Have any plans for Halloween? Yes? Well, I have your hourly forecast for your spooky Halloween night!
Highs will be slightly below the average. It will remain cloudy throughout the day. Cold air will stay in place, which could bring a few scattered showers in the evening. The sky will become overcast starting after 8pm, with our best chance of a scattered shower after 11pm. Winds are calm from the Northwest. Unfortunately, October 31st won't have a full moon, but it will be a first quarter moon. Hourly Forecast:
Note: FORECASTGMU's own Winter Forecast is included at the bottom of this article!
So I have received these
questions immensely in the past couple of weeks. And rather me just answer them
individually giving the same lengthy explanation that which I will attempt to
give here. I just said, “Wait until I put up my explanation on the ‘Winter
Forecast 2014-2015’ and your questions will probably be answered.” So without
further ado, I want to apologize for the delay for this article. I was debating
on whether I should just do the article right when networks, experts and the
almanac decided to give their full winter synopsis, or wait and see if the
recent fall weather would further influence their overriding opinion. Their
overriding opinion was that this winter was going to be one of the worst within
recent history. Temperatures several degrees below average on a consistent
basis and more of the heavy snowfall. For winter and snow lovers, this is
paradise and music to many meteorologists’ ears (hey we love to track these
storms too!) Where are they getting this information from though? How can they
just say that?
To
be honest there has been many times that I have thought a long range forecast
involves a lot of hope and not a lot of visual and quantitative analysis using
longer range climatological models. I cannot even count on my hand the amount
of times that the line “This winter is going to be one of the snowiest ever.”
And there be no snow or a lame excuse for a snowstorm once in mid to late
February where the snow melts before midday. Though the opposite of that has
been the case as well, mostly due to the fact a 2-3 foot blizzard had occurred
that year.
Back to the original
question: where do they get the information to produce their season long
climatological forecast?
We will start with the most
obscure…Farmer’s Almanac (pictured below): This North American periodical has been a mainstay
for people’s perception on how the year is going to be seasonally. Though it
contains many different other elements to it, such as topics on conservation,
gardening and even a bit of humor and trivia, people’s real lull to it is the
weather prediction section. They claim that their system of prediction produces
80-90 percent accuracy, though independent samples do not have them to be that
accurate. How they actually go about this prediction is mostly a secret sadly.
They are actually kept in a secret box in New Hampshire. The main founder of
the almanac though, Robert B. Thomas, claims that it is solar activity and
sunspots that has the largest influence on our weather.Over the years though, this theory has been
since refined to fit the meteorological discoveries of the day, along with
historical weather data. They maintain though that their main source of
information is solar observations.
The Old Farmer's Almanac
Other winter forecasts from
weather networks and websites, both on a regional and national level use a
completely different method. Starting months in advance, upper air motions and
atmospheric levels can be analyzed, quantified and therefore ran in complex
computer models. These predictions also take into account things like the
area’s climatology, meaning the typical weather expected for that area on a
yearly basis based off of observed results from years before. These ‘analog
forecasts’ as they are called lines up patterns dating back more than 100 years
back. This might seem like it works really well…but weather is so chaotic and
unpredictable statistically that this would definitely not suffice.
Want to know more about analog forecasting? Click here!!
A great visual example of an analog forecast for temperature anomalies
What also needs to be taken into account is
the sea surface temperature. This of course varies along the cycle of warmth
and cooling in the Southern Pacific called ENSO. The water temperature distribution
is a key look into how we will predict the forecast values such as temperature
anomaly and snowfall amount compared to the average. In an El Nino winter,
which this winter is starting to look more and more like according to the
readings, there has been higher level snowfall amounts in the Midwest, Northeast
and Mid-Atlantic respectively. Also El Nino winters are not warm as people
might expect, they are much colder on average (see last winter) and produce
wetter conditions in the East, and drier conditions in the West. So far the
models are in agreement that the El Nino is supposed to strengthen in the next
couple of months to produce said conditions, though this could be subject to
change.
What this winter could look like with weather patterns
Though ENSO seems like the
only way that long term forecasts can be evaluated, this is surely not the
case. Other oceanic oscillations play in important role in climatic
predictions. There is also the Pacific Decadal Oscillation (PDO) and the
Atlantic Multidecadal Oscillation (AMO) that play major roles in how the winter
forecast is formed. Currently the PDO is in a highly positive phase. This
warming of the waters has produced above average temperatures for western
Canada along with Alaska. This accompanied by a stronger El Nino event could
act as a booster to create even warmer and more above average conditions in the
North and West and more below average conditions in the Midwest and East. To
fully observe this, we can take a look at statistics from last winter.
