Hurricane Names Harvey, Irma, Maria and Nate Retired

There will never be another hurricane by the name of Harvey, Irma, Maria, or Nate. The World Meteorological Organization (WMO) has announced that it is officially retiring these names from its list of Atlantic cyclones.

The WMO is responsible for naming tropical storms and hurricanes around the world.  It maintains a set of six rotating lists for each hurricane-prone region. After a six-year cycle, names are re-used.  Names are only retired when a storm was particularly noteworthy – causing a large number of fatalities or an extraordinary amount of damage.

The 2017 Atlantic hurricane season was brutal, but four storms were particularly destructive. Hurricane Harvey, a category-4 storm, made landfall in Texas and dumped a record-breaking amount of rain in the Houston area, unleashing catastrophic flooding. Irma clobbered the Florida Keys as category-4 hurricane, but its impacts were felt throughout the entire Sunshine state. Hurricane Maria made landfall in Puerto Rico as a high end category-4 storm and knocked out power to more than 90% of the island for months. Nate hit the US Gulf Coast as a category-1 storm, but most of its deadly impacts were felt in Central America when it was still a tropical storm.

According to the National Hurricane Center, 86 storm names have been retired since the current naming system began in 1953. This year marks the fifth time that four or more names have been retired from a single season. Three of those -1955, 1995, and 2004 – each had four names retired. In 2005, five names were retired – the most ever from one hurricane season.

Starting in 2023, when last year’s list is recycled, the names Harvey, Irma, Maria, and Nate will be replaced by Harold, Idalia, Margot, and Nigel. Some other notable retired Atlantic Basin storm names include: Andrew, Katrina, Irene, and Sandy.

The 2018 Atlantic hurricane season officially begins on June 1.

Four names from the 2017 Atlantic hurricane season are retired. Credit: WMO

March 2018 was More of a Lion Than a Lamb in NYC

There is an old saying that March comes in like a lion and goes out like a lamb. It refers to the transition from winter to spring that takes place during the month and the change in weather that usually follows. In New York City this year, however, that tradition went out the window as March turned out to be colder than February.

This type of temperature flip-flop, according to the NWS, has only occurred three other times in New York City history – 1890, 1891, and 2017.

This March, twenty-six out of thirty-one days posted below average temperatures. Four of those days had highs that did not get out of the 30s. In the end, the city’s mean temperature for the month was 40.2°F, which is 2.3°F below normal.

The month was also unusually wet. The four nor’easters that blasted the region in as many weeks brought the city copious amounts of precipitation. In all, we received 5.17 inches of rain, which is 0.81 inches above average. Snowfall was also abundant, with 11.6 inches measured in Central Park. Of that total, 8.4 inches fell during the fourth and final nor’easter of the month. March, on average, usually only brings the city 3.9 inches of snow.

New York City weather records date back to 1869.

March was colder than February in NYC. Credit: The Weather Gamut

Fourth Nor’easter of the Month Slams NYC

The calendar says spring, but it felt more like winter in New York City on Wednesday as the fourth nor’easter of the month slammed the region.

According to the NWS, the storm dumped 8.4 inches of heavy, wet snow in Central Park, setting a new daily snowfall record for the date. The previous record of 7.1 inches had been in place since 1958. The city, on average, gets 3.9 inches of snow for the entire month of March.

This storm was the fourth nor’easter to affect the city and region in less than three weeks. The others were on March 2, March 7, and March 13. This one, however, was by far the snowiest. It was also the first time since 1992 that the city saw at least 6 inches of snow from a spring storm.

The reason for the plethora of nor’easters this month involves something called the North Atlantic Oscillation (NAO). Stuck in its negative phase for weeks, it has caused the jet stream to dip south over the eastern US and steer storms toward the northeastern seaboard.

View of the fourth nor’easter to hit the east coast this March. Credit:  RAMMB/CIRA/CSU

Why Are We Seeing So Many Nor’easters?

The east coast of the United States has been slammed with three nor’easters in just eleven days – March 2, March 7, and March 13. The reason for this barrage of storms involves something called the North Atlantic Oscillation (NAO).

Based in the North Atlantic Ocean, this weather pattern is driven by the pressure differences between the semi-permanent Icelandic Low and Azores/Bermuda High. When the pressure difference between these two systems is low, the NAO is said to be in a negative phase. This means the winds of the jet stream are relatively relaxed and cold air from the north can spill down into the eastern US. The positive phase of NAO is characterized by a strong pressure difference between the two areas and a robust jet stream that keeps cold air bottled up in the northern latitudes.

