As you navigate through the shoals of daily discourse in our travels along the coast and islands of Maine, it is always a good idea to keep an eye on the weather with its always interesting and often confusing patterns.
That means knowing something about what is likely to be happening on a day to day basis, not necessarily from your TV or radio weatherman-although they are getting better-but more importantly from relating what the weather is predicted to do with what is actually happening in your local area.
We have come to expect the cool rainy springs of black fly season, which lasts from Mother’s Day to Independence Day, if you’re inland and counting, and the long Indian summers that can stretch into early November on the outer islands after the seas finally warm and slowly give up their heat. To understand these seasonal patterns, it helps to know something about the atmospheric and oceanographic influences that come “from away,” which shape Maine’s climate. Weather is daily, while climate is seasonal and inter-annual.
In New England, it sometimes seems that there is more weather lore than weather. For instance, we have all heard the bit of wisdom that says you can predict the severity of the winter from the width of the bands on wooly caterpillars you see in the fall-an appealing if unsupported bit of local hokum. Then there’s the notion that mare’s tales and mackerel skies foretell a rainy spell-which is simply untrue.
Reliable weather signs, however, abound all around us everyday. Clouds, especially those coming from the west and south-the source of most major weather systems in the northern hemisphere-are reliable indicators of what is happening in the atmosphere. Red skies at night actually do foretell fair weather, as the sun sets behind clouds departing eastward; while red skies in the morning from high clouds approaching from the west and reflected in the rising sun means wet weather is on the way.
Cloud shapes, sizes, colors, and heights all indicate the kinds of air masses headed toward us as well their relative temperature and moisture content which will control the weather for the next 12 to 36 hours, depending on the size and speed of the weather system. You cannot tell the size of a system from the approaching clouds (in this regard satellite imagery and weather radar are really useful technological advances), but you can tell when the weather is about to change from the clouds. Then you have to keep looking at the sky to detect cloud changes-which is what mariners mean by keeping a weather eye peeled.
White puffy clouds are fair weather clouds; they are white because their droplets are widely dispersed, letting lots of sunlight through, and thus don’t contain enough moisture to hit the ground. Other fair weather clouds include white, wispy upturned streaks of clouds called mare’s tales or the mottled patterns of mackerel skies. These fair weather clouds form over land as water evaporates from lakes, ponds and rivers-and green leafy trees transpire-pumping tens of millions of gallons of water and water vapor into the air.
Everyone recognizes dark (cumulo-nimbus) clouds or thunderheads that are saturated enough with moisture that rain is likely to fall out of those heavily laden clouds-even though they may be widely scattered.
Many of these fair weather clouds and most thunderheads hover over the mountains and coastline of Maine rather than migrating out over the islands and Gulf of Maine. This is due to the influence of onshore winds that rush in over the water as air over the land heats and quickly rises in the atmosphere, drawing in cool winds underneath. This is why tourists come to our shores, and why our summers are cooler and less buggy as a result.
The biggest cloud systems form over the ocean as the atmosphere sucks up water evaporating from the surface of the ocean. These large clouds form themselves into systems and come in every shade of gray. Not all gray clouds mean rain, but high gray cirrus clouds are an indication of approaching rainy weather from an approaching swirling low-pressure cell. A ring around the sun, called a sundog, is the highest, streaky edge of those clouds-actually frozen ice crystals that refract sunlight and moonlight-and are advance warning of rainy weather that might still be deflected to the south of us if high pressure on the mainland holds the system off.
When clouds come in lower, however, you know the edge of the system is approaching. Put on your rain gear; close your windows and hatches. Take your sheets off the clothesline. Put on a pot of soup, because the system will take a day or two-or sometimes three-to pass by, depending on how fast they are moving. The less wind, the longer they linger. Sometimes these systems stall along the coast-really the worst of all weather in the spring and summer. I call this pattern a schmoo. It’s like a head cold that will not go away. But then, long low dark, puffier, broken clouds signal the trailing edge of a low-pressure system, usually a cold front of air pushing the schmoo away, with red skies that delight. The rain that accompanies the back edge of a schmoo can be intense, but also means the system is passing through and clearing weather is behind it-although like a persistent cold, the congestion can take its time to clear away.
Mariners know that you cannot just study the horizon; you must also study the water to understand local weather and climate. Fog is a cloud at sea level. Along the Maine coast, we have at least three different kinds of fog: thick-o-fog (off Portland), pea soup fog (Midcoast) and dungeon thick-o-fog (Downeast).
The further east you go toward the mouth of the Bay of Fundy, the more persistent, frequent and thick the fogs due to the influence of the colder Eastern Maine Coastal Current. This current turns offshore in the region of Penobscot Bay and is replaced altogether in Casco Bay by the warmer Western Maine Coastal Current, so fogs are more moderate to the westward and up at the heads of bays where the waters are warmer. Those who learned navigation in the fog the old fashioned terrifying way before GPS, chart plotters and radar made mariners out of way too many people, regret no longer having the coast to themselves when a fog shuts the horizon down. A elitist sailing friend used to say, “Hello fog; good bye jerks,” but like most other places in the world, Maine’s waters get buiser each year and not even the fog, to mix a metaphor, separates the sheep from the goats anymore.
Next time, a word about how the climate in the Gulf of Maine is changing and what that portends for lobsters.
Philip Conklng is president of the Island Institute.