“March comes in like a lion, and goes out like a lamb”. This old proverb refers to March’s famously changeable weather.
As a month where we transition from winter to spring, March can often start off cold and blustery, but end warm and calm. From the beginning to the end of the month, the average daily temperature increases by 10°F. Exact conditions, of course, vary from year to year.
Although the precise origins of this popular phrase are unknown, many believe it is based on the constellations. At the beginning of March, Leo (lion) is highest in the midnight sky, while Aries (ram) begins to rise toward the end of the month.
The “Dead of Winter” is an old saying that refers to the coldest part of the winter season. For most of the northern hemisphere, that usually means the month of January.
While actual daily weather varies, historical average temperatures typically reach their lowest point of the year between January 10 and February 10. In the US, the western half of the country, with the exception of high elevation areas, tends to see its coldest day before the eastern half. This is because the mountainous areas of the west and much of the eastern US tend to be snow covered in winter, reflecting much of the sun’s heat. Here in New York City, mid to late January is usually the coldest part of the winter season.
Air temperature depends on both the amount of energy received from the sun and the amount of heat lost or absorbed by the oceans and continents. From the start of winter through mid-February, both the oceans and land are losing more heat than they gain.
Autumn is a transitional season when the heat of summer fades away and the chill of winter gradually returns. But, sometimes winter can be aggressive and show up overnight.
When this type of rapid temperature change happens, it is often called a Blue Norther. This is a fast-moving cold front marked by a quick and dramatic drop in temperature. A fall of 20 to 30 degrees in just a few minutes is not uncommon. They also usher in a dark blue sky and strong northerly winds. Hence, the name.
Blue Northers are most common in the central US, where there are few natural barriers to slow or block arctic air masses from moving south. They can occur throughout the year, but are most common between November and March.
One of the most famous examples of this weather phenomenon was the “Great Blue Norther” of November 11, 1911. As the front passed through the southern plains, temperatures dropped from highs in the 70s and 80s to the teens in just ten hours. In Oklahoma City, for example, the temperature reached a record high of 83°F in the afternoon and then plummeted to a record low of 17°F by midnight. Both records, according to the NWS, are still in place.
Twenty-four temperature changes from The Great Blue Norther of 1911. Credit: FOX
During the summer months, a change in wind direction known as a monsoon brings a major shift in the weather for the southwestern US. The season is well known for producing intense dust storms known as haboobs.
Haboobs form when thunderstorms collapse and create a strong downward flow of wind. When this downdraft of air hits the ground ahead of the storm, it blows the loose sand and soil from the desert floor high up in the air, creating a giant wall of dust. Rising quickly, haboobs often reach heights between 5000 and 8000 feet and can span out nearly 100 miles in length. Traveling at speeds ranging from 30 to 60 mph, they can cover large distances rather quickly.
Often called “black blizzards”, these storms turn day into night. Engulfing entire communities in dust, they cause respiratory problems and create serious travel hazards both in the air and on the ground. Luckily, they usually only last a few hours.
Many dry regions of the world experience haboobs, but they were first described in Sudan, along the southern edge of the Sahara Desert. As such, the word comes from Arabic and means, “blowing or blasting furiously.”
A haboob moves across Phoenix, AZ in August 2018. Credit: ChopperGuy/Twitter
While these phrases can make it sound like the flooding is cyclical, only happening once every 100 or 500 years, it is not. Storms are not on a schedule. Rather, these terms refer to statistical probabilities. For example, the “100-year flood” means there is a 1% chance of a flood of that magnitude happening in any given year in a given location. For the 500-year flood, the probability is 0.2%.
Given the right conditions, it is possible to see multiple 100-year or 500-year flood events in a relatively short period of time.Ellicott City, MD, for example, recently saw two 1000-year flood events only two years apart. For more information, watch the video below from the NWS.
From a light breeze to a strong gale, wind speed can be described in numerous ways. All of which are categorized on the Beaufort Wind Force Scale.
Developed in 1805 by Sir Francis Beaufort, an officer in the UK’s Royal Navy, the scale is an empirical measure of wind speed. It relates wind speed to observed conditions at sea and over land instead of using precise measurements. Simply put, it allows a person to estimate wind speed with visual clues.
Initially, it was only used at sea and was based on the effect the wind had on the sails of a frigate – the most common type of ship in the British Navy at the time. By the mid-1800s, the scale was adapted to also reflect a certain number of anemometer rotations – a device that measures wind speed.
In the early 20thcentury, most ships transitioned to steam power and the scale descriptions were changed to reflect the state of the sea instead of the sails. Around the same time, the scale was extended to land observations. For example, the amount of leaf, branch, or whole tree movement is a visual indicator of the force of the wind.
Today, the scale has 13 categories (0 -12), with 0 representing calm winds and 12 being hurricane force. It is in use in several countries around the globe.
