Hurricane Maria disintegrated the 39-foot-wide protective dome that surrounds the sensitive electronic equipment inside. It will be months before the radar can be rebuilt.

This is especially alarming in Puerto Rico, where tropical moisture can bubble up into highly localized downpours. With weak winds aloft and slow-moving rains, it’s easy for lots of water to become trapped in the valleys of the territory’s mountainous terrain. Flash flooding, mudslides and torrential rains can wreak havoc on already vulnerable communities still in recovery. The lack of radar coverage means that these destructive events were, quite literally, not on meteorologists’ radar — paving the way to more reactive forecasts and an overall decrease in forecast quality.

Tim Gallaudet, assistant secretary of commerce for oceans and atmosphere, described this as a “massive data gap.”

“Radar is one of the tools we have to use, especially for warnings and short-term forecasts,” said Roberto Garcia, the meteorologist-in-charge at NWS San Juan, in an interview. “But when the radar went down, we had to go to lightning mapping and satellite. After the hurricane, the ground was saturated, and we really needed radar at that point.”

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But on Tuesday, the San Juan forecast office announced a solution — the Department of Defense installed two temporary weather radars to survey the skies above Puerto Rico and the U.S. Virgin Islands. This is welcome news to meteorologists that are reliant on real-time precipitation data. For the six weeks before, forecasters had been forced to resort to GOES-16 imagery to make their predictions. While the 30-second imagery was of phenomenal spatial and temporal resolution, it was literally an “eye to the sky,” and it did not reveal what was happening closer to the ground.

Because the radars “have limited scope … they are not a permanent solution,” according to a news release by the National Oceanic and Atmospheric Administration that accompanied the original announcement.

That’s because they are X-band Doppler radars. With wavelengths between 2.5 and 3.5 centimeters, the waves can’t penetrate as far as the longer 10-centimeter signals transmitted by typical weather radar. As such, their range is restricted; while shorter wavelengths can be more sensitive in clear air, they’re more easily “tricked,” falling victim to fall signals spurred by ground clutter.

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The short range — only on the order of 100 miles — means that two were necessary to get a clear picture of the condition affecting the island. After some brief testing, the pair are up and running, transmitting valuable information internally to the National Weather Service every minute. That data has not yet been made available to the public.

“FEMA put them in to strategic locations, for safety, and coverage,” Garcia said. “Since we’ve been looking at the data, we’ve issued at least four flood advisories, which are very important for the isolated municipalities in the middle part of the island. We have a drier air mass over us right now though.”