The Difference Between a Snowstorm and a Blizzard

The biggest snowstorm of the year is expected to blast the northeastern US on Tuesday. In New York City, on top of the significant snow totals that have been forecast, a blizzard warning is in effect.

Different than a typical winter storm, a blizzard is characterized more by wind speeds and reduced visibility than the amount of snow it produces. According to the NWS, the three main factors for blizzard conditions are:

  • Wind – Sustained winds or frequent gusts of 35mph or higher.
  • Visibility – Falling and/or blowing snow that reduces visibility to ¼ mile or less.
  • Time – High winds and reduced visibility must prevail for at least 3 hours.

These conditions heighten the risk of power outages and often produce whiteout conditions on roadways, making travel extremely dangerous.  Stay Safe!

A blizzard warning is in effect for NYC. Credit: NWS

Ice Thickness Guidelines for Winter Activities

On Monday night, a group of teenagers fell through the thin ice on a body of water in Central Park known as The Pond. Luckily, all were saved by the quick actions of good samaritans and NYC’s outstanding first responders. That said, this unfortunate incident is a salient reminder about safety issues for all winter activities that take place on the ice.

Winter is usually the time for ice-skating, ice-fishing, cross-country skiing, and snowmobiling. This year, however, unseasonably mild conditions have limited the opportunities for many of these popular pursuits. While there have been a few blasts of cold air, they have not lasted long enough to produce ice that can sustain significant weight. Below are some guidelines on how thick the ice needs to be to support different activities.

It is also important to remember that the thickness of ice can vary dramatically at different locations on the same body of water. Therefore, it is always best to follow the instructions of local officials and posted signs. Moreover, as the old saying goes: “If in doubt, don’t go out!”

Credit: NWS

Dressing for Cold Weather

When winter rolls around, I am often reminded of the old Scandinavian saying: “There is no such thing as bad weather, only inappropriate clothing.”

Since the weather is going to do whatever it is going to do, we all need to be aware of our environment and prepare for what Mother Nature throws our way. In winter, that means cold temperatures.

Extreme cold causes the body to lose heat faster than it can be generated. Prolonged exposure, according to the CDC, can cause serious health problems such as hypothermia and frostbite.

To stay safe this winter, remember to bundle up in layers and wear hats and gloves to minimize the loss of body heat.

Credit: NOAA

Credit: NOAA

The Weather Gamut Becomes a Weather-Ready Nation Ambassador for NOAA

It’s official! The Weather Gamut is now a Weather-Ready Nation (WRN) Ambassador for the National Oceanic and Atmospheric Administration (NOAA).

As a member of the WRN Initiative, The Weather Gamut is committed to working with NOAA to help increase awareness and strengthen resilience to our nation’s increasing vulnerability to extreme weather and climate events.

Be it hurricanes, tornadoes, snowstorms, heat waves, cold waves, drought, or flooding, every part of this country is subject to extreme weather. Therefore, it is vital that we, as a nation, improve our readiness, responsiveness, and resiliency to these environmental hazards that threaten lives and property.

Look for articles tagged “WRN” on our website to learn more about different types of extreme weather and climate events and how to prepare for them.

 For more info on NOAA's WRN Initiative: http://www.nws.noaa.gov/com/weatherreadynation/

Weather-Ready Nation Ambassador™ and the Weather-Ready Nation Ambassador™ logo are trademarks of the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, used with permission. For more information, click  here.

How Dangerous is Lightning?

Big summer thunderstorms are impressive to watch. However, they are also extremely dangerous.

According to NOAA, lightning is the second deadliest type of weather in the US after floods. On average, it claims the lives of 49 people every year in this county and seriously injures even more. This year, to date, lightning has killed 16 people across nine states. Two were struck just this week.  Sadly, this number will likely go up before the summer is over.

Lightning comes in variety of forms, but the cloud to ground variety is the most threatening to us at the surface. 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.

Around the globe, lightning hits the Earth about 100 times per second. In the US, the odds of a person being struck by lightning in any given year are 1 in 960,000 or 1 in 12,000 during an average lifetime of 80 years.

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

Credit: NOAA

Credit: NOAA

thunderroars_goindoors

Credit: NOAA/NWS

The Positive and Negative Sides of Cloud to Ground Lightning

Thunderstorms can illuminate the sky with a number of different types of lightning. The most threatening to us at the surface, however, is the cloud to ground variety. Interestingly, it comes in two forms: positive and negative.

While not completely understood, lightning – an intense electrical discharge – is believed to form as a result of the separation of charges in a cumulonimbus cloud. Within these towering clouds, both negatively charged hailstones and positively charged ice-crystals exist at the same time. As the storm’s updraft moves through the cloud, the lighter ice-crystals are carried upward, leaving the denser hailstones to fall to the bottom.

As the negative charge builds at the base of the cloud, it induces a strong positive charge on the ground, especially in tall objects such as buildings and trees. When the charge separation becomes large enough, a negatively charged stepped leader, a channel of ionized air, initiates a lightning strike from the base of the cloud. Moving down toward the ground, it meets a channel of rising positive charges known as a streamer. When they connect, they form negative cloud to ground lightning (-CG), which is the most common type.

