Weather Radar Faq Second Set

7/31/2019 Weather Radar Faq Second Set

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28/12 WEATHER RADAR FAQ SECOND SET

eweatherprediction.com/radared/radarfaq2/

The reflectivity gradient is important because it can give clues to ifsevere convective wind gusts

are occurring. Severe convective wind gusts are more likely to occur when there is a strong

reflectivity gradient. The leading edge of severe thunderstorms often have an abrupt transition

zone ofheavy precipitation and wind. In this region the outflow from the storm is progressing into

the environmental air ahead of the storm. Strong convective winds will force the reflectivity into

an abrupt zone where the reflectivity changes rapidly over a small distance. Look for severe

convective wind gusts when red reflectivity is next to very little or no reflectivity. This is

especially true if the storms are in a line segment that is bowing.

22. What are echo tops and their importance?

An echo top is the radar indicated top of an area of precipitation. Once the precipitation intensity

drops below a threshold value as the radar beam samples higher elevations of a s torm or

precipitation region then the echo top is located. The cloud top will often extend above the echo

top since clouds are more difficult to detect by radar.

Echo tops can be used to assess the intensity of a storm. The rule of thumb is that the higher the

echo tops are in a storm then the stronger the updraft is that produced that storm. A stronger

updraft makes convective wind gusts andlarge hail more likely. When there are several stormson radar, the ones with the higher echo tops may be the most likely ones to produce the most

significant severe weather (convective wind gusts and hail).

23. What is bright banding and how does it occur?

Bright banding occurs due to the higher reflectivities associated with snow that is melting as it is

falling aloft. Ice is a better absorber of radar radiation compared to liquid water. Because of this,

snow will show a lower reflectivity on radar when it has the same moisture content as a rain event.

When the snow is melting however, a film of water forms on the outside of the snowflake. Since

snowflakes can be fairly large, when there is a film of water on the snowflake it has the same

reflectivity as a a giant raindrop or small wet hail.

A radar beam will generally sample a higher elevation as it moves away from the radar site.

Because the melting of the snowflakes occurs within a specific elevation range aloft, there will be

a higher reflectivity as the radar beam moves through this layer. This can produce a circular or

arcing band of higher reflectivity around the radar site on the reflectivity display.

Below are some bright banding examples (more examples will be added over time):

Dallas / Ft. Worth Area Bright Band


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24. VIL and updraft strength?

VIL (Vertically Integrated Liquid) is a summation of reflectivity through a vertical column of the

troposphere. VIL is most accurate at the medium ranges from the radar site since the radar is

able to sample most of the vertical column of the storm. If the storm is too close to the radar then

part of the storm will be in the cone of silence and if the storm is too far from the radar then the

bottom portion of the storm under the lowest tilt angle will not be sampled.

The higher an updraft penetrates through the troposphere then it is more likely significant

moisture has been funneled and suspended in that vertical column. If it is not apparent on

reflectivity which storms have the strongest updrafts then the VIL can be used to determine which

storms are most likely to have the strongest updrafts. Higher VIL values occur with suspended

hail, heavy rain and precipitation extending through a deep vertical depth of the troposphere.

25. How does snow look on radar?

Snow often has the following features on radar:

a. A fairly low reflectivity for dry snow. Wet snow can have a much more significant reflectivity.

Determine the likely water content of the snow along with examining the radar images.

b. The gradient between colors tends to be gradual. Often there are varying shades of the lower

reflectivity colors.

c. It tends to have a grainy or fuzzy appearance. The edges of the precipitation areas may not

have a well defined edge in light snow situations.

Below are some examples of snow on radar (more examples will be added over time):

SNOW ON RADAR


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26. What creates a bow echo?

