Forecast: Warm, Wet and Windy

Brain doctors tell us that our short-term memory capacity is more acute, but also more fleeting, than our long-term memory, which, by definition, is persistent but spotty and unreliable. Perhaps this basic neurological fact helps explain why we have such a hard time distinguishing between weather and climate. Weather is what happens to us on a day-to-day basis, while climate is averaged over periods of time of a decade or more. Who can remember last year’s weather—or the weather 10 years ago, for that matter? I do recall, however, that I took my first outdoor shower last week—and continued to do so for the rest of the week, in fact—but this week the dog’s water bowl froze solid and we are burning our remaining oak logs in the woodstove. Homeowner hint: remember to drain outdoor faucets after an early spring thaw before a seasonable hard freeze. How soon we forget. Although the rest of this week is going to be cold and raw, this past December, January, February and March have all been warmer than the 30-year average by between 3 and 5 degrees Fahrenheit here in Maine. It was also the fourth warmest winter on record in the contiguous U.S., and it is interesting to note that six of the 10 warmest autumns in Maine have occurred since 2000. Leaf peepers, pay attention!

Going back to last year, the spring, summer and fall of 2011 were also all warmer than average, not just in Maine, but across most of the eastern United States. Texas positively baked in an unprecedented drought. But ultimately it was not the heat that hurt us; it was the number of extreme climatic events that swept across almost all parts of the country—mostly sparing Maine, unless we count the first-ever 100-degree day in July at the Portland Jetport on the 22nd. Three massive tornado outbreaks across the South and Midwest—between April 14-16, April 25-28 and then May 22’s EF Category 5 tornados that ravaged Joplin, Mo.—combined to kill hundreds of people. 2011 was the second most active tornado year since records have been kept, beginning in 1980. Seven of the tornados and severe weather outbreaks caused damage exceeding $1 billion, with a cumulative total of $28 billion in damages from some 1,190 tornadoes. Unprecedented. The tornadoes that touched down February 28-29 from Nebraska to Tennessee killed 13 people and were one of the earliest tornado outbreaks on record.

As if this violent weather were not curse enough, the floods that surged over the banks of the Ohio and Mississippi river valleys last spring left huge swaths of damage in their wakes. Shortly afterward, a second wave of severe flooding along the Missouri and upper Mississippi river valleys ultimately threatened New Orleans as the Mississippi crested downstream. The only reason New Orleans was spared an epic flood was the Army Corps of Engineers’ decision to open the Atchafalaya flood diversion gates above Baton Rouge that destroyed thousands of acres of oyster beds rather than the city itself. After New Orleans was spared, the news cycle, along with our short-term memories, moved on.

Last year there were also 19 named tropical storms, including seven hurricanes, three of which made landfall in the U.S. Many of us recall Irene, which made a landfall on the islands of the Outer Banks, where the storm surge destroyed roads and bridges that have since been rebuilt with $70 million of state and federal funds, but which are now rapidly eroding again. Irene churned up the East Coast, spun past lower Manhattan, barely avoiding the creation of epic floods of the financial district’s storm water system. It would have barreled into Maine except for a last-minute, left-hand turn through western Connecticut, Massachusetts and Vermont, where 200-year-old covered bridges floated away.

This year, the National Oceanic and Atmospheric Administration (NOAA) predicts an 85 percent chance of an above-normal hurricane season—the 12th in the past 17 years of predictions—with an anticipated 14 to 19 tropical storms, seven to 10 hurricanes and three to five major hurricanes in the Atlantic. NOAA does not predict hurricane paths, so there is no knowing how many are likely to reach land. If they don’t reach land, we simply forget about them and keep on with our daily business.

So what is behind all this record-breaking, extreme and violent weather? The simplest answer from climatologists is found in a warmer ocean, especially in the tropics and subtropics—in the Caribbean Sea and the Gulf of Mexico, in particular. As the air over the oceans warms, it also is able to hold more moisture. Warm tropical air sucks up a lot of warm ocean water and moves northward, and as these air masses move over land, a couple of things can happen. One is that the air will cool and dump its load of moisture as rain or snow. The warmer the ocean and the warmer the air, the more precipitation that will fall, which means heavier rainfall and a higher probability of flooding. Alternatively, if these warm, humid air masses collide with colder air moving south, as happens in the spring and early summer, the collision of air masses with extreme temperature differences results in conditions that spawn intense spinning cyclonic vortices—or tornadoes. Toto, we are back in Kansas—and everywhere across the southern and Midwestern United States, too.

When the sea surface temperature of the Caribbean and Gulf of Mexico is warmer than average, more ocean water evaporates, which rises with the air and spins into larger and larger low- pressure cells over the ocean. The larger cells become tropical storms, and the giant ones spin up into hurricanes if the high altitude jets of air do not decapitate them. So meteorologists predict hurricane activity based on sea surface temperature and the strength of high-altitude tropical jets. Sea surface temperatures are already approximately 1 degree Fahrenheit warmer than average in the tropical Atlantic and Gulf of Mexico—slightly warmer than at this time last year, so the likelihood of major hurricanes is increased. Let’s hope they spin aimlessly in the North Atlantic or are deflected away from the Gulf Coast (sorry, Mexico) this summer, so we can forget about them and go on about our daily business.

What does all this mean to us on the Maine coast? We do not live in Tornado Alley, although at least three tornadoes touched down in Maine last year, so we can be thankful for that. We are less vulnerable to being in the eye of a major hurricane than the rest of the East Coast between Florida and North Carolina or the Gulf Coast between the Florida Keys and Texas, if the lottery of past hurricane landfalls is any guide. But as weather systems move northward, there will be more energy—and more wind associated with them. We are also likely to experience wetter weather over the long haul—even though this winter has been exceptionally dry (remember the difference between weather and climate). Both our winters and summers are likely to be warmer—not each summer and each winter, just generally warmer on average. The Gulf of Maine is likely to get warmer, especially the western Gulf of Maine, meaning the center of lobster abundance is likely to continue moving eastward.

Bottom line, the climate (not weather) forecast is for warmer, wetter and windier conditions—and we have not even talked about carbon dioxide yet! Stay tuned for more news.

March 28, 2012