Frequently Asked Questions
DesktopDoppler has a few
questions that often get asked by users that are evaluating the
product or are unable to locate the answer elsewhere in our help
section. Use the menu below to jump to the question and answer.
to the Help Home Page
- Sometimes I see a message on the
screen that says "no radar data available at
this time" on a particular radar location, its been going
on now for 24 hours or more, why can't you fix that?
- I downloaded DTD, love it, but it
displays oddly on the screen- or won't run at all! What's wrong?
- My Anti-virus program or Personal
Firewall is showing DTD as having a "malicous script"
or preventing DTD from running altogether, why? Is DTD Safe to
- How do I get the radar images ?
- Is there a MONTHLY CHARGE for Radar
image service ?
- Why doesn't the radar display in DTD
look the same as the NWS images ?
- Why is there sometimes a lot of bright
red and yellow radar echoes but no rain outside ?
- What is the update frequency of the
radar images ?
- What is the range of the radar image
- When does the Storm Zone Alert popup
and warn me of a storm in my area ?
- How can I determine what color levels correspond to
what storm intensities?
- Why do I sometimes see what
looks like a searchlight beam stuck on a radar image?
- Why do I sometimes see a solid
circular pattern on the radar image?
- I notice the rotating sweep
on DTD is wider at the perimeter than at the center, does this
have a purpose?
- I'd like to run more than one copy
of DTD, on my Laptop and on my Home Computer, how do I do that?
- I'm having trouble getting the
time on the radar image to match my computer time- the
downloaded radar image always seems to be out of sync with my PC
clock- how do I fix that?
- Do you have a version for Macintosh?
Sometimes I see a message on the screen that says
"no radar data
available at this time" on a particular
radar location, its been going on now for 24 hours or more, why
can't you fix that?
That message screen comes from the National Weather Service, itís
the screen they put up when the radar is down for maintenance or
there is some other problem that requires the radar image to be
offline. Like any system, they have scheduled maintenance and
occasional failures. Since we obviously don't control the NWS radars
around the USA, it's not something we can change.
The best you can do is to select the next nearest radar location
that is operational until the NWS fixes the problem. Usually they
have radars back online within 48 hours.
downloaded DTD, love it, but it displays oddly on the screen- or
won't run at all! What's
DTD has very specific Desktop resolution and color depth
requirments. This is becuase the radar image provided by the NWS is
620x620 and thus is larger than even an 800x600 SVGA screen. To
display the complete image, DTD has to run is 1024x768 pixel mode at
24 bits or 32 bits.
Two things could be wrong:
1- You don't have your Desktop Display set for 1024x768 pixels
and 24/32 bit (16.8 million colors) just simply go to your Display
Properties in windows control panel and set it this resolution to
see all of the DTD screen if its being cut off. We have to use this
resolution because of the size of the radar images being transmitted
by the National Weather Service.
2. You may be using LARGE SYSTEM FONTS on your desktop. Its
very important not to be running LARGE SYSTEM
FONTS as are selectable from the Windows Display Properties.
Large System Fonts will cause the display of DTD to shift in
unpredictable ways. If you want larger fonts to make text easier to
see, use the Windows Desktop Schemes rather than the System Font
size control to get around this problem.
Here's how to turn off large system fonts:
Right click on the desktop.
Left click on the "settings" tab.
Left click on the "advanced" button.
Left click on the down arrow next to the "Font Size" box.
Left click on "small fonts. Normal size (96 dpi)"
Left click "OK" in the Change system font notification box.
Left click "OK"
If you want to have larger fonts on the desktop then use a
Windows Desktop Scheme:
Left click on the "appearance" tab.
left click the down arrow next to the "scheme" box.
Select a scheme, IE: Windows Standard (Large).
Restart the system
Desk Top Doppler should work fine at this point.
My Anti-virus program or Personal
Firewall is showing DTD as having a "malicious script" or
preventing DTD from running altogether, why? Is DTD Safe to use?
Yes DTD is safe to use, but certain "Paranoia-ware"
programs think otherwise. We have prepared an entire web page
dedicated to this topic, click
here to see help on Antiviral Programs and Personal Firewalls
The images are provided by the National Weather Service image-server.
DTD has all of the radar image locations for the entire United
States, including Alaska, Guam, Hawaii, and Puerto Rico already
built in. All you have to do is connect to the internet and then
select the location you want (in the Tools section) and then set it to be your
"default" radar location if you wish. DTD will
automatically download them anytime you are connected to the
internet and the DTD program is running.
