WASHINGTON — An anticipated delay in launching a next-generation weather satellite threatens aviation, emergency planning and other federal government activities that depend on reliable forecasts.

The Joint Polar Satellite System (JPSS) received about a third of the almost $1.1 billion the National Oceanic and Atmospheric Administration sought for this year. As a result, an 18- to 30-month gap is looming between the launch of the first JPSS satellite later this decade and the end of the useful lifespan of its predecessor in late 2016, according to a recent report by the Commerce Department’s inspector general.

“This is not a business-as-usual complaint,” said William Hooke, director of the policy program at the American Meteorological Society. “This is a serious problem.” Weather, for example, “plays the largest role” in determining how the nation’s air traffic control system runs on any given day, said Paul Takemoto, a spokesman for the Federal Aviation Administration. Weather data is so critical that NOAA employees are posted at the FAA’s command center in Warrenton, Va., he said. But he declined to discuss the possible effects that weather data gaps could have on air traffic management.

At the Agriculture Department, which uses satellite imagery for weather and crop forecasts, “it wouldn’t stop the analysis, but it would definitely hinder it,” Chief Meteorologist Raymond Motha said. “We would definitely like to see it launched.”

Weather satellite information also figures into preparations for tornadoes and other natural disasters.

“The late April tornado outbreaks in Alabama are just one recent example,” NOAA Deputy Administrator Kathryn Sullivan said in a Space News interview.

JPSS “absolutely did alert Federal Emergency Management Agency headquarters and regional offices to take inventory of where their assets were and to be ready for the high likelihood of having to mobilize that area. It absolutely did cue the American Red Cross for response, and it absolutely did cue school district superintendents and hospital managers to remind their folks what goes on when there’s a tornado warning,” she said.

For FEMA, data gaps could affect “our ability to be effective in carrying out our mission,” spokeswoman Rachel Racusen said in an email. The agency has been working closely with NOAA “to understand the potential impacts and solutions,” she added. If a data gap occurs, FEMA seeks to fill it with weather information from other agencies or industry.

A group of lawmakers framed the stakes more forcefully in a letter last month urging support for the project. Without accurate long-range weather forecasts, “unnecessary death and destruction” could result, Sen. Mark Begich, D-Alaska, and 13 colleagues wrote the top members of the Senate Appropriations Committee. And although the Defense Department runs its own weather satellites, the military also uses data from NOAA to plan overseas military operations, they said. The Defense Department referred questions to the Air Force, where attempts to get comment from several officials were unsuccessful. Neither the Senate committee nor its House counterpart has acted yet on NOAA’s 2012 budget request that again seeks almost $1.1 billion for the satellite program. But last week, a House Appropriations subcommittee approved $812 million, accompanied by new reporting requirements to keep better tabs on the program’s price tag and schedule.

Polar-orbiting satellites have been a key part of global weather forecasting since the 1960s. But NOAA’s existing fleet of both polar-orbiting and geostationary satellites is aging, the inspector general, Todd Zinser, warned in congressional testimony in February.

Coverage gaps would hurt the nation’s ability to forecast catastrophic weather, Zinser said, “increasing the potential for loss of life or damage to property and infrastructure.”

But NOAA’s efforts to replace its current generation of weather satellites are lagging. The Joint Polar Satellite System program was created last year after the Obama administration disbanded a previous effort involving NOAA, the Defense Department and NASA that had fallen behind schedule and went over budget. That project was awarded to Northrop Grumman.

The fallout, even without this year’s congressionally ordered spending cuts, has hampered NOAA’s ability to move forward.

Although a final launch schedule has not been set, the first JPSS satellite — being built by Ball Aerospace & Technologies Corp. — will not head into space before September 2016, NOAA Administrator Jane Lubchenco said in April, and could slip well into 2018.