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Java NEXRAD Viewer Tutorial

Tornado Example: Level-III Data

NEXRAD and Tornado
NEXRAD Tower

How can the Java NEXRAD Viewer be used to view or identify a tornado? What type of data is needed? What does a tornado look like on radar? These are some of the things that will be covered in this tutorial.

Jump to a section:
Data
Alphanumeric Properties
Backgrounds
What a Tornado Looks Like on Radar

Data

The first step in any NEXRAD project is ordering and obtaining data. By default, the NEXRAD Data Selector window opens when the Viewer is first opened. If you already have saved data, you can load it now. If you wish to order data, choose Order NEXRAD from the Data menu.

tornado signature
           F4 Tornado, Kansas City, May 4, 2003

Useful data for tornadoes:
Level-III:  Reflectivity
N0R, N1R, N2R, N3R
Level-III:  Velocity
N0V, N1V, N2V, N3V
Level-III:  Storm Tracking*
NST
Level-III:  Tornado Vortex Signature*
NTV
Level-III:  Storm Structure*
NSS
Level-III:  Mesocyclone*
NME
* Alphanumeric Products

For more information on radar products, please visit the NEXRAD Level-III Products page.

Alphanumeric Properties

There are a number of alphanumeric Level-III data products. Some are geographic and some are not. Those recommended above have geographic components and can be plotted on the map.

Alphanumeric Display
Tornado Vortex Signature (NTV)

The display can be enhanced by choosing custom items through Overlay Selector and WMS (see the basics tutorial or the help files for more details).
Alphanumeric Properties Window

You can also access more options by choosing Alphanumeric Properties from the View menu. Symbol and color for the markers can be changed, as with other viewer options. The attributes table can be accessed through the Alphanumeric Properites window by choosing Show Attribute Table. Specific information about each point can be found here.




KEAX attribute table

The supplemental data buttons will also bring up windows with additional information, based upon the specific product selected:

Show Supplemental Data 1 Window
TVX Supplemental Data 1

Show Supplemental Data 2 Window
TVX Supplemental Data 2

Backgrounds

The Alphanumeric properties window is also where you can add a radar image background and set the transparency (via the WMS options). If you have multiple radar products in the same directory, the viewer will automatically display the possible backgrounds for your image (note that the Alphanumeric Properties window displayed above has five possible images: N0R, N0S, N0V, NCZ, and N0Z).

KEAX NTV with NCZ background
KEAX TVX with Composite Reflectivity background

What a Tornado Looks Like on Radar

What is the radar signature of a tornado? The image above depicts a tornado that touched down near Kansas City, KS on May 4, 2003. The Tornado Vortex Signature (TVS; product NTV) shows two storm IDs in the viewable area of the image: H2 and F1. The background image is composite reflectivity. Below is the same time with a velocity background:

KEAX H2 with base velocity and annotations
KEAX TVS with Base Velocity
(click for larger version)

Manually composed (outside the Viewer) composite of NTV, N0R, and N0Z:

KEAX H2 with base reflectivity and annotations
KEAX TVS with Base Reflectivity, Base Velocity Superimposed
(click for larger version)

In this instance, the NME (Mesocyclone product) also notes the same location (H2) for a mesocyclone. The mesocyclone signature consists of the obvious rotation of radial winds (as seen above) and the hook echo.

More information about this event can be found at: