HailTrax™

Co-developers of the Hail Detection Algorithm for the NEXRAD Weather Radar Program have come together at Weather Decision Technologies to develop HailTrax™ the first fully automated report generator capable of determining the areal extent and size of hail that fell based upon a four-dimensional data set available from multiple radars, observed hail sightings, and unique and patented algorithms developed by leading meteorologists at WDT.

HailTrax™ has the capability to accurately map where hail has fallen utilizing sophisticated computer algorithms written by world leading meteorologists at WDT. These algorithms utilize Doppler Weather Radar data and other proprietary data sets to determine, with great accuracy, where hail has fallen and the size of the largest hailstones in a given area. When ordering a HailTrax™ report you define the area of concern and the time of interest. Once the report is produced, a meteorologist will personally check the results to ensure the accurate mapping of hailswaths before the report is delivered to you. The report will contain a map showing hailswaths and hail sizes near your location of interest, and a note detailing the size of hail that is estimated to have occurred at that location.

An example of the HailTrax™ product image is shown below. The area where hail fell is mapped according to the estimated hail size. HailTrax™ maps areas that hail fell that had diameter greater than ¾ inch. It is also able to delineate between hail that is ¾ inch to 1 and ¾ inches and hail greater than or equal to 2 inches in diameter.

Figure 1:  Example of HailTrax™ image from large hail event near Lubbock, Texas on May 30, 2001.

Background

The United States National Weather Service, Federal Aviation Administration and Department of Defense deployed a network of 140 state-of-the-art Doppler Weather Radars (called NEXRAD) throughout the Continental United States (Figure 2). The NEXRADs collect data continuously and provide full 3-D coverage of their local region every 6 minutes. In addition, the NEXRAD has a number of algorithms, many developed by scientists at the National Severe Storms Laboratory (NSSL), that automatically detect severe weather phenomena. A number of these scientists are now employed by WDT. One of those algorithms is called the Hail Detection Algorithm (HDA). The HDA determines which storms are likely producing hail at the present time. In addition, the HDA provides an indication of the size of hail presently being produced by a storm. This information is used by the National Weather Service (NWS) to aid in the process of warning the public of storms that have the potential to produce hail that may damage property or result in injury.

Figure 2:  Nationwide coverage provided by 140 NEXRAD Doppler Weather Radars.

Studies have shown that the HDA is skillful in determining whether a given storm will produce hail. One study performed in Colorado showed the HDA correctly determined which storm was producing hail 92% of the time with an extremely low false alarm rate of 4 %; (Witt et. al. 1998). Also, based upon a geographically diverse radar dataset, the HDA has demonstrated very accurate detections of severe hail including the probability of detecting hail greater than 1 inch (87% of the time) and 2 inches (96% of the time). These accuracy numbers are based on using only one radar to detect hail. WDT's proprietary algorithm utilizes overlapping data from multiple NEXRADs that cover the area of interest. This allows us to achieve probability of detection of hail nearing 100% over the lifetime of hail generating storms. Of course, performance is a function of atmospheric conditions, proper operation and calibration of the radar and quality reports of hail.

The HailTrax™ Algorithm

When we receive your order, our experts determine which NEXRAD radars provide coverage over your area of interest. We then extract from our extensive archive of NEXRAD data the appropriate information for input into the HailTrax™ algorithm. A second algorithm examines the HailTrax™ output, takes into account all hail observations made during the event of interest and plots hailswaths showing the areal extent of hail and the estimated size of the largest hailstones for each hailswath. Local landmarks such as state and count boundaries, interstates, state highways and county roads are added to the images for reference. Custom features or user assets may also be added to the maps, for a small fee, such as city streets, significant industrial centers/structures, customer locations, and even proprietary geographically based information. The HailTrax™ product is a valuable tool for accurately determining which locations, assets and areas were impacted by hail, especially large damaging hail.

Because of WDT's unique knowledge base and our archive and computing infrastructure, we are able to provide the HailTrax™ product within 2 business days of your order. The unique HailTrax™ product is the only product available anywhere in the world that accurately maps the areal extent and size of hailstones.

References:

Conway, John W.^*, Dusan S. Zrnic, 1993: A Study of Embryo Production and Hail Growth Using Dual-Doppler and Multiparameter Radars. Monthly Weather Review: Vol. 121, No. 9, pp. 2511–2528.

Witt, Arthur, Michael D. Eilts^*, Gregory J. Stumpf, J. T. Johnson^*, E. DeWayne Mitchell^*, Kevin W. Thomas, 1998: An Enhanced Hail Detection Algorithm for the WSR-88D. Weather and Forecasting: Vol. 13, No. 2, pp. 286–303.

^* WDT Employees