Tag Archives: storms

Why Hurricanes Hit the East Coast and Not the West Coast of the US

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It is mid-September and hurricane season is in full swing in both the Atlantic and Pacific. With these mighty oceans bordering both sides of the US, have you ever wondered why hurricanes only make landfall on the east coast?

The answer is two-fold, involving the direction of prevailing winds in the tropics and the difference in water temperature in the two basins.

Hurricanes develop at tropical and sub-tropical latitudes in both the Atlantic and Pacific, where water temperatures are at least 80°F. This part of the globe is also where the Trade Winds prevail, flowing from east to west.

In the Atlantic, storms traveling west-northwest often run into the east coast or Gulf Coast of the US. There, the warm waters of the Gulf Stream that flow along the eastern seaboard sustain them as they move northward.

In the Pacific, storms tend to be pushed out to sea by the Trade Winds.  Any hurricanes that manage to move north quickly dissipate when they encounter the cooler waters of the California current that flows southward along the west coast from Canada.

Only two tropical systems have ever made landfall on the west coast of the US. A hurricane slammed San Diego, CA in 1858 and a tropical storm battered Long Beach, CA in 1939. That said, hurricanes and tropical storms generally have indirect impacts on the western states. When a named storm makes it as far north as Baja California, remnants of it can travel across the border and cause heavy rain and flooding in parts of the American southwest.

1851_2013_hurr

All North Atlantic and Eastern North Pacific hurricanes, through 2013. Credit: NOAA/NWS

How Dangerous is Lightning?

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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

Names for the 2016 Atlantic Hurricane Season

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Today is the first day of the Atlantic Hurricane Season. Although two named storms – Alex and Bonnie – have already formed this year, the season officially runs from June 1st to November 30th.

Since 1950, each tropical storm or hurricane to form in the Atlantic has had a unique name. They come from a set of six rotating lists produced by the World Meteorological Organization. A name is retired only when a storm was particularly noteworthy – causing a large number of fatalities or an extraordinary amount of damage. Some retired Atlantic Basin names include: Andrew, Katrina, and Sandy.

The names for this year’s storms are listed below.

2016 Atlantic Storm Names

AlexHermineOtto
BonnieIanPaula
ColinJuliaRichard
DanielleKarlShary
EarlLisaTobias
FionaMatthewVirginie
GastonNicoleWalter

 

2016 Atlantic Hurricane Season Outlook

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The number of hurricanes that develop in any given year varies, and this year, NOAA’s Climate Prediction Center is forecasting a “near normal” season in the Atlantic.

Tropical cyclones, known as hurricanes in the United States, develop around the globe at different times of the year. In this country, we are most affected by the Atlantic hurricane season, which impacts the North Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. It runs from June 1 through November 30.

Overall, NOAA predicts a 70% likelihood of ten to sixteen named storms forming this season, of which four to eight could become hurricanes, including one to four major hurricanes. A major hurricane is one that is rated category 3 or higher.

The numbers for this season’s outlook include Hurricane Alex, the unusual storm that developed in the eastern Atlantic in mid-January.

One of the main drivers behind this season’s average to slightly above average forecast is the diminishing presence of El Niño and the likely development of La Niña in the autumn. El Niño conditions tend to suppress tropical activity in the Atlantic while La Niña conditions do the opposite.

After three consecutive below average hurricane seasons in the Atlantic, a normal season will likely feel very active. But regardless of the number of storms that actually form, it is important to remember that it only takes one landfalling system in your community to make it a memorable season.

Source: NOAA

Source: NOAA

Blizzard of 2016: Fourth Most Powerful Snowstorm on Record in Northeast

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The blizzard that slammed a large section of the northeastern US, including NYC, last weekend was one of the most powerful winter storms to hit the region in decades.

According to NOAA, the storm was given a value of 7.66 on the Northeast Snowfall Impact Scale (NESIS). That is considered a category 4 or “crippling” snow event.  It was also the 4th most powerful winter storm to impact the northeast since 1950.

Covering 434,000 square miles across 26 states, the storm impacted more than 102 million people. Of those, approximately 24 million people saw more than 20 inches of snow.

The region’s strongest storm on record was the so called “Super-Storm” of March 1993.

Source: NCEI

Source: NCEI

Source: NOAA

Source: NOAA

The Northeast Snowfall Impact Scale

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Similar to the national Saffiir-Simpson Scale for hurricanes and the Enhanced Fujita Scale for tornadoes, major winter storms that occur in the northeastern US have a special rating system. It is called the North East Snowfall Impact Scale or NESIS.

Developed in 2004 by Paul Kocin and Dr. Louis Uccellini of the National Weather Service, the scale is used to rank and compare storms in the region. It classifies large snow events into one of five categories based on the size of the area covered, number of people affected, and snowfall totals. The higher the NESIS value, the more impactful the storm.

Source: NCEI

Source: NCEI

What is a Blizzard?

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A blizzard is expected to blast a large part of the northeastern United States, including NYC, this weekend. Different than a typical winter storm, a blizzard is characterized more by its winds than the amount of snow it produces.

According to the NWS,  the three key factors in a blizzard are wind, visibility, and time. More specifically, they 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 – Wind and reduced visibility conditions must prevail for at least 3 hours.

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

The 2015 Atlantic Hurricane Season Comes to a Close

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The 2015 Atlantic Hurricane Season officially ends today.  For a third year in a row, it was slightly below average in terms of numbers.

According to NOAA, there were eleven named storms this season. Of these, four developed into hurricanes and only two – Danny and Joaquin – were rated category 3 or higher on the Saffir-Simpson Scale. On average, the Atlantic produces twelve named storms, six hurricanes, and three major hurricanes (category-3 or higher) every year.

Throughout the season, which runs from June 1st to November 30th, only two named storm made landfall in the U.S.  Tropical Storm Ana, a somewhat rare pre-season storm, brought powerful winds and heavy rain to the coastal regions of both North and South Carolina in early May. It was the second earliest tropical cyclone on record to make landfall in the US. In June, Tropical Storm Bill slammed southeastern Texas with winds measured up to 60 mph and relentless rain that caused widespread flash flooding.

The strongest storm to form in the Atlantic this year was Hurricane Joaquin. With winds measured up to 155 mph, it was rated category 4 – the strongest since Hurricane Igor in 2010. It was also a slow mover, battering the Bahamas for several days between late September and early October.

This relatively quiet hurricane season was largely the result of El Niño conditions in the Pacific that generated wind-shear across the Gulf of Mexico and helped hinder most tropical development in the Atlantic basin.

Source: NOAA

Source: NOAA

The Positive and Negative Sides of Cloud to Ground Lightning

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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

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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