Over the course of several days during the last week of February, homes located along the eastern edge of Lake Erie in Hamburg, New York, were quickly transformed into ice-covered igloos. While mesmerizing images like the one above depict the dramatic scene that unfolded along the shore, the situation was nearly disastrous for residents of the area, darkening their homes and forcing them to navigate ice nearly everywhere they went. But, how did these ice structures form and why don’t we see this type of phenomenon happen every winter? Let’s investigate this particular event.
First, let's consider the geographic location of Hamburg. It is a small town that sits approximately 20 minutes south of Buffalo and borders the eastern edge of Lake Erie, a 255-mile long lake that stretches between Michigan and New York. Most winters, a large portion of the lake freezes over by the end of February. In fact, the Great Lakes Environmental Research Laboratory (GLERL) reports that over the last 40 years, ice-coverage during the last week of February has averaged 60%, with 92% coverage just last year in 2019. On February 29th, 2020, Lake Erie was merely 10% covered with ice. It is important to note that water changes temperature more gradually than air, this is why lakes do not instantly ice-over as soon as air temperatures drop below freezing, but instead slowly freeze as the air temperature remains below freezing for an extended period of time. Therefore when combined with strong winds directed over the lake and out of the west, a lack of significant ice-coverage can allow for the formation of very large waves along the shoreline. When these waves crash onto land and into surfaces such as houses and walkways with temperatures well below the freezing mark, the liquid molecules instantly freeze and, over time, can create the captivating yet dangerous scenic picture above.
These ice structures occur so rarely because they require this perfect combination of weather conditions. A majority of Lake Erie must remain liquid water well into the winter months and requires a storm that contributes high winds from just the right direction to cause high waves that crash into surfaces cold enough for instantaneous freezing to occur. While coinciding only rarely, this particular meteorological setup helped create some of the most fascinating and unique homes in America for a few days at the end of February along the eastern shoreline of Lake Erie.
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©2020 Weather Forecaster Dennis Weaver
Winter of 2019-2020 was a very mild winter when compared to the blasts of Arctic air we saw in January 2014. The reason for this mild winter can be attributed to the polar vortex. One question you may be asking yourself is what exactly is the polar vortex and how does it affect whether we have a mild winter or not? The term polar vortex refers to a cone of low pressure that sits directly over the poles. The polar vortex is made up of a fast-flowing stream of air that envelops the North Pole.
The polar vortex is strongest in the winter due to the increased temperature gradient between the mid-latitudes and the poles that, in turn, strengthens the jet stream. This takes place in the stratospheric layer which is typically around 6 to 30 miles above ground. When the polar vortex is the strongest, all the cold Arctic air is trapped at the poles, but when it starts to weaken, Arctic air will plunge into North America or Europe. For much of the winter of 2019-2020, the polar vortex has remained strong which has kept the CONUS warmer than average.
(Image Credit: NOAA)
The image above shows that during a stable polar vortex like this current Winter all the cold air is contained to the north; however, when the polar vortex starts to collapse cold air will move south while warm air moves to the north causing a wavy polar vortex to sweep across North America or Europe. The wavy polar vortex will produce blasts of cold air as the pattern progresses across the Northern Hemisphere. This trapping of Arctic air in the polar latitudes has allowed record heat to dominate over colder temperatures for the last part of 2019 and first part of 2020.
According to the Weather Channel, the polar vortex should remain strong at least through March. This means the CONUS can expect above average temperatures this spring.
Sources and more information:
©2020 Weather Forecaster Hannah Peters
DISCUSSION: When it comes to looking at snowfall forecasts and snowstorms themselves, there are always many questions about why different snowflakes form and even when the same types of snowflakes are falling, why they may take on slightly different shapes. One classic example of this type of occurrence is when the most famous type of snowflake (i.e., dendrites) are fully part of a major winter storm. As shown in the picture above, which is one classic example of a stellar dendrite, they can be quite complex and stunning at the same time. However, there is much more that goes into how a snowflake forms the way it does and how complex the various outgrowth of the snowflake becomes as if all stored the surface of the Earth.
