Introduction:
RadarLab is a weatherTAP feature which allows the user to have interactive
control over weather graphic presentation. Using RadarLab, the user may
select a background image which contains radar data, then select one or
more "overlays" such as county boundaries or highways which is
displayed over the base image. The user can zoom up to 5x and scroll around
the zoomed image. Animations can be created by loading up to 20 frames of
images. The user can single-step through animations, or control the playback
speed. Overlays and zooms also apply to animations. An advanced filtering
option is available and images may be automatically reloaded.
The RadarLab screen consists of a radar image, an overlay toggle section,
a storm attributes window, and various image controls.
Using RadarLab
When a RadarLab image is initially displayed, a base reflectivity image
will be loaded and none of the overlays will be selected. Once the image
has completely loaded, you may manipulate the image by turning on or off
overlays or using the image controls.
Overlays
All available overlays will be listed at the top of the RadarLab window
with checkboxes displayed beside the text. To enable an overlay, simply
click on the checkbox (a check should then appear in the box) and the overlay
will be drawn on the radar image. If the overlay has not previously been
used, then a short delay will occur as the overlay is being downloaded.
To turn off the overlay, simply click the check box (this time, the check
should disappear in the box) and the overlay will be removed from the radar
display. Note overlays work even if the image is animated, or zoomed.
Selecting a Background
When you initially display a RadarLab screen, the base reflectivity image
from the radar you selected will be displayed. You may, however, choose
another image type by clicking the appropriate option in the "Background
Image" pane on the upper right hand portion of the RadarLab screen.
Changing background images will cause the browser to reload the new data
(which could take a few seconds) and redraw the overlays on the new image.
Note that if you change backgrounds while an animation is playing, the animation
will be stopped and the new image will not be animated. To restart the animation
with the new background, simply press the "Play" button.
Zooming
You may zoom any image (animated or still) by pressing the "+"
or "-" buttons found in the "Zoom Controls" pane. You
may zoom from 1x (normal size) up to 5x (5 times normal size). You may scroll
the zoomed image by using the arrow buttons, also located in the "Zoom
Controls" pane. Overlays may be turned on or off while the image is
zoomed. Animation can also be started even while zoomed. To return to normal
size and recenter, simply click the "O" button located in the
middle of the pan arrow buttons.
Animation
RadarLab allows the user to control many aspects of animation. All animation
controls are contained within the "Animation" pane of the RadarLab
display. To start an animation, simply press the "Play" button.
The browser will begin loading the animation and you will see "Loading"
appear in the browser status window. When all images have been loaded, the
animation will begin to play. To temporarily pause the animation, press
the "Pause" button (which was previously labeled "Play").
To completely stop the animation and return to a still frame image, press
the "Stop" button..
Animation works by rapidly flipping pages (frames) of images. The frames
are numbered starting at 0 for the most current frame up to a maximum of
20 frames in the past. The user may set the number of frames in the animation
by changing the "# Frames" parameter (default is 10). When you
play an animation, the browser simply starts with the highest numbered frame
(oldest) and begins counting down to the zero frame (most current). You
may step through the frames of a stopped animation one at a time by using
the "<" and ">" buttons while the animation is
paused. The "<" button will cause the browser to load an older
(higher number) frame. The ">" button will cause the browser
to load a newer (lower number) frame. The user may also control speed of
the animation by manipulating the delay between frames. To increase the
delay (slowing down the animation), press the "-" button next
the "Play" button. To speed up the animation, press the "+"
button.
You may change zoom factors, turn overlays on or off, or view the storm
attribute window while an animation is running
Storm Attributes
Nexrad radar sites analyze data from each volume scan to identify storm
cells. Each identified cell is assigned an alphanumeric identifier and certain
attributes of that cell are tabulated. RadarLab allows the user view the
storm attributes table. RadarLab also provides the ability to graphically
plot the storm cells along with a predicted track.
Storm tracks can be toggled on or off just like any other overlay by using
the "Storm Tracks" toggle. When activated, storm tracks are plotted
on top of the background image. The identified center of the cell is plotted
as a centroid symbol with the cell identifier printed below. If a cell has
been tracked for more than one volume scan, a "track" will be
plotted showing the direction of cell movement. Marks along the track indicate
predicted positions at 15 minute intervals up to 1 hour. Newly identified
cells will have a centroid, but not a track since speed and direction has
not yet been determined.
Storm tracks are calculated by examining wind speed and direction data
from the storm attributes table. All of the data in the table may be viewed
by clicking the "Storm Table" checkbox located in the Overlay
Toggles section of the RadarLab screen. When selected, the storm attribute
table will appear in a seperate window. A
detailed description of the various storm attributes is available.
