Eye On Weather: The Spring Forecast
BOSTON (CBS) - From the April Fool's Blizzard of 1997 to the record floods of May 2006 to the sizzling heat of the 2012 Boston Marathon, we are vulnerable to a veritable potpourri of weather in the spring.
Author and humorist Mark Twain famously said "In the spring, I have counted 136 different kinds of weather inside of 24 hours so if you don't like the weather in New England, just wait a few minutes."
It has been a crazy winter with the mean temperature below average for the last 5 months!
While there have been a few breaks providing brief relief, the cold has been relentless and that combined with the above average snowfall, most people are craving balmy days and signs of spring.
The reality is that this was an old-fashioned New England winter and much colder than the last 5-to-6 years.
After having really no winter at all in 2011-12, we were all spoiled. You know that the strengthening sun will eventually win out and warmer days are ahead.
However, the outlook for spring is not so great if you want to transition into a long stretch of warm days.
Joe D'Aleo, senior meteorologist at Weatherbell Analytics, is the master of seasonal forecasts. He's predicting that April will be plagued by more bouts of unseasonably cold weather.
His research of analog years for the present pattern show strong support for a cold April transitioning into a warmer May.
The real driver of the very cold weather from Canada across the northern Plains into the Midwest, Great Lakes and northeast through the winter was a pool of warm water in the northeast Pacific especially in the Gulf of Alaska.
This warm pool resulted in a big ridge of high pressure poking up across that region into Alaska. The resultant downstream winds to the east of the ridge line were blowing southeastward across Canada so masses of air would come down from Siberia and the North Pole. This warm pool remains in place with a slight shift eastward.
Consequently, the WBZ Weather Team agrees with Joe that this would suggest more masses of air will rush out of Canada and periodically chill us through the next 4-to-6 weeks. With the very cold Atlantic Ocean and the prospects of chunks of cold air revisiting, especially eastern Canada, the potential for a more typical spring yielding bone-chilling backdoor fronts looms as we go forward.
As zones of high pressure build into eastern Canada, there will be a tendency for the cold to drop into the Canadian Maritimes with the fronts backing in from the ocean to make us shiver along the coast while the Connecticut River Valley experiences much warmer conditions away from the cold sea.
The good news is that this pattern favors normal precipitation and without a sudden massive extended warm up, the outlook is for a more orderly melt of the deep snowpack up north which would lower the threat of significant spring flooding. The precipitation prospects decrease going forward later in spring into the summer, so drier than average weather may be in the works.
This same pattern favors less tornadic activity across the nation but there will be an increase in numbers over last year which, thankfully, was the tamest tornado year in a very long time. The potential for a blossoming El Nino will eventually lead to more severe weather this year than last year.
PLANTS FLOWERING EARLIER
We look forward to signs of spring, such as the flowering and leaf-out of trees and shrubs, so I traveled out to Walden Pond in Concord to chat with Richard Primack, a biology professor at Boston University.
Thanks to long-term plant records initiated here by Henry David Thoreau in the 1850's, studies by Primack and his associates reveal that, in general, mean leaf-out and flowering dates of most trees and plants are about two weeks earlier than about 150 years ago.
This is a result of recent climate change, but it is uncertain if flowering times will continue to advance IF temperatures continue to rise.
They found that the mean flowering dates of 32 species have shifted from May 15, according to Thoreau's records, to May 4 in the past decade.
However, in 2010 and 2012, the plants flowered about 3 weeks earlier than Thoreau's times. Clearly, there is a significant relationship between mean spring temperatures and mean first flowering dates. Interestingly, on the other hand, some individual species were unresponsive to spring warming when they had insufficient winter chilling.
I asked Primack if the temperature and variety of weather in the winter or early spring alters the leaf-out and flowering times of trees and plants.
He says that all of the months starting from January onward are important but more so in March and particularly in April or even early May. These are the most critical times in terms of determining when the trees and shrubs start to leaf out.
Even if temperatures skyrocketed now, it would not lead to an earlier leaf-out because that warming goes into snow melt and warming of the ponds and thawing out of the root systems.
SILVER LINING TO BRUTAL WINTER
There is a silver lining to a brutally cold winter and start to spring. The really low temperatures this year are going to cause high mortality of many of the insect pests that have been attacking the New England trees. In particular, the woolly adelgid, which is attacking the hemlock trees, and the emerald ash beetle, which is attacking the ash trees, will be killed off giving a break to these trees.
Unfortunately, a few of these pests will survive leading to more infestations in subsequent years.
Another Boston University study headed by Professor Pamela Templer shows another consequence of milder winters.
A small or no snowpack leads to the ground freezing deeper and longer and this has a negative impact on trees and water quality of nearby aquatic ecosystems well into the growing season.
DEEP FREEZE STUDY
The study was undertaken in New Hampshire's Hubbard Brook Experimental Forest in Woodstock, where acid rain was discovered in North America many years ago.
Templer and her colleagues shoveled snow off sections of this forest to simulate the effects of a warm winter and they discovered that lowered the temperature of the soil by as much as 10 degrees.
This deeper freeze forms ice which damages the roots by cutting into them which limits their ability to absorb nutrients and nitrogen. This nitrogen then runs off into ground water and nearby streams and she says that this action can deteriorate water quality and create harmful consequences to humans and the environment.
Interestingly, the trees have an ability to repair themselves but the damage can cause a delay in leaf-out.
Templer concludes that this winter was ideal because of the insulating snowpack and she adds that it would be great to see a gradual warm-up so the leaves come out and the plants flower, but they don't do it so early that they are susceptible to a potential late frost that could damage them.
With the current outlook for spring, it looks like we'll get just what the doctor ordered.
HAPPY SPRING ONE & ALL!
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