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Winter Storms: The Deceptive Killers
Matt Baraby
Dr. Scott
09/23/03
Environmental Hazards
Winter in North America brings dropping temperatures and the
chance of several different types of winter storms. Winter storms create
environmental hazards that are often overlooked due to the beauty of the
winter landscape until we find ourselves caught in a very dangerous
situation. Winter storms of varying magnitude and severity affect most
regions of the United States on a seasonal basis bringing frigid temperatures,
winds, snow, and ice that create situations hazardous to life and property.
The key to preparedness for any environmental hazard is knowledge,
forethought, and decisive action can be the difference between survival and
demise. To build a knowledge base this paper will focus on the types of
winter storm how they form, there magnitude, duration, spatial extent, some
impressive historical and recent storms, and how mitigation may reduce the
impact of winter storms.
Winter Storms in North America form in a variety of ways. All
winter storms derive there energy from the collision of warm and cold air
masses of differing moisture levels. In order to form and gain power a
winter storm needs three main components cold air, moisture, and lift
created in several ways as moisture rises to the upper atmosphere forming
clouds and precipitation. The normal formation of storms that affect the east
coast of the United States form as cold dry air from Canada moving south
and east on the jet stream collides with warm moist air moving north and
slightly east out of the Gulf of Mexico. The position of the jetstream over
The United States which usually is elevated from between the south/MidAtlantic during the spring and summer months to from the Midwest across
the northeast during the winter months. This positioning of the jetstream
which forces the cold dry Canadian air across the northeast is the reason why
precipitation in this area is most often snow, while the farther south you
move the precipitation is more likely to be sleet, freezing rain, or just a cold
rain. The area where an air mass collides is called a front of which there are
three types. A cold front is one in which a large strong advancing cold air
pushes warm air along in front of it. A warm front is one in which a strong
warm air mass pushes against and over the top of a cold air mass due to the
fact warm air is less dense than cold air. A stationary front occurs as a
stalemate between the colliding warm and cold front and neither air mass is
advancing. We often here about a type of winter storm called lake effect
that most often occurs around the great lakes. This type of storm forms as a
front moves over a body of water picking up large amounts of warm moist
air to the front creating massive snowfall and other precipitation around the
lakes shore areas. If you have ever seen snow capped peaks you have seen
another type of winter storm phenomenon that occurs in mountainous
regions called mountain effect snow. This type of snowfall occurs as winds
push warm moist ground level moisture up mountain slopes to the upper
atmosphere where the moisture is cooled and condensed and then falls back
to earth settling on the mountains peak and surrounding areas. Now that it is
understood how winter storms form we can discuss some other parameters
of these storms.
There are five types of precipitation associated with winter storms.
Rain occurs in a winter storm as precipitation frozen in the upper
atmosphere falls through a large band of above freezing temperatures and
melts before reaching the warm earth and does not re freeze. Freezing rain
occurs as precipitation frozen in the upper atmosphere falls through a
smaller warm band of air in the mid level of atmosphere then enters a cold
band along ground level and upon contact with cold surfaces refreezes and
creates a sheet of ice. Sleet occurs as frozen precipitation in the upper
atmosphere falls through a short warm band of air and then a large cold band
of air refreezing into ice pellets before reaching earth. Hail is sleet of larger
diameter that due to up drafting wind currents is circulated through the upper
atmosphere several times combining with other freezing and thawing
precipitation and increasing in size, hail stones are capable of reaching
several inches in size. The final type of precipitation is snow which is
frozen in the upper atmosphere and falls though cold air to earth and does
not melt. Snow storms are a specific type of winter precipitation that are
separated into there own categories
Winter snow storms are categorized based on several factors the
amount of precipitation (accumulation), rate of precipitation, wind speed,
and duration. There is no real system of separation only five general
categories that snow storms are put into. Snow flurries are light snow falling
for short durations with little or no accumulation or a light dusting expected.