In the US, when winds reach force 6 or higher, the NWS begins issuing advisories and warnings for different environments. For marine areas, force 6-7 winds would prompt a small craft advisory, force 8-9 would warrant a gale wind warning, and a wind reaching force 10-11 would call for a storm warning. Force 12 would constitute a hurricane-force wind warning. On land, winds expected to reach force 6 or higher would cause a high wind warning to be issued.
If the winds are connected to a tropical cyclone, they would be measured on the Saffir-Simpson scale. The same type of special circumstances would also hold for a tornado, which would be measured on the Enhanced Fujita Scale.
The Beaufort Wind Force Scale. Credit: Isle of Wight Weather Ctr
Temperature is one of the basic elements of weather. Our perception of it, however, is often influenced by other environmental conditions. Wind, for example, can make a cold day feel even colder. This phenomenon is called the wind chill factor.
Wind chill is a measure of the apparent or “feels-like” temperature. It calculates the heat loss from exposed human skin through the combined effects of air temperature and wind speed.
Essentially, the wind is carrying heat away from the body and allowing the skin to be exposed to cold air. As the winds increase, heat is carried away at a faster rate and the colder the body feels. For example, a temperature of 20°F and a wind speed of 5mph will produce a wind chill index of 13°F. At that same temperature, but with a wind speed of 10mph, the wind chill index would be 9°F.
Today is the December solstice, the first day of winter in the northern hemisphere. The new season officially begins at 22:23 UTC, which is 5:23 PM EST.
The astronomical seasons, which are different than meteorological seasons, are produced by the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the winter months, the northern half of the Earth is tilted away from the sun. This position means the northern hemisphere receives the sun’s energy at a less direct angle and brings us our coolest temperatures of the year.
Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been dropping southward and daylight hours have been decreasing. Today, it will reach its southernmost position at the Tropic of Capricorn (23.5° south latitude), marking the shortest day of the year. This observable stop is where today’s event takes its name. Solstice is derived from the Latin words “sol” for sun and “sisto” for stop.
Soon, the sun will appear to move northward again and daylight hours will slowly start to increase. Marking this transition from darkness to light, the winter solstice has long been a cause for celebration across many cultures throughout human history.
Earth’s solstices and equinoxes. Image Credit: NASA
Winter snowstorms have a variety of names, such as Nor’easters and Alberta Clippers. It all depends on where and how they develop. In the Great Lakes region of the US, the vast bodies of fresh water influence the weather and create something known as lake effect snow.
Lake-effect snowstorms, according to NOAA, develop when cold air blows across the warmer waters of a large unfrozen lake. The bottom layer of the air mass is warmed by the water and allows it to evaporate moisture, which forms clouds. When the air mass reaches the leeward side of the lake its temperature drops again, because the land is cooler than the water. This releases the water vapor as precipitation and enormous amounts of snow can accumulate. The effect is enhanced if the air is lifted upward by local topography.
With the clouds typically forming in bands, the snowfall is highly localized. Some places can see the snow come down at a rate of more than 5 inches per hour, while nearby, others will only get a dusting. The shape of the lake and the prevailing wind direction help to determine the size and orientation of these bands.
Fetch, the distance wind travels over a body of water, also plays a key role. A fetch of more than 60 miles is needed to produce lake effect snow. In general, the larger the fetch, the greater the amount of precipitation, as more moisture can be picked up by the moving air.
The impressive depths of the Great Lakes allow them to remain unfrozen longer into the winter season than more shallow bodies of water. This combined with their massive surface area, make them excellent producers of lake effect snow. With northwesterly winds prevailing in the region, communities along the southeastern shores of the lakes are often referred to as being in the “Snowbelt.”
Autumn is a season known for colorful leaves and falling temperatures. Every once in a while, however, summer warmth makes a resurgence. When this happens, it is often dubbed “Indian Summer”.
This weather phenomenon, according to the NWS glossary, is defined as “an unseasonably warm period near the middle of autumn, usually following a substantial period of cool weather.” In the northeastern US, it is generally associated with an area of high pressure to the south that ushers warm air northward.
In popular use since the 18th century, the exact origins of the term are a bit foggy. One of the more reasonable explanations behind this unique phrase suggests a connection to when Native Americans began their hunting season, but no one knows for sure.
In other parts of the world, this summer-like weather goes by a variety of different names. In Europe, a number of countries associate the unusual warmth with the nearest saint’s day. It is known as “St. Luke’s Little Summer” if it develops in October or a “St. Martin’s Summer” if it occurs in November. In temperate parts of South America, it is simply known as “Veranico” (little summer).
The timing and intensity of these autumn warm spells vary from year to year. Nevertheless, when they do occur, they usually only last a few days. So, as we inevitably move toward winter, enjoy them while you can.