Monthly Archives: December 2018

The Historical Chances for a White Christmas

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The Holiday Season is here and many people are dreaming of a White Christmas. The likelihood of seeing those dreams come true, however, are largely dependent on where you live.

According to NOAA, a White Christmas is defined as having at least one inch of snow on the ground on December 25th. In the US, the climatological probability of having snow for Christmas is greatest across the northern tier of the country. Moving south, average temperatures increase and the odds for snow steadily decrease.

Here in New York City, the historical chance of having a White Christmas is about 12%. This low probability is largely due to the city’s proximity to the Atlantic Ocean and its moderating influence on the temperature.

This year, with temperatures forecast to be in the 40s on the big day, the city’s already minimal chance for snow has largely melted away.

Snow or no snow, The Weather Gamut wishes you a very Happy Holiday!

Source: NOAA

What is the Winter Solstice?

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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

November 2018: Earth’s Fifth Warmest November on Record

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Our global temperature continued its upward trend last month. November 2018 not only tied 2004 and 2016 as the fifth warmest November on record, but it also closed out the planet’s second warmest September to November season – a period known as meteorological autumn in the northern hemisphere.

According to the State of the Climate report by NOAA’s National Centers for Environmental Information, Earth’s combined average temperature for November – over both land and sea surfaces – was 56.55°F, which is 1.35°F above the 20th-century average. This November also marked the 407th consecutive month with a global temperature above its long-term norm. That means the last time any month posted a below average reading was December 1984.

Globally, the collective period of September, October, and November was also unusually warm. NOAA reports that Earth’s average temperature for the season was 1.44°F above the 20th century average of 57.1°F. That makes it the second warmest such period on record. Only 2015 was warmer.

While heat dominated most of the planet during this three-month stretch, some places were particularly warm, including parts of Europe, Scandinavia, Alaska, and eastern Russia. For the contiguous US as a whole, the season was only slightly above average. To put this disparity into context, consider that the mainland United States constitutes less than 2% of the total surface of the Earth. This detail highlights the fact that climate change is a complex global phenomenon that involves much more than the short-term weather that is happening in our own backyards.

These soaring temperatures are largely attributed to the long-term trend of human-caused climate change. ENSO-neutral conditions prevailed in November, which means there was neither a warm El Niño nor a cool La Niña in the Pacific to influence global weather patterns.

Year to date, the first eleven months of 2018 were the fourth warmest such period of any year on record. Global temperature records date back to 1880.

Credit: NOAA

The UN Climate Change Conference in Poland Keeps the Paris Agreement Moving Ahead

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The UN Climate Change Conference in Katowice, Poland, known as COP 24, concluded on Saturday. After two weeks of tough negotiations, delegates from nearly 200 countries drafted the rules and processes needed to translate the spirit of the historic Paris Agreement into action.

Years in the making, the 2015 Paris Agreement set the target of holding global warming to 2°C (3.6°F) above pre-industrial levels and urged countries to pursue an even tighter cap of 1.5°C (2.7°F) if possible. To achieve this goal, almost 200 countries submitted individual voluntary emissions reduction plans known as nationally determined contributions (NDCs). But when added up, the current collection of NDCs, which vary widely in ambition, will miss the 2°C goal.  In fact, they would allow for a 3.2°C (5.76°F) rise in our global temperature. This is why the agreement requires countries to reassess their plans every five years once it goes into effect in 2020.

One of the main goals of COP 24 was to create a standardized rulebook for the monitoring and reporting of these independent undertakings.  China – the world’s largest carbon polluter – was pushing for different sets of rules for developed and developing countries. However, in the end, a universal and transparent methodology was agreed upon that subjects all countries to the same level of scrutiny. Every country, regardless of economic status, will have to report their emissions – and the progress made in reducing them – every two years starting in 2024. The deal also calls on countries to deepen their planned emission cuts ahead of 2020.

