Hurricane Sally inched its way over the Gulf of Mexico before making landfall Wednesday morning.
At times, official advisories from the National Hurricane Center indicated that Sally’s forward progression was only 2 mph. In fact, Sally’s forward motion remained at 2mph from 4 a.m. Tuesday, September 15 to 2 a.m. Wednesday, September 16. Its forward movement increased shortly after landfall, but even then, its speed is only 5-8 mph.
With such a slow movement, Sally was pummeling the Gulf Coast for hours with damaging winds as high as 105 mph, catastrophic storm surge, and rainfall that measured in feet instead of inches.
And to be clear: 2 mph is certainly very, very slow with respect to tropical systems’ forward movement. Dr. Jeff Masters, a tropical meteorologist, states that the average forward speed of a tropical cyclone (depression, storm and/or hurricane) is approximately 11 mph.
When tracking the tropics, it is not unusual to see forward speeds around 10-15 mph, so a movement of 5-10 mph is considered slow; 2 mph is a snail’s pace.
But was Sally the slowest moving hurricane in the Atlantic Basin?
It’s hard to give a definite answer, and one way to verify is to average the speed of a tropical system from genesis to dissipation. However, some storms are very short-lived, and others track for weeks, at times speeding up and slowing down.
But by analyzing Advisory vs Advisory for tropical systems while they maintained hurricane status, was Sally the slowest moving hurricane?
Short Answer: No. Dorian was the slowest moving hurricane
The record for the slowest moving hurricane goes to 2019’s Hurricane Dorian, which literally remained stationary over the Grand Bahama island for 14 hours.
National Hurricane Center advisories indicate that Dorian was stationary at 5 p.m. EDT on September 2, and it had no forward speed until 7 a.m. EDT on September 3.
During this time, Dorian was a Major Hurricane, packing winds as high as 120 to 145 mph, making it a Category 3-4 while it was parked over the Bahamas.
But Dorian never moved over the Gulf of Mexico. It impacted the Eastern Seaboard of the United States.
But what was the slowest moving hurricane in the Gulf of Mexico?
Averaged over the entire length of a hurricane’s lifespan,
As a technicality, 2012’s Hurricane Isaac is the slowest moving Gulf of Mexico hurricane. This tropical system crawled along the Gulf shoreline near Mississippi and Louisiana for roughly four days, and it exhibited two different landfalls in southeast Louisiana within 8 hours of each other on August 28 and August 29, each time with maximum sustained winds of 80 mph.
After the first landfall and before the second, Isaac stalled just offshore of Louisiana, with a stationary movement between 1 a.m. and 2 a.m. on August 29. After this, Isaac continued its forward movement, but at a slow speed of 5-8 mph.
What about 2017’s Hurricane Harvey?
2012’s Hurricane Isaac wins as a technicality, because it remained a hurricane the entire time it was stationary.
It is important to note that 2017’s Hurricane Harvey made landfall at 10 p.m. on August 25 as a Category 4 hurricane with maximum sustained winds of 130 mph and a forward movement of 7 mph.
It made a second landfall at 1 a.m. on August 26 with maximum sustained winds of 125 mph and a forward movement of 6 mph.
Harvey remained a hurricane with forward speeds around 6 mph for the next 9 hours…
And then it just stopped. Moving. Forward.
By 1 p.m. on August 26, Harvey’s winds diminished to tropical storm status.
However, the storm either remained stationary or moved no faster than 2 mph for the next 21 hours.
In other words, the storm stat over the same area of Texas for nearly a full 24 hour period, dumping copious amounts of rain well inland, and producing rainfall totals as high as 50-60 inches of rain.
Other notable slow-moving hurricanes and tropical storms
- 2018 Hurricane Florence slowed to 2-3 mph over coastal North Carolina September 14 and 15
- 2017 Tropical Storm Cindy remained stationary between 1 p.m. and 7 p.m. on June 20