With tornado season in full swing and the start of hurricane season less than a month away, the first line of defense -- the National Weather Service is critically short of employees, according to the union that represents the workers.

There are currently a total of 548 unfilled jobs, and 396 of them are classified as "emergency-essential" at National Weather Service offices around the country, according to the National Weather Service Employees Organization.

The group's president, Dan Sobien, says that increases the chance for mistakes.

"It tires people out, they're prone to mistakes," Sobien said. "I'm afraid at some point something disastrous might happen.”

In early 2013, as a result of sequestration, Congress cut the weather service's budget by more than 8 percent and forced a hiring freeze that lasted until January.

Now that it's over, Sobien says critical jobs are not being filled fast enough.

Currently the National Hurricane Center in Florida is still short one lead forecaster, two meteorologist programmers and three other positions.

At the Houston/Galveston NWS office in Dickinson, a director's job and a journeyman forecaster position are still unfilled.

"Thirteen possible positions at the Houston office... two of them are down. That's almost 20 percent of the staff, so that does make a difference," said Sobien.

Sobien says that doesn't mean forecasts should not be trusted, but that the system is under unnecessary stress.

Weather service spokesman Chris Vaccarro disagrees.

"Talk about negative impact is purely speculative," said Vaccarro.

Vaccarro insists there have been no missed forecasts, or undermanned shifts in the last two years.

He says the National Weather Service is currently advertising to fill almost 200 jobs.