09 October 2018

Hurricane Michael strengthens as it heads for a Florida landfall on Wednesday

Michael is now a Category 2 hurricane and poised to strengthen even more during its final day before landfall.  Little has changed in the forecast or expected impacts, which means a major hurricane is likely going to hit a part of the coastline that has very little experience with such things.

As of 8am EDT, peak winds are up to 100 mph and it's centered 265 miles west of Key West FL and 390 miles south of Panama City FL.  The storm has a decent chance at another round of rapid intensification today, meaning that it can strengthen a lot in a short amount of time due to conducive environmental conditions.

Hurricane Threats and Impacts graphics for Hurricane Michael as of Tuesday morning. (NOAA)
The hazards associated with a hurricane include wind, storm surge, flooding, and tornadoes.  As of Tuesday morning, the maps above summarize the spatial extent of these hazards, with the "cone of uncertainty" overlaid.  Note that the cone only relates to the probable track, and is not at all meant to depict impacts.  NOAA made these Hurricane Threats and Impacts (HTI) graphics operational in June 2015 and they've been available for every storm since then... you can find the current versions at https://www.weather.gov/srh/tropical or https://digital.weather.gov/.

The rainfall swath and amounts look typical for a landfalling hurricane, and flash flooding is likely along its inland trajectory.  The storm surge however, is amplified in this area, so even a Category 1 or 2 hurricane can produce surges of 10 feet or more in Florida's 'Big Bend'.  Zooming in on an inundation forecast map shows the extent of significant surge that is expected.

The total water level, or storm tide, is maximized when the regular tides and the storm surge act in concert.  Landfall is predicted sometime in the early afternoon hours on Wednesday, and some regional high tide cycles are as follows:
11:00pm (tonight) and 10:30pm for Panama City
4:40am and 6:10pm for Apalachicola
2:50am and 3:40pm for Cedar Key
While the tidal range isn't huge in these places, every foot or two can make a difference when it comes to what gets flooded and what doesn't.


Tropical Storm Leslie is gradually strengthening again, and is forecast to regain hurricane status on Wednesday.  It is in virtually the same place it was when it formed on September 23, but is now destined to make a final exit toward the Azores and then Portugal/Morocco this weekend. While definitely rare to have a tropical or recently-post-tropical cyclone hit this area, it's not unprecedented.  Vince hit Portugal as a tropical storm in October 2005, a handful of post-tropical cyclones have hit Portugal, and Delta ran into Morocco in November 2005 shortly after becoming extratropical.

In the deep tropics, the easterly wave that exited the African coast on Saturday has been upgraded to Tropical Storm Nadine.  Peak winds are estimated to be 40mph and it's centered about 500 miles southwest of the Cabo Verde islands.  However, it's going to turn north and run into higher wind shear and cooler water by the weekend and that will be the end of it -- long before it has a chance to get near anything.

Enhanced infrared satellite loop of TD15. (CIRA/RAMMB)

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