Summer Nights are Getting Warmer Across the US

Summer is the time of year when warm temperatures are expected. As our climate changes, however, the season is getting even hotter, especially at night.

Since 2010, according to NOAA, there have been 34% more record-warm low temperatures set than record-warm high temperatures. Nationally, summertime lows have increased an average of 1.8°F since 1895, according to an analysis by Climate Central, a nonprofit science news organization. The southwestern part of the country has seen the greatest warming, with Reno and Las Vegas, Nevada showing an increase of 16.9°F and 9.1°F respectively. Not far behind are El Paso, Texas at 7.7°F and Salt Lake City, Utah at 6.6°F.

In addition to climate change, land use issues also play a role in our warming nights. Paved surfaces hold more heat than vegetated ones, so cities tend to be hotter than rural areas, particularly during the overnight hours. This is known as the urban heat island effect.

When temperatures do not significantly cool off at night, people do not get a chance to recover from the heat of the day. This can cause serious health concerns, especially for young children, the sick, and the elderly. Warmer nights also drive up energy bills, as people with air conditioning units use them more. This in turn, if they are powered by fossil fuels, adds even more greenhouse gases to the atmosphere.

Credit: Climate Central

Weather Lingo: Haboob

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

Lightning: A Deadly Weather Hazard

Thunderstorms are impressive displays of the power of nature. However, they are also extremely dangerous.

On average, according to NOAA, lightning claims the lives of 27 people every year in the US and seriously injures hundreds more. To date in 2019, lightning has killed 12 people across ten states. The most recent victim was struck on Sunday in Richarton, ND. Local officials say the man was outside doing volunteer trail work at a recreation center when a storm moved through the area.

Lightning comes in a variety of forms, but the cloud to ground variety is the most threatening to people. A typical bolt carries a current of about 300 million volts and can heat the air around it to 50,000°F. That is five times hotter than the surface of the sun.

This type of lightning, NOAA says, strikes the US about 25 million times a year. However, 70% of lightning fatalities occur during the summer months. The season marks not only the peak of thunderstorm activity in the United States, but also the time of year when people spend more time outdoors.

According to a NWS report on lightning deaths in the US from 2006 to 2017, the vast majority of victims were men engaged in an outdoor leisure activity. Listing a variety of different pastimes at the time they were struck, fishing topped the list as the most deadly water-related recreational activity.

To avoid becoming a statistic, follow the advice of the NWS – “When thunder roars, go indoors.”

Credit: NOAA

What is the North American Monsoon?

The summer phase of the North American Monsoon is underway. But what, you may wonder, are monsoons and how do they impact the United States?

While most people associate a monsoon with rain, that is only half the story. It is actually a wind system. More specifically, according to NOAA, a monsoon is “a thermally driven wind arising from differential heating between a landmass and the adjacent ocean that reverses its direction seasonally.” In fact, the word monsoon is derived from the Arabic word “mausim”, meaning seasons or wind shift.

In general, a monsoon is like a large-scale sea breeze.  During the summer months, the sun heats both the land and sea, but the surface temperature of the land rises more quickly. As a result, an area of low pressure develops over the land and an area of relatively higher pressure sits over the ocean. This causes moisture-laden sea air to flow inland. As it rises and cools, it releases precipitation. In winter, this situation reverses and a dry season takes hold.

Monsoon wind systems exist in many different parts of the world, with the most famous one setting up over India and Bangladesh. In the US, we have the North American Monsoon that impacts states across the southwest. Summer temperatures in the region, which is mostly desert, can be extremely hot. Readings in the triple digits are not uncommon. This intense heat generates a thermal low near the surface and draws in moist air from the nearby Gulf of California. In addition, an area of high pressure aloft, known as the subtropical ridge, typically moves northward over the southern Plains in summer. Spinning clockwise, this shifts the winds in the area from a southwesterly to a southeasterly direction and ushers in moisture from the Gulf of Mexico. This combination of heat and moisture-rich air produces thunderstorms and heavy rainfall across the region. Monsoon rains reportedly supply 50-70% of the area’s annual precipitation.

