Break out the snow shovels! Meteorologists predict above
average snowfall in the Northeast this winter and especially bitter cold in the
Northern states. According to forecasters, that shakes out to least 6 inches more snow than usual in
the New York City and Boston areas and high totals in the Great Lakes areas in
Pennsylvania, Ohio and upstate New York. The Southeast should be warmer than
normal, but with a risk of tornadoes, forecasters say.
Overall, long range weather forecasters predict a wet winter in much of the country with
temperatures colder than the last two years, but still higher than usual. Indeed, the last two winters have been
particularly warm. The 2015-16 winter in the United States was the warmest on record,
and last winter was among the top ten warmest.
Even so, it is worth remembering that even mild winters bring
bitter temperatures and the threat of destructive snowstorms. That is one reason winter storms are the third largest cause of catastrophe losses, behind hurricanes and tornadoes. The 2015-16
winter was the warmest ever and it still caused more
than $1.5 billion in insured losses and brought one of the heaviest snowstorms
ever in several Eastern cities.
Besides, snowfall during warmer temperatures produces
wetter and heavier snow than snow at colder temperatures. Heavier, wetter snow
causes more roof collapses and downed tree limbs than dryer, lighter snow that
forms at more frigid temperatures.
Winters have been warmer on average in recent years due to
climate warming but natural variability is the largest driver season to
season. A significant part of that natural
variability stems from the La Nina / El Nino water temperature patterns in the Pacific Ocean. El Nino
describes an extended period of unusually warm water around the equator in the eastern Pacific. La
Nina is the opposite. It occurs when sea surface temperatures in that part of
the Pacific are colder than normal.
These temperature cycles in the eastern Pacific Ocean can
be a major driver of weather in the continental United States. Even water temperature
fluctuations of just a degree or two can have a huge impact.
This year, meteorologists set the odds at 55% to 65% that a La Nina pattern develops in the eastern
Pacific Ocean. If it develops, the La Nina pattern is
likely to be relatively weak, forecasters say.
But even a weak La Nina can shape the winter for many of us.
Historically, La Nina brings colder and wetter winters to
the northern part of the U.S., and drier and warmer winters to the South. While
forecasters look at other factors too (amount of snow on the ground in Siberia
and extent of Arctic sea ice in the preceding months are other data points) predictions for the upcoming winter generally line up with the traditional La Nina
effect.
That is a main reason that forecasters expect somewhat warmer temperatures across the Southern states and on the
East Coast, but unusually cold temperatures and wetter conditions through the Northern
states. Whatever the precise outcome this winter – ice, snow and plummeting temperatures
are guaranteed!
Posted by Jeffrey Gordon