Three nor’easters in eleven days. Credit: NOAA

Fluctuating between positive and negative, the strength and duration of these phases vary. Since late February, however, a strong negative phase has been locked in place. With an area of high pressure over Greenland, the jet stream is blocked and therefore dipping southward over the eastern US. As the jet stream is essentially a storm track, this pattern has allowed areas of low pressure to be steered over the warm waters of the Gulf Stream off the eastern seaboard, where they have intensified into nor’easters.

In terms of climate change, the connection between the warming Arctic and the storm track across the mid-latitudes is an active area of research. Sea level rise, however, is clearly amplifying the coastal flooding associated with these powerful storms.

NAO Patterns. Credit: NOAA

Second Nor’easter in Less Than a Week for NYC

For the second time in less than a week, a nor’easter slammed New York City.

The storm intensified quickly and brought heavy snow, strong winds, and even thundersnow to the area. It downed trees and caused a number of travel disruptions, including nearly 2000 flight cancelations and the temporary suspension of all NYC Ferry service.

While the snow fell quickly, the surface temperature hovered just above freezing and did not allow much to accumulate. Only 3.2 inches of snow was reported in Central Park, according to the NWS. Areas north and west of the city received much higher storm totals.

GOES-16 image of nor’easter on March 7, 2018. Credit: NOAA

Powerful Nor’easter Slams NYC

A powerful nor’easter slammed the northeastern United States on Friday. Heavy precipitation, strong winds, and coastal flooding were reported across the region.

LGA airport. Credit: Chris Rudnick/Instagram

Here in New York City, 2.24 inches of rain fell in Central Park and wind gusts as high as 67mph were reported at JFK airport. These powerful winds canceled hundreds of flights, knocked down trees, and caused power outages in four of the city’s five boroughs. They also tore off a section of the roof of the American Airlines hangar at La Guardia airport and caused two tractor-trailers to flip over on the Verrazano Bridge.

Starting as an area of low pressure moving in from the west, this storm developed into a nor’easter over the Atlantic and then rapidly intensified. It underwent a process known as bombogenesis, the threshold for which is a drop in pressure of 24mb in 24 hours.This storm dropped 26mb in only 21 hours, producing its damaging winds.

Nor’easter of March 2, 2018. Credit: NOAA

Weather Lingo: Alberta Clipper

The winter season can produce a number of different types of storms. One of these is an Alberta Clipper.

These systems originate in western Canada, on the lee side of the Rocky Mountains. As  Pacific air spills downslope, an area of low pressure develops. From there, it gets caught up in the jet stream and moves to the southeast across the US. Traveling over land, these systems lack a significant source of moisture and generally do not produce much snow- usually around 1 to 3 inches. However, they are known for their strong winds and bitterly cold temperatures.

This type of quick-hitting storm takes its name not only from its place of origin near Alberta, Canada but also from the clipper ships of the 19th century – the fastest ships of the time.

Credit: NOAA

Report Finds Hurricane Harvey’s Record Rainfall Linked to Climate Change

Hurricane Harvey – one of the big names of the 2017 Atlantic hurricane season – unleashed catastrophic flooding in southeast Texas at the end of August. Now, after months of reviewing the data, scientists say the storm was exacerbated by climate change.

According to a peer-reviewed report by World Weather Attribution (WWA), an international coalition of scientists, human-caused climate change made Harvey’s devastating rainfall three times more likely to occur and fifteen percent more intense. Using historical rainfall data and high-resolution climate models to compare conditions in a pre-warming world to those at the time of the storm, the WWA team was able to separate the climate signal from natural variability. They found that the deluge caused by Harvey would have been a 1-in-2400-year event in the absence of global warming, but is now a 1-in-800-year event and becoming more likely.

Heavy rainfall events, in general, are becoming more frequent in many different places, because as the atmosphere warms it can hold more moisture. In fact, it can hold four percent more moisture for every 1°F of warming. This means there is more water vapor available in the air that can fall as precipitation.

After rapidly intensifying in the Gulf of Mexico, Hurricane Harvey made landfall as a category-4 storm in the Texas Coastal Bend region on August 25. It then stalled over the area for several days, unleashing massive amounts of rainfall. Cedar Bayou, outside of Houston, reported a staggering 51.88 inches of rain, setting a new record for the continental US. The storm claimed the lives of 80 people and more than 120,000 residents across the area had to be rescued from their homes. The economic impacts of the deluge are still being tallied, but it is expected to be one of the most expensive in US history.

The WWA study only analyzed the impact of climate change on Harvey’s rainfall, not its role in the storm’s formation or strength.  Those connections remain an active area of research.

Climate change made Hurricane Harvey’s rainfall worse. Credit: Climate Central. (World Weather Attribution is led by Climate Central, a non-profit research group.)