No, its free! DTD Personal Edition has no monthly charge for radar
images. You can use as many as you like as often as you like for any
location. There are no restrictions! Once you register the DTD
Personal Edition software, there are no other ongoing charges of any
Users of DTD Professional edition, such as TV stations,
professional meteorologists, and others needing more detailed radar
information do have a monthly charge for custom enhanced radar
imagery provided by IntelliWeather and software support. For those
users needing the ultimate in radar imagery, or those wishing to
have their own custom private branded Doppler Radar service, or that
have a radar and want to use DTD with it, they should
look into DTD Professional.
This is because we have DTD run image processing on the radar image before
we display it to you. We change the lower level preciptitation from
blue to green, and lower the intensity to make the image more
pleasing to the eye and to provide proper intensity cueing so that
very light precipitation does not overload the image visually and
detract your eye from the more important middle and higher level
colors. It also makes the image less busy and allows you to see road
and boundary details easier. See examples below and see also the
section on Storm Intensity below
NWS Color Scheme
(click to enlarge)
DTD Enhanced Color
(click to enlarge)
This is because the NWS NEXRAD radar is operating in CLEAR AIR
MODE. In Clear air mode, the radar sensitivity is increased and it
can detect dust, fog, temperature inversions and other atmospheric disturbances
that are not precipitation related. When the radar detects
precipitation again, it automatically switches back to PRECIPITATION
mode. See the section on NWS radar
information for more details.
left is an example of a Clear Air Mode radar image from Los
Angeles that has large areas of yellow echoes...most likely
from a fog bank. Click to enlarge
If you see something like this,
don't panic, its probably not a big storm coming...be sure
to check the DTD status bar to determine if the radar
is operating in CLEAR AIR mode first. There is also another
ways to tell, the radar Color table has negative number
values when in Clear Air Mode.
When the radar is in CLEAR AIR MODE, DTD will display that in the
status bar in the top of the DTD frame as shown below:
|Radar in Clear Air Mode- DTD Storm Zone
Detection is Disabled
||Radar in Precipitation Mode- DTD Storm Zone
Detection is Enabled
NOTE: DTD is designed to ignore any echoes the radar
detects while in Clear Air Mode- otherwise you'd get false
alarms. DTD will only popup alerts when the radar is running in
Image updates are based upon the operation mode of the radar at
the time the image is generated. The WSR-88D Doppler radar is
operated in one of two modes -- clear air mode or precipitation
air mode, images are updated every 10 minutes.
precipitation mode, images are updated every five to six
What is the range of the radar image in DTD?
The maximum range of the composite reflectivity image is 124
nautical miles (about 143 regular miles) from the radar location.
This means that from edge to edge the radar image is 246 miles. This
view will not display echoes that are more distant than 124
nm/143mi, even though precipitation may be occurring at greater
distances. This is why sometimes you'll see a circular "cutoff edge"
to precipitation at the perimeter of the image. The radar
image processor limits the range automatically and removes echoes
even if they may still fit on the image (like in a diagonal corner).
DTD provides a scale on the image (marked in regular US Miles) to
help you judge distances. You can also use the storm zone box to
show exact distances by positioning it on the screen and reading off
the distance between corners displayed on the DTD Tools menu.
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This depends on several settings that you have to set correctly
in the DTD Tools section. DTD tools are available by clicking the
tools icon in the upper left of the DTD frame. To get an alert to
popup and sound an alarm, four things have to be set and/or occur:
- There must be an active Storm Zone box defined on the map
- You must have the Precipitation intensity slider set so that
it will warn you for the type of storm you are concerned about
- You must have the Sensitivity intensity slider set to a level
that will trigger an alert.
- There must be a sufficiently large and intense area of
precipitation inside the Storm Zone box that you defined on the
Generally, you can use the default DTD settings that are
shipped with the program for the sliders and you'll get a popup
alert on most types of storms. However, if you only want to
trigger on very serious storms, or you want to detect when light
precipitation enters your Storm Zone area, you may wish to changes
the settings. If you are unsure, just set both sliders to the
These colors correspond to storm intensity levels when the radar
is operating in Precipitation Mode. Note that in DTD we image
process the original NWS color levels as shown below to make the
radar image easier to view and interpret.
Rate/type and Description
||75 DBZ Undetermined
intense echoes or radar range folding
||70 DBZ 16"+ /hr Very
heavy rain and hail; large hail possible.
||65 DBZ 8" to
16"/hr Very heavy rain; marble size to golf ball sized hail
||60 DBZ 4" to
8"/hr Very heavy rain; marble size hail possible.
||55 DBZ 2" to
4"/hr Very heavy rain; pea to marble sized hail possible.
