Tides are not all that easy to understand. For example, can you explain why there are no tides at the equator? It's complicated because the earth revolves and rotates, the moon revolves on an angle to the equator, and then there's the sun too. Lots of moving parts. Plus local factors.
My need to refresh my understanding arises because hurricane Sandy, who will likely be visiting the northeast somewhere between Chesapeake Bay and Boston at the end of this weekend, is coming during a full moon - the Hunter's Moon as the redskin Injuns termed it.
(The latest tracking guesses show it mostly missing New England and turning inland somewhere between Delmarva and Jersey. Meteorologists love this sort of unusual weather event. I heard one on the radio saying that he had always wondered why conditions were so rare for a storm to make a left turn due to a low cold front sucking in a storm. The Weather Nerd is following things, and posted this pic showing the Clash of Titans - the polar cold front and Sandy:)
Full Moons indicate that the moon and the sun are on the same side of the earth, illuminating the moon, and New Moons when they are pulling from opposite sides. Thus both of these phases exaggerate the tidal effect by combining lunar with solar gravity. They're called Spring Tides.
In Maggie's Farm's part of the world, high tide and low tide vary from 6-10' in each tide change, and increase around 20% during Spring Tides. Thus a storm surge during a Spring Tide is likely to cause more damage and flooding to structures (ie, structures which are built where they don't belong in the first place - on coastal beaches, waterfronts, flood plains, and on old marshes covered with a thin layer of fill back before the laws were changed).
Storm surges in New England, whether from Nor'easters or the occasional hurricane, can be 5-10 feet above high tide. A very large or slow-moving storm can effect more than one tide cycle.
Here's a simple, straightforward piece on tides.
Re storm prep, I fetched a fresh bottle of Dalwhinnie, some smokes, charcoal for cooking, good veggies to grill, and I topped off my gas can for the chain saw so I don't get trapped here by fallen trees and limbs. Firewood? Check. My ancient, second-hand diesel generator seems to be on the blink, but we can cope. Sometimes it will start if I kick it in the kidneys while pushing the button.
Meanwhile, I eagerly await the first lunatic to blame the storm on global warming climate change HotColdWetDry, as the Pirate terms it.
Bring it on! Give us your best shot, Gaia.