While the meeting did produce a deal to keep the Paris Agreement alive and moving forward, it was a bumpy road. In fact, the negotiations were almost completely derailed by a debate over climate science of all things.  Many of the delegates wanted to formally endorse the IPCC’s special report on the consequences of 1.5°C (2.7°F) of warming – the more aspirational goal of the Paris Agreement – that came out in October. However, several major oil producing countries, including the US, Russia, Saudi Arabia, and Kuwait, balked at the idea and pushed to downplay the report’s significance. In the end, a compromise was reached. Instead of a full-fledged endorsement, the conference statement expressed “appreciation and gratitude” for the report’s timely completion.

The question now is, will individual countries make pledges to deepen their emissions cuts and take the necessary steps to make them a reality.

The Paris Agreement, although ratified in record time, is a fragile accord. All commitments are voluntary and vulnerable to the political will of individual governments – both now and in the future. Moreover, there are no penalties for those who do not live up to their promises.

The Katowice meeting was the 24th session of the Conference of the Parties (COP) to the U.N. Framework Convention on Climate Change (UNFCCC). The next conference (COP 25) will take place in November 2019 in Chile.

Credit: UN

2018: Not Yet Over, But Already Among the Top Ten Wettest in NYC

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The northeastern United States has been rather soggy this year. With more than two weeks still left in 2018, many locations have already posted their wettest years on record.

Here in New York City, we have received 59.68 inches of rain to date, which is 12.08 inches above average. That means 2018 now ranks among the top ten wettest years ever recorded in the Big Apple.

Much of this impressive, and still building, total came down during several heavy rain events over the course of the year. Each of these caused street and subway flooding around the five boroughs. For the northeast region as a whole, heavy precipitation events increased 55% between 1958 and 2016, according to the latest National Climate Assessment.

Scientists attribute the increase in both frequency and intensity of heavy rain events to climate change. As greenhouse gases warm the atmosphere, the air is able to “hold” more water vapor. More specifically, according to the Clausius–Clapeyron relation, for every increase of 1°F, the saturation level of the atmosphere increases by about 4%. That means there is more water vapor available in the air to condense and fall as precipitation.

Credit: Climate Matters

The Snowiest Places in the US

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Snow is a common occurrence during the winter months for many parts of the US. But, some places tend to get more than others. In fact, there are locations that see triple digit snow totals every year.

In the east, the Great Lakes region is well known for lake effect snow events. With moisture laden snow bands forming down-wind of the massive lakes, it is not uncommon for some communities to see more than 100 inches of snow each season.  For example, Syracuse, NY, on average, gets 123.8 inches of snow annually.

In the west, even more snow is par for the course in the Cascade Range of Washington state. The Paradise Ranger Station in Mount Rainier National Park holds the record for the greatest average annual snowfall in the US. At 5400 feet in elevation, they see 643 inches of snow (53.6 feet) each year.

Storm systems that move in from the Gulf of Alaska run into the Cascade Mountains and are forced upward. As they rise, the moisture in the air cools, condenses, and falls as precipitation. At lower elevations, it comes out as rain, but at higher elevations, where the air is colder, it falls as snow. Standing at 14,410 feet above sea level, Mount Rainier is the highest peak in the Cascades.

Mount Rainer National Park sees the highest average annual snowfall in the US. Credit: Hemmings

Weather Lingo: Lake Effect Snow

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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.”

Credit: NOAA

November 2018: Seventh Wettest and Fourth Snowiest on Record in NYC

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November was unusually cold in New York City this year. Highs ranged from a relatively balmy 72°F to a chilly 28°F. But, with 22 days posting below average readings, the cold won out in the end. The city’s mean temperature for the month was 44.5°F, which is 3.3°F below average.

In terms of precipitation, November was a month for the record books. The city received 7.62 inches of rain in Central Park, making it the seventh wettest November on record. Snowfall was also abundant, despite the fact that it all fell during a single storm. Central Park reported 6.4 inches of snow, setting set a new daily record for the date. It was also the earliest 6-inch one-day snowfall on record for the city and the largest one-day November snowfall since 1882. Moreover, that one snow event was enough to make this November the city’s fourth snowiest on record.

New York City, on average, sees 4.02 inches or rain and 0.3 inches of snow for the entire month of November.