Correction: Earlier versions of this article misidentified the agency that plans to launch a polar-orbiting satellite in October. It is NASA, not the National Oceanic and Atmospheric Administration. This version has been updated.

In this year of extreme weather and a contentious budget climate, federal officials are warning Congress that funding cuts and program delays will create a gap in weather satellite coverage starting in about 2016. That’s when a key polar-orbiting satellite is expected to exceed its design lifetime, with no ready replacement.

The gap could last as long as a year or more, depending on final funding levels, the condition of other satellites and additional variables, officials say. The key question is what effect it will have on weather forecasts.

Meteorologists and emergency managers warn that it could significantly reduce the accuracy of three- to seven-day weather forecasts, the kind that gave the first hints — five days out — that a major tornado outbreak would take shape in the Southeast this past April, for example.

Bill Hooke, a senior fellow at the American Meteorological Society, compared what forecasters would experience when a polar-orbiting satellite is lost to waking up after having a small stroke. “The world that you’re looking at wouldn’t seem quite right to you, and you wouldn’t be able to function quite as well,” he said.

Unlike geostationary weather satellites that hover over a particular point, polar-orbiting satellites continuously circle the planet in a nearly north-south orbit. While other weather satellites mainly relay images of clouds and have blind spots near the poles, the polar satellites have instruments that gather a wider array of data from a more expansive area.

They beam back more than 16,000 observations each day, which are fed into computer models used for weather and climate prediction. Polar-orbiting satellites also gather information used for monitoring volcanic eruptions, keeping tabs on sea surface temperatures and detecting the signals of emergency beacons for search-and-rescue operations.

NASA has three polar-orbiting satellites that work in conjunction with those operated by the Defense Department and the European Organization for the Exploitation of Meteorological Satellites. To keep coverage continuous, aging satellites need to be replaced. Two of NASA’s current satellites are not fully functional, and the third is nearing the end of its life.

NASA has a polar satellite slated for launch in October that was meant to have been a prototype but is being rushed into service. It is expected to near the end of its design life in 2016, or possibly earlier, before a replacement will be on the launchpad.

That’s when a gap in weather satellite coverage is likely to occur. Ball Aerospace and Technologies Corp., the main contractor building new polar satellites, hopes to launch the first one in 2017, about two years later than planned.

The new satellite program, known as the Joint Polar Satellite System, or JPSS, is estimated to cost $11.9 billion between fiscal 2011 and fiscal 2026. During fiscal 2011, however, Congress provided only $382 million for the satellite program, $679 million less than President Obama’s budget request.

That shortfall, combined with previous program delays, knocked the first satellite off its launch schedule of fiscal 2015.

The next generation of polar satellites will carry instruments that scientists consider essential for taking the planet’s pulse, including one known as the “cross-track infrared sounder,” which can perform the equivalent of an atmospheric X-ray, revealing information about the temperature, winds and moisture of a column of air. Those data are crucial to providing information about regions of the planet where there are no weather stations, such as over the oceans.

“Arguably one of the most important ingredients in your everyday weather forecast will go away if we don’t have that sounder,” said Kathryn Sullivan, deputy administrator of NOAA.

Simulations by NOAA’s National Weather Service have shown that losing the information gathered by one polar-orbiting satellite would have caused forecasters to underestimate the snowfall from the “Snowmageddon” storm of 2010 by 50 percent five days in advance. That would have transformed a forecast of a massive snowstorm into a forecast for a relatively routine event.

Jon M. Nese, a meteorology professor at Pennsylvania State University, said the “high-impact events” are where the missing satellite data will cause the most forecasting headaches. “The partly cloudy and warm forecast probably won’t be impacted,” he said.

But Bob Ryan, chief meteorologist for WJLA-TV in Washington, said that although the polar-orbiting satellites are key to making accurate weather forecasts, NOAA may be overstating their importance.

“I think the loss of any data will have a negative impact,” Ryan said. “You can pick and choose big, significant events and worst-case scenarios, but on the other hand, I don’t think it’s going to have a major day-to-day impact on forecasts.”

“We’re going to have to, for a while, deal with a bit more uncertainty than we’ve come to
[expect],” he added.

Last month, the House Appropriations Committee approved a bill that would provide just over $900 million for the satellite program in fiscal 2012, which would be $169 million below the president’s request. (The Senate has not taken up any of its 2012 appropriations bills.)

Rep. Frank R. Wolf (R-Va.), who chairs the House Appropriations subcommittee on commerce, justice and science, said NOAA faired extremely well compared with the other agencies under the subcommittee’s jurisdiction.

Wolf said the House appropriations bill would boost funding for the polar satellite program by $430 million compared with the previous year. “No other program in the budget got an increase of $430 million,” he said.

NOAA’s Sullivan said the House bill would help fund the satellite program by curtailing other programs that are related to weather forecasting.

“While I am pleased that the gap isn’t any larger than it is,” she said, “the House mark basically funds weather and satellites at severe expense to many other functions in NOAA, some of which, like our ocean-based buoys, are contributors to our forecast enterprise.”