Michael Upgraded to Category 5 Status

Hurricane Michael, October 2018 (Source: NOAA)

On April 19, NOAA determined that Hurricane Michael was indeed at Category 5 intensity when it made landfall in the Florida panhandle last October.  At the time, it was an upper end Category 4 hurricane, just below five status with sustained winds of 155 mph.  Now, according to NOAA’s post-analysis Michael had sustained winds of 160 mph.  While there is little tangible difference between these wind speeds in terms of damage, reclassifying Michael as Category 5 changes a host of historical records.

The upgraded Michael became only the fourth Category 5 hurricane to ever make landfall in the United States and the first since Andrew in 1992.  The two other Category 5 hurricanes to make landfall in the United States are Camille (1969) and the unnamed Florida Keys 1935 hurricane.  While Michael’s sustained winds were the lowest of the three other hurricanes, it’s minimum central air pressure of 919 millibars was the third lowest air pressure for a hurricane at its time of landfall, ahead of Andrew (922 mb) but behind 1935 and Camille.  

Hurricane Michael also did an estimated $25 billion worth of damage in the United States after its landfall on October 10, 2018.  No Category 4 or 5 hurricane had ever made landfall in the Florida panhandle before, so that’s another dubious record that Michael now holds.  Both Andrew and Camille impacted the United States in August, while the 1935 hurricane occurred on Labor Day.  That makes Michael the latest land-falling Category 5 hurricane of the season.  

While there have been a number of Category 5 hurricanes later in the season than Michael, such as Mitch in October 1998 and Wilma in October 2005, they, did not impact the United States at that intensity.  Some may remember that Hurricane Maria reached Category 5 intensity in 2017.  However, an eyewall replacement cycle caused Maria to weaken slightly below Category 5 intensity before its Puerto Rico landfall.

Hurricane Michael had some key similarities to Hurricane Andrew.  Not only were they each upgraded to Category 5 hurricanes in post-storm analysis done by NOAA, but both hurricanes intensified up until their respective landfalls.  That’s unusual as hurricanes often weaken shortly before they make landfall, especially if they are slow-moving storms, as the interaction with land masses tend to weaken them.   

A minor difference, however, between Michael and Andrew is that it wasn’t until Andrew’s 10^th anniversary in 2002 that it was upgraded.  Hurricane Andrew also became the costliest natural disaster in U.S. history for more than a decade.  Meanwhile, despite causing $25 billion in damage, Hurricane Michael ranks behind costlier U.S. hurricanes such as Katrina, Harvey, Irma, and Maria.