Bow echoes, when they occur, usually occur with a grouping of multicell storms that are arranged

into a squall line. The upper tropospheric winds steer storms. These winds help determine the

speed and direction that the storms move. The upper tropospheric winds will not always be

constant along a squall line. In the regions these winds are stronger that portion of the squall line

will surge forward. Also, in regions these winds are drier that portion of the squall line will surge

forward because evaporative cooling creates negative buoyancy that will further accelerate a

downdraft toward the surface. Since the downdraft from a squall line approaches the earth's

surface at an angle, the faster the downdraft winds the faster the storms may migrate forward.

Below is an example of a bow echo:

BOW ECHO

The next example is that of a bow echo with a line-end vortex on the north side of the squall line:

LINE-END VORTEX


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27. What is an inflow notch?

There are two types of inflow notches that will be discussed which are the low level inflow notch

into the updraft of a storm and the mid-level rear inflow notch into the back side of a storm. The

characteristic that both types of inflow notches have is that there tends to be reduced reflectivity

in the region they occur since the air is either too dry or is moving too quickly to allowprecipitation to develop or fall through this air.

First will be shown a couple of examples of inflow notches into a supercell. Within the inflow

region is the updraft. There tends to be lower reflectivities in the updraft region and higher

reflectivities in the downdraft region. Within an inflow notch is the low level wind into the updraft

of the storm. A classic supercell will take on a hook like feature and an HP supercell will take on a

kidney bean feature. An example of each is shown below:

Classic Supercell

HP Supercell

A rear inflow notch enters the backside of a storm in the middle levels of the troposphere. These

inflow notches are particularly conducive to severe weather if they ingest high momentum and dry

air into the storm. If the air is dry it will cool through evaporative cooling. This will increase the

negative buoyancy of the air and it will accelerate toward the earth's surface. This negative

buoyancy acceleration along with the air's initial high momentum can produce severe convective

wind gusts at the leading edge of the storm or storm complex. An example of a storm complex with

a rear inflow notch is shown below:


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28. Anvil blowoff on radar

Much of the light precipitation detected on radar does not reach the ground. This is especially

true if there is a dry layer of air between the surface and from where the precipitation is falling.This is even more especially true if the precipitation falls through a deep dry layer and the

precipitation begins the fall from high aloft. Rain falling from high aloft is very common in the

downwind portion of a thunderstorm.

Mammatus and virga are common on the downwind side of a storm. When the radar beam gets

high enough it will detect these thick clouds and virga aloft. This may mislead the radar operator

into thinking precipitation is reaching the ground in those locations when it is not.

Strong winds will shear the top of a thunderstorm. This moves thick cloud, precipitation and virga

downwind from the storm. If this shows on radar as a green color it is likely not reaching the

ground.

Keep the following in mind:

1. Anvil blowoff will be especially evident at long ranges from the radar since the radar beam

increases in elevation away from the radar site.

2. Anvil blowoff will generally show as light reflectivity (usually color coded green) and this

reflectivity generally does not result in precipitation reaching the ground.

3. Strong updrafts in a strong shear environment (strong upper level wind) will often have the anvil

blowoff showing on radar.

4. Anvil blowoff tends to show up best on composite reflectivity since it is using multiple tilt angles

and showing reflectivity from all the different angles.

Here are some example of anvil blowoff from storm(s) on radar:


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29. Recognizing flooding potential on radar

Radar is an important nowcasting tool for recognizing flooding potential. Flooding occurs when too

much rain falls over a given time period for the ground surface to support. The flooding potential

will be greater when storms move over previously saturated land, snowmelt combines with rainfall

or rain falls over land that has a low permeability. Any of the following seen on radar can produce

flash flooding especially if the land is already saturated:

1. Training thunderstorms- thunderstorms developing and moving over the same areas that

previously had thunderstorms.

2. Very intense slow moving thunderstorms- a single slow moving thunderstorm can produce

several inches of rainfall per hour.

