Wind from the:
North
If the wind is light, the wind can bend around the Nothe point giving a right-hander at the NW section of the bay. Likely to oscillate from the land so track the wind. It will be gusty.
East
Clean wind May move right on a sunny day (rare to get a SE sea breeze) but possible enhancement if easterly gradient might get waves/swell near entrances.
South East
Portland starts to play a role, the east side of the harbour will have cleaner wind than the right, wind shadow near the academy area, prominent wind bend around the Bill, left-hander at the top of the beat.
South
Wind will bend around the bill, depending on how south the breeze is the East side of the harbour will be very light and patchy best bet to go middle right and play the shifts.
South West
Sea Breeze
This usually sets in around 210 and moves slowly right to 240 and can get fresh, bends as per the detail above.
West
Clean wind with pulses of breeze (rolling over the causeway) If in the northern part of the harbour you may get influence from the land to the north.
North West
Gusty and shift as it rolls off Weymouth and the hills, Gust and Shift sailing, eyes out of the boat for pressure.
Tide
This is negligible in the harbour, check the buoys in the area as you sail out but less than 3/4 kt (maximum near the gaps in the harbour wall).