A federal agency has reversed course on the question of whether Donald Trump tweeted stale information about Hurricane Dorian potentially hitting Alabama, upsetting meteorologists around the country.

On Sunday, Trump had warned that Alabama, along with the Carolinas and Georgia, was “most likely to be hit (much) harder than anticipated”.

The National Weather Service (NWS) in Birmingham, Alabama, tweeted later: “Alabama will NOT see any impacts from Dorian. We repeat, no impacts from Hurricane Dorian will be felt across Alabama. The system will remain too far east.”

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But the president has been adamant throughout the week that he was correct, and the White House has deployed government resources and staff to back him.

The latest defense came out on Friday evening, when the National Oceanic and Atmospheric Administration issued a statement from an unidentified spokesman stating that information provided by Noaa and the National Hurricane Center to the president had demonstrated that “tropical-storm-force winds from Hurricane Dorian could impact Alabama”. The advisories were dated from last Wednesday, 28 August, through Monday, the statement read.

The statement also said the Birmingham NWS tweet on Sunday morning “spoke in absolute terms that were inconsistent with probabilities from the best forecast products available at the time”.

The statement from Noaa contrasts with comments the agency’s spokesman, Chris Vaccaro, made last Sunday. “The current forecast path of Dorian does not include Alabama,” Vaccaro said at the time.

Friday’s Noaa statement, released just before 5pm, points to a few graphics issued by the National Hurricane Center to support Trump’s claims. The maps show percentage possibility of tropical storm force winds in the United States. Parts of Alabama were covered, usually with 5% to 10% chances, between 27 August and 3 September. Maps on 30 August grew to cover far more of Alabama, but for only 12 hours, and the highest percentage hit 20% to 30% before quickly shrinking back down.

Alabama was not mentioned in any of the 75 forecast advisories the hurricane center sent out between 27 August and 2 September.

From 28 August to 31 August, a handful of locations in Alabama were mentioned in charts that listed percentage chance of tropical storm force winds or hurricane winds, maxing out at about an 11% chance that Montgomery would get tropical storm force winds.

‘So disappointing’

The former National Hurricane Center director Bill Read blasted Noaa leadership on Friday night on his Facebook page calling the situation “so disappointing” and saying he would comment because Noaa employees were ordered to be quiet.

“Either NOAA Leadership truly agrees with what they posted or they were ordered to do it. If it is the former, the statement shows a lack of understanding of how to use probabilistic forecasts in conjunction with other forecast information. Embarrassing. If it is the latter, the statement shows a lack of courage on their part by not supporting the people in the field who are actually doing the work. Heartbreaking,” Read wrote.

Dan Sobien, president of the union representing weather service employees, tweeted on Friday: “Let me assure you the hard working employees of the NWS had nothing to do with the utterly disgusting and disingenuous tweet sent out by NOAA management tonight.”

In a phone interview with the Guardian, he explained his deep concern over Noaa’s statement, which he said was unprecedented in his decades with the NWS. (Sobien stressed that he was speaking in his capacity as president of the union and not for the NWS, which is overseen by Noaa.)

“It’s unheard of that [Noaa] would – with no scientific basis whatsoever – undermine their own employees for political reasons. That’s never happened before under any administration ... This doesn’t happen. This is a scientific agency. People gather data and they make the best decisions they can make form that data.”

Sobien’s union represents about 4,000 employees of the NWS, including meteorologists, flight engineers, technicians and others.

“The NWS’s job is to save people’s lives, and if you undermine that authority, you’re going to cost people’s lives,” he said. “If they don’t believe hurricane warnings or tornado warnings, it will cost lives. That’s what Noaa’s doing. It’s irresponsible, managerial malpractice, and frankly someone should look into them. They have no right to be running an organization if that’s what they’re going to do.”

He said NWS employees were expressing displeasure on social media.

“I’ve seen from our own members that they’re up in arms. People are asking us to do something and I don’t know what to do. It’s just disgusting. The whole thing is just ridiculous.”

Other meteorologists also voiced concerns about Noaa’s actions on Friday.

“I am very disappointed to see this statement come out from Noaa,” the Oklahoma University meteorology professor Jason Furtado told the Associated Press. “I am thankful for the folks at NWS Birmingham for their work in keeping the citizens of Alabama informed and up to date on weather hazards.”

Julia Carrie Wong contributed reporting