3. Consistent rain- rain (especially heavy rain) falling over an extended period of time.

30. Calculation of radar shear

There are many different types of shear. When it comes to the use of the term shear on a Doppler

radar product what is usually being referred to is the addition and inbound and outbound winds

that are adjacent to each other. For example, if a radar meteorologist says there are 80 knots of

shear it means the winds going toward the radar added to the winds going away from the radar on

two adjacent radar range gates is 80 knots.

Another term that is used in radar meteorology is the rotational velocity. This is found by adding

the inbound and outbound winds and dividing by 2. If the inbound velocity is 30 knots and the

outbound velocity is 52 knots, then the rotational velocity will be 41 knots.

31. Inversions and radar ground clutter

The temperature profile of the troposphere makes a strong contribution to how radar emitted

radiation will refract in the troposphere. Superrefraction is the beam bending more toward the

earth's surface than in normal tro os heric conditions and subrefraction is the beam bendin less


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toward the earth's surface than in normal tropospheric conditions.

An inversion is a situation in which the temperature increases with height. Thus it is a situation

where there is colder air under warmer air. An inversion layer is a layer of stability since cold air

under warm air is a stable situation. A common type of inversion is the radiational cooling

inversion in which overnight the earth's air near the surface cools by ground surface longwave

radiation emission. The optimum conditions for a radiation inversion is a dry, clear and long night.

Inversions at and near the earth's surface can also occur due to shallow cold front passages and

evaporative cooling in the boundary layer. An inversion promotes superrefraction.

Ground clutter is returns to the radar from radar emitted energy scattering off of objects on and

near the earth's surface. Ground clutter is most evident when low tilt angles are used since the

radar energy travels close to the earth's surface especially at close ranges to the radar. Since a

superrefraction situation causes the radar beam to travel closer to the earth's surface,

superrefraction will promote an increase in ground clutter.

Thus, the combination of a low tilt angle and an inversion at and near the earth's surface promotes

an abundance of ground clutter. Below is an example radar images using the lowest tilt angle (0.5

degrees) taken in the morning when a radiation inversion was in place.


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32. Rmax and Vmax as it relates to the Pulse Repetition Frequency

The Pulse Repetition Frequency (PRF) is the number of radiation pulses emitted by radar in 1

second. For example, if the radar emits 400 pulses in one second then the PRF is 400

pulses/second. Think of pulses like the pulses of a strobe light. A strobe light alternates between

light and dark and there is light a certain number of times within a given period of time. Radar issimilar except the number of pulses is much more per second than a strobe light and radar emits

microwave type wavelength radiation. Another difference is that the radar spends less than 1% of

the time emitting radiation and over 99% of the time sensing for returned radiation. Radar can

sample the troposphere very fast because the speed of light is fast (about 300,000,000 meters per

second).

Rmax stands for the maximum range the radar can detect. If the radar emitted a pulse of energy

and waited as long as needed for returning radiation then the radar could detect to any range.

However, since the speed of light is so fast compared to the distances we need to measure returns

in the troposphere the radar is not required to wait more than a tiny fraction of a second for return

energy to come back. Thus, the radar can be set to emit and listen for 100s of pulses per secondand we can still measure ranges that cover a broad area. However, the faster the PRF becomes

the smaller of a range that can be detected. If the PRF is set too fast then there is not as much

time to sample the troposphere in one pulse before the next pulse is sent out. Energy returned

from one pulse after another pulse has been sent will be range folded.

Suppose the PRF is 500 pulses per second. The formula for Rmax is C / (2 * PRF). C stands for

the speed of light. With a PRF of 500 pulses/s, the Rmax is = 300,000,000 m/s / (1,000 s^-1) =

300,000 m which is equal to 300 km. Thus the radar can sample up to 300 km during each pulse. If

a return is beyond 300 km then it will be range folded and will show up at a distance closer to the

radar than the return really is because the radar thinks it is getting returns from a second pulse it

already sent out.