A look at last winter's temperature pattern
The Atlantic Multidecadal Oscillation
is a long term variation of changes in the sea surface temperature in the North
Atlantic Ocean. This pattern has been a huge indicator in global air
temperature anomalies, or deviation from the average temperature. Positive
AMO’s are a sign of high overall temperatures. For example in 1998 the highest
AMO of 0.402 was recorded. This coincided with the warmest year ever recorded
globally. Within the years 1995-2008, this value remained fairly positive. This
has not been the case though within the last 5 years. The values have declined
and gone almost negative, which has historically been a sign of cooler winters
for the Northern Hemisphere. The problem is, is that the climatological models
are very inaccurate in predicting the patterns within the AMO, so a correlation
could be proven null.
Other oscillations that play a major role in winter forecasting are the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). The Arctic Oscillation is pattern of pressure shifting in the higher latitudes. The higher the pressure in the Arctic, or when the oscillation is in a negative phase. This also means that the mid-latitudes have lower overall pressure and they receive more cold, stormy weather than normal. In a positive phase this is reversed. Storms move into higher altitudes while warmer drier weather stays to the south. The record low or negative phase was observed in 2009, which coincided with heavy blizzards and snowfall. We are looking at another year with a negative phase Arctic Oscillation this winter. The NAO is also a shift in pressure. It is the going back and forth between the subtropical high and the polar low. Phases for the NAO tend to last several years. A positive phase means a stronger subtropical high and warmer, wetter winters for the Eastern US. A negative phase means a weak subtropical high and Icelandic low. This means there is a weaker pressure gradient and results in colder temperatures to settle into the Eastern US, making them more susceptible to snowstorms.
The NAO's positive and negative modes
There are also upper level
wave patterns that have great influence over long-term weather forecasts for
the Northern Hemisphere. These polar waves as they are called can be easily
detected as they circumvent the upper latitudes. Rossby waves as they are known in the field
help move cold air equator-ward and warm air pole-ward in large wave-like
patterns. What has been detected within these long waves that is noteworthy is
the large meandering and looping patterns that they seem to be producing along
with the slowing velocity which has caused droughts in the west, floods in
Europe, and cold winters here in the Eastern US. They are said to have less
zonal flow (west to east) and more meridonal (north to south) flow, which means
more energy is being transferred and higher west to east temperature variations.
What are Rossby waves and how do they influence weather? Click here
Sea Ice loss is a strong
influence of upper level waves. During the summer with well above average
temperatures globally warming Arctic Ocean waters disproportionally, there are increased
amounts of sea ice melt. Now along with the positive feedback of the sea ice
melt, with the now more exposed ocean waters, more and more solar energy is
absorbed by the ocean. In a study done in 2012 by the American Meteorological
Society, they studied whether or not a warming Arctic really meant harsher
winters for the Eastern US. There may be more than just a subtle connection
between higher energy storms in the mid-latitudes, which in the case for winter
is regarding heavier snowfall events such as blizzards, and the increase of sea
ice melt. This also means that there will be an increase in something known as
Arctic Amplification, which can be best explained as the increase in amplitude
of upper level atmospheric waves. This will cause larger troughs and ridges to propagate
and sustain for large periods of times over one area as the air moves slower
with higher amplitude. As we saw with last winter, extreme cold temperatures
can be ‘blocked’ in for weeks at a time in a process known as Arctic Amplification.
This winter could prove to be no different.
There are many other factors that could be game-changers this winter. The one's that I have listed above are just the main few that can be attributed to within a longer seasonal forecast.
FORECAST GMU's Forecast
Here is our forecast for the winter for the DC region specifically:
Overall temperatures: slightly below the climatological average, but warmer than last year. With a stretch, most likely in the timeframe of middle of January-early
February, there could produce some extremely cold temperatures.
Snowstorms: 3-5 with no large one truly taking hold of the region, though an ice
storm could prove just as dangerous.
Total snowfall predictions: 18-24 inches regionally with variations higher to our west and lower to our
east.
How long will this winter be: This winter will also be much shorter than last winter with an
early start to Spring beginning in March, there may be some cold spells after,
but not consistent enough to cause any concern.
On a larger scale, I think this winter will be a bit different than last winter. To start I think that the Western US (especially California) will receive more rain this last year with a revitalized Pineapple Express pumping in warm moist air from the South and West due to an active El Nino. The jet stream dip and patterns could play a large role in how and when storms form and what path they will take. Many have compared this winter to the winter of 2009-2010 and 1977/78 due to the presence of a weak El-Nino system. These years were highlighted by heavy snowstorms/blizzards and slightly below average temperatures.
Of course, I have a firm
belief that the climate system on the whole is merely impossible to accurately
fit into a model and the models that we currently have running are just a best
guess given the information that we have. Not to say that they are complete
rubbish, but the amount of variables that go into one forecast is one thing.
This does not account to all the variables that now being added to the equation
due to human interaction with the atmosphere and ocean.
Also this article has a bunch
of things I can imagine are unfamiliar with all of you. If you have a question
about what things are or how they work on a simpler scale, please let me know.
I have provided links after paragraphs to help explain topics that I covered within this article. Also I attached videos below attached which I have found to be great source points
even for my own education within forecasting.
How climate change and humans interact
A look inside a forecast (if you are interested, watch more of his videos)
