NWS Radar on the Web

The National Weather Service has presents Doppler radar images on the web in two manners; a Standard version (an all-in-one image) and an Enhanced version by individual interactive layers. Follow are the differences and strengths/weakness of each.

Standard Version Enhanced Version
In the Standard version, each radar image is combined with a legend, highways, and county/state outline overlays into one graphic which is made available via the web. In the Enhanced version, individual radar images are transmitted as well as individual overlay maps for highways, rivers, cities, county boundaries and severe weather warnings.
Advantages:
  • Smallest file size to download for both loop and non-looping images.
  • Toggle loop on/off just by clicking on image.
  • No Java/Javascript needed.
  • Can save any image by right clicking on the image then select "Save As".
  • Printer friendly "white" background.
Disadvantage:
  • Each radar image is on a separate webpage that must be downloaded.
  • Overlays are fixed and always visible.
  • Unable to stop looping on any image. Stopping the loop always takes you to the most recent image page.
 Advantages:
  • Radar data available for GIS programs.
  • Individual non-changing overlays, such as topography, can be cached on the local computer eliminating retransmission for each update.
  • Individual images that change often (radar image itself, watches/warnings, etc.) are much smaller in file size (compared to the standard version image).
  • Overlays can be toggled on/off and settings are preserved when bookmarked or moving between adjacent radar locations.
  • Can measure distance and direction between points.
  • Can determine latitude and longitude of objects.
Disadvantage:
  • Initial download size of files are much larger (compared with the standard version).
  • Extensive use of Java/Javascript.

How can you quickly tell which version of the radar you are viewing? The two obvious differences are in the border color around the radar image and background image. The standard version have a light blue border with a white background. The Enhanced version will have a dark blue border with a map background showing topography. (Samples below)

Standard Version Enhanced Version
A sample standard version radar display A sample enhanced version radar display


In addition, below every radar image, standard or enhanced, are thumbnail images of different sectors of the nation. These thumbnails contain live radar information providing, at a glance, a quick overview of where precipitation is occurring from the base reflectivity data.

National
Radar
Mosaic
Sectors		 Alaska
Go to the Alaska sector		 Pac. NW
Go to the Pacific Northwest sector		 N. Rockies
Go to the Northern Rockies sector		 Upr. Miss.
Go to the Upper Mississippi Valley sector		 Grt. Lakes
Currently at the Central Great Lakes sector		 Northeast
Go to the Northeast sector		  
Go to the Guam sectorGuam Go to the Hawaii sectorHawaii Go to the Pacific Southwest sectorPac. SW Go to the Southern Rockies sectorS. Rockies Go to the Southern Plains sectorS. Plains Go to the Southern Mississippi Valley sectorLwr. Miss. Go to the Southeast sectorSoutheast Go to the Puerto Rico sectorPuerto Rico

Clicking any of these images provides a high resolution sector image. Another click takes you to individual radar images.

These sector views are also divided into standard and enhanced. However, all sector images are non-interactive. The delineation of standard and enhanced allows you to know which version of individual radar you can obtain from each sector.

The 'oval' 124 nm range ring

Radar Map Projections


Except for the state of Alaska, the radar images provided by the National Weather Service are in an unprojected latitude/longitude format. This allows geographic information system (GIS) software to ingest NWS radar data for display with other information such as population density, etc.

Because of this unprojected format, the radar images appear "squashed" or oval shaped. The squashing of the radar image increases with increasing distance north (and south) of the equator. The oval ring in the image (right) is the 124 nautical mile range ring, which is the distance "seen" in a "short range" Doppler radar image.

Next: NWS Radar Images