Suppose we increase the PRF to 1,200 pulses per second. Rmax then becomes 300,000,000 m/s /

(2,400 s^-1) = 125 km. From these two examples you can see that as the PRF increases, then the

Rmax becomes a smaller range. This makes sense because the faster pulses are emitted the less

time there is for the pulse to travel and come back to the radar before the next pulse is emitted. If

we want to detect echoes beyond 125 km we will need to decrease the PRF from 1,200 to a

smaller number.

When a reflectivity image is put into motion we can see where the precipitation areas are moving

toward and how fast they are moving. However, we can not see the motions within the

precipitation areas very well. To help with that problem Doppler radar has come along.


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Look at the image below depicting an idealized veering wind. The winds near the radar are from

the east. We know this because of the yellow colors immediately to the west of the radar (motion

away) and the blue colors immediately to the east of the radar (motion toward). The white curving

line on the image is the zero radial motion. Within the area in white motion is neither toward or

away from the radar but is rather motion that is remaining equidistant from the radar site at that

point in space. A key point to remember is that the winds will flow perpendicular to this white zero

radial velocity line. At the middle ranges from the radar site the winds are from the southeast and

south. We know this is the wind direction here because winds cross the white radial velocity

perpendicularly and motion is from the blue and green colors toward the yellow and red colors. Atthe outer ranges of the radar the wind is from the southwest. The outer ranges of the radar will be

the highest in elevation sampled.

Thus, going from the surface to aloft the winds shift from easterly to southeasterly to southerly to

southwesterly. This is a veering wind since the wind is turning clockwise with height. A veering

wind is associated with warm air advection since low level winds from a southerly direction will

generally transport in warmer air. Remember the initials CVW, where these letters stand for

Clockwise, Veering, Warm Air Advection.

A veering pattern on radial velocity will have an S-shaped pattern. See the veering wind image

below and notice the S-shaped signature made by the white zero radial velocity radial. A student

posted a message for the way to remember that an S-shaped pattern is associated with warm air

advection is to remember that Superman has a warm heart. Superman has an S on the shirt.

The second image below shows a backing wind. The wind is from the east at the surface, then

gradually shifts to the northeast and then to the north at the outer range. A backing wind will shift

counterclockwise with height. Remember the initials CCBC, where these letters stand for

Counter-Clockwise, Backing, Cold Air Advection. A backing wind pattern will have a backward-S

shaped radial velocity pattern.

VEERING WIND WITH HEIGHT

BACKING WIND WITH HEIGHT


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34. Wavelength and frequency of light and perspective of observation

In a vacuum light travels at the maximum velocity which is 299,792,458 m/s. Light will travelslower than this speed and will decelerate when it travels through gases (such as the earth's

atmosphere), liquids (such as the earth's ocean) and land. The denser the object and the longer

light has to travel through the object, the more light will slow down and absorb into the object. If

the substance is dense enough such as land or very deep waters it will absorb the energy

completely.

Light has a couple of important properties which are frequency and wavelength. Light travels as

both a particle and a wave. Waves have a frequency (number of waves passing a fixed point

through time) and a wavelength (length of one complete wave). The frequency is measured in

Hertz (waves passing per second) and the wavelength is measured in meters or fractions of a

meter.

While the maximum speed that light travels is not a function of relativity, the motion of an object

compared to the motion of surrounding objects will cause the wavelength and frequency to be

different from different perspectives. Suppose an object emits radiation with a wavelength of 7

micrometers and this object is moving quickly away from an observer. The observer will discover

the wavelength as being greater than 7 micrometers when it reaches the observer. This is called a

red shift since the wavelength is observed as being longer than what the emitter radiates. The

light from many galaxies is red shifted and this is used as evidence that the universe is expanding

since many galaxies are moving away from each other.

Imagine a very long rope with waves traveling through the rope. Suppose you are stationary and


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notice 100 waves passing you per minutes. Now suppose you are set in motion in the same

direction the waves are moving through the rope. From this new observational perspective you will

notice less than 100 waves passing you per minute. The frequency has decreased. This is a red

shift. When the frequency of light decreases the wavelength increases.

