On Monday, the U.S. Department of Defense announced it would immediately stop ingesting, processing, and transmitting data essential to most hurricane forecasts.
The announcement was formalized on Tuesday when NOAA distributed a service change notice to all users, including the National Hurricane Center, that by next Monday, June 30th, they would no longer receive real-time microwave data collected aboard three weather satellites jointly run by NOAA and the U.S. Department of Defense.
The permanent discontinuation of data from the Special Sensor Microwave Imager Sounder (SSMIS) will severely impede and degrade hurricane forecasts for this season and beyond, affecting tens of millions of Americans who live along its hurricane-prone shorelines.
The news on Tuesday sent users across the weather and climate community – including those monitoring changes to sea ice extent in the polar regions – scrambling to understand the rationale behind the abrupt termination. Though not immediately clear why the real-time data was suddenly discontinued, the decision appears to have stemmed from Department of Defense security concerns.
Officials at the National Hurricane Center were also caught off guard by the announcement and are preparing their team for the loss of critical forecast data for the rest of the hurricane season.
Increased risk of a “sunrise surprise”
Since hurricanes form and strengthen over the open water where direct observations are scarce or nonexistent, forecasters rely largely on data remotely gathered from satellites. While hurricane hunting airplanes help to close that gap, they’re only available for about 1 in every 3 hurricane forecasts in the Atlantic and virtually none – except for a handful of stronger storm exceptions – in the Pacific.
Traditional weather satellites are helpful, but they don’t allow forecasters to peer beneath the clouds to understand important structural changes that can tip them off to episodes of rapid intensification. At night especially, geosynchronous satellites most familiar to the general public can fail forecasters, often missing important details only seen by visible satellite or critical microwave pictures from polar-orbiting satellites that provide MRI-like scans to forecasters every few hours.
The Defense Meteorological Satellite Program and its constellation of three weather satellites provide roughly half of all microwave satellite scans to forecasters. Those go dark beginning next Monday.
“Their loss is a big deal,” says retired National Hurricane Center branch chief James Franklin, who oversaw all NHC hurricane forecasters until his retirement in 2017. “Without this imagery, there will be increased risk of a ‘sunrise surprise,’ the realization from first-light images that a system had become much better organized overnight, but it wasn’t recognized because structural details are so hard to discern from [infrared satellite].”
Microwave data are also used to help “fix” or position the center of storms, a task not always easily or accurately accomplished using visible or enhanced satellite pictures. As the butterfly effect demonstrates, small errors in the initial positioning of a storm can lead to outsized forecast errors in four or five days.
“For weaker systems, [it’s] increased initial position error (in the tens of miles) that will cascade into poorer track forecasts,” warns Franklin.
Microwave data such as those from the DoD Special Sensor Microwave Imager Sounder are essential to hurricane forecasts, not a nice-to-have. They’re used in a variety of critical applications, including estimating hurricane intensity through AI-driven neural networks like the Deep Multispectral INtensity of TCs estimator or DMINT. In the absence of hurricane hunters, DMINT has been shown to be one of the most crucial tools in a hurricane forecaster’s arsenal for estimating storm intensity, largely because of the microwave data it utilizes.
Though other microwave data will still be available to forecasters, the DoD weather satellites comprise half of all microwave instruments, which means data availability will be sliced in half, greatly increasing the odds of missing rapid intensification episodes, underestimating intensity, or misplacing the storm and degrading forecast accuracy.
While the Department of Defense did successfully launched another weather satellite known as the Weather System Follow-on Microwave (WSF-M) in April 2024, that data isn’t currently available to forecasters and it’s not clear if or when data access will be permitted.
Ending June with no Atlantic concerns
Forecast models continue to show a quiet Atlantic through the waning days of June, with no development expected over at least the next week or so.
CLICK HERE to download the Local 10 Weather Authority’s 2025 hurricane survival guide.
