6/26/2023 0 Comments Doppler radar oahu![]() These doppler radars give the National Weather Service Forecast Office in Honolulu both reflectivity and velocity data about storms affecting the area. ![]() One each on Kauai and Molokai, and two on the Big Island of Hawaii. The radar tilts up so it’s never aimed towards the ground or us, but instead through the varying parts of thunderstorms. There are four WSR-88D weather radars in the state of Hawaii. It’s a giant piece of machinery, and if a human were to stand in the way of the emitting waves, which is strongly discouraged, the human would feel themselves start to heat up like a microwave. As fast as it physically can,” explains Tony Freund, Electronic Technician for the National Weather Service in New Braunfels. During very violent weather, like tornadoes possibly, it’s really spinning fast, and it’s making cuts in the air very quickly. “During calm air, during calm ’s going much slower. Once inside the iconic “soccer ball” in the sky, we saw the giant dish that spins 360 degrees all day long. KSAT climbed almost 90 feet to get inside the “radome” for a better look at what makes these radar images possible. One near Brackettville and one in New Braunfels. ![]() Here in San Antonio, we utilize two Doppler radar stations. The reason? They could see the debris field on the Doppler radar image. The NWS issued a tornado warning that day with the wording “tornado on the ground” without any eyewitness evidence. KSAT Meteorologist Adam Caskey shows the radar image during what is later determined to be an EF-2 tornado in Guadalupe County on March 21st, 2022. Improvements are constantly being made to radar technology. Today, there are 159 weather radars strategically placed throughout the U.S. So, after wartime, some of the radars were donated to the Weather Bureau. It was detecting weather where radar proved to be most useful. “Radar was a boon for air traffic controllers, it was also later developed for radio astronomy, and traffic cops now use it to check for speeders,” adds Purifacto. Radars then really took off, and experiments all over the world began. Of course, it was the Japanese invasion fleet of Pearl Harbor,” said Purifacto. “They spotted a flight of planes, they believed was a flight of planes, 136 nautical miles north of Oahu. On December 7, 1941, the first major example of what radar could do took place. The radars eventually started being used to detect aircraft. “In 1934, they conducted experiments on behalf of the United States Navy because the Navy was concerned again about maritime navigation,” said Rudy Purifacto, Senior Air Force Historian. The Army Signal Corps coined the acronym RADAR, which stands for “radio detection and ranging.” In the early 1900′s, military ships and planes needed radar to avoid collisions in the fog, but the technology became a means of defense for the first time in World War II. In this episode of KSAT Explains, KSAT meteorologist Justin Horne visits the National Weather Service station in New Braunfels for answers, as well as the Bracken Bat cave, a common hotspot on radar images. Since hail can cause the rainfall estimates to be higher than what is actually occurring, steps are taken to prevent these high dBZ values from being converted to rainfall.Meteorologists and weather experts in South Texas rely heavily on Doppler radar technology, but how does it work? How can a giant soccer-ball-shaped tower, known as the radome, detect clouds hundreds of miles away and send them to a computer as rain? Hail is a good reflector of energy and will return very high dBZ values. These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time. Depending on the type of weather occurring and the area of the U.S., forecasters use a set of rainrates which are associated to the dBZ values. The higher the dBZ, the stronger the rainrate. Typically, light rain is occurring when the dBZ value reaches 20. ![]() The scale of dBZ values is also related to the intensity of rainfall. The value of the dBZ depends upon the mode the radar is in at the time the image was created. Notice the color on each scale remains the same in both operational modes, only the values change. The other scale (near left) represents dBZ values when the radar is in precipitation mode (dBZ values from 5 to 75). One scale (far left) represents dBZ values when the radar is in clear air mode (dBZ values from -28 to +28). Each reflectivity image you see includes one of two color scales. The dBZ values increase as the strength of the signal returned to the radar increases. So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (dBZ), is used. Reflectivity (designated by the letter Z) covers a wide range of signals (from very weak to very strong). "Reflectivity" is the amount of transmitted power returned to the radar receiver. The colors are the different echo intensities (reflectivity) measured in dBZ (decibels of Z) during each elevation scan.
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