Wobble watching begins in earnest today, but all signs are pointing to the mouth of Tampa Bay as the most likely landfall. Crazy. Here's the difference 20 miles could make in the landfall impacts for surge (just my analysis):
1) Current track (Anna Marie Island landfall)
Tampa Bay gets onshore flow for at least 12 hours. Winds will start to shift just before landfall, but the main wind vector for most of the bay will still be onshore (roughly due northeast, or NNE). The northern bay will get offshore flow starting around landfall, but this won't help push the surge out of the bay since most of surge will have entered the bay already. It may cause an amplified surge on east side of the bay, particularly for St. Pete and Old Tampa Bay.
This would be the 10-12 foot scenario for Tampa. Siesta Key to Anna Marie Island get 15+ feet of surge.
2) 20 miles north (Clearwater landfall)
Tampa Bay gets onshore flow for at least 12 hours + the eyewall, which will also have an onshore wind vector. This is likely the absolute worst case scenario for surge due to the constant onshore flow throughout landfall.
This would be the 12-15ft scenario for Tampa, 15+ feet for Madeira Beach down to Siesta Key
3) 20 miles south
If Milton jogs 20 miles south of the current track, Tampa Bay is spared most of the surge impacts (although some reverse surge is possible). Tampa will experience onshore flow for 6-8 hours before landfall, but winds will abruptly shift to the ENE and push water out of the bay.
In this scenario, Tampa might see 5-6 feet of surge. Siesta Key to Venice would get 15+ feet, and Ft Myers Beach / Sanibel would see substantial, 10-12ft surge as well.