There are a number of different ways to gauge a hurricane season. One of these is the Accumulated Cyclone Energy index, which is widely referred to as ACE.
It expresses the combined intensity and duration of individual cyclones and provides a measure of activity for an entire hurricane season. For a single storm, it is calculated by summing the squares of the maximum sustained wind speeds measured every six hours while they are at least tropical storm strength. This number is then divided by 10,000 to make it more user-friendly. Overall, the stronger and longer-lived a storm is, the higher its ACE value.
The ACE for a season is the sum of the ACE values from individual storms that occurred that year. NOAA considers a season with an ACE of 111 or higher to be above average, while an ACE of 66 or lower is regarded as below average.
The Atlantic hurricane season runs from June 1 through November 30.
(Note: Year to date the Atlantic Basin has had 13 storms with a combined ACE of 202 and there are still two months left in the 2017 hurricane season.)
The temperature in Central Park hit 87°F on the equinox. Then on Sunday, it soared to 91°F, setting a new record high for the date. The previous record of 89°F had been in place since 1959.
At this point in September, temperatures usually peak in the lower 70s. But with a stubborn ridge of high pressure sitting over the region, warm equatorial air is flowing further north than it normally would at this time of year.
If you are ready for autumn, fear not. Temperatures that are more seasonable are expected to return to the city later this week.
It is hard to believe, but today marks the sixth anniversary of The Weather Gamut.
Initially begun as a way to deepen and share my knowledge about weather and climate change, this blog has allowed me to expand on my interests and concerns in ways that I never thought possible. This past year, I presented original research about climate communication at the Annual Meeting of the AMS and was invited to speak at a variety of venues in both the US and Europe.
Through writing this blog, I have also met many wonderful people working in this fascinating field. I am grateful for all their support and encouragement. Looking ahead, I am excited to continue this rewarding journey.
Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially begins at 20:02 UTC, which is 4:02 PM Eastern Daylight Time.
The astronomical seasons, as opposed to the meteorological seasons, are a product of Earth’s axial tilt – a 23.5° angle – and the movement of the planet around the sun. During the autumn months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.
Since the summer solstice in June, the arc of the sun’s apparent daily passage across the sky has been moving southward and daylight hours have been decreasing. Today, the sun appears directly overhead at the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.
With the sun sitting lower in the sky and daylight hours continuing to shorten, autumn is a season of falling temperatures. According to NOAA, the average high temperature in most US cities drops about 10°F between September and October.
Earth’s solstices and equinoxes. Image Credit: NASA
Coming ashore with sustained winds measured up to 155mph, Maria was classified as a high-end category-four hurricane. Its powerful winds sheared roofs and balconies off buildings, uprooted trees, and toppled power lines. In addition, the storm’s torrential rain unleashed devastating flooding across the island. More than 30 inches of rain was reported near Caguas, PR.
Local authorities say the entire island, home to 3.5 million people, is without power. They do not expect it to be fully restored for four to six months. This unusually lengthy timeframe is largely due to the fact that Puerto Rico is an island with rugged terrain and an electrical grid that has been crumbling for years from a lack of maintenance. The Puerto Rico Electric Power Authority, the territory’s sole provider of electricity, effectively filed for bankruptcy in July.
Before making landfall in Puerto Rico, Maria roared through the Caribbean and reached category-five strength. It battered several other islands, including the US Virgin Islands, which were still reeling from the devastation caused by Hurricane Irma less than two weeks ago. As of Thursday, the death toll from Maria stands at seventeen. But sadly, this number is expected to increase as search and rescue efforts continue across the region.
Maria 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, this has never happened before.
Hurricane Maria moves across Puerto Rico. Credit: NOAA/NASA
Our global temperature continued its upward trend last month. August 2017 marked not only the third warmest August on record but also closed out the planet’s third warmest June to August period, which is known as meteorological summer in the northern hemisphere.
According to the State of the Climate report by NOAA’s National Centers for Environmental Information, Earth’s combined average temperature for August – over both land and sea surfaces – was 61.59°F, which is 1.49°F above the 20th-century average. Only August 2015 and 2016 were warmer.
This August also marked the 392nd consecutive month with a global temperature above its long-term norm. That means the last time any month posted a below average reading was December 1984.