One such factor which has a major influence on the way in which a given snowflake such as the one shown above (courtesy of www.snowcrystals.com) will form is the variable moisture profile which is present through the depth of the middle to lower portions of the atmosphere. The reason for this is because whenever you have increased moisture in the presence of developing snowflake crystals, there is an increased potential for more accumulation of supercooled water and/or other nearby ice crystals onto the developing snowflake which can make them much larger or smaller depending upon the amount of water vapor available. In addition, whenever there is a lot more water vapor available within the depth of the atmosphere were the most snowflakes are forming (which is often referred to as the dendritic snow growth zone in atmospheric science terms), this can also allow snowflake generation processes to be much more effective and much more robust. Thus, when there is a greater presence of deeper lower to mid-level moisture content in the presence of a developing or mature snowstorm, there will often be much more efficient snowflake development as a storm wraps up and/or matures.
A second major factor which has a substantial influence on how and to what extent a given snowflake will form is the variable temperature profile through the depth of the middle to lower portions of the atmosphere. The reason for this is a result of the fact that when there is either a warmer or colder net temperature trend as this snowflake is going from its height of formation for the surface of the Earth, a snowflake can take on many different shapes depending upon the variable temperatures the ice crystal is exposed to as it is growing and developing during its path towards surface of the Earth. This reality is also reflected by the context of the second graphic shown above in an approximate sense since this is a rough approximation of the realistic temperature ranges for various case crystal types.
It is for these reasons that when people use the metaphor no two snowflakes are ever quite the same at any point in the world, this statement is completely true in every sense of the word. The reason is simply because as an ice crystal is following towards the Earth, the precise environmental conditions the ice crystal is encountering during its path downward will always be at least slightly different than the snowflake right next to it even at a very minor level. So, the next time someone uses the metaphor when there is a snowstorm or a threat of an upcoming snowstorm, you now have some real context behind that age-old phrase.
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©2020 Meteorologist Jordan Rabinowitz
If you’re living in the midwestern United States, you were probably confused and possibly unmotivated because in this area there was a lack of sunlight for the entire week of January 27. There are multiple factors that can contribute to the consistent cloudiness that persists for multiple days, and weather patterns that have brought on coincidental cloudiness. The dreary days that have been in effect for that week may seem like the usual wave of January weather — but fear not, winter is no stranger to seeing the sun.
Projecting our weather analysis to the 300 mb level, which is where the jet stream lies, we can see patterns of where warm or cold air patterns are to be directed. At this level, we can see a closed low that is often very slow moving since it sits out of the general stream of westerly air that is seen. Consequently, the closed low has little to move it along and can persist over the course of multiple days. This can also be called a cut-off low because it is removed from the general flow pattern and moves slower than typical weather patterns. Since low pressure systems are associated with cloudiness, rain and snow — this is a cause of persistent cloudiness.
Image: Gathered from the 12z GFS on 2/28, this depicts a closed low that is separated from the general flow of the upper atmosphere at 300mb. (Photo courtesy of Pivotal Weather)
Of course, weather patterns work together throughout the atmosphere and pure coincidence could lead to extended periods of cloudiness. Coincidental passings of multiple low pressure systems to a certain area can occur, along with multiple cold frontal passages can lead to extended periods of cloudiness.
Warmth can even lead to persistent cloudiness with the formation of fog when warm air moves over a cold surface. Since the atmosphere is built of many different levels that are working at different rates, we can experience different weather systems closest to the surface, instead of deep through the atmosphere. For example, a small area could experience low clouds and fog which can exist in the depth of the boundary layer. This layer extends about one kilometer above the surface, most commonly where lake effect convection occurs and can be specific to a small area.
While these are all possibilities for cloudiness to occur in a given region, it’s not particularly common to see this happen for such a long period, but it certainly can. For the specific case of the week of January 27th in the midwestern United States — almost all of these factors made an appearance. From passing snow showers and a wintery mix, to slight warmth leading to fog, a strong enough front with a proceeding high pressure system is necessary to conclude a period of cloud coverage.
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© 2020 Meteorologist Jason Maska
Unfavorable Teleconnections for US Winter Weather in 2020? (Credit: Eric Fisher and NOAA Climate Prediction Center)
DISCUSSION: For much of the US east of the Rocky Mountain Front Range, the winter of 2019-2020 has not shown much in the way of persistent chilly Arctic air infiltration. Instead, many areas east of the Rockies have witnessed weather patterns found with large-scale ridging (general poleward motion of air associated with high-pressure systems) while the Intermountain West and Pacific coast have remained fairly cool under the influence of large-scale troughing. So what is a potential cause for the unusually warm winter season? One hypothesized answer lies in the unfavorable combination of teleconnections that are currently being observed. An article previously published here goes into more detail on how these teleconnections work so for brevity, the teleconnection patterns responsible will be mentioned in the light of influencing multi-day/multi-week weather patterns as of late.
