NOAA, the National Oceanic and Atmospheric Administration, part of the U.S. Department of Commerce, is responsible for monitoring and forecasting weather conditions of behalf of the United States for the safety of the public.
On Friday, NOAA had disavowed a tweet from the National Weather Service's Birmingham, Alabama, office contradicting Trump's claim.
"I am pursuing the potential violations of our NOAA Administrative Order on Scientific Integrity," acting Chief Scientist Craig McLean wrote in the memo.
"My understanding is that this intervention to contradict the forecaster was not based on science but on external factors including reputation and appearance, or simply put, political."
"If the public cannot trust our information, or we debase our forecaster's warnings and products, that specific danger arises," McLean wrote.