The three-month period of June, July, and August was also unusually warm. NOAA reports that Earth’s average temperature for the season was 1.46°F above the 20th century average of 60.1°F. That makes it the third warmest such period on record, trailing only the 2016 and 2015 seasons.
While heat dominated most of the planet this summer, some places were particularly warm, including parts of Europe, the Middle East, and the western United States. For the contiguous US as a whole, it was our fifteenth warmest summer on record.
These soaring temperatures are largely attributed to the long-term trend of human-caused climate change. ENSO-neutral conditions prevailed in August, which means there was neither an El Niño nor a La Niña in the Pacific to influence global weather patterns.
Year to date, the first eight months of 2017 were the second warmest such period of any year on record. Global temperature records date back to 1880.
This annual global summit takes place alongside the UN General Assembly and brings together leaders from a variety of sectors, including business, government, and civil society, to discuss climate change. Organized by The Climate Group since 2009, the goal of the conference and its affiliate events is to raise awareness and keeping climate action at the top of the global agenda. This year’s event will focus on the implementation of the Paris Climate Agreement and UN sustainable development goals.
Public events in support of the summit’s mission are scheduled all week around the city, from September 18-24. They range in style from panel discussions and seminars to concerts and exhibitions. For the full program of events, go to the Climate Week website.
Hurricane Irma, the 9th named storm of this Atlantic Hurricane season, made two landfalls in Florida on Sunday. First, its eye crossed Cudjoe Key, just east of Key West, as a category-4 hurricane. Then, a few hours later, it came ashore at Marco Island on the state’s Gulf Coast as a category-3 storm.
Measuring about 425 miles in diameter, Irma was wider than the Florida peninsula and its effects were felt across the entire Sunshine state. Powerful winds, heavy rain, and storm surge flooding caused catastrophic property damage in the Keys and along both coasts.
In the west, Naples, FL experienced wind gusts up to 142mph – the strongest recorded during the storm. On the east coast, gusts were clocked up to 109mph in the Miami/Fort Lauderdale area, where three high-rise construction cranes collapsed in the strong winds. The storm surge in both Biscayne Bay and Naples was about four feet above normal tide levels. In the hard hit Keys, according to FEMA, 25% of homes were completely destroyed and about 65% sustained serious damage.
Reports of toppled trees and downed power lines are widespread. The Department of Homeland Security says 15 million people lost power, making it one of the largest power outages in US history.
Moving north and shifting inland, Irma was downgraded to a tropical storm on Monday. Nevertheless, it continued to pack a powerful punch. Jacksonville, FL reported a record six-foot storm surge and the worst flooding it has seen since Hurricane Dora moved through the area in 1964.
Irma’s wrath was also felt in parts of Georgia and the Carolinas. Along the coast, storm surge flooding inundated communities from Savannah, GA to Charleston, SC. Further inland, the NWS issued its first ever tropical storm warning for the metro-Atlanta area.
Coming just sixteen days after Hurricane Harvey, Irma was the second category-4 storm to make landfall in the US this season. In 166 years of record keeping, never before have two Atlantic hurricanes of such intensity hit this country during the same year.
The death toll from this historic storm currently stands at forty-three, including five fatalities reported in Florida, three in Georgia, and one in South Carolina. The rest are from the Caribbean, where Irma hit multiple islands as a Category 5 storm late last week. Sadly, these numbers are expected to rise as search and rescue efforts continue. The entire region faces a long and expensive road to recovery ahead.
Hurricane Irma makes landfall in southern Florida as a Category-4 storm. Credit: NASA
Hurricane Irma’s final chapters have yet to be written, but the storm has already earned its place in the history books.
According to NOAA, Irma’s winds peaked at 185 mph. That means it is tied as the second strongest hurricane ever recorded in the Atlantic Basin. It shares this dubious honor with the Labor Day /Florida Keys Hurricane of 1935, Hurricane Gilbert of 1988, and Hurricane Wilma of 2005. Only Hurricane Allen in 1980 was stronger with winds clocked at 190 mph. That said, Irma now ranks as the strongest storm on record in the Atlantic outside of the Carribean Sea and the Gulf of Mexico.
Irma’s winds remained at 185 mph for 37 hours. That is the longest any storm on the planet has maintained that level of intensity. The previous record of 24 hours was