Ken Harrison 6:45 p.m., Aug. 23
Poinsettias, Exceptional Tides, the Moon of Longs Nights, and the Geminid Meteor Shower
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 -- Sunday, December 21.
Exceptionally High and Low Tides are set to occur on several days in mid-December. These tides closely coincide with the full moon, and approximately coincide with the winter solstice -- two factors that influence tide-level extremities. On Thursday, December 11, a peak high tide of +6.8 feet occurs at 7:08 a.m. Friday's high tide of +7.1 peaks at 7:53 a.m. Saturday's high tide of +7.1 feet peaks at 8:40 a.m. Sunday's high tide of +6.8 feet crests at 9:29 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 mid-December dates. On Thursday, December 11, the tide falls to -1.6 feet at 2:22 p.m. On Friday, the tide drops to -1.8 feet (almost as low as it can possibly go) at 3:09 p.m. On Saturday, an equally low tide level of -1.8 feet occurs at 3:56 p.m. On Sunday, the tides drops to -1.6 feet at 4:45 p.m. (very near the time of 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, only a few minutes after the time of sunset, on the evening of Friday, December 12. Some 14 hours later the moon sets in the west near the time of sunrise. Winter-solstice full moons spend a long time (14 hours) in the night sky (as seen from San Diego), just as the summer-solstice sun spends about 14 hours arcing across the daytime sky. The month's full moon is also notable for being a "perihelion full moon," which means that the moon is in a position closest to Earth along its elliptical orbit. The moon appears to be a little larger than normal in the sky as a result of this.
The Geminid Meteor Shower peaks the evening of Saturday, December 13 and the morning of December 14. The glare from full moon however, will largely spoil the viewing of this, the most intense dependable meteor shower of the year. Because of the glare, you will only see perhaps 10 or 20 meteors per hour, instead of upwards of 80 or 100 per hour.
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
- Moon of Long Nights, High and Low Tides — Dec. 20, 2010
- Temperature Inversions, Tides, Sunrise/Sunset, and the Leonid Meteor Shower — Nov. 12, 2008
- Observers of marine life in the intertidal zone can take advantage of this week's extreme low tides. — Jan. 20, 2000