The USAF determines pressure and winds which determines the classification.
Gotta give props to those Hurricane hunters...that is one job that takes a pair!!
Excerpt:
More at link.
Areas Affected...ERN NCConcerning...SEVERE POTENTIAL...TORNADO WATCH likely
Valid 262358Z - 270130Z
The threat for tornadoes will become increasingly likely as rotating cells move onshore this evening. A Tornado Watch will likely be issues by 0030Z for areas across ERN, NC and the Outer Banks.