When an emitter of radiation is getting closer to the observer over time the observer will notice a

higher frequency and shorter wavelength than what the emitter is radiating. This is known as a

blue shift. Suppose you are stationary and notice 100 waves within a very long rope passing you

per minutes. Now suppose you are set in motion in the opposite direction the waves are moving

through the rope. From this new observational perspective you will notice more than 100 waves

passing you per minute. The frequency has increased. When the frequency of light increases the

wavelength decreases.

See this link for information on universe expansion and evidence for it:

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/ExpandUni.html

35. Increasing the power returned to the radar

The power returned to the radar is much less than the power transmitted by the radar. Imagine

the sun as a transmitting radar and the planets are the hydrometeors. Some of the sun's energy

goes from the sun and is reflected off the planets back toward the sun. This energy that makes it

back to the sun is only the slightest of a tiny fraction of the original energy the sun emitted.

The return that makes it back to the radar is a function of several variables. The radar equation

will show us these variables.

The radar equation (power received back to radar) is =

(Pi^3*Pt*g^2*O*o*h*K^2*l*z) / 1024*Ln(2)*wavelength^2*r^2

Where Pt is power transmitted, g is gain, 0 and o are beam widths, h is pulse length, K isrefraction term, l is attenuation term, z is radar reflectivity factor, wavelength is the wavelength

used by the radar and r is the radius from the radar to the precipitation echoes.

Most of the variables in the radar equation are constants for any given radar, thus the equation

simplifies to:

Pr (power returned to radar) = (c2*z)/r^2

c2 is the single value of all the constants put together. This constant will be different for different

radars and we will go over how power received can be increased by using a different radar later in

this essay.

First we will look at the power received as a function of the radar reflectivity factor and the radius

from the radar to the precipitation echoes. Notice in the equation Pr = (c2*z)/r^2, that z is in the

numerator while r is in the denominator. Since z is in numerator, if z increases while r remains

constant then the power returned to the radar must increase. This makes sense because z

increases by increasing the size or number of hydrometeors. The return to the radar will be

stronger for larger and more numerous drops for any given radius to the hydrometeors. Since r is

in the denominator, when r increases and z is constant then the power returned must decrease.

This makes sense because an object further from the radar will receive less radar radiation to

scatter off of it than an ob ect closer to the radar. Think of the lanet exam les a ain. Mercur


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and Venus ge t much more solar energy scattering off of them than Pluto does since Mercury and

Venus are closer to the sun. Thus, both the size/number of hydrometeors and the distance (radius)

to those hydrometeors determines how much radiation is scattered back to the radar.

We mentioned earlier that some of the constants in the radar equation are different for different

radars. These terms include the power transmitted, gain, beam widths, pulse length and

wavelength. If a term is in the numerator of the radar equation and that term is increased, then

the power returned to the radar should increased. An example exception to this is when increasing

one term in the numerator causes another term in the numerator to decrease more than theoriginal term was increased. Let's go through intuitively how a different radar will cause the

returned energy to the radar to increase.

Power transmitted: If the radar emits more energy than it is intuitive there will be more energy to

scatter back toward the radar if hydrometeors are present. Thus, more powerful radars are going

to receive more backscattered radiation. For example, if our sun in the solar system increased it's

power transmission then the earth would receive more solar radiation and more solar radiation

would be scattered off of the earth.

Gain and beam widths: These terms are intimately links because changing one can change the

others. The more confined a beam is the more energy that will be within that beam. If there ismore energy within a beam then there will be more scattering of radiation off of the hydrometeors

that beam intersects. Increasing the gain will increase the power returned. Increasing the beam

widths however will decrease the power returned because the increase in beam width is more than

offset by the decrease in gain caused by the beam being more spread out.

