This year my friends and family have had more than their usual share of destruction from the few hurricanes that hit the United States. Hurricane Irene and the remnants of Lee have been headline news for weeks and even Hurricane Katia, who's missing the U.S. entirely, is affecting friends on a cruise in Greenland.
So I wondered... how and why do hurricanes form? I did a little research and found that even the basic facts are fascinating.
Hurricanes are tropical cyclones, complex dangerous storms that occur around the world. In the North Atlantic and on the eastern side of the Pacific we call them hurricanes. In the northwest Pacific they're called typhoons.
Tropical cyclones are not completely understood but scientists know that six ingredients are required for a hurricane to form. The ingredients, listed at NOAA, are:
A warm ocean surface of at least 79.7oF to a depth of 160 feet. To get an idea of how warm this is, the water temperature at the Eastern Maine Shelf this morning is 54-52o from the surface to 160 feet.
Rapid cooling of the air as it moves upward, causing condensation and thunderstorms which release heat to drive the storm.
High humidity in the mid troposphere 3 miles (15,800 feet) above the ocean. If you were on a trans-Atlantic airplane, you'd be flying high above it.
The Coriolis effect must cause the storm to spin. There is no Coriolis effect at the equator so the storms cannot form at less than 50 of latitude (345 miles) from the equator.
A pre-existing disturbed weather system near the ocean surface which provides the nascent storm with something to organize around.
Low wind shear where the storm is forming. Wind shear is an abrupt difference in wind speed and direction and can break up a cyclone before it gets going.
In August and September hurricanes often form off the Cape Verde Islands near the north coast of Africa. They are then carried by the trade winds across the Atlantic and sweep over the Caribbean islands and sometimes the U.S. or Central America. Right now Tropical Storm Maria is heading for Puerto Rico and Tropical Storm Nate is about to hit Mexico.
Thank heaven we're over the hump of hurricane season for 2011. We've certainly seen enough of them this year.
Last Saturday we encountered some unexpected flying objects at Acadia.
The first was a one-man helicopter the size of a Volkswagen beetle. It appeared over the mountain just above the trees and quickly and quietly maneuvered into the valley behind the Asticou Inn where it landed in a tiny clearing the size of a parking space.
By the time we got there it was tethered like a horse, its rotor tied to the front with a long strap. We had never seen such a small quiet helicopter but we obviously don't travel in the right circles.
That was the well-behaved flying object. The second was another story.
It happened while my husband and I sat on the shoreline boulders, watching the waves and eating lunch. There was a Labor Day crowd on the Shore Path and some were feeding the gulls. We were not, but the local gulls knew that handouts were a possibility.
I was holding my sandwich up, ready to take a bite, when I saw a herring gull about to land on me. His pink legs and large wings filled my view. He was nearly on top of my sandwich when I shouted and ducked. The gull flew over me... and hit my husband on the head! My husband nearly dropped his sandwich but the gull could not snatch it.
Foiled in his attempt at our food the gull flew over the water and stole a crab from an unsuspecting eider. How dare he! It actually made me mad.
Herring gulls apparently do this the world over. This photo is from Belgium.
(photo from Wikimedia Commons. Click on the photo to see the original.)
Every clear night brings a new wave of migrants to Mt. Desert Island.
The warblers I see leaving Maine right now are running late. They've flown south across Canada and are quickly fueling up before continuing their journey west.
West? At Acadia the Maine coast is an east-west line at the Gulf of Maine. When the birds reach Mt. Desert they island-hop westward until the coast curls south.
Some Canadian migrants don't turn soon enough and end up on Nova Scotia. Surrounded by water, they launch due west over the Gulf of Maine from Halifax to Bar Harbor.
On the Whale Watch I've seen solitary robins and hummingbirds flying hard toward the Acadia mountains, dimly visible in the distance. They've almost reached land by the time I see them from the boat near Mt. Desert Rock. Only 25 miles to go.
Fortunately, most of the birds don't travel over open water. Instead they hug the coast in mixed flocks and make the journey in easy stages.
Each warbler wave is here for a short while. Soon they'll all be gone.
Razorbills and puffins are birds of the open ocean who only come to land to nest. In Maine their land-based period ends in August so I always miss seeing them on their nesting islands when I vacation here in September.
If I came in April I'd see them courting and claiming nest sites,and perhaps I'd be lucky enough to see something as unusual as this...
In this video from April 2008 at Lundy Island (UK), an Atlantic puffin -- about the size of a pigeon with orange feet -- is puttering outside his nest cave while amorous razorbills court all around him.
In their excitement a pair of razorbills walks into the puffin's nesting area.
Normally razorbills bully the puffins but in this case the encroachment is more than the puffin can take.
Even though the razorbills are twice his size, the puffin attacks ... and wins!
Click on the photo to watch the video. At the end you'll see his lady come join him at the nesting site.
I come from a place where I can identify most trees but few of them are evergreens so I'm a bit overwhelmed by the number and variety of conifers in Maine.
As I walk through the woods I try to identify what I see. I usually can't see an entire tree (they're tall!) so I focus on the needles, twigs, and cones to figure them out: pines, spruces, firs and hemlocks.
Pines: If the needles are in bundles attached to the branches, then it's a pine.
White pines are unique because they have 5 needles per bundle, shown above. It's easy to remember "5" because the word "white" has five letters. Pitch pines have three needles per bundle. Red pines have two. Unfortunately their names don't help to memorize them.
Spruces: If the needles are sharp, four-sided (square or rhomboid) and grow all around the twig it's a spruce, shown above. Maine has black, white and red spruces but I've not made the effort to tell them apart yet.
Firs: Firs have flat needles, green on top and whitish below. The needles appear to grow in rows so the twigs sometimes look flat. Hemlocks share these characteristics but their twigs droop at the tips while balsam twigs are stiff and stand straight out. If the balsams had cones I could identify them easily because the cones stand erect on top of the branches. I haven't found any fir cones yet. They disintegrate when they mature at the end of the summer.
Hemlocks: Hemlocks also have flat needles with two white stripes on the underside. The needles grow in only two rows on opposite sides of the twig. The twig is flat and flexible and droops at the tip. Hemlocks have tiny cones that hang below the branches. Of all these conifers I know hemlocks best because they're native to Pennsylvania.
As hard as I look I still get confused, first by spruces, then by firs.
I've got a lot to learn in this coniferous state.
(photo from Wikimedia Commons. Click on the photo to see the original)
This morning I really examined a nasturtium for the first time.
Though it has five petals and sepals, the flower is slightly irregular in shape. The two upper petals have crenellated stripes, the lower three have feathery edges. Together they form a bowl but the bowl is porous. If you pull on a petal you can see that the petals and sepals aren't connected.
Like many flowers, nasturtiums raise their stamens and pistil at different times in the blooming period. These line up behind the feathery lower petals and force visiting hummingbirds to hover rather than perch. No problem for hummers!
I say "hummingbirds" because the nectar in this flower is inaccessible to bees. It's not in the bowl but in the long, narrow nectar tube whose entrance is a tiny hole. When I looked at the nectar tube I said "Aha!" It's the same shape and size as a hummingbird's bill.
We humans see the nasturtium's face -- and so does the hummingbird -- but the real goal is that insignificant tube.
(photo from Wikimedia Commons. Click on the photo to see the original)