In times of intense convective activity a large number of storm cells may
be identified. When this occurs the storm track overlay tends to become
very cluttered. The storm attribute window contains many options to allow
the user to control which cells are plotted as well as how
the cells are plotted. By default, when an image is loaded, tracks will
be displayed for all cells. The "DISPTRK" value indicates whether
or not the track for a particular cell should be plotted. The DISPTRK status
for any particular cell can be toggled on or off by double-clicking on the
cell in the list.
A number of options are available for quickly turning the DISPTRK status
on and off based on different criteria.
Show All - Turns the DISPTRK status on for all cells in the
current table
Show None - Turns the DISPTRK status off for all cells in
the current table
MESO Only - Turns DISPTRK off for all cells, except those
that have a MESO value other than "NONE"
TVS Only - Turns DISPTRK off for all cells, except those
that have a TVS value other than "NONE"
Top 10 DBZ's - Causes the list to be sorted by max DBz. The
top 10 cells with the highest DBz value are turned on.
Top 10 VIL's - Causes the list to be sorted by VIL. The top
10 cells with the highest VIL value are turned on.
The six buttons buttons normally operate only on the currently displayed
frame. The user can force all frames to be acted on by clicking the "Apply
to all frames" checkbox. The main RadarLab screen is normally not immediately
updated when changes are made to the storm track display options. To force
the main RadarLab screen to update, simply click the "Redraw"
button. When activated, the "Auto-Reload" option will force the
main screen to redraw automatically when any display option is changed.
This may not always be desirable since it may take a long time when large
animations are loaded.
The size and color of the storm tracks may be changed by using the "Size"
and "Color" controls.
Image Controls
Image filtering
RadarLab can be configured to filter certain reflectivity values on the
radar display. This could be used to filter out weak echoes to reduce ground
clutter, or to filter out heavy echoes to isolated a particular weather
phenomenon. To select which scale values should be filtered out, simply
click the appropriate color in the vertical color scale located in the "Image
Controls" section. An 'X' will appear inside the box to indicate that
this color will be removed from the display if image filtering is enabled.
To turn the color back on, simply click again in the box. The 'X' should
disappear. To activate image filtering, configure the filter by removing
the appropriate values then click the "Filter" checkbox. The filter
will them be applied to the displayed still or animated image.
Optional Timestamp
The image timestamp can be displayed in the lower righhand corner of the
image. This is useful if the image is zoomed and the normal time stamp is
out of view. To activate the option time stamp, simply click on the "Timestamp"
checkbox.
AutoRefresh
RadarLab can be set to automatically reload a still image every 5 minutes.
To activate this feature, simply click the the "Auto Refresh"
checkbox. Animations may also be auto-reloaded, however, the auto-reload
option will revert back to still images after 1 hour of reloading animations.
Cursor Data
RadarLab can provide information about the cursor location and reflectivity
values. To activate this feaure, click and hold the left mouse button over
a location in the image. A window will be displayed giving the cursor position
in latitude and longitude. The radar data value of the cursor location will
be displayed. An arrow shaped pointer will also appear on the filter color
selection tool indicating the color value of the pixel under the cursor.
Distance and Bearing Tool
A simple tool is provided for determining the distance and bearing between
any two points. To use this feature, move the cursor to the first point
and hold the right mouse button. Now drag the cursor around the screen.
A window beside the cursor will indicate the direction and bearing from
the first point to the cursor location.
Interrogate Mode
RadarLab can be used to query NWS stations for the latest observation data.
To use this feature, turn on Interrogate mode by clicking the "Interrogate"
checkbox located at the top of the RadarLab window. Once activated, the
status line will indicate the interrogate mode is on and the cursor will
change to a hand shape. To get observation data, simply click on the map.
The station closest (geographically) to the location you clicked will be
polled and the observation data will be displayed in a separate window.
The location of the observation station will be indicated on the map by
a green X and the station ID will also be printed. Interrogate mode can
be used to gather as many observations as desired. Deactivate interrogate
mode by unchecking the "Interrogate" checkbox.
MyRadarLab
A special feature called "MyRadarLab" is available to allow the
user to create their own overlays. To display overlays (previously configured
in the MyRadarLab configuration tool), simply check the "MyRadarLab"
checkbox. If any of the user locations are located within frame of view
of the currently displayed image, then they will be plotted on top of the
radar image just like any other overlay. Refer to the MyRadarLab
help page for more information.
Helpful Hints
RadarLab relies on Java technology to run. You must have a Java-enabled
web browser and Java must be turned on to use RadarLab.
RadarLab is an advanced feature of weatherTAP which is intended for more
advanced users running newer equipment and software. If you experience major
problems with RadarLab, we recommend that you revert back to the standard
weatherTAP imagery.
RadarLab works best at 1024x768