Replenishing reservoirs and nourishing agriculture, these seasonal rains are a vital source of water in the typically arid southwest. Conversely, they can also cause a number of hazards such as flash flooding, damaging winds, dust storms, hail, and frequent lightning.

The wet phase of North American Monsoon typically runs from mid-June to the end of September.

The North American Monsoon pulls most air (green arrows) inland over the typically arid southwest region of the US. Source: NOAA/NWS

Summer Safety: What is a Rip Current and Why is it Dangerous?

Summer vacation season is in full swing across the US. As millions of people head to beaches to have fun and beat the heat, it is important to remember that the ocean is a dynamic environment that can pose a number of hazards for swimmers. Chief among these are rip currents.

Rip currents are fast, localized channels of water moving away from the shoreline. According to NOAA, they are a result of “complex interactions between waves, currents, water levels, and nearshore bathymetry.” They can form in several different ways on any beach with breaking waves. That said, they are typically found at breaks in sandbars and along permanent structures that extend out into the water such as jetties or piers.

Moving at speeds up to 8 feet per second – which is faster than an Olympic swimmer – rip currents can easily drag unsuspecting swimmers hundreds of yards out to sea.  While they will not pull anyone underwater, they can cause fatigue and panic. According to the U.S. Lifesaving Association, rip currents are responsible for 80% of all surf zone rescues. Nationally, they cause more than one hundred deaths every year.

To spot a rip current, look for a gap in the breaking waves.  This is where the water is forcing its way back out to sea. The area also usually appears murky and darker than the surrounding water.  On guarded beaches, red flags often indicate hazardous conditions for swimmers.

If caught in a rip current, the Red Cross recommends not trying to swim against it.  Instead, they say to swim parallel to the shoreline until you are out of the current. Once free, you can start swimming back toward the beach.

For more information on beach safety, visit: http://www.redcross.org/prepare/disaster/water-safety/beach-safety

Credit: NOAA

July 2019: Tenth Hottest July on Record for NYC

July is usually the warmest month on the calendar for New York City, but this year it was especially hot. In fact, it tied July 1949 as the city’s tenth warmest July on record.

In all, it produced 26 days with above-average readings, including ten days in the 90s. Four of those days came during a heatwave in the middle of the month when the air temperature reached 95°F and the humidity made it feel well above 100°F.

Overnight lows were also mostly warmer than normal throughout the month. On July 20, the mercury only fell to 82°F, setting a new record warm low temperature for the date. In the end, the city’s mean temperature for the month was 79.6°F, which is 3.1°F above average.

It is important to note that four of the city’s ten warmest Julys on record have now occurred since 2010. The warmest was July 1999, when the average temperature for the month was 81.4°F.

This July was also above average in terms of precipitation. With several intense thunderstorms rolling through the area, a total of 5.77 inches of rain was measured in Central Park. The city, on average, gets 4.60 inches of rain for the month.

Credit: The Weather Gamut

First Heatwave of 2019 Brings Extreme Temperatures to NYC

A heatwave gripped a large swath of the eastern United States this weekend. For many areas, the temperatures were extreme.

The threshold for what constitutes a heatwave varies by region, but here in the northeast, it is defined as three consecutive days with temperatures reaching 90°F or higher. In New York City, the official temperature in Central Park reached 91°F on Friday, and 95°F on both Saturday and Sunday. Overnight lows were also well above average. In fact, on Saturday, the temperature only cooled down to 82°F, tying the record warm low termperature for the date that was set in 2015.

When the humidity was factored in, it felt even hotter. The heat index ranged from 105°F-110°F.

The city’s airports, LGA and JFK, both in the borough of Queens, posted record high temperatures over the weekend, according to the National Weather Service. JFK hit 99°F on Saturday, breaking the previous record of 96°F that was set in 2013. On Sunday, LGA reached the century mark (100°F), tying the high-temperature record for the date at the site that was set in 1991.