Now, all teleconnections are important in some degree since they help modulate, or control, the flow patterns across the world. In other words, a certain pattern that favors milder, more stable weather patterns over one part of the world may be countered by cooler, more progressive (stormier) weather patterns downstream, and several of these large-scale patterns are observed at the same time at different parts of the world. But, these teleconnections can undergo changes throughout the course of a year, more so on an inter-monthly time frame. Therefore, the essence of understanding large-scale patterns is to chain information from multiple teleconnections in order to gain a clearer depiction of what is occurring.
The Arctic Oscillation, or AO for short (pictured above), has remained predominantly positive. Recall that a +AO pattern yields a tendency to retain colder Arctic air north of the midlatitudes while keeping a zonal flow pattern. In essence, there is limited to no buckling in the mean flow that will help displace cold Arctic air equatorward. The North Atlantic Oscillation (NAO), which corresponds to the phenomena located between Icelandic Low and Azores High, shows as being predominantly positive as well. The East Pacific Oscillation (EPO), after being mostly positive through much of winter, is trending towards neutral and negative values. Normally, the EPO can play a key role in modulating the flow pattern across North America such that -EPO leads to large-scale ridging over Alaska and the Pacific Northwest with subsequent troughing over the northern half of the US. However, this is countered by a negative Pacific/North American (PNA), which encourages advection of polar air over the Pacific coast and intermountain west with subsequent large-scale ridging over the eastern two-thirds of the US. Storm tracks are also favored out west due to the strong grip of a typically dominant high-pressure system over the mid-latitude Pacific Ocean. When putting all of the pieces together, the result favors colder, more progressive patterns to the west and milder, subtler conditions over the east. To see all of the teleconnections described in the article, be sure to visit the Climate Prediction Center’s teleconnection page located here.
The science behind the teleconnections and is still a dominant topic in the world of climate science as researchers continue to investigate the impact that different teleconnections have as a unit. There is much to learn about these teleconnections and the interplay between them as certain patterns, such as that of recent, are not always an end-all for distinct weather patterns over the US and the rest of the world. So next time that a weather report indicates longer periods of mild and stable weather or colder and stormier weather patterns, teleconnections may provide clues into the true state of the atmosphere.
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© 2020 Meteorologist Brian Matilla
Flooding is the number one natural disaster in the United States (FEMA Mitigation Directorate), causing more property destruction and financial loss than any other extreme weather event. While these hazards are talked about heavily during the summer months, flooding can cause dangerous impacts throughout the year. This is especially true in areas already prone to flooding such as along rivers or lake shores, and those that routinely deal with significant winter weather. For example, substantial melting of snow and ice in early spring can cause devastating results. Similar outcomes occur when rivers and streams are obstructed by large chunks of melting ice, a phenomenon popularly known as an ice jam. Many meteorological and hydrological processes can result in winter time flooding and it is important to be both aware of and prepared for these circumstances.
One way winter weather can contribute to flooding conditions is simply through the rapid melting of heavy snowpacks. Despite melting on the surface, early spring ground temperatures are often still below freezing. In this instance, water is not actively absorbed by the ground beneath and instead flows along the surface toward nearby rivers and lakes, raising water levels and increasing the chance for significant flooding. Flooding is also common as ice from frozen waterways begins to melt, break apart and flow downstream. If these often large pieces of ice approach either a natural or man-made obstruction (such as a river dam), the rivers flow can be impeded. This ice jam essentially blocks the natural movement of a river or stream and causes significant flooding. When the ice jam finally releases, built up water that was blocked from its usual flow rushes downstream and consequently contributes to serious flooding impacts.
Currently, not much can be done to prevent ice jams from occurring. However, it is essential for anyone living in areas prone to winter flooding to be aware of the danger and what can be done to minimize potential damage. In addition to purchasing flood insurance, the Federal Emergency Management Agency (FEMA) suggests making a flood evacuation plan and keeping important papers in a safe, waterproof place. Taking these precautionary steps can help reduce loss and destruction even during the most obscure or improbable of flooding scenarios.