Pulse length: Pulse length is a function of how long the radar emits radiation within a beam. For

example, a flashlight that is turned on for 30 seconds will emit more total radiation than a

flashlight turned on for 15 seconds. Increasing the pulse length will increase the returned energy

to the radar.

Wavelength: Wavelength is in the denominator of the radar equation. Thus, when wavelength

increases then the power returned decreases . Thus, radars that emit shorter wavelength radiation

will get a more powerful return. Shorter wavelength radiation has more energy than longer

wavelength radiation.

The Pi term and 1024*Ln(2) term are simply numbers thus they are always constant.

The last two terms we need to discuss are the attenuation (l) term and the complex index of

refraction term (K^2). Attenuation is power loss due to radar radiation absorbing into the

atmosphere or less radiation being able to scatter back toward the radar do to the presence of

hydrometeors. For any given radar, this term varies depending on the weather conditions thus this

term is often ignored and set to a constant of 1 since multiplying the radar equation by 1 yields the

same result. Attenuation does have a function of the wavelength of radar used. Shorter

wavelength radars will attenuate more than longer wavelength radars.

The complex index of refraction is a function of the material state of the hydrometeor. Generally

less energy will be scattered off of ice than liquid water. With the same mass, there will be less

returned radiation from dry snow than from rain.

36. Range folding and detecting range folded echoes


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.

echoes will show up at a distance from the radar equal to R - Rmax, where R is the distance from

the radar to the actual echo returns and Rmax is the maximum unambiguous range. For example

if a storm is 300 miles from the radar and the maximum unambiguous range is 270 miles, the

storm will be shown on radar at a range of only 30 miles. This is because the reflectivity echoes

from this storm arrive after the radar has sent out another pulse. The radar assumes it gets

reflectivity only from the pulse it has most recently sent.

The following information covers how a radar operator can distinguish between real reflectivity

and range folder reflectivity:

1. Look outside to visually verify the precipitation

2. Range folded echoes are often long and thin. The range gates are skinnier closer to the radar.

Thus, precipitation that is far from the radar will be compacted into skinnier bands when it is

brought closer to the radar.

3. Range folded echoes generally have anomalous low cloud tops. This is because the radar beam

generally increases in altitude further away from the radar. Thus when a storm top far from the

radar is brought closer to the radar the height of that echo will decrease.

4. Range folded echoes generally do not have a high reflectivity. Since storms at the outer edge of

the radar are sampled at a very high altitude, the reflectivity from this precipitation will generally

be low. Thus, range folded echoes often show in the low reflectivity colors such as green near the

radar.

5. Range folded echoes will change location when the Pulse Repetition Frequency (PRF) is

changed. As the PRF is decreased, the range folded echoes will eventually go away.

6. Check other nearby radars to see if the reflectivity in question shows up on those radars also.

7. Use multiple tilt angles . Range folded echoes if they show on a low tilt angle may not show on a

higher tilt angle.

37. Echo height errors due to superrefraction and subrefraction

A standard radar will assume normal refraction takes place. Radar determines an echo height by

calculating how much the beam changes in elevation with distance from the radar and how the

earth's surface curves under the radar beam.

Errors in the echo height can occur from the beam not refracting normally and land surface

elevation changes at the earth's surface. The land surface elevation change errors can be

removed if the radar is given topographic data of the earth's surface. The refraction errors can be

reduced from soundings inputted into the radar so that the radar determines whether refraction

will be more than normal, normal or less than normal.

If the radar assumes normal refraction, significant echo height errors can occur when

superrefractionand subrefraction take place. Suppose there is a storm that is 100 kilometers from

the radar site and the echo top of the storm in the actual troposphere is 40,000 feet. Suppose

superrefraction is taking place and the radar assumes normal refraction. The radar will not

indicate the actual echo top of 40,000 feet since the beam is not refracting as the radar assumes it

is. The radar under superrefraction conditions will indicate an echo top greater than 40,000 feet in


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this example. Thus superrefraction overestimates the echo top height. Using this same line of

logic, subrefraction underestimates the echo top height thus it will indicate a echo top of less than

40,000 feet in this example.

