Pacific/Atlantic Hurricane Patterns

As some of you know, I’ve for quite a while been very fascinated by hurricanes, although most of the time I spent mystifying myself by them was before I made this blog. Because this is, after all, my blog, I guess I should add a touch of hurricane research here as well.

So I wanted to make a few charts comparing Accumulated Cyclone Energy (ACE), a property of hurricanes that is ideally the integral of its strength over its lifetime. Of course, hurricane strength can’t quite reasonably be sampled all the time real time, and in fact the National Hurricane Center samples it once every six hours. I remember a few years ago charts showing the ACE of hurricanes were on Wikipedia hurricane season pages, but for some reason someone deleted them. Darn. Because I don’t want to find a database and recalculate all the ACEs of the hurricanes by hand, I decided instead to invent a new unit which would mean approximately the same thing as ACE; this is done by giving each hurricane a score equal to n points for each six-hour interval it is a Category n hurricane. Like ACE, a hurricane will thus have a higher ACE with a higher general strength, measured by wind speed, as well as a higher ACE with lasting longer.

I decided to call this unit describing hurricanes the “hurrscore,” since, well, this unit is pretty hurr. In any case, note that the assignment of the scores do not flow linearly with wind speed, as remember that Category 1 does not start until 74 miles per hour winds. Thus, this system assigns higher scores in comparison to ACE to hurricanes that generally achieve a higher maximum wind speed than to hurricanes that display high endurance.

In the following chart, I list the hurrscores of all hurricanes in the Atlantic Basin since 1979, as well as for a few major ones before (in which I think I included every cat-5 since 1953 with the exception on 1977’s Anita).

In the following chart, the light grey highlight is for hurricanes that achieved at least category 3 status (and thus would be meteorologically dubbed a “major hurricane”) at some point in their lifetime, and the grey highlight is for hurricanes that achieved category 5 status at some point in their lifetime. The single asterisk designates a hurricane name that is retired that year.

Here is the same for the Eastern Pacific Basin.

(For those of you wondering what retiring hurricane names means, each year hurricanes are named from a list of names with the first storm named a name starting with A, the second named a name starting with B, and so on. Since 1979, convention is to recycle hurricane name lists every six years, with the exception of hurricanes that caused devastating damage, which are removed from the name list (“retired”) and replaced with new names (although sometimes for some reason they start using it in another basin…hmmph). Three things: note that storms are named when they become a storm, i.e. reach 40 mph winds; not all named storms make it to hurricane status. Also, the name list contains no entries for QUXYZ in the Atlantic Basin and QU in the Eastern Pacific Basin. Furthermore, wonder what happens when they run out of alphabets? The answer is actually in the chart (it’s only happened one year). Double asterisks represent hurricane names retired due to political complaints or pronunciation complaints. Take a look at the Eastern Pacific basin and despair at how this causes more hurricane name retirings there than for the original reason.)

Looking at the ACE totals given on Wikipedia, my hurrscores comes pretty close, although somehow the top seasons in both basins are different: by ACE, 2005 and 1992, respectively, are the strongest seasons in the Atlantic and Eastern Pacific, respectively, a result I would agree with.

By hurrscore, the eight strongest seasons in the Atlantic Basin are, in order, 2004, 2005, 1995, 1998, 1999, 1996, 2003, and 2010, with the eight weakest seasons being 1983, 1987, 1994, 1982, 1991, 1993, 1986, and 1997. By hurrscore, the eight strongest seasons in the Eastern Pacific Basin are, in order, 1990, 1992, 1993, 1984, 1994, 1991, 1984, and 1997, with the eight weakest seasons being 2003, 2007, 2010, 1981, 1979, 1996, and 2004.

Here is a line chart and a scatterplot:

El Niño years tend to see more Pacific hurricane activity and less Atlantic hurricane activity than usual. Many meteorologists note cycles in the history of the Atlantic Hurricane Basin, with periodic decades of increased hurricane activity, like 1880-1900 and 1950-1970, as well as the current 1995-?. Although Eastern Pacific hurricane records go back barely past what I’ve included, it seems like not only do Pacific and Atlantic hurricane activity receive coupled action from El Niño cycles, but that their activity seems coupled in the larger cycles as well: with the current onslaught of Atlantic hurricanes, Eastern Pacific hurricanes seem to clearly be ebbing in quantity.

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