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©2019 Weather Forecaster Dennis Weaver
Like it or not, winter is officially here. For the next three months or so Midwesterners will endure cold temperatures and, of course, the dreaded “S” word—snow. But did you know that snow is favored in some areas more than others? These areas are called snow belts and lake-effect snow bands amplify these areas. Let’s dive in and take a look.
The official definition of a snow belt is rather simple; it is any area where heavy snowfall is particularly common with the help of lake-effect snow. Also, wind direction helps position these snow belts in the Great Lakes region. As you can see in the image above, most of the snow belts are on the leeward side of the Great Lakes. Cold winds in the winter usually prevail from the northwest. This wind direction produces substantial lake-effect snowfall across the Great Lakes region. The wind direction influences the amount of time cold air is over the lakes, which aids lake-effect snow. Lake-effect snow results from cold air passing over relatively warm waters of lakes. This causes lake water to be evaporated into the air, thus warming it. This warmer, wetter air rises and cools as it moves away from the lake. Once cooled, this causes the moisture to be released in the forms of snow. The greater the temperature difference between the air and water, the greater the potential of a more intense lake-effect snow event.
The Upper Peninsula Snow Belt experiences probably the vastest effect of lake-effect snow in terms of area, with the exception of the Lake Michigan snow belt. Stretching from the Porcupine Mountains (Western U.P.) to Canada, anywhere in this region can experience upwards of 250 inches (20.8 feet) of snowfall per year. For comparison, Duluth, Minnesota which is located on the southwestern tip of Lake Superior, only experiences 78 inches (6.5 feet) of snowfall per year.
Another snow belt in the Great Lakes region that experiences dramatic snow fall is the Lake Ontario and Lake Erie snow belts. These two belts can clearly be seen from the first image above. These two regions see daily snowfall totals that are higher than anywhere in the United States. This is due to intense lake-effect snow bands blasting the region with whiteout conditions. The average snowfall for these regions is roughly around 116 inches (9.6 feet) of snowfall. Due to Lake Erie’s relatively shallow depth, this lake is the only lake that is capable of completely freezing over. If this happens, the moisture source for lake-effect snow bands is cut-off, thus ceasing lake-effect snow events. This is why early in the season lake-effect snow is favored for snow accumulation.
The Lake Michigan and Lake Huron snow belts are similar in terms of intensity. The Lake Michigan side, however, can be rather unique. Under the right conditions, northerly winds can form a single band of lake-effect snow stretching along the Lake Michigan coast. This produces intense and localized snow fall. Lake Huron can experience this same intensity for the Bruce Peninsula and Georgian Bay regions. Lake-effect snow is almost a given during any winter precipitation event. It is only when small bays in this area freeze over that lake-effect snow is cut-off, other than that, localized, heavy snowfall blankets the region.
Are you in a Great Lakes region snow belt? If so, make sure proper plans are in place in case heavy snowfall impacts your area. Even if you are not in a snow belt, the winter months in any area in the Great Lakes region has their fair share of heavy snowfall.
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©2019 Weather Forecaster Alec Kownacki
Winter weather can have a major impact on all aspects of life. From school closings to travel delays and cancellations, snow and ice cause a wide range of difficulties during the winter months. Additionally, snowflakes are present in almost all clouds (as most clouds exist at altitudes that experience below freezing temperatures) and as such, it is important to learn about the processes by which they grow. Whether falling to the ground as a melted summer rain or a frozen mid-winter snowstorm, ice crystals play a major role in our weather and the hazards it can sometimes produce.
Once an initial snowflake has formed, there are three primary mechanisms by which it may grow: deposition, accretion and aggregation. In the deposition process, ice crystals grow as a result of the difference in saturation vapor pressure between liquid water and ice at a given temperature. Saturation vapor pressure is the pressure exerted outward by a vapor (in this case water vapor) when the surrounding air is saturated. Since liquid water has a much higher saturation vapor pressure than ice, and molecules in the atmosphere move from high pressure toward low pressure, water vapor travels from liquid droplets toward the lower-pressure crystals. This flow of water vapor aids the growth of ice crystals and development of snowflakes. It is important to note that deposition relies heavily on the presence of both ice and liquid water and is thus temperature dependent. Maximum rates of growth by deposition occur around -15℃.