38. Radar reflectivity pitfalls

Below is a list and explanation of radar reflectivity pitfalls:

1. Earth's curvature- The Earth's curvature causes more of a storm to be unsampled the further

the storm is from the radar site. This makes it more difficult to detect accurate VIL values and

mesocyclonic circulations at long ranges from the radar.

2. Topography- Elevated terrain can increase ground clutter and anomalous propagation. Valley

regions are not sampled if the radar is on the other side of elevated terrain.

3. Unusual temperature gradients- Strong inversions and other strong temperature lapse rates will

refract the radar beam atypically. This will result in echo height errors, can increase ground

clutter in the case of inversions, and can causes sampling errors of storms.

4. Ground clutter- Overestimates precipitation intensity for echoes near the radar site. Ground

clutter will be reduced by using a higher tilt angle. Ground clutter also tends to be less when the

lower troposphere is unstable.

5. Beam spreading- The resolution of range gates decreases as range from the radar increases.

Precipitation areas will look bigger and pixilated at the longer ranges.

6. Attenuation- Radar beam is less powerful as it moves into the longer ranges from radar as the

radar beam moves through precipitation areas that scatter away the beam progressively as it

moves away from the radar. This causes an underestimation of echo intensity at the long radar

ranges.

7. Unsampled regions- The cone of silence (cone created immediately above radar bounded by

rotating highest tilt angle used 360 degrees) is not sampled. The regions below lowest tilt angle is

also not sampled.

8. Location of precipitation- Position of precipitation aloft may not be position precipitation strikes

the Earth's surface.

9. Virga- Often much of the light precipitation that shows on radar evaporates before reaching the

ground.

39. Severe storm tracking techniques

The most dangerous portion of a storm is the mesocyclone. If a tornado and large hail occur it will

generally be near this portion of the storm. Thus, it is a good idea to use this portion of the storm

as the central position of the storm when plotting the storm's movement.

It is a good idea to remind that storms and severe thunderstorms often produce tornadoes even

when no tornado warning is out yet. While radar can be used to determine the circulations

associated with a tornado, the radar can not tell if the circulation is connected to the ground.

Storm s otters are ver hel ful in determinin whether the circulation is in contact with the


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ground.

When plotting the movement of a storm focus on the cities in the path of the storm since the storm

is likely already impacting those cities. Radar data is often several minutes old.

When plotting the movement of a storm it will not always move in a straight line. Development

within the storm and shear can cause the storm to take a curving and wobbling path. Adjust the

anticipated path of the storm on each radar update.

Be aware of new storms that develop and do not become overly fixated only on storms that have a

warning out on them. Severe storms can develop in a matter of minutes.

Geographic features, roads and landmarks make it easier for viewers to understand where a

storm is located.

Be careful about zooming in too close for too long on a storm when running the radar. Keep a

close watch on all the viewing area. Also keep radar display simple enough so that viewers can

understand what is going on.

40. What is a pulse storm?

A pulse storm is a thunderstorm that produces strong to severe weather in a short period of time.

The environmental conditions conducive to pulse storms are strong CAPE and weakwind shear.

The strong CAPE contributes to a strong thunderstorm updraft. Strong and severe thunderstorms

often have strong updrafts associated with them. The weak wind shear is what causes the duration

of the storm to be small. Contributing to weak shear are weak upper tropospheric winds and weak

winds within the troposphere in general. Since the shear is weak, the downdraft will fall into the

vicinity of the updraft and cut off the inflow into the updraft. The downdraft will also reduce the

momentum within the updraft.

Radar Processing

Ideal for single radar sites and multi-tiered remote radar systems.www.SSReng.com

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Weather Radar Faq Second Set