The cause of this exceptional heat was two-fold. First, a large area of high pressure sitting over the central US was pumping hot air from the southwest toward the northeast. At the same time, a strong Bermuda High off the east coast was pumping warm, moist air from the Gulf of Mexico into the region. Together, they made it dangerously hot, which is why the NWS issued an excessive heat warning for the city. It is also why several outdoor events around the Big Apple were canceled, including the NYC Triathlon.

The hottest day ever recorded in New York City occurred on July 9, 1936, when the air temperature hit 106°F in the shade. The city’s normal high temperature this time of year is 84°F.

A Tale of Two Highs: The Science Behind the Excessive Heat in the Northeast

Summer is the season for warm weather and even the occasional heatwave. But, the excessive heat that is gripping the eastern United States this weekend is exceptional. Its source is essentially a tale of highs – two areas of high pressure, that is.

The first is a Bermuda High. This is a large, semi-permanent, area of high pressure situated off the east coast. Spinning clockwise, it is strongest in the summer months and often steers hot, humid air from the Gulf of Mexico toward the northeast. It is usually the main cause of heatwaves in the region.

This current heatwave, however, is getting an extra boost from a second area of high pressure that is sitting over the central US. Also spinning clockwise, it is funneling hot air aloft from the southwest toward the northeast. Traveling eastward, this hot air must pass over the Appalachian Mountains, which run parallel to the eastern seaboard from Georgia to Maine. Following the topography downslope on the lee side of the mountains, the air compresses and warms even further. This is producing the exceptionally high air temperatures, such as the upper 90s and triple digits reported in cites across the region.

Combining this excessively hot air with the humidity being pumped into the area by the Bermuda High, the heat index or real feel temperatures are well above 100°F in many places.

This type of weather is more than just uncomfortable, it is dangerous. To avoid health complications, the American Red Cross recommends avoiding strenuous outdoor activity, drinking plenty of fluids, and cooling off in air-conditioned spaces when possible.

Credit: NOAA/NWS

Extreme Heat Can Pose a Danger to Your Health

A heat emergency has been issued for New York City.  As temperatures soar, it is important to remember that intense heat can cause serious health problems.

According to the CDC, extreme heat – temperatures that are significantly hotter than the average local summertime high – is one of the leading causes of weather-related deaths in this country. Claiming hundreds of lives every year, excessive heat kills more people across the U.S. than hurricanes and tornadoes combined.

Extreme heat is deadly because it forces the human body beyond its capacity to cool itself. Linked to overheating and dehydration, heat-related illnesses can range in severity from mild to life-threatening.  Symptoms for each stage include:

Heat Cramps:  Painful muscle spasms in the legs and/or abdomen

Heat Exhaustion:  fatigue, weakness, clammy skin, and nausea

Heat Stroke:  rapid pulse, hot and dry skin, no sweating. This is a medical emergency

To beat the heat, the American Red Cross suggests:

  • Avoid strenuous activity
  • Dress lightly
  • Eat lightly
  • Drink plenty of water
  • Replenish salts and minerals lost through perspiration with sport-drinks
  • Limit caffeine and alcohol
  • Stay out of the sun
  • Cool off in an air-conditioned building, when possible

Credit: NWS/WRN

Aphelion 2019: Earth Farthest from Sun Today

The Earth will reach its farthest point from the Sun today – an event known as the aphelion. It will officially take place at 22:10 UTC, which is 6:10 PM Eastern Daylight Time.

This annual event is a result of the elliptical shape of the Earth’s orbit and the slightly off-centered position of the Sun inside that path. The exact date of the Aphelion differs from year to year, but it’s usually in early July – summer in the northern hemisphere.

While the planet’s distance from the Sun is not responsible for the seasons, it does influence their length. As a function of gravity, the closer the planet is to the Sun, the faster it moves. Today, Earth is about 152 million kilometers (94 million miles) away from the Sun. That is approximately 5 million kilometers (3 million miles) further than during the perihelion in early January. That means the planet will move more slowly along its orbital path than at any other time of the year. As a result, summer is elongated by a few days in the northern hemisphere.

The word, aphelion, is Greek for “away from the sun”.

Earth’s Perihelion and Aphelion. Credit: Time and Date.com