Last winter behaved quite well based on our forecast. Quite frankly,
though, it's rather difficult to mess up the forecast in a rather
strong La Nina season. La Nina seasons are strongly negative in
terms of snowfall in relation to normal amounts. To be clear, the
trend is strong in terms of frequency of La Nina seasons having
below normal snowfall. The snowfall amounts, however, do not tend
to be far below normal. Last season was a perfect example of this...
though some folks saw snowfall far below normal a few small regions
(including my own city) saw snowfall above normal. So, on average
across the Northeast the snowfall was somewhat below normal.
Well, things have changed a lot in one season! With the La Nina
pattern backing off, we are faced with near neutral El Nino/La Nina
conditions for the upcoming season. There's an important note to
make along these lines... various folks will define their El Nino
and La Nina conditions differently. Many folks use the wind field
as that is the driving force behind the sea surface temperature
(SST) anomalies. Other use the SSTs directly, with the thought that
these SST anomalies are the driving force behind the varying weather
patterns in the mid-latitudes. Moreover, using the SSTs imparts
variations as well. The SST anomalies are grouped into varying
regions and different people focus on different regions for their
SST anomalies. Most typical are regions called "Nino-3" and
"Nino-4". There is also a combined region called "Nino-3.4". The
differences in using the winds versus SSTs and the varying SST
regions creates timing difference with regard to the changing phases
of El Nino/La Nina. This can result in differring expectations of
the phase during the winter months. FYI, the methodology used
herein is the Nino-3.4 SSTs.
With that, we are able to examine past seasons for their trends and
patterns under similar conditions to those expected this year. The
expectations this year are for near neutral SSTs in the Nino-3.4
region. Conditions may well start out slightly cooler than normal,
but very possibly may end up slightly warmer than normal. So, all
in all, things are expected to run very close to zero anomaly in the
Nino-3.4 SSTs.
Of course, it is critical to note that the El Nino/La Nina phase is
absolutely NOT the only factor involved in the prediction of the
winter season predictions. However, it is one of the stronger
indicators and one of the stronger parameters to relate to winter
expectations. As such, it is one of our primary forecast tools.
Data for the past 50 years, roughly, is available for comparison of
the SST anomalies. With that, the following seasons were obtained
as analog seasons for the upcoming winter conditions (note that the
seasons are listed by the Jan-Mar year... that is, 1957 represents
the 1956-1957 winter season):
1957: This season had near normal snowfall, slightly less than or
greater than normal, depending on precisely what region one examines.
Temperatures, meanwhile, ran slightly above normal for that season.
1960: This season, though also warmer than normal, was much more
snowy than normal, with an average of about 10" more snow than
normal.
1961: This was an extreme season. Snowfall for many locations ran
25" higher than normal with temperatures averaging fairly
significantly below normal.
1979: This was an odd season with snowfall well below normal in
northern regions and well above in southern regions making for an
average of near normal snowfall. Temperatures in this season ran
slightly below normal.
1982: This season was somewhat the reverse of 1979 with northern
regions seeing rather high snowfall totals. The south, however, was
not generally below normal... just closer to normal. Seasonal
temperatures this year ran a little below normal.
1990: This is one of few neutral seasons with below normal snowfall
throughout the Northeast U.S. It was not extremely below normal,
but it was fairly significant... about 5-10" on average. Meanwhile,
temperatures were above normal.
1994: Most folks remember this winter for its bitter cold. The
snowfall totals in southern regions were below normal. However,
this was not for lack of wintry weather. Major ice events hit this
area. North of about the Mason-Dixon snowfall was well above
normal. Temperatures ran well below normal this season.
Well, these analog seasons yield a fairly clear-cut scenario for
this winter. Only one of the seasons saw below normal snowfall,
while the remainder all had above normal snowfall (though two of
the seasons varied with some locales above and some locales seeing
below normal snowfall). The temperature forecast is less
conclusive, though, as various seasons fell on either side of
climatology. The tendency, however, is for colder than normal
temperatures. In some cases, temperatures were extremely cold.
Looking at more specifics...
In terms of snowfall northern regions of the Northeast averaged
about 20-25% above the normal seasonal snowfall in these analog
seasons. Southern regions averaged 30-40% above the long-term
mean snowfall. Finally, west of the Appalachians the snowfall
from these seasons ran about 15-25% above normal. Temperatures,
meanwhile, averaged about 1.0 to 1.5 degrees Fahrenheit below
normal. This is not a major cold deviation, but it is significant.
Quite frankly, I have little reason to deviate from these averages.
The ENSO phase should hold very nearly exactly zero. Few seasons
have held so precisely close. As such, I see this season falling
very well into line with the averages given above.
Therefore, I am expecting snowfall across the Northeast to run
above normal. The percentage deviations given above yield
deviations inversely proportional to climatological snowfall
amounts. In other words, the actual number of inches more snow
than usual is rather uniform across the Northeast. Throughout
these analog years the average above normal snowfall is roughly
10 inches across the entire Northeast. As such, this is about
what I'd expect. Obviously, in the southeasternmost regions this
may be more like an 80% deviation; as such, this region may see
more like 6-8 inches more than normal. Likewise, the furthest
north and northwest regions may see more like 12-15 inches more
snow than normal. On average, though, we're looking at 10" above
normal across the board.
As for temperatures, I expect these to be rather close to normal
throughout the winter. They may run slightly below normal, but
this is a tough call. Of the analog seasons three were above
normal and four were below. The problem with this forecast is
that none were right around climatology. As such, forecasting
"slightly below normal" temperatures is a nice way to hedge my
bets, but, given the past record, is unlikely. More than likely,
if it's actually colder than normal, it will be much colder than
normal. Likewise, if it's warmer than normal, it will be somewhat
(not slight nor much) warmer than normal. Nonetheless, I'm
sticking to that, calling for a slightly colder than normal winter.
Incidentally, after the past few winters, that may feel much colder
than normal.
The last two paragraphs about say it all for the expected winter
conditions in the Northeast this season... roughly 10" above normal
snowfall across the board (with some exception for the extreme
regions) and temperatures expected to hover near or slightly below
normal. The snowfall forecast is of higher confidence than the
temperature forecast. Nonetheless, at least compared to the past
two seasons, the temperatures this winter should seem quite cold.
So, cold and snowy seems to be the order of the winter. One final
important note, though, most major blizzards of the past have
occurred in El Nino winters, believe it or not. Neutral ENSO
winters have their fair share as well. So, I'm not saying that such
a storm or storms is/are not possible this winter. However, this
type of storm is not a foregone conclusion simply due to the high
snowfall expectations. Such snowfall amounts can be achieved with
frequent lesser snowfall events. As stated, a major storm or storms
is/are certainly possible. I am just mentioning this point because
some may here "snowy and cold" and automatically think, "blizzard,
blizzard, blizzard". This is not necessarily the case. It is an
event-by-event scenario that we can only wait and see on. In the
end, though, the higher than normal snowfall totals are expected.
-Gary