A total solar eclipse is just around corner, and the Tropical Atlantic is stirring with activity. Karl Etters/Democrat
TALLAHASSEE — The grand spectacle of a total solar eclipse is traditionally accompanied by many other rare events. The midday air cools and stills. Birds stop singing and prepare for night. Words like “syzygy” leap off the Scrabble board and into the vernacular. Godfathers are obligated to grant favors.
But this time, many skywatchers are wondering whether there will be an additional participant (or participants) in the cosmic dance. Will the shadow of the eclipse fall on tropical activity in the Atlantic Ocean?
It may sound like the plot of a direct-to-airplane movie in which Z-list celebrities wield chainsaws, but there is a good chance that at least one tropical storm or hurricane will be within the region of 50% or more solar obscuration on Monday afternoon. Should this occur, it would be the first time an Atlantic tropical system has coincided with a total eclipse since the beginning of regular weather satellite imagery in 1966.
That fact foremost speaks to the true rarity of total eclipses.
Over the past 50 years, just five total solar eclipses have crossed the Atlantic during the June-to-November hurricane season, and the tropics have been inactive during all five events.
Two things make the timing and track of the 2017 eclipse special from the perspective of a potential hurricane-eclipse conjunction. First, this is the first eclipse in 50 years to occur during the most tropically active two-month period between Aug. 15 and Oct. 15. Second, after leaving the U.S., the path of totality will cross from the Carolinas south and east into the Main Development Region of the eastern Atlantic, prime territory for tropical cyclones in late August.
So, the odds of an Eclipse-o-cane are better than average in 2017, but are they ever in our favor?
I used the National Hurricane Center’s HURDAT2 dataset of hurricane climatology to take a snapshot of all recorded tropical cyclone activity occurring at 2 p.m. ET on Aug. 21 for every year since 1900. If a total eclipse occurred every year at that time, in only two of the 117 theoretical eclipses would totality have intersected the center of a tropical storm or hurricane.
Oddly enough, one of those cases is Andrew, which on Aug. 21, 1992, was a tropical storm north of Puerto Rico with 60 mph sustained winds.
However, there are around 15 and 40 historical instances in which an Aug. 21 tropical cyclone was within 2017’s 90% and 50% eclipse bands, respectively.
The upshot here is that having the path of totality cross a hurricane is like hitting a rolling bowling ball with a tennis ball while blindfolded, but intersecting the path of partiality is significantly more achievable, perhaps replacing the bowling ball in this metaphor with a giant human hamster ball.
A check on Atlantic tropical activity reveals one possible candidate to be in the path of totality, and several good opportunities for tropical storms to at least be in the partiality.
The National Hurricane Center is issuing advisories Thursday afternoon on Tropical Storm Harvey, which is forecast to be a hurricane near the northern coast of Honduras on Monday. The sun will be about 40% blocked at peak coverage in this part of the Caribbean. A second tropical wave, Invest 92L, has about a 50% chance of development into a tropical depression and may be positioned in a region of 75%-85% coverage north of Hispaniola in four days should it do so.
Finally, a tropical wave now in the far eastern Atlantic, which the NHC gives a 40% chance of development in the next five days, may be the most interesting.
If it develops, the track may lift far enough northeast of the Lesser Antilles on Monday to cross the tail end of totality. The outlook for this system is the most uncertain, but it is also the best chance for a total eclipse and tropical cyclone to coincide.
There is no word on if Taco Bell plans to give a free Doritos Locos Taco to every man, woman, and child in America should that occur, but it would certainly be a nice gesture if they did.
If you’re wondering about the potential effects of the eclipse on the tropical storm, don’t look for any major impacts.
Hurricanes are fueled by the warmth of the ocean, and a few hours of dimmer sunlight won’t change sea surface temperatures noticeably. The convective activity of tropical cyclones sometimes dips a bit around sunset, so very slight weakening is possible.
While we are in uncharted territory, I would expect any effect to quickly disappear as the eclipse ends.
The bottom line is I wouldn’t bet on a head-on collision of a Category 5 hurricane with a total eclipse (plus sharks), but it’s very likely that the partial shadow is going to fall on at least one and possibly as many as three Atlantic tropical storms or hurricanes.