Hurricanes, Earthquakes, and the Whirlpool Galaxy

Some of you are probably aware that here in Hawaii we just had the first hurricane landfall in twenty-two years. Hurricane Iselle made landfall late Thursday afternoon (although it was downgraded to a tropical storm about the same time), becoming the first hurricane to hit the Hawaiian islands since Hurricane Iniki hit Kaua'i in 1992, and the first cyclonic tropical storm to make landfall on Hawai'i island itself since 1958 (when it was only known as “Tropical Storm Seven”).

For a while it seemed like hurricane Julio might follow in its metaphorical footsteps, but it appears to have swung north and not be a threat anymore. Thankfully, Iselle doesn't seem to have caused any catastrophic damage (in the sense that no lives were lost), although it certainly downed a lot of trees, and a lot of people south of Hilo in Puna suffered power outages (and since most people down there are on their own wells or catchment tanks, losing electricity means losing water too). I came through the storm with only a few flickers of the lights, though I was beginning to worry about the structural integrity of my roof in some of the stronger gusts of wind.

Speaking of gusts, that was probably the part of the storm that surprised me the most. I had assumed that the intensity of the storm would more-or-less smoothly rise, peak, perhaps stay high for a while, then gradually fall. Instead, relatively long periods of calm would be interspersed with periods of torrential rain and howling wind. And when I say calm, it really was quite calm; little or no rain, and the air almost dead still. All in all not what I had expected.

Thinking it over after the fact, this periodic series of heavy weather followed by relative calm put me in mind of the typical appearance of a hurricane, that of a spiral with many arms...in fact, very similar in appearance to something else I know a lot about, spiral galaxies.

The picture below was inspired by an incident at work, where both me and a co-worker independently, upon seeing the picture of hurricane Iselle shown below in the newspaper, remarked that it looked highly reminiscent of a famous spiral galaxy, in this case, Messier 51, also known as the Whirlpool galaxy.

I think it was the long arm of Iselle on the right that put me and my co-worker in mind of M51 (although there's nothing corresponding to M51's little companion galaxy NGC 5195 seen below it).  There are other differences, but I find this comparison of two spirals of such vastly differing sizes appealing.

M51 also hold a special place in my heart for being the location of the very first supernova I ever managed to photograph, a little over three years ago now.

Oh, and to justify the "Earthquakes" in the title, about 6:30 Thursday morning, a scant few hours before Iselle hit, we had a small earthquake (magnitude-4.5 on the Richter scale) up near Waimea. It wasn't enough to wake me (4.5 is just a bit above the threshold it's possible for humans to detect), but our telescope operator on duty noted it (and at first thought it was just someone walking up the stairs to the control room!). As I've said before, life's never dull when you're living on a live volcano in the middle of the mighty Pacific ocean!