Hurricane Dorian Vs. Jupiter’s Red Spot

Satellite view of Hurricane Dorian off the east coast of Florida on Sept. 2, 2019. NOAA

Hurricane Dorian, now weakening, became a monster Category 5 hurricane this past weekend. As of today, it’s down to a Category 2 but still threatens the southeastern coast of the U.S. When it still perched over the Bahamas sporting with crisp eye and a diameter of 280 miles (450 km) the storm sustained winds of 185 mph with gusts to 220 mph!

Dorian in context in a full-globe photo of Earth taken by the GOES-East satellite at 3 p.m. Central Time this afternoon (Sept. 3). NOAA

280 miles is wider than most of my state, Minnesota. Photos showing the storm parked off the Florida coast give one pause. It’s a BIG DEAL. Still, other storms that have ravaged the western hemisphere have been larger like Irma did in Sept. 2017, when it swelled to 420 miles across, wider than any state except Texas, Alaska and Montana. That set a Florida record for size.

NASA’s Juno spacecraft took this photo of Jupiter’s Great Red Spot on July 10 from a distance of 5,600 miles (9,000 km). NASA/JPL-Caltech

But when it comes to record storms Jupiter is still king. It’s the proud owner of the Great Red Spot (GRS), an enormous anticyclonic storm in the planet’s southern hemisphere where the winds flow in the opposite direction of those found in southern hemisphere hurricanes. Hurricane winds spin counterclockwise in the northern hemisphere and clockwise in the southern. Winds in the GRS can reach speeds up to 300 mph (483 km) and are strongest not in the Spot’s center but around its edge.

Photos from the Voyager spacecraft were combined to create this short movie showing the Great Red Spot spinning. NASA

As for size, you may have read that the GRS, an iconic feature that appears to have been around for some 350 years (based on observations with some of the earliest telescopes), has been shrinking in the past few decades. While true, it’s still 1.3 times the size of the Earth or 10,290 miles (16,650 km) across. That’s big enough to see in a 4-inch telescope on a good night at Jupiter’s average distance of 484 million miles (778 million km).

Enormous by earthly standards, Dorian spans a small fraction of its big brother, the Great Red Spot. NASA

But compared to Hurricane Dorian the Big Red Hurricane is nearly 37 times larger. There are several reasons it’s been around so long. The Spot sucks wind energy from jet streams running along either side of it and taps into vertical air flows that bring warmer air up from below and remove colder air on top. It also eats up other smaller oval storm like it, absorbing their energy.

Jupiter and Earth approximately to scale. At this level, Dorian is tiny indeed! The photo of Jupiter is a recent one, taken this summer by the Hubble Space Telescope. NASA / ESA (left) and NOAA

And unlike a hurricane, which sooner or later makes landfall and loses energy, the Great Red Spot lacks the option — there’s no land on Jupiter to bump into! Like the Rolling Stones song Jumpin’ Jack Flash, Jupiter’s just a “gas, gas, gas!” With a whole bunch of clouds.

If there is something solid it’s deep down in the planet’s core.

Despite it smaller size, Dorian is large not only because it’s close and present, but it’s darn big storm for a small planet!