While hurricanes on TV and weather maps are depicted as flat, spinning discs, their actual structure is vastly more intricate and three-dimensional. Gaining insight into their inner workings, beyond the visible cloud tops, is pivotal for accurate weather predictions, particularly when a storm is poised to rapidly escalate in intensity. However, a crucial data source that offers a detailed glimpse into these storm structures is set to cease operation by June 30, just as the hurricane season ramps up.

James Franklin, the former head of the National Hurricane Center’s Hurricane Specialist Unit, emphasizes the significance of this data, which he regards as one of the most valuable tools for understanding the internal dynamics of forming cyclones. This data is essential for forecasters to anticipate sudden changes in a storm’s intensity, providing them with a lead time to alert those in danger.

The indispensable data comes from the Defense Meteorological Satellite Program (DMSP) satellites. Regrettably, this data will soon no longer be processed or made available to the National Hurricane Center and other non-military entities. The reasons for this cessation are not entirely clear but seem to involve security issues.

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Kim Wood, an atmospheric scientist at the University of Arizona, points out the unfortunate timing of this data source shutdown, which coincides with other recent reductions and constraints affecting the National Oceanic and Atmospheric Administration.

Insights from Microwave Data on Hurricanes

Satellites in orbit collect data across various light wavelengths, including visible, infrared, and microwave. Though typically hurricanes are seen in the visible spectrum, they also emit microwaves. According to Wood, microwaves are naturally emitted from all objects above absolute zero temperature, including us.

Microwave signals are particularly useful for observing hurricanes because they penetrate through cloud tops, revealing critical changes in the storm’s eye and surrounding eye wall. These modifications can indicate whether a hurricane is gaining or losing strength.

This capability is especially valuable at night when visible satellite images are unavailable. Microwave imagery, which offers 16 times the resolution of infrared, allows continuous monitoring of a storm. This can help forecasters prevent being caught off-guard by overnight developments in the storm’s intensity or structure, described by Franklin as a “sunrise surprise.”

The ability to detect rapid intensification, a phenomenon where a storm’s winds increase by at least 35 miles per hour within 24 hours, is a crucial advantage of microwave data. This was notably demonstrated during Hurricane Otis in 2023, which intensified to a Category 5 hurricane before making landfall, causing extensive damage. Microwave data also play a critical role in identifying the centers of weaker storms, which may lack a defined eye and eye wall, thereby enhancing the accuracy of hurricane tracking models significantly.

Sources and Discontinuation of Microwave Data

Microwave emissions from the Earth’s surface and atmosphere are faint, hence detectable only by satellites in low-Earth orbit. These satellites, unlike their geostationary counterparts, need to be closer to Earth due to the weak nature of microwaves. This proximity means they cover less ground at any given time, necessitating a greater number of satellites to monitor the planet comprehensively.

Currently, the U.S. relies on six satellites for such data, which is already a limited resource. The imminent deactivation of three DMSP satellites equipped with Special Sensor Microwave Imager Sounder (SSMIS) sensors will further reduce the availability of these crucial observations. While the exact reasons for their discontinuation involve security concerns, there is no indication that the issue is with the data sharing itself or funding.

A U.S. Space Force spokesperson confirmed that while DMSP satellites and instruments are still operational, only Department of Defense users will continue receiving the data. Further inquiries have been directed to the U.S. Navy, which has yet to respond.

Maria Torres, a spokesperson for the NHC, reassured that the DMSP represents just one of many tools in a robust suite used for hurricane forecasting. She highlighted other resources like additional satellites, ocean buoys, and Hurricane Hunter flights that collectively ensure comprehensive weather forecasting capabilities.

While new Department of Defense satellites might potentially offer microwave data, there has been no move to make these data widely accessible. Transitioning to a new data source is not straightforward due to the specific integration of current forecasting models with existing data streams.

Expectations for This Hurricane Season

The loss of microwave data is particularly concerning for tracking distant storms or those in the Pacific, where fewer monitoring missions occur. This data gap, compounded by other cuts to the National Weather Service and NOAA, could significantly impact forecast accuracy. There’s a high likelihood that at least one forecast this season will miss significant storm intensification by several hours due to these limitations, which could have devastating consequences, particularly for coastal and maritime communities.

Overall, numerous challenges are complicating weather forecasting this year, making accurate predictions more difficult than usual, according to Franklin.