Is that rain or is it chaff?
An interesting phenomenon occurred during the evening of June 7, 2022, in the Boston, Massachusetts area when weather radars began showing what looked like moderate rain working over downtown Boston that came out of nowhere. What made it more interesting, was the fact the unknown radar signatures were moving off to the north-northeast while additional known rain to the west was working more west-northwest towards the Boston area. While it’s not unheard of for precipitation to do that, the rate at which it was tracking and the overall look of the radar signature was not that of a natural rain shower.
When looking deeper into the various radar options, one will quickly begin to piece together that the radar signature showing up was in fact not rain working into the area, but instead military chaff. Chaff is used as a radar countermeasure by military aircraft. It is made up of small pieces of aluminum, metalized glass fibers or plastics, and will show up as a giant cloud often times on radars. On radar, it often shows up as whispy in nature, will be classified as not biological, and will have a much lower Correlation Coefficient than normal precipitation. You can see an example of this in the video above from Boston, MA this evening.
It is not uncommon to see the military-run training experiences off southern Florida and in the Gulf near Corpus Christi where they will use chaff and it will see the signature show up on the weather radars in the area. In this case, the military was likely running a military training exercise and releasing chaff during its operations. That being said, this is the first time I have personally seen this occur up in the Boston, MA area. I came to the conclusion it was likely Chaff from the radar presentation, but also decided to check the ADS-B Exchange to see if there were in fact any military operations in the area. To no surprise, there were a couple of SIKORSKY UH-60 Black Hawk Helicopters flying in the area and likely releasing the Chaff while they were training just south of Newport and east of Long Island.
The National Weather Service in Boston also later confirmed my suspicions in the following Tweet.
[8 pm] Those returns over southeast MA are non-meteorological targets - chaff. The correlation coefficient (cc) dual pol product shows it well, higher values of CC associated with the showers in western MA/CT and lower much lower values over southeast MA. #Science is cool 😎 pic.twitter.com/8DQsEDvRR5
— NWS Boston (@NWSBoston) June 8, 2022
