Sub-Tropical Storm To Major Hurricane

[Ptarmigan]

I wonder if there has been a sub-tropical storm that eventually developed into a major hurricane. I know sub-tropical storms have become hurricanes in the past.

[Cyclenall]

Good thought, as I say anything is possible and this is definitely possible. The question is how rare is this if there has never been a recorded case yet. My guess is once in 50 years. Since almost every STC forms north from the deep tropics, and they usually occur either early or late in the season; it's difficult to get the system into a very favorable environment for significant strengthening to MH status.

Another related question is will the NHC ever start classifying tropical cyclones that were previously fully tropical to sub-tropical status and then lastly to extratropical. As of right now, the NHC just waits until it is fully extratropical before re-classifying it.