HailStrike uses Level III NEXRAD radar data from NOAA to plot a series of markers along a path which represent activity within a super cell storm cloud containing hail signatures. Each marker includes a numerical designation showing the approximate maximum size of hail stones expected to have made ground fall at or near the marker. The maximum size of hail is a probabilistic result of several factors calculated together by NOAA’s NHI product.
The weather radar you see on your local TV news or The Weather Channel is Doppler radar. Doppler radar emits beams (pulses) of microwave energy from a transmitter into the atmosphere. When these beams collide with objects in the atmosphere such as raindrops or hail stones, some of that energy bounces back towards the radar. A receiver on the radar then displays the data in different ways. Doppler radar came into common use when the Weather Surveillance Radar – 1988 Doppler radar (WSR-88D) was installed. Currently, over 160 such WSR-88Ds operate around the United States and other U.S. territories. They are part of a network of Doppler radars called NEXRAD, which stands for NEXt generation RADar. All radar sites in the lower 48 U.S. states are given a four-letter call number starting with “K.”
When you see a radar image on TV, you are likely looking at a combination of individual Doppler radars or a section of the NEXRAD network. Why is this? An individual radar sits inside a dome resting on a tower almost 100 feet in the air. As the transmitter on the radar emits beams of microwave energy, it also rotates in all horizontal directions and sends energy to every part of the lower atmosphere. Radar beams can only travel out so far before becoming useless. Therefore, a Doppler radar’s effective range extends to a radius of about 217 miles. HailStrike disregards the scan’s farther extremities, as it is largely unreliable data.