Winter of 2014-15 Summary – Part I
Overview
The winter of 2014-15 served up some wild weather extremes but depending on where you lived in the
U.S. they were at opposite ends of the spectrum. While parts of the West experienced some of their
warmest and least snowy conditions on record, the East meanwhile suffered through one of the
snowiest and at times coldest winters on record.
Much of this dichotomy had to do with the overall position of the jet stream across North America.
Figure 2a shows the 500mb height anomaly for the meteorological winter, or December through
February. Note how much stronger the ridge/trof couplet across N. America was compared to normal.
As a result of the more pronounced, or meridional, ridge/trof combination, the winter temperatures
were much warmer overall in the Southwest and much colder in the Northeast. Those temperature
anomalies are shown in Figure 2b.
Even before winter officially began however, much of the U.S. was hit with a round of very cold
temperatures and in one particular part of the nation, very heavy snowfall. This was due in part, of all
things, a tropical weather system. Typhoon Nuri, which reached the level of a category 5 typhoon in the
tropical Pacific, moved into the higher latitudes of the North Pacific in early November, resulting in one
of the worst storms on record to move through the Bering Sea. That system had a significant impact on
the weather pattern downstream across North America as it sat over the Bering Sea, effectively
pumping up a ridge over the West Coast of North America, which in turn produced a very deep trough
over the rest of the continent. Figure 3 shows the 500mb pattern in the first week of November and the
resulting pattern for the 10 days afterwards. Look at how that ridge built up over the west coast of
North America.
As a result, surface temperatures were much colder than normal for that time of the year across the U.S.
as shown in Figure 4. This was put into perspective in a great blog by Chris Burt, Weather Channel
Historian, when he discussed the change in temperature in Cheyenne, Wyoming from early to midNovember. “It was the coldest November since 2000 for the contiguous U.S. (and 16th coldest on
record) thanks to an exceptional arctic outbreak in the middle of the month. In Casper, Wyoming the
temperature fell to -27°F (-32.8°C) on November 12th, its coldest on record for November. Amazingly,
this was a drop of some -99°F (55°C) between November 1st, when the temperature peaked at 72°F
(22.2°C) tying the record for warmest November temperature ever observed in the city to November
12th when the monthly record low occurred.”
I would be remiss if I did not mention what some would call the biggest snowfall of the season for a
populated area, that is the major lake-effect snow storm that hammered the suburbs just to the south
of Buffalo, NY during the week before Thanksgiving. The lake-effect snow was due in part to the
unseasonably cold air that set up over the Great Lakes due to the arctic outbreak. Two successive bouts
of snow off a relatively warm and ice free Lake Erie produced phenomenal snowfall totals of as much as
70” in some places. The storm shut down a 132 mile stretch of the New York State Thruway and was
accompanied by several rounds of lightning and snowfall rates as high as 6” per hour !! Figure 5 shows
the total snowfall from this mesoscale snow storm and a view of the cloudband in all of its glory cutting
across the south side of the city of Buffalo, NY.
The winter pattern relaxed somewhat during December and early January. However, winter really
came in with a vengeance by mid to late January. During the late January through February time frame
the meridional pattern became most pronounced, resulting in the coldest conditions in decades for
much of the Northeast as shown in Figure 6.
For parts of the Lower Great Lakes and New England the time frame from the last week of January
through all of February produced some of the greatest total snowfall and coldest temperatures on
record, many of which go back well over 100 years. In the West the opposite was true. The February
state average temperature rankings in Figure 7 reveal the entire Northeast experienced their second
coldest February on record while at the same time out West they experienced their warmest February
on record. The February average temperature rankings for selected cities are also shown below in Table
1.
The seasonal snowfall exhibited a similar pattern in general between the West and Northeast. As an
example, while the Sierra through the Cascades and the Wasatch experienced very low to record low
snow pack conditions this past winter, some eastern locations saw their snowiest winters on record.
Figure 8 shows the 2014-15 seasonal snowfall in relation to above or below the normal for several cities
across the U.S. As you can see, for the most part, locations west of the Mississippi were below normal
while to the east were above normal. Some exceptions were along the Front Range of the Rockies
where upslope flow in a few events provided locally heavy snowfall amounts. In addition, a series of
snow storms in the mid-February through March time frame followed a southern track that favored
snow for the Southern Plains in locations like Texas and Oklahoma. Figure 9 tabulates the stats for
selected cities.