||50 DBZ 1" to 2"/hr Heavy
rain; small granular or pea sized hail
||45 DBZ .50 to 1"/hr
||40 DBZ .50"/hr Moderate
to Heavy rain
||35 DBZ .25"/hr moderate
||30 DBZ .10 to .175"/hr
light to moderate rain
||25 DBZ .075" to .10"/hr
||20 DBZ trace to .05"/hr
||15 DBZ trace to .025"/hr
||10 DBZ .01" /hr to trace
|| 5 DBZ
|| 0 DBZ no
Contours of echo reflectivity, also known as "VIP levels" (for
Video Integrator and Processor), are plotted on the radar image as a
color coded display. The colors within these contours provide an
indication of the precipitation intensity and the size (or number of
pixels of a certain color) depicts the areal extent of the detected
precipitation. Sixteen VIP levels are related to the rainfall rate
for the steady "stratiform" precipitation typical of winter time and
for showery "convective" precipitation. Note that in very low
levels, "ground clutter" (reflections off objects on the ground) may
appear as precipitation to the radar.
Why do I sometimes see what looks like a
searchlight beam stuck on a radar image?
"death rays" by some meteorologists, these occur because the radar
sometimes picks up a radar pulse from another radar, such as another
NWS radar, or a ship or aircraft radar operating on the same
frequency. The energy pulse from the other radar source just
coincidentally lines up with the rotating sweep of the radar beam
and fools the radar into thinking its seeing echoes from rain.
Just ignore these, they occur
once and then disappear.
See example image at left.
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Why do I sometimes see a solid circular
pattern on the radar image?
Nicknamed "nuclear explosions"
by some meteorologists, these patterns occur when the radar operator
places the WSR88D doppler radar into a test or calibration mode.
They are supposed to set the radar status to "offline" (in which
case you'll see a message on the image saying so) but sometimes they
don't, and you get the resulting circular test pattern sent to the
radar distribution network.
These are rare, and usually are gone within the hour. Don't
worry, the radar operators don't usually conduct these tests during
See example image at left:
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notice the rotating sweep on DTD is
wider at the perimeter than at the center, does this have a purpose?
Yes, this is due to a phenomena
of radar beams called "aspect ratio". Just like a flashlight or a
lighthouse beam widens as it reaches further, so does a radar beam.
This means that the radar has less resolution further away from the
center. Thus you may also notice that areas or precipitation near
the perimeter of the radar image appear "blocky" while the
precipitation near the center appears as smaller pixels.
The DTD program takes this into
account in the way it generates its moving sweep beam, making it
wider near the perimeter and narrow at the source. The DTD sweeping
beam isn't just a special effect, it serves as a template for
analyzing pixels under its path so that the Strom Zone trigger
properly alerts you. The moving sweep also serves as a visual
indicator that the DTD program is analyzing the radar image.
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like to run more than one copy of DTD, on my Laptop and on my Home
Computer, how do I do that?
The DTD program uses a copy
protection scheme that prevents you from running on more than one PC
at a time, but we do have very lenient pricing for additional
licenses that allow you to install on more than one computer.
Additional licenses are available for only $14.95, half off!
To get the additional license feature, you have to purchase DTD on
CD-ROM rather than as an internet download.
See our "Buy DTD"
section for details.
We also have an
unlimited use site license
available for organizations, companies, clubs etc that wish to
distribute the program to many PC's in their organization. See our "Buy
DTD" section for
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trouble getting the time on the radar image to match my computer
time- the downloaded radar image always seems to be out of sync with
my PC clock- how do I fix that?
The DTD program uses your own
computers clock to determine when the next download of a radar image
should occur. Sometimes, your PC clock may "Drift" enough
that you are a minute or more off the correct time, resulting in a
radar image downloaded that may be older than you'd
like...essentially your PC gets "out of sync" with
the radar image clock because of the time difference between the
To prevent this, we suggest
making sure your PC clock is always synchronized to the US
Government Atomic Time.
If you are running Windows
XP, this feature is built in to
your Windows Time Control Panel but must be enabled. See your
Windows help on how to do that.
For other Windows versions 98,
ME, NT4, and 2000 We have provided a FREE download of an Atomic Time
program to help you solve this problem. See
our Downloads section to get your free copy. This program will
automatically connect to the US Government Time Server and set your
PC clock anytime you are connected to the internet.
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Do you have a version for Macintosh?
Well, no, and I'm sorry to say
we'll probably never have one. We'd like to offer one, but, we used
to develop hardware and software for Macintosh back in the mid 80's,
but after getting "hung out to dry by the great and powerful Steve
Jobs" during that period, it just left such a bad taste in our mouth that it just doesn't
make much business sense to go through that all over again for the
5% of total market share that they have left.
Our apologies, but we are a
small company and just can't justify the risk given Apples penchant
for pulling the rug out from under developers or locking down their
system with silly and super restrictive licensing schemes.
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to the Help Home Page
FAQs prepared by Anthony Watts, Meteorologist.
Copyright © 2002 ItWorks/IntelliWeather. All rights reserved.
September 13, 2002