:::::While there is no "official" lower limit for tropical depressions, NHC tends not to start tropical depressions with maximum sustained winds below 25 mph; usually 30 or 35 mph is their lower limit.  You can see on this link that they think the maximum sustained winds are 25-30 mph currently.  When HPC continues advisories for tropical depressions and their remains when they are inland, there is no real lower limit respected.