I captured these time lapse weather radar snapshot's of the Squall Line that hit Jupiter Inlet Friday afternoon. I confirmed the squall line hit several land based weather stations, including Juno Pier, at 1:30PM local time (Eastern Time). The local time of the radar images below is on the upper right hand corner.
What we see here is at 11am , when they were fueling up their boat, the sky was very clear. Two hours later at 1 PM, the sky overhead and west of Palm Beach County was still clear, with a slow moving area of heavy rain moving E across St. Lucie County (a good distance away to the north). At 1 PM , a new squall line/gust front was just starting to form over the East edge of Lake Okeechobee, well to their west. In the 30 minutes between 1 PM and 1:30 PM this new squall line to the west rapidly intensified east of Lake Okeechobee and surged rapidly offshore. Anyone offshore Jupiter Inlet had virtually no advance warning of the threat posed by this newly forming squall line to the west, as confirmed by several reports of fishermen literally running to shore for their lives to reach safe harbor. This rapid storm development phenomenon is not uncommon for this specific area, it is due to the influence of Lake Okeechobee, combined in this case with the outflow boundary coming south down the coast from Martin County. The meteorological conditions mid-day Friday were ideal for what quickly turned into a worst case scenario.
I will add one more comment here, this is 100% just my personal opinion based on all the information we have to work with. I feel the boys recognized the weather threat, but experienced a mechanical failure as evidenced by the engine cover being off when the boat was discovered by searchers. I think they tried to start the motor and run for safety, and the engine failed to start. My guess is, the battery failed, and the engine would not start. Without power, the boat was quickly turned sideways and flipped over in the intense sea/weather conditions in the gust front that hit them. I believe if the boat was under full power, it would be able to motor through the worst of that weather event. Without a running motor, the boat was at the mercy of the wind and seas. Again this is just my personal opinion.