Garrett Harris 4 p.m., July 31
Moon of Long Nights, High and Low Tides
Extreme High and Low Tides are set to occur on a string of days next week, during a period that coincides with both the moon reaching full phase and Earth reaching the winter-solstice position in its orbit. These two factors amplify the tide-level range: the high tides will be much higher, and the low tides will be much lower than average. On Monday, December 20, a peak high tide of +6.3 feet occurs at 7:40 a.m. Tuesday's high tide of +6.4 feet peaks at 8:19 a.m. Wednesday's equally high tide of +6.4 feet peaks at 8:59 a.m. Thursday's high tide of +6.3 feet crests at 9:42 a.m. There are at least two consequences of such high tides. If any strong winter storm happens to arrive from the west during these peak tides, some flooding of low-lying coastal areas around San Diego is likely. On the brighter side, birdwatchers have an opportunity to spot species of rare shorebirds that get pushed to the edges of local bays and coastal marshes by the high water. Several exceptionally low tides will also occur within the same string of late December dates. On Monday, December 20, the tide falls to -1.2 feet at 2:52 p.m. On Tuesday, the tide drops to -1.4 feet at 3:29 p.m. On Wednesday, a low tide level of -1.3 feet occurs at 4:09 p.m. On Thursday, the tide drops to -1.2 feet at 4:49 p.m., which is just after sunset. Any of these low-tide occasions are perfect for exploring marine life in the tidepool areas along San Diego County's coastline.
December's Full Moon, named the "cold moon," "oak moon," "wolf moon," and "moon of long nights" according to the traditions of certain past cultures, rises spectacularly over the eastern horizon at around 4:30 p.m., just before the time of sunset, on the evening of Monday, December 20. The moon's night-long (14-hour) journey will take it nearly to the zenith of the sky by midnight, and then down to a setting position over the ocean by dawn on Tuesday morning. Midway between the moonrise and the moonset, you can look forward to 2010's most impressive astronomical event — a total lunar eclipse taking place late Monday night through early Tuesday morning.
Poinsettias, a favorite of backyard gardeners, are now exhibiting their scarlet, petal-like bracts, just in time for the holidays. The onset of 14-hour-long nights triggers their behavior: In San Diego this condition is met just before the date of winter solstice — December 21.
More like this:
- January's Extreme Tides, High Rainfall, and a Quiet Moon — Jan. 14, 2011
- The Quadrantid Meteor Shower, Extreme Tides — Jan. 2, 2011
- Venus, Tides, and December Hikes — Dec. 1, 2010
- Exceptionally High and Low Tides — Jan. 27, 2010
- Poinsettias, Exceptional Tides, the Moon of Longs Nights, and the Geminid Meteor Shower — Dec. 10, 2008