Ice storms are among the most impactful, dangerous and damaging storms winter can bring New England. These storms need a very specific setup to occur in order to happen, so they don't often reach truly potent levels, but when they do, the results can be devastating. This is exactly what happened in the middle of December 2008. When this storm ended, it coated central New England in a thick coating of ice, knocked out power to well over one million customers and caused hundreds of millions of dollars in damage.
THE SETUP
Just before this storm hit, it was very mild across New England with widespread mid 40s to mid 50s across the region on December 10. This mild weather abruptly ended when a strong cold front swept through later that day. This front allowed for a shallow layer of cold air to return to the surface across central New England.
At this time, the low-level jet stream had plunged south toward the Gulf of Mexico. This jet was unusually strong as it moved over New England on December 11. This jet stream position prevented a deeper layer of cold air to work into central and southern New England, instead allowing conditions aloft to remain mild.
On the morning of December 11, an area of low pressure plunged from the central plains into the Gulf of Mexico. This system brought a rare snowfall to New Orleans on December 11, when the city picked up an inch of snow (this event is in the top 10 heaviest snowfalls in the city's history).
After blanketing parts of the deep south in snow, this storm worked up the east and into northern New England. As the storm moved into the northeast, a secondary area of low pressure formed off the Mid-Atlantic and tracked across southeast Massachusetts. This secondary low trapped the cold air at the surface across southern and central New England on December 11.
So, at this point, there was mild air aloft and cold air at the surface. This setup is a perfect recipe for mixed precipitation. Depending on how deep the warm and cold layers of air are, it will result in either sleet, freezing rain or a mixture of both. In this storm's case, the warm layer was deep with only a shallow layer of cold air at the surface. This is perfect for freezing rain to develop.
One last factor went into setting up this devastating ice event. This factor goes back to the low-level jet stream. As stated before, this jet was unusually strong. This allowed for very moist air to ride the jet stream up from the Gulf of Mexico into New England. This highly moist air allowed for heavy precipitation to fall during the storm, so a lot of freezing rain was able to come down the night of December 11-12.
THE STORM
Precipitation began to fall across western New England on Thursday morning (December 11). This precipitation was light, with freezing drizzle falling across southern Vermont and the Berkshires of Massachusetts. With colder air aloft across the northern tier of New England, central and northern Vermont as well as northern New Hampshire saw primarily snow.
Heading into Thursday afternoon, the storm complex continued to move northeastward. Lower elevation areas of southern New England would see the warm air aloft sink toward the surface, nudging temperatures just above freezing, preventing major icing. Higher elevations (the Berkshires, Worcester Hills and Litchfield Hills) remained just below freezing at the surface, allowing for more icing.
In northern New England, it was generally the opposite: with the excpetion of the Monadnock region of New Hampshire, it was the lower elevation areas (the Connecticut River Valley, Merrimack Valley and the coastal plain) that saw the most icing. Higher elevations saw generally 3-6 inches of snow.
Ice storm damage footprint:
By Thursday night, the storm complex arrived in New England. This allowed precipitation rates to increase. Across the areas in blue on the map above, freezing rain turned from a drizzle to a constant steady to heavy freezing rain. By early Friday morning, an average of a half an inch to a full inch of ice had coated everything outside.
This much ice simply can't be handled by trees. By early Friday morning (December 12), the rain had finally begun to ease up from west to east. Before daybreak, the sound of pounding rain was replaced by the nearly constant sound of branches and trees crackling, breaking and smashing to the ground.
Not only was there the sound of utter tree destruction, there were blue and green flashes seen all night long as transformer after transformer blew and power lines were torn down. By Friday morning, the freezing rain once again became a drizzle before quickly clearing out that afternoon. Colder temperatures and gusty winds were left in the storm's wake. Some areas saw up to two inches of ice accretion.
THE AFTERMATH
What made the 2008 ice storm so devastating was not only the sheer intensity of the freezing rain, but the large area that freezing rain fell. All of southern Vermont, all of southern New Hampshire, the western two thirds of Massachusetts and portions of New York all saw heavy accumulations and damage. Typically, freezing rain falls within a narrow band during a winter storm with most areas seeing either snow, sleet or plain rain.
Over one million customers lost power across New England. Of these outages, about 440,000 occurred in New Hampshire, which was the hardest hit state. In New Hampshire alone, over 1,300 transformers blew, 780 utility poles were damaged and over 100 miles worth of power lines needed replacing.
Massachusetts saw about 375,000 outages statewide, with the Worcester Hills seeing the brunt of the damage in the state. Outages lasted over two weeks in parts of both states as arctic temperatures, additional snowfall and questionable response plans slowed restorations to a crawl. Some school districts remained closed for over a week after the storm, mainly due to the prolonged outages. Maine saw about 220,000 outages. The final outages were restored on Christmas Eve.
After this storm, utility companies were forced to make comprehensive plans for future significant weather systems that could cause massive power loss to the region. A 400-page report was released in October 2009 assessing the 2008 ice storm power outages and restoration in New Hampshire. This full report can be viewed here (it will be a .pdf download).
Former Director of Public Works in Peterborough, NH stated "I’ve been in the public works industry in New Hampshire for almost 30 years at this point. I’ve been through a number of hurricanes, ice storms, snow storms, floods. I think the one issue here that was not clear for a number of days was the amount of damage that had occurred. If you never left your town, you didn’t know just how bad it was throughout southern New Hampshire.”
For the first couple of days after the storm, it was nearly impossible to leave your town across the affected areas as immense tree damage blocked most roads, leaving people stuck in their homes. A major disaster declaration was approved by the White House on January 2, 2009. Three people died from carbon monoxide poisoning after the storm, one in New Hampshire and two in New York.
The weather didn't slow down after this storm, with wild temperature swings shortly after the storm and two notable snowstorms during the restoration effort, including a nor'easter that dropped up to a foot of snow on the state. On December 22, at the tail end of the restoration, thousands again lost power thanks to heavy snow.
CONCLUSION
This storm came just ten years after a devastating ice storm struck portions of northern New England, northern New York and Canada. The 1998 storm was worse in regards to the sheer amount of ice accretion (up to 5 inches of ice accumulation was seen in Canada and northern New York), but in relation to New England, this storm only clipped the region.
The 1998 storm saw very light freezing rain over the course of several days. The areas in New England that were hit hard in 1998 were much less populated than 2008, leading to much lower power outage numbers.
There have been a handful of ice storms in New England's history and the 2008 ice storm stands among the most impactful.
Photo credits: Telegram & Gazette; bhardy; oandphotos; Maurice Boudreau; pianorollkid3; BmaxPhD; kmccullough; Travis Warren; Jeff Giles