Now that I'm back in the tropics again, I got to experience a uniquely tropical phenomenon today: at noon, the sun stood directly at the zenith overhead. In Hawaii, such days are known as “lāhainā noon” days, after a contest held by Bishop Museum in 1990 in which that was the winning entry. Briefly, as the Earth travels around the sun, the latitude at which it appears directly overhead (the subsolar point) varies from +23.5° on the June solstice to −23.5° on the December solstice. Points at those latitudes will see the sun reach directly overhead on just that one day, but points between the Tropics of Cancer and Capricorn will see the sun pass directly overhead twice a year. On the equator this happens on the equinoxes, then steadily closer to the solstices the further away you get.
Here in Hilo, at a latitude of +19.7°, the two lāhainā noon days are May 18 and July 24 (at least for 2022, it's possible the exact day could shift by one depending on e.g., whether it's a leap year). So this is the first one I've experienced since moving back at the end of September last year. For the next two months, roughly, the sun will appear north of zenith in the sky. Directly at lāhainā noon, however, shadows are cast straight down, so tall straight objects like flagpoles effectively have no shadow. I tried to get some photos, but there was a haze of clouds over the sun that made shadows very faint—I could make them out by eye, but they didn't really come out well on camera. I'll just have to wait for July to try again.
Oh, and if you're wondering about the name, it comes from the Lāhainā region on the island of Maui, which, being on the leeward side of the island, is prone to droughts. It can be translated fairly literally as “cruel sun.” Another, older, Hawaiian name for this phenomenon is “kau ka lā i ka lolo,” which has the humorous translation of “the sun rests upon the brain.” Anyway, that's all for now. Hopefully I'll be able to get some photos next time the sun comes around overhead. A hui hou!