The Northeast exhibited some amazing snowfall stats. Notable locations include Boston MA, where they
set a seasonal snowfall record of 110.6”, surpassing their old mark of 107.6” set back in the winter of
1995-96. Much of New England set snowfall records as well. In Eastport ME, 132.5” of snow fell in only
a 5-week period from late January through February with the snow depth topping out at over 6 ft. or
78.5”! Providence had the snowiest season on record at 76.2” and February was their 2nd snowiest
month ever. Worcester set a record at 119.7” blowing away their previous record of 86.7”. In Bangor
the seasonal total of 139.0” was the second highest but the snow depth actually got as high as 50” in
late February. The incredible depths were a result of the cold air that was locked in across New England
for all of February, not allowing any snow melt.
At The Weather Channel we name winter storms anticipated to impact the U.S. at a level of at least 2
million population or an area that covers at least 400,000 sq. km. Though not as prolific in terms of
named storms as our two previous seasons, the winter of 2014-15 produced 22 named storms. This
compares to 26 named storms during the 2013-14 season and 27 storms in 2012-13 as shown in Figure
10.
To get significant snowfall you need two main ingredients, temperatures that are cold enough to
produce snow, and enough moisture that can be lifted into the atmosphere to be wrung out in the form
of precipitation. That lift is generated on a large scale by Low pressure systems that track along the cold
air. The track of these major winter weather systems has everything to do with the type of wintry
weather and the amount of snow that falls.
Figure 11 shows all named storm tracks for the 2014-15 season. It is somewhat complicated to follow
these tracks but there are some lessons we can take from plotting them. The Northeast was much
snowier than normal, a result of some very juicy storms systems that moved through cold air on a track
just south of New England which is a favorable track for heavy snow. The Midwest through Great Lakes
also had significant snowfall. However, the Upper Midwest, including population centers from
Milwaukee through Minneapolis had much less snowfall than normal. Their typical big snow producers
are storms that originate from Colorado through Oklahoma, which often tap Gulf moisture then
transport it northward into colder air. This past season the storms were more of the Clipper variety,
coming out of Canada or the Northern Rockies. The Clippers are typically moisture starved and produce
little snow until they get closer to the East Coast, where they can tap Atlantic moisture. The West of
course had that huge ridge in place through the entire winter keeping most systems from tracking
across the area to produce snow.
In the East, there were some fascinating “stories within the story” during the winter of 2014-15. I have
separated part of the winter season into two sub-categories, a period that extended from late January
to mid-February and one that extended from mid-February through early March.
During the late January through mid-February period, when places like Boston and Eastport tallied up so
much snowfall, no less than 5 separate storms impacted New England. Around February 12th, the
overall large scale weather pattern changed somewhat across the nation as the ridge/trof couplet
intensified, becoming even more meridional. The ridge built farther north and retrograded a bit and the
trof over the eastern U.S. as shown in Figure 12.
This pattern resulted in two impacts; it pushed colder air much deeper south across the entire eastern
half of the nation, and it drove the storm track much farther south with Lows developing off the
Southern Rockies then moving through the Southeastern U.S. As a result, areas from the South through
the Tennessee Valley were impacted by several winter systems. In Lexington, KY two separate storms,
one in mid-February and another in early March combined to produce some record snowfalls. During
Octavia 17.1” of snow fell in less than 2 days making this the heaviest two-day snow storm on record. It
was the 6th snowiest winter, the 3rd snowiest February and 2nd snowiest March on record. In addition
the temperature dropped as low as -18F on February 20th making it the 2nd coldest February day on
record. Farther south in Texas, Dallas experienced 3 snow events in February and another in March. A
comparison of the tracks before Valentine’s Day and after are shown below in Figures 13.
By mid-March the cold air retreated northward into Canada and the winter had pretty much abated
across the continental U.S. However, even in May, a cold Upper Low moving from California across the
Central Rockies put down nearly 2 feet of snow in parts of Colorado, South Dakota and Nebraska.
So in summary I would say the winter of 2014-15 across the continental U.S. was almost polar opposite
depending on whether you lived in the East or West. In particular a favorable storm track from midJanuary through mid-February in the Northeast resulted in significant to record snowfall accumulating
and from mid-February through early March, a very deep Upper level trof ensured an abundance of cold
air which resulted in a lengthy period of high impact weather conditions consisting of deep snow pack
and very cold temperatures. In a nutshell, the Northeast suffered from a long and severe period of
wintry weather. In the West however, very little snowfall and record warmth not only significantly cut
the ski season for many, it had much greater impacts on places like already drought stricken California.
As we get into part two of the winter summary for 2014-15 we will discuss impacts from the 22 named
storms.