Positively charged lightning (+CG), on the other hand, originates in the upper section or anvil of a cumulonimbus cloud. In this case, the descending stepped leader carries a positive charge and travels horizontally as it makes its way toward an area with negatively charged particles on the ground. It can travel more than 10 miles – a distance where thunder from the parent storm cannot be heard – to areas with relatively clear skies. For this reason, positive lightning is often called a “bolt from the blue”.  It is most often associated with super cell thunderstorms and is considered rare. According to NOAA, it makes up less than 5% of all lightning strikes.

While uncommon, positive lightning is extremely powerful. Originating at a higher level of a storm cloud, it has to travel through more air to reach the ground, intensifying its electrical field. Its peak charge can be 10 times greater than that of a negative strike. This immense power combined with a lack of warning makes positive cloud to ground lightning particularly dangerous. It is also believed to be responsible for a large percentage of wildfires.

To visually identify positive and negative cloud to ground lightning, look at the shape of the bolt. Negative lightning will have a downward branching pattern and positive lightning will generally display a single bright stroke without branches.

Regardless of these differences in charge and shape, it is important to remember that all lightning is dangerous. Stay safe!

Negative Cloud to Ground Lightning.  Credit: NOAA

Negative Cloud to Ground Lightning. Credit: NOAA

Positive Lightning.  Credit: MD Weather

Positive Lightning. Credit: MD Weather

A Look at the Different Types of Lightning

Summer is the season for thunderstorms and the lightning they produce can light up the sky in a variety of ways. Here is a quick look at the different types of lightning.

While there are variations within each, these are the four primary categories:

Intra-Cloud: This is the most common type of lightning. It happens completely inside a single cloud, jumping between regions with different charges. It is sometimes called “sheet” lightning.

Cloud to Cloud: This is lightning that occurs between two or more separate clouds.

Cloud to Air: This type of lightning occurs when positive charges at the top of a cloud reach out to the negatively charged air around it.

Cloud to Ground: This lightning occurs between the cloud and the ground. It can be either positively or negatively charged.

While thunderstorms can be fascinating things to watch, is important to remember that all lightning is dangerous and strike locations are unpredictable. So, as NOAA recommends, “When Thunder Roars, Go Indoors.”

Different types of lightning.  Credit: mshuntergi.com

Different types of lightning. Credit: mshuntergi.com

Rip Current Awareness for the Summer Beach Season

Summer vacation season has arrived and millions of people will be heading to beaches to beat the heat over the next few months. As such, 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 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 water in this area is also usually murky and darker than the surrounding water.  On guarded beaches, red flags 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

rip-current

Image Credit: NOAA.

How Thunder and Lightning Form

Flash! Bang! Thunderstorms are impressive displays of the power of nature. But how, you may wonder, do lightning and thunder form?

First comes the lightning, an intense electrical discharge. While not completely understood, it is believed to form as a result of the separation of charges within a cumulonimbus cloud.  One theory of how this happens involves the collision of particles within these towering clouds, including hailstones, super-cooled liquid water droplets, and ice crystals.  When they mix and collide, according to NOAA, “electrons are sheared off the ascending particles and collect on the descending particles.” This results in a cloud with a negatively charged base and a positively charged top.

As the atmosphere is a good insulator, generally inhibiting the flow of electricity, the strength of this electrical field has to build up substantially before lightning can occur. Most discharges, about 75%, occur across the electrical field within the storm cloud itself. This is known as intra-cloud lightning.

Another electrical field can also develop below the cloud. Since the cloud base is negatively charged, it induces a positive charge on the ground below, especially in tall objects such as buildings and trees. When the charge separation becomes large enough, a negatively charged stepped leader – an invisible channel of ionized air, moves down from the base of the cloud. When it meets a channel of positive charges reaching up from the ground, known as a streamer, a visible flash of lightning can be seen.  This is called cloud to ground lightning.

Lightning can be as hot as 54,000°F, a temperature that is five times hotter than the surface of the sun. When it occurs, it heats the air around it in a fraction of a second, creating an acoustic shock wave.  This is thunder.  A nearby lightning strike will produce thunder that sounds like a sharp crack. Thunder from a distant storm will sound more like a continuous rumble.

While thunderstorms can be spectacular events to watch, they are also very dangerous.  So, as the National Weather Service recommends, “When thunder roars, go indoors.”

Credit: NWS

Credit: NWS

Green Skies

Thunderstorms are fairly common in the late spring and summer in the United States. Every once in a while, though, they can be severe. When they are, the sky often turns green. You may wonder, what causes this odd coloration?

According to scientists, the phenomenon of green skies is not completely understood. The leading theory, however, involves the dense moisture content of cumulonimbus clouds and the time of day. Most thunderstorms develop in the late afternoon, a time when the sun’s rays have to travel a long way through the atmosphere before reaching the ground. This causes the light we see around sunset to be reddish-yellow. Thunderstorm clouds contain large amounts of rain and hail. This water and ice scatters blue light. So, when these towering clouds form in the late afternoon, the two colors mix to give the sky a green or blue-green appearance.

While severe thunderstorms can produce tornadoes, a green sky does not necessarily mean a twister is coming. Nonetheless, the color is associated with dangerous weather. If you see a thunderstorm heading your direction and the sky appears green, you should seek shelter immediately.

Green Sky.  Image Credit: Sky7WX

Green Sky.   Image Credit: Sky7WX