28 August 2023

Idalia to bring significant impacts to Florida, Franklin becomes Category 4 hurricane

The two features of interest in the Atlantic, Idalia and Franklin, continue to strengthen...

Idalia is just a sneeze away from becoming the season's third hurricane as it nears the western tip of Cuba.  It is finally moving slowly to the north and will enter the Gulf of Mexico tonight.  It has been affected by some moderate northerly vertical wind shear which has kept the thunderstorm activity displaced to the south of the surface circulation, but as the day goes on, that displacement is decreasing and it appears that Idalia is close to beginning a period of rapid intensification.  We've been fortunate to have continuous radar coverage of the storm since Friday from Cancun in Mexico and from La Bajada in Cuba: https://bmcnoldy.earth.miami.edu/tropics/radar/

This set of Hurricane Threats and Impacts (HTI) graphics is from Monday morning but in the few hours since then, these maps have not changed much.  These graphics have been an operational NWS product for every single tropical cyclone near the U.S. since 2015, and I've been a big proponent of them because they put the focus on the hazards rather than the track.  There are four threat levels for each of four hurricane hazards: wind, storm surge, rainfall, and tornadoes.

Idalia is forecast to make landfall in Florida's Big Bend region as a Category 3 hurricane on Wednesday morning, with tropical storm conditions beginning Tuesday evening. There are too many evolving watches and warnings to put in here, but visit https://www.nhc.noaa.gov/graphics_at5.shtml?start#contents for the latest.  And remember, being outside of "the cone" does not mean you are safe... the cone has nothing to do with impacts -- that's what watches and warnings are for.

Meanwhile, south of Bermuda, Franklin was upgraded to the season's first major hurricane today, and subsequently strengthened even more to reach Category 4 status. As of early Monday afternoon, Franklin had 145 mph peak sustained winds and is still forecast to strengthen... perhaps briefly reaching Category 5 status later today.

Bermuda is under a tropical storm watch, and tropical storm winds could reach the island on Tuesday evening, with the storm's closest approach on Wednesday morning.  But Franklin's winds are also driving some hefty swells and elevated water levels along the US east coast, aggravating what are already-high tides this week around the full moon.

The ACE has just popped back above 100% of average for the date for the first time since August 18 (now at 107%).  The next 2-3 days will produce a big spike in the tally.

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