9 Nov 2018
About Deer Crossings and Hurricane Seasons
Every time I pass a “Deer Crossing” sign, I always wonder how the deer know where to cross. (Obviously, the sign makers put the signs where the deer cross; the deer don’t cross where the sign makers put the signs. Deer can’t read. Really.)
I once asked a highway engineer about this. He told me that, in many cases, they actually force the deer to cross in certain places by putting breaks in the guard rails or perimeter fences that run along many highways. What about the roads that don’t have guard rails or perimeter fences? He said: “In those cases, the deer have to take their chances along with the rest of us.”
But this is about hurricanes, not deer crossings, and the question is, “How do the hurricanes know when the hurricane season begins and ends?”
This is of utmost importance to me, because I live in South Florida where, from May through November, I log onto Hurricane Central every morning to find out if there’s any bad weather heading our way. The hurricane season runs from May 1st through November 30th in the Atlantic Basin, and the occurrence of hurricanes is directly related to the surface temperature of the water in the Atlantic basin and, to a lesser extent, the air temperature above the water. Hurricanes can’t read calendars.
As the water temperatures rise, they hit a point at which the water is warm enough to provide the energy required for tropical temperature inversions to start generating the cyclonic action that spawns hurricanes. (Hurricanes are really just very big, long lasting cyclones.
A cyclone is really just a very big, long lasting tornado that forms over water instead of land, as tornadoes do. They are really quite different, meteorologically speaking, although they feel just about the same if you happen to get caught in one. A tornado that forms over water is usually very short lived and is usually referred to as a water spout rather than a tornado, which sounds a lot less threatening unless you happen to be out on a boat in the water when a water spout happens to appear.
So, my somewhat facetious question is, “How do the hurricanes know when to start and stop forming? Do they watch Hurricane Central?”
Of course not. This is really a matter of nomenclature rather than the conscious intent of the hurricanes. It turns out that, if a storm develops before May 1st or after November 30th, it almost never gets a name. If it has winds of less than 74 mph (119 km/h), it’s called a tropical storm, in the southern states, and a nor’easter in the northern states on the Eastern seaboard. If it sports sustained winds above 74 mph, it’s a Category 1 storm but, if it is outside the date range, it almost never gets a name….nor does it get the coverage that named storms get. (Some sources cite June 1 as the beginning of Hurricane season. Others cite May 1 as the starting date.)
Category 1 storms are nothing to sneeze at, but they are not to be run away from either because they usually die down once they come ashore. You have to be a real chicken to run from a Category 1 storm.
The good news is that, going back to 1771, there have only been two Category 2 storms that have ever been spawned outside of the hurricane season, one in 1863 and one in 1908.
The bad news is that the ocean is getting warmer. It turns out that hurricanes don’t form until the water temperature in the Atlantic basin goes over 82F or 28C, which occurs in May these days rather than June, and they stop forming once the water temperature falls below 82F again, usually by the end of November, if things were still usual, which they aren’t.
The really bad news is that water temperatures have been increasing annually since 1980. In 2018, water temperatures were 1.5 degrees warmer than the 1971 baseline, and the 1971 baseline is .25 degrees higher than the 1880 starting point for the historical data. Climatologists believe that once the water temperature hits two degrees above the average mean temperature, even more bad things will happen. (If you haven’t seen The Day After Tomorrow, you really should. Talk about things to come…)
One of those bad things will be the expansion of the hurricane season from April to December, which begins to sound like the definition of a bad marriage.
So, as it turns out, whether or not Florida gets hit by another hurricane in 2018 depends more on the water temperature than it does on the calendar.
Everyone in Florida knows that there’s a really big hurricane in our future, and we all know that, when the big one hits, it’s going to be very, very bad because (a) storms approach Florida quickly because of how the state sticks out into the ocean, (b) it is really quite impossible to fully evacuate South Florida, and (c) there’s no place to run to once you get there, wherever there is.
Anyone want to buy a house in Florida? It’s a really nice house but it really is a sucker bet. Still, I am sure there must be some suckers out there somewhere.