range of the mesocyclone detection algorithm?
65 nautical miles.
How is the mesocyclone product affected by range-folded data?
Range-folded data can mask features.
No-data gaps are most prevalent in what volume coverage pattern?
VCP 21.
Does the mesocyclone detection algorithm establish time continuity? Explain.
No, that is left up to the operator.
The azimuthal diameter between the maximum inbound and maximum outbound velocity must be
less than how many nautical miles?
Five nautical miles.
What is the second step for identifying mesocyclones?
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To determine vertical continuity.
What overlay product can assist the operator in the identification of a mesocyclone?
The rotational velocity/shear display.
The TVS product provides the location of what two signatures?
TVS and ETVS.
What is the graphic symbol for a TVS and ETVS?
The TVS symbol is an inverted, red-filled isosceles triangle. The ETVS symbol is an inverted, red, open,
isosceles triangle.
How does the TVS product aid forecasters?
In the identification, forecasting, and warning of severe weather associated with tornadoes.
Describe a TVS.
A TVS is a three-dimensional circulation with a base located on the 0.5º slice or below 600 meters ARL.
The depth of the circulation must be at least 1.5km. Additionally the maximum shear detected anywhere in
the circulation must be at least 36m/s (≅ 72 knots), or at least 25m/s (≅ 50 knots) at the base of the
circulation.
Describe an ETVS.
An ETVS is a three-dimensional circulation with a base above the 0.5º and above 600 meters ARL. The
depth of the circulation must be at least 1.5km. Additionally, the delta velocity at the base of the circulation
must be at least 25m/s (≅ 50 knots).
List the steps of the TDA algorithm.
There are three steps: 1-D step, 2-D step, and 3-D step.
What is gate-to-gate shear?
Doppler velocities of opposite sign, located on adjacent sample volumes.
Describe the limitations posed by beam broadening on the TVS product.
Beam broadening may cause small scale features to be missed or improperly identified, especially at ranges
past 60km from the RDA. Beyond 60km, the TDA will most likely trigger by a strong mesocyclone.
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What may result when the TVS product gives false alarms?
False alarms may result in an over-warning, or desensitizing of forecasters.
What is the total number of vertical wind profiles that can be displayed on a single VWP?
Eleven.
What is the smallest altitude interval that can be selected for wind display purposes on the VWP?
1,000 feet.
If you want an estimate of the current climb winds, what is the best product to use?
VAD winds profile product.
What are the inputs to the VAD algorithm?
Velocity and base reflectivity.
What does a low RMS at a particular height on the VWP mean?
The more reliable the wind data at that level.
To compute the RMS offset, what is the amplitude of the VWP sine wave divided in half by?
The zeroth harmonic.
Whenever the VAD algorithm finds that velocity data for a particular altitude does not meet
reliability thresholds, what symbol does the product display for that altitude?
ND
What are the SRM/SRR products used for?
To aid in the visual identification of storm rotation in the mean radial velocity field when rotational
signatures are obscured by storm motion.
From what base product are the SRM/SRR products derived?
The velocity product.
What algorithm does the SRM/SRR depend on?
The storm tracking algorithm.
For the SRM, how is storm motion determined?
Storm motion defaults to the average track that is determined by averaging all the tracks calculated by the
storm tracking algorithm.
What information does the SWA products provide?
Radial shear, spectrum width, mean radial velocity, and reflectivity, in 27 × 27nm areas at the highest
resolution available.
What is the primary intention of the SWA?
Its primary use is for a detailed analysis of severe weather.
What resolution is the severe weather analysis reflectivity product available in?
0.54nm by 1°.
What is the limitation that causes small features at long distances to go undetected?
Beam broadening.
To interrogate a feature over 60nm in size, what product(s) would be best?
Base products.
What do cross-section products provide?
A vertical cross-section of the particular base moment on a height (in the vertical) versus distance (in the
horizontal) axis.
Cross-section end points must be within how many nautical miles of the RDA?
124 nautical miles.
In clear-air mode, what is the reflectivity cross-section used to determine?
The depth of the moist layer, frontal slope, changes in the refractivity index, and cloud bases and tops.
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What is the most important thing to keep in mind when requesting a velocity cross-section?
It must be cut either parallel or perpendicular to a radial.