When ice crystals collide with supercooled water droplets, the crystals grow by a process known as accretion. Supercooled water simply refers to liquid water molecules that exist in liquid form at a temperature below freezing (0℃). As an ice crystal falls through a cloud, any supercooled water it comes in contact with will freeze to the crystal surface, quickly increasing the crystals size. This mechanism is most efficient between 0℃ and -10℃, where supercooled water droplets are commonly present.
Lastly, snowflakes can grow in size by aggregation, a process by which ice crystals collide with one another to form larger ice crystals. The probability that two random snowflakes collide and combine depends strongly on the shape of each crystal and the presence of liquid water on each molecule. This liquid water helps ice crystals bond together molecularly, creating larger and larger ice crystals over time. In fact, snowflakes formed by aggregation can reach 3 to 4 inches in diameter. It is important to keep in mind that all of these mechanisms for snowflake growth refer to the ice crystals within a cloud, not near the surface. However, if the temperature is consistently below freezing between the cloud and surface, these crystals can fall toward the ground and create dangerous winter weather conditions!
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©2019 Weather Forecaster Dennis Weaver
FORECAST DISCUSSION: The start of winter for the United States has already proved to be an impressive one, and despite Hawai’i’s mild weather year-round, it does not disappoint to bring an intriguing forecast to the island chain. The islands have seen unsettled weather patterns in recent days, and it isn’t expected to improve within the immediate forecast period.
Winter often brings slightly cooler temperatures, with a wet pattern, and it has not failed to show itself. West of the island chain an area of low pressure, which is expected to propagate northeastward, will pump in winds from the south. In recent days, high wind advisories have been issued and this forecast period proves no different. Beginning Tuesday afternoon through Wednesday a High Wind Watch is in effect for Kauai Windward-Kauai Mountains-Oahu North Shore-Oahu Koolau-Olomana-Central Oahu-Waianae Mountains. In fact, there is a High Surf Advisory until 6 AM HST Tuesday for Kauai Windward-Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-Windward Haleakala-South Big Island-Big Island North and East. These winds have the potential to cause damage and power outages of note in downslope mountainous areas of Oahu and Kauai. As the front moves eastward, its strength will decrease significantly towards the Big Island and will generate a more typical trade wind pattern as high pressure moves in behind the front.
In addition to concerns with the immediate weather pattern the National Weather Service (NWS) has issued a special weather statement regarding coastal flooding coupled with strong southerly winds. With high water levels being apparent around the Hawaiian Islands, coastal flooding is possible over the next few days, but chances for coastal flooding reduce in the latter part of the week when the high-pressure system with trade wind pattern are expected to return.
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© 2019 Meteorologist Jessica Olsen
DISCUSSION: Areas farther north generally see their first measureable snowfall earlier than other places. For example, Montana typically sees it first snowfall in October to November. However, this year parts of Montana received their first snowfall earlier than normal this past weekend in late September. In addition, given Montana’s distance from water and its generally colder temperatures (colder air has a lower capacity to “hold” moisture), individual storms usually don’t produce that much snow in comparison to places near the Great Lakes, for example. However, from 27-29 September, Browning, MT received 48 inches of snow. The 19.3 inches that fell in Great Falls, MT is the second highest 2-day snow total there at any time of year, not just in September, further indicating that large amounts of snow over short periods usually don’t occur in Montana. The picture above is from a webcam in Glacier National Park after the recent snowstorm. Given the topography and latitude of Montana, they are familiar with dealing with snow and winter storms. However, the unusually large amount of snow and early timing of that snow could exasperate the impacts of this particular winter storm (e.g., road closures, power outages, etc.).
The storm was followed by unusually cold temperatures for late September/early October with lows dropping as low 7°F and 9°F on 1 and 2 October, respectively, at Browning, for example. It is important to keep in mind that transient (occurring over a short time period) regional cooling or warming is completely different than global cooling or warming. Global climate change is observed over large space and time scales. Superimposed on this global change are long-term trends in regional warming or cooling. On top of these regional longer-term trends are high-frequency variation. The recent cold spell in the northern U.S. is an example of such high-frequency, regional variation and cannot be used to explain anything related to global climate.
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© 2019 Meteorologist Dr. Ken Leppert II