Radar Help


There are 159 NEXRAD radars systems deployed in the United States and around the world. Each of these radars implements the WSR-88D technology. The "Doppler" capability of these radars uses shifts in the phase of the reflected energy to determine the velocity of the particles towards or away from the radar. The effective detection range is between 80 and 140 nautical miles, depending on the intensity of the precipitation. In clear air mode, these radars transmit data every 10 minutes. In precip mode, they transmit every 4 to 6 minutes.

All of the images on the ADDS radar page are generated by the NWS. ADDS simply provides a custom interface to the information already available on the NWS website.

Regional Radar

Regional plot use the MRMS mosaic to produce the plots. These are produced every 10 minutes for 18 regions.

Single Site Radar

There are roughly 140 radar sites across the U.S. Each site has static images create for base reflectivity, composite reflectivity and total precipitation. Clicking on a site on the map will bring up the latest image for that site and allow the user to loop the latest 2 hours of images.

National Radar

The national radar is a composite of the 140 or so radar sites. This provides a single view of the entire country or 12 regional views. The page will show the latest image or loop through the latest 2 hours of images.

Radar Coded Message Composite Image

The display is an image representation of the Nexrad radar reflectivity overlayed with cloud tops and centroid movement. The Nexrad Radar Coded Message (RCM) product originates as an automated text message generated at each NWS radar site. The RCM reflectivity data has spatial resolution of about 12 km and is updated every 30 minutes. The RCM is a legacy product which will be replaced sometime in the near future. The raw RCM has considerable false echoes, so an automated process that checks the RCM for meteorological validity when compared to current satellite images, synoptic conditions, neighboring radar sites, and lightning.

The displayed image is the edited reflectivity. The RCM includes the max top for each radar's area of coverage. The other tops shown on the display are derived from the satellite images at the centers of convective activity. Movements shown are the radar centroid movements as generated by the Nexrad processor.

NOTE: The echo tops shown can in some cases be erroneous. The algorithm that computes this value uses any echo within the range of the radar. This can lead to spurious values when precipitation is far from the site. Values greater than 50,000 feet (500 on the plot) can be disregarded especially if their locations don't correspond to any precipitation.

The images are updated twice hourly and are posted at HH:15 and HH:45. The main radar page will show the latest image or loop the latest 4 hours of images.

URL Options

Here is a list of the URL options:

  • date=yyyymmddhhnn - This selects a specific date and time to display.
  • time=hr - This selects the initial time on the time slider (def: 0).
  • timelabform={full|simple} - This selects time slider labels. Full shows -/+ hours from current. Simple shows just the time and "Forecast for" if it's a future time.
  • refresh=min - This sets the auto-refresh time interval (def: 5 min).
  • tz=tz - This sets the time zone to show in the date header. This can be "local" which is the browser time zone or "label,offset" which is the zone name and offset in hours. For example "CDT,-5". (def: UTC).
  • region=reg - This will center the map to a specific region. Options include: "conus", "us", "northeast", "ne", "southeast", "se", "northcentral", "nc", "southcentral", "sc", "northwest", "nw", "southwest", "sw", "alaska", "ak", "hawaii", "hi", "gulfmexico", "gmx", "caribbean", "car", "europe", "eur", "southamerica", "sam", "easia", "eas", "australia", "aus", "zab", "zau", "zbw", "zdc", "zdv", "zhu", "zfw", "zid", "zjx", "zkc", "zla", "zlc", "zma", "zme", "zmp", "zny", "zoa", "zob", "zse", "ztl" (def: none).
  • center=lat,lon - This will center the map at a specific latitude and longitude. The default is 39,-97.
  • zoom=level - This sets the zoom level. The default is 4. A higher number zooms in. A lower number zooms out.
  • fullmode=(screen|window) - This sets the full screen mode. "screen" sets it to full screen. "window" sets it to fill the current browser window. The default is screen.
  • fullscreen=(on|off) - This sets the display to go into full window if fullmode=window.
  • basemap=(light|dark|simple) - This selects the type of basemap. The default is light.
  • rad={on|off} - This turns the radar layer on or off. The default is on.
  • radprod={rala|cref} - Specifies the type of radar image: "rala" for reflectivity at lowest altitude or "cref" for composite reflectivity. The default is rala.
  • radopacity=# - Specifies the radar image opacity (0=transparent to 1=opaque). The default is .75.
  • radloop={on|off} - Specifies whether the radar is looping on page load. Default is on.
  • radimages=# - Specifies the number of images in radar loop. The default is 5.
  • radlabform={on|full|simple|off} - Specifies the radar label format. The choices are "on" or "full" which shows type of radar and time, "simple" which shows only radar type and "off" which shows no label. The default is "full".
  • radarsite={on|off} - Turns the radarsite layer on or off. This layer shows the location of all Nexrad sites. The default is off.
  • highways={on|off} - Turns highway layer on or off. These are primarily interstates. The default is off.
  • roads={on|off} - Turns roads layer on or off. These are primarily US and state highways plus some city streets. The default is off.
  • counties={on|off} - Turns county layer on or off. The default is off.
  • cities={on|off} - Turns city outline layer on or off. The default is off.
  • jetroutes={on|off} - Turns the jetroutes layer on or off. The default is off.
  • airways={on|off} - Turns the airways layer on or off. The default is off.
  • firs={on|off} - Turns the ARTCC/FIR layer on or off. The default is off.
  • navaids={on|off} - Turns the Nav Aids layer on or off. The default is off.
  • navscale=## - Specifies scale factor for the Nav Aid icon. The default is 1.
  • navlabel={on|off} - Turns the Nav Aid labels on or off. The default is off.
  • airports={on|off} - Turns the airports layer on or off. The default is off.
  • arpttype=param - Specifies the types of Airports to display. The default is all. The types are:
    • pub - public airports
    • priv - private airports
    • mil - military airports
    • hel - heliports
    • sea - seaplane bases
  • arptscale=## - Specifies scale factor for the airport icon. The default is 1.
  • arptlabel={on|off} - Turns the airport labels on or off. The default is off.
  • metric={on|off} - Specifies to display data in metric units. The default is off.
  • mouseformat={deg|dm|dms} - Specifies to format for the mouse location: degrees, degree/frac. minute, degree/minute/second. The default is deg.
  • level=## - Specifies value of the level in the level slider. The default is none.
  • hover={on|off} - Turns on hover for features. The popups will come up when mouse hovers. Default is off.