Which cross-section product is most often used with other cross-sections to verify the existence
of turbulence?
The velocity cross-section.
The velocity cross-section is limited to how many nautical miles?
124 nautical miles.
What data collection limitation of the reflectivity cross-section product causes reduced values at
long ranges?
Beam broadening.
What algorithm uses the output of the SCIT algorithm?
The hail algorithm.
What is the first algorithm employed within the SCIT algorithm?
Storm cell segments.
What is the lowest minimum reflectivity threshold used to identify a storm cell segment?
30dBZ.
What is the minimum segment length threshold used to identify a storm cell segment?
1.1nm.
What algorithm processes the output of the storm cell segments algorithm?
Storm cell centroids algorithm.
What is the purpose of the storm cell centroids algorithm?
To identify the center points of identified storm components.
What is the maximum number of storm cells that can be identified by the storm cell centroids
algorithm?
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100 storm cells.
What is the purpose of the storm cell tracking portion of the storm cell tracking/position
algorithm?
To monitor the movement of storm cells by matching cells found in the current volume scan to the cells
from the previous volume scan.
How does the storm cell tracking portion of the storm cell tracking/position algorithm label a
storm if it is unable to correlate a centroid with a centroid from a previous volume scan? Is a track
forecasted for this storm?
It labels the storm as “NEW” and does not forecast a track.
What is the determining factor for the length of a storm position forecast?
The accuracy of the previous volume scan’s forecast.
What product receives data developed by the SCIT algorithm?
Storm track information product.
What information is contained on the storm tracking information alphanumeric product?
Storm ID, current cell position, direction and speed of movement, azimuth and range for the 15, 30, 45, and
60 minute forecast positions and the mean and forecast tracking error.
List two limitations of the storm cell tracking/position forecast algorithm.
If stronger reflectivity values exist in a storm above the lowest component, the algorithm may misconstrue
that component as the lowest component. This would cause a misinterpretation of the storms overall mass
and would affect other algorithm calculations. Also, when in VCP 21, large errors may occur in the cell
attributes of storms. Storm calculation can be adversely affected by what the radar is not sampling in the
data gaps associated with this VCP.
What is the purpose of the hail detection algorithm?
To identify which storms have the potential to produce hail.
What three estimates does the hail detection algorithm provide?
Probability of hail, probability of severe hail, maximum hail size expected.
How is the probability of hail represented graphically?
With a small, open, or solid green triangle.
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What information is displayed on the hail index alphanumeric product?
Storm ID, probability of hail, probability of severe hail, and maximum expected hail size.
Name two limitations of the hail detection algorithm.
Include any two of the following: the HDA needs accurate and timely measurements of the MSL altitudes
for the 0°C and –20° C levels. Failure to update this information will degrade the algorithm’s performance.
In limited operational use, the POSH and MEHS have tended to overestimate the chances and size of hail in
weak wind and tropical environments. The accuracy of the hail estimates partially depends upon the
accuracy of the cell component information provided to the algorithm.
What information does the storm structure alphanumeric product display?
Storm ID, azimuth and range of centroid, base height of storm, top height of storm, cell-based VIL,
maximum reflectivity in the cell, height of maximum reflectivity.
What is the cell trends product?
A graphic display that gives up to a 10-volume scan history of cell parameters for algorithm-identified
storms cells. Cell trends is not an actual product. It has no product ID# or mnemonic.
List three uses of the cell trends product.
Cell trends provides continuity on individual storm cells over a period of time. By tracking the increase or
decrease of storm tops, maximum reflectivity values, and cell-based VIL, you’ll have a better idea of what
to expect from storms in the area. You can also determine the status of supercells and the potential for
microbursts. After a weather event occurs, the cell trends display may be used for post-storm analysis.
Describe a limitation of the cell trends product.
Include any of the following: the volume coverage pattern employed has a direct impact on the cell trends
display. VCP 21 has fewer slices, resulting in more variability of displayed data. Range to the cell is
another concern when using the cell trends display. At far ranges, data may be unreliable due to the cell
being sampled by only the lowest elevation slices. Storm cell bases will be overestimated. Inversely, cells
in close proximity to the RDA, may be effected by the cone of silence, resulting in the mid and upper levels
of the storm not being sampled.