Anomalous propogation (AP), a false reflectivity echo that is not precipitation but may be produced by unusual rates of refraction in the atmosphere, can be a problem when interpreting the Nexrad image. WxWorx uses a software program to automate the elimination of AP. According to Baron, most of the AP is eliminated by the automatic program.
"But it's a little bit challenging. We seek to automate it as much as possible so we can get the information to the cockpit as rapidly as possible. Nevertheless, there are times, normally in the spring or fall, when the automatic system believes there's precipitation when there's not and we get some anomalous propagation."
Although the automatic system "works pretty darn well," occasionally there has to be intervention from WxWorx's 24/7 forecast team. A brand new facility in Huntsville, described as "a Starship Enterprise," and a new process that will allow cleaning up the AP instantaneously is in the works, "so we won't have any delay in the radar product," Baron said.
According to Baron, the metars are instantaneously collected a little before each hour and inserted into the data stream. "We send the metars on a 12-minute schedule. We wanted a pilot to be able to get the metar before taking off and figured it would be 12 minutes before they'd complete their run-up. In that time they'd also have two radar images before taking off." The satellite images take about 15 minutes to be digitized and shipped back to earth at Wallops Island where they're massaged for accuracy and then distributed.
"The new ones are 15 minutes old when we get them, but by the time they're downlinked to a cockpit they can be as old as half an hour because of the way they're collected," Baron said. It's been said before, but Baron reiterated that the weather products "are for situational awareness, not a tactical tool. The rules of thumb that have been in place are the rules of thumb pilots still need to follow. You don't want to cut it too close to a thunderstorm. The rule of at least five or 10 miles from a thunderstorm and 20 miles from a super cell is still valid advice. The advantage we have with the equipment today is we can tell how far away we are."
As pilots we should be thankful that while everybody talks about the weather, we've got WxWorx doing something about it.