A few quick points:
The barometric pressure has dropped six millibars to 985mb in the last three hours.
The eye of the storm as of 6:25pm is looking more impressive on radar. As with the drop in pressure, this is a sign of strengthening. Compare it to the depiction of the eye in the posting below. Note the yellow (stronger radar echo) is now a full 360° around the eye.
So, the forecast of strengthening appears to be on track.
Here is AccuWeather’s forecasts of the effects of Isaias on Florida. These look reasonable to me.
West Palm Beach and Ft. Lauderdale may have higher winds than Miami.
Finally, the American Meteorological Society tweaked its advice statement on hurricane sheltering in the COVID era this afternoon. The revised statement is here. I recommend you read it.