Hurricane Forecasts Face Setback as Key Data Source Ends

A critical tool used in hurricane forecasting is being abruptly terminated, as the U.S. Department of Defense (DoD) has announced it will cease processing and delivering essential data used in most hurricane forecasts. This decision, formalized in a NOAA service change notice, impacts real-time microwave data collected by weather satellites jointly operated by NOAA and the DoD.

The discontinuation of data from the Special Sensor Microwave Imager Sounder (SSMIS) poses a significant threat to the accuracy of hurricane forecasts, potentially affecting millions residing in vulnerable coastal areas. The move has sparked concern within the weather and climate community, particularly among those monitoring sea ice changes.

The reasoning behind this sudden termination appears linked to Department of Defense security concerns, although the specifics remain unclear. National Hurricane Center (NHC) officials were reportedly caught off guard and are now preparing for the loss of crucial data as the hurricane season progresses.

Increased Risk of Forecast Surprises

Hurricanes develop over vast stretches of ocean where direct observations are limited, making forecasters heavily reliant on satellite data. While hurricane hunter aircraft provide valuable information, they only cover a fraction of storms, especially in the Pacific. Traditional weather satellites, while useful, can’t always penetrate cloud cover to reveal critical structural changes that indicate rapid intensification.

The Defense Meteorological Satellite Program, with its constellation of weather satellites, provides a significant portion of the microwave satellite scans used by forecasters. With this data source going dark, the risk of “sunrise surprises”—where a storm intensifies overnight without warning—increases substantially.

James Franklin, retired National Hurricane Center branch chief, emphasizes the importance of this data: “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.”

Microwave data also plays a critical role in accurately positioning storms, which is essential for precise track forecasting. Small errors in initial positioning can lead to large forecast errors in the long run.

Franklin warns that for weaker systems, increased initial position error will cascade into poorer track forecasts.

The Importance of Microwave Data

Microwave data from the DoD Special Sensor Microwave Imager Sounder is not just helpful, it’s essential. It’s used in various critical applications, including AI-driven neural networks like DMINT, which estimates hurricane intensity. DMINT relies heavily on microwave data, making it a crucial tool for forecasters, especially when hurricane hunters are unavailable.

Although other microwave data sources exist, the loss of the DoD weather satellites effectively halves the available data, increasing the chances of missing rapid intensification events, underestimating storm intensity, and misplacing storms, ultimately degrading forecast accuracy.

While the Department of Defense launched the Weather System Follow-on Microwave (WSF-M) satellite in April 2024, its data is not yet accessible to forecasters, leaving a significant gap in observational capabilities.

Calm Before the Storm?

Current forecasts indicate a quiet Atlantic through the end of June, with no anticipated development in the coming week. However, the loss of this critical data source raises concerns about the accuracy of forecasts as the hurricane season progresses.