Snow Showers is snow falling at varying intensities for brief periods of time
with some accumulation expected. Snow Squalls are brief intense snow
showers accompanied by strong gusty winds, usually significant
accumulation is expected, and squalls are often associated with lake effect
snows seen in the great lakes region. Blowing Snow is wind driven snow
that reduces visibility and causes significant drifting, this may also include
loose snow that is already on the ground but is picked up and carried by the
wind. Blowing snow is a significant problem across the flat virtually
featureless landscapes of the Midwest where cars are often stranded in drifts
along the highway. The final category of winter snow storm is the blizzard
which is characterized by winds over 35 miles per hour and very heavy
snowfall that reduces visibility to less than a quarter of a mile for a period of
at least three hours. These high winds and extreme cold temperatures are
another interesting feature of winter storms.
Winds are a factor in almost all winter storms and create some of the
most dangerous conditions during the winter months. Winds combined with
cold temperatures create a logarithmic condition called the wind chill in
which the perceived temperature to humans is much colder than the actual
ambient temperature. Exposure to cold and windy conditions can cause the
onset of frostbite and hypothermia in minutes and also have severe effects
on livestock and crops.
Winter storms for and effect different regions of the country in
different ways. There are five general regions that winter storms affect. The
first region is from the Mid-Atlantic to New England Coastal region which
are impacted by a specific type of winter storm called a Nor’easter. This
type of storm occurs as a low pressure system forms off of the Carolina
coast and gains strength as it moves north. Strong wave action batters
coastal areas and large amounts of moisture can combine with strong winds
to create blizzard conditions and dump large amounts of snow throughout
the northeast. The next region is compromised of the Gulf Coast and
Southeast this region is especially sensitive to winter storms because of a
low awareness and preparedness level. Occasionally cold air sweeps this
region and if precipitation occurs it tends to be wet snow or a freezing rain
that ices this unprepared area of the U.S. The next region of interest is the
Midwest and plains states. Winter storms that affect this area develop on the
leeward side of the U.S. and Canadian Rockies, fueled by intense cold air
from Canada these storms create blowing and drifting conditions along with
extreme wind chill temperatures reaching seventy degrees below zero! The
next region of concern compromises the area from the Rockies to the
western coast of the U.S. In this area storms over the Pacific slam into the
coast of Northern California Oregon and Washington with unlimited
available moisture drawn from the Pacific pushing through the mountains
and valleys with high winds and deep drifting snows. This region is also
prone to avalanches due to steep mountain slopes and narrow passes that
funnel winds creating damage to structures and closing roads. The Final
Region Alaska is an entity in and of itself. This area of the U.S. is affected
by storms that move across the bearing straight and intensify slamming the
coast with intense wave action, ice flows and coastal flooding. The
combination of heavy snows, very little sun light and extreme cold
temperatures as low as ninety degrees below zero create massive
accumulation and treacherous conditions for most of the winter months. As
you can see the vast majority of the United States is affected by winter
storms but advance warning for many of these storms saves thousands of
lives every year.
There are several types of advance warnings that prepare citizens of
the United States for forthcoming and potential hazardous winter storms. By
listening for and understanding the different types of winter storm warnings
available from radio and television news sources citizens can become better
prepared and informed about winter’s wrath. There are four basic
preparedness warnings issued by the national weather service; these are
outlooks, watches, warnings and advisories. An outlook is intended to
inform people about possible winter storm conditions impending in the next
2-5 days. A winter storm watch tells the public that possible winter storm
conditions are in the outlook for the next 36-48 hours and now is the time to
prepare. A winter storm advisory warns of winter weather conditions that
are expected to cause significant inconveniences and may be hazardous, but
using caution these storms should not be life threatening. A winter storm
warning warns of life-threatening severe weather conditions that have begun
or will begin within twenty four hours and demand action now. By listening
to these warning and take some simple steps of precaution all but the most
severe winter storms should not be life threatening to the average person.
There are several steps that the average person can take to prepare for
the primary concerns during winter weather events. Being prepared for loss
of a heating source, loss of power, loss of telephone service, and a shortage
of food, water, medicine, and general supplies is the main concern during a
winter storm. There are several websites (www.NOAA.gov,
www.FEMA.gov) that list items that should be kept on hand to prepare for
winter weather as well as detailed emergency plans. The young and the old
as well as pets and livestock are especially vulnerable to winter weather
events and these websites also list detailed plans of action to deal with
specific crisis and problems. The best plan to survive a winter storm or any
similar environmental hazard is to stay alert informed and prepared prior to
the weather event, by doing this most will survive this environmental hazard
unscathed.