Extremely Active 2017 Atlantic Hurricane Season Comes to a Close

The 2017 Atlantic Hurricane Season officially ends today.  Not only was it above average, as predicted, it was the basin’s fifth most active season on record.

According to NOAA, there were seventeen named storms this season. Of these, ten developed into hurricanes and six were major hurricanes with ratings of category 3 or higher on the Saffir-Simpson Scale. An average season produces twelve named storms, six hurricanes, and three major hurricanes. It is also interesting to note that this year’s ten hurricanes developed consecutively over the course of ten weeks, marking the largest number of hurricanes to form in a row in the satellite era.

This season’s Accumulated Cyclone Energy (ACE), which measures the intensity and duration of storms, was also exceptionally high. On average, a season will post an ACE of 104 in the Atlantic. This year, according to researchers at Colorado State University, it was 226 – the seventh highest in the historical record.

Officially running from June 1 to November 30, the season got off to an early start this year. Tropical Storm Arlene was a rare pre-season storm that developed in April. Another interesting outlier was Hurricane Ophelia in October. It was the easternmost major hurricane ever observed in the Atlantic Basin and the strongest storm on record to hit the Republic of Ireland. The biggest names of the season, however, were Harvey, Irma, and Maria.

In August, Harvey made landfall in Texas as category-4 hurricane. It was the first major hurricane to hit the United States since Wilma in 2005. It was also the wettest storm on record, dumping more than 50 inches of rain in southeastern Texas. This extreme precipitation caused catastrophic flooding in the Houston area.

Hurricane Irma maintained category-5 strength winds for 37 hours before making landfall as a category-4 storm in the Florida Keys. Measuring about 425 miles in diameter, Irma was wider than the Florida peninsula and its effects were felt across the entire Sunshine state in early September.

Just two weeks later, Hurricane Maria devastated Puerto Rico. It was the third category-four hurricane to hit the US, or one of its territories, in less than a month. In 166 years of record keeping, that never happened before.

Causing so much destruction, Harvey, Irma, and Maria will likely be retired from the World Meteorological Organization’s list of storm names.

This active hurricane season was largely the result of above-average sea surface temperatures in the Atlantic and ENSO neutral to cool La Niña conditions in the Pacific. With warm water to fuel storms coupled with reduced wind shear across the Gulf of Mexico, tropical development in the Atlantic basin was essentially unhindered.

In terms of economic impact, ENKI Operations, a private research firm, estimates the property damage, clean up costs, and lost business productivity from this year’s storms to be $206 billion. That would make 2017 the costliest hurricane season on record for the US. The official tally from NOAA will not be available until early 2018.

Data: NOAA

Ex-Hurricane Ophelia Batters Ireland

The remnants of Hurricane Ophelia, the 15th named storm of the 2017 Atlantic Hurricane season, slammed the Republic of Ireland on Monday. It was the strongest storm on record to hit that country.

Ophelia peaked as a category-3 hurricane near the Azores over the weekend, becoming the most intense storm ever observed that far north and east in the Atlantic Basin. Then, it rapidly transitioned to a post-tropical storm that was labeled Ex-Hurricane Ophelia by Met Éireann, Ireland’s national weather service. This means the storm was drawing energy from the difference in air masses rather than the heat and moisture of the ocean.

Despite this technical downgrade, Ophelia still packed a punch. The storm’s powerful winds, which averaged around 57mph, uprooted trees and downed power lines. It also produced significant storm surge flooding along the country’s west coast. Officials say at least three fatalities have been reported and more than 300,000 people are without power.

At Fastnet Rock, off the coast of County Cork, a wind gust of 119mph was reported. If confirmed, it will be the fastest wind gust ever recorded in Ireland.

On the eastern side of the storm, smoke and dust from the wildfires burning in Spain and Portugal were funneled northward over the UK. This caused the sun and sky to appear red in a large part of the region.

It is not unheard of for Europe to be hit by the remnants of a hurricane. However, the storms typically travel west across the Atlantic Ocean in the Trade Winds and then re-curve to the northeast if they do not make landfall in the US, Mexico, or the Caribbean. Ophelia, however, skipped the transatlantic voyage and moved northeast toward Europe after forming southwest of the Azores.

Scientists say the storm’s rapid intensification and unusual track are the result of warmer than normal sea surface temperatures at northern latitudes and a steering current known as the mid-latitude jet stream. This current of air flows from west to east and carried the storm toward Ireland.

As the climate changes and sea surface temperatures continue to warm, the area of the ocean that supports hurricane development will likely expand northward. This will make Europe even more vulnerable to post-tropical storms.

MODIS satellite image of Ex-Hurricane Ophelia over Ireland. Credit: NASA