May 2019: A Soggy Month for NYC

May was another month of wild temperature swings in New York City. Producing several cases of weather whiplash, highs ranged from a chilly 48°F to an unseasonably balmy 86°F. In the end, however, these extremes balanced each other out. The city’s mean temperature for the month was 62.2°F, which is only 0.2°F below average.

On the precipitation side of things, May was unusually wet. The month brought the city a relatively rare spring nor’easter and several impressive thunderstorms. One of which produced golf ball sized hail on Staten Island, one the city’s five boroughs. Overall, 19 out 31 days posted measureable rainfall that added up to 6.82 inches for the month. While that is a soggy statistic, it was not the wettest May the city has seen. That dubious honor belongs to May 1989 when 10.24 inches of rain was measured in Central Park. The city, on average, gets 4.19 inches for the month.

Credit: The Weather Gamut

Summer Preview Brings NYC First 80° Day of the Year

It felt more like June than April in New York City on Friday. The temperature in Central Park soared to 80°F, marking the city’s first 80-degree day of the year.

Topping out at 17°F above average, the day was unseasonably warm. However, it was not a record breaker. That honor belongs to April 19, 1976, when the mercury soared to 92°F. The low temperature was 58°F, which is also warmer than normal for the date.

This spring heat was the result of a ridge in the jet-stream that allowed warm southern air to move further north than it normally would at this time of year.  These balmy conditions did not last long, though. A heavy rainstorm moved through the region over night and brought temperatures back to more seasonable levels.

Summer does not officially begin until June 21.

Credit: The Weather Gamut

Do April Showers Really Bring May Flowers?

The phrase, “April showers bring May flowers “ has been around for centuries. It is derived from a poem written in the 1500s by Thomas Tusser – an English poet and farmer. This old adage, however, does not hold true in the northeastern United States.

Coming on the heels of the snowy months of winter, April typically produces more rain than snow. Many people, therefore, consider it a rainy month. Since water is necessary for the overall survival of plants, they also associate it with the bloom of flowers in May. Nevertheless, according to botanists, perennials – the plants that go dormant in winter and re-grow in the spring – are more dependent on the soil moisture derived from winter snowmelt and the long-term local precipitation pattern.

In the end, though, temperature is the most significant factor in determining when a flower will bloom. As soon as the weather becomes more spring-like, flowers will start to blossom, regardless of how much it rained in April or whatever the prior month was. That said, a “false spring” – a warm spell that triggers flowering but is followed by a hard frost – can kill the fragile blooms.

It is also worth noting that April is not typically the wettest month of the year for most places in the US. In New York City, July, on average, takes that honor because of the downpours associated with its strong summer thunderstorms.

Spring Peonies. Credit: Melissa Fleming

Weather Safety: Flooding and the Power of Water

It is no secret that heavy rain can cause flooding. However, it can be surprising to learn how little water is required to create significant impacts.

As anyone who carries a water bottle knows, water is heavy. In fact, just one cubic foot of fresh water weighs 62.4lbs (28.3kg).  Multiplied many times over, raging floodwater can carry away or destroy most things in its path. Moving at just 4-mph, water has enough force to cause structural damage to an average home.

Flowing floodwaters can also pose a danger when hiking or driving. According to NOAA, it only takes six inches of fast moving water to knock a person off their feet. Twelve inches of water can sweep a small car off the road and eighteen to twenty-four inches can float most large vans and SUVs.

Since it is impossible to know how deep water is just by looking at it, it is best to err on the side of caution. As the saying goes, “Turn around, don’t drown!”

Credit: NWS/NOAA

A Look at Rainbows and their Legendary Pots of Gold on this St Patrick’s Day

According to Irish folklore, a pot of gold can be found at the end of a rainbow. In reality, however, it is impossible to locate the terminus of this optical phenomenon.

Refraction and reflection inside a raindrop. Credit: Met Office

For a rainbow to form, rain has to be falling in one part of the sky while the sun is out in another. The water droplets in the air act like prisms that refract and reflect the sunlight, revealing the colors of the visible spectrum. Red is refracted the least and is always on the top of a single bow while blue is on the bottom. Since we only see one color from each drop, it takes a countless number to produce a rainbow.

A double rainbow is seen when the light reflects twice inside the raindrops. Since each reflection weakens the intensity of the light, the second bow appears dimmer. The order of the colors is also reversed, with blue on top and red on the bottom.

That said, these colorful arcs are not physical entities that can be approached. No matter how close they appear to be, they are always tantalizingly out of reach. Nevertheless, most people consider seeing one to be a treasure with no gold required.

With a little luck, you can spot a rainbow if you face a moisture source – rain or mist from a waterfall – while the sun is at your back.

Happy Saint Patrick’s Day!

Rainbow and faint second rainbow form after a rainstorm in Bermuda. Credit: Melissa Fleming

From Snow to Freezing Rain, Winter Precipitation Can Take Several Forms

The winter season can produce various types of precipitation – rain, freezing rain, sleet, or snow. The form we see at the surface depends on the temperature profile of the lower atmosphere.

All precipitation starts out as snow up in the clouds.  But, as it falls toward the Earth, it can pass through one or more layers of air with different temperatures.  When the snow passes through a thick layer of warm air – above 32°F – it melts into rain.  If the warm air layer extends all the way to the ground, rain will fall at the surface.  However, if there is a thin layer of cold air – below 32°F – near the ground, the rain becomes super-cooled and freezes upon impact with anything that has a temperature at or below 32°F.  This is known as freezing rain.  It is one of the most dangerous types of winter precipitation, as it forms a glaze of ice on almost everything it encounters, including roads, tree branches, and power lines.

Sleet is a frozen type precipitation that takes the form of ice-pellets. Passing through a thick layer of sub-freezing air near the surface, liquid raindrops are given enough time to re-freeze before reaching the ground. Sleet often bounces when it hits a surface, but does not stick to anything.  It can, however, accumulate.

Snow is another type of frozen precipitation.  It takes the shape of six-sided ice crystals, often called flakes.  Snow will fall at the surface when the air temperature is below freezing all the way from the cloud-level down to the ground.  In order for the snow to stick and accumulate, surface temperatures must also be at or below freezing.

When two or more of these precipitation types fall during a single storm, it is called a wintry mix.

Precipitation type depends on the temperature profile of the atmosphere. Credit: NOAA

December 2018: Ninth Wettest on Record for NYC

December 2018 felt like a weather roller coaster in New York City. Highs ranged from a relatively balmy 61°F to a chilly 36°F. But, with 17 out of 31 days posting above average readings, the warmth won out in the end. The city’s mean temperature for the month was 40.1°F, which is 2.6°F above average.

In terms of precipitation, December was a month for the record books. The city received 6.48 inches of rain in Central Park, tying December 1996 as the ninth wettest December on record. Three different days produced rainfall totals greater than one inch. The end of the month saw a soggy New Year’s Eve with 0.99 inches of rain. It was the first time in 24 years that it rained on the revelers at the Times Square ball drop festivities.

Snowfall, however, was scarce. Only a trace amount was reported for the month. New York City, on average, sees 4 inches of rain and 4.8 inches of snow in December.

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

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

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

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 recordSnowfall 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.

 

Weather and Art: Rainworks

Rainy days can sometimes make people feel sad or depressed. This is what inspired artist Peregrine Church to create Rainworks – artwork activated by rain. His goal, he says, is “to give people a reason to smile on a rainy day”.

Based in Seattle, a city known for precipitation, he uses a super-hydrophobic spray to create images and sayings on concrete surfaces that are only visible when wet. As concrete gets wet, it gets darker. However, the areas covered in the waterproof coating stay dry and therefore lighter in color. This contrast allows the images and sayings to be visible to passersby.

Essentially street art, his first piece in 2014 was written on a city sidewalk and said “Stay Dry Out There”. He was soon joined his friend by Xack Fischer in creating Rainworks across the Emerald City.

In 2016, they started selling their specially formulated spray online. They also offer tutorials on their website to help people create their own Rainworks around the world. The spray according to the artists, is eco-friendly and biodegrades over the course of 2 to 4 months.

To date, more than 200 Rainworks have been created across five continents. You can find their locations (and add your own) on the Rainworks map.

A Rainwork in Yokohama, Japan. Image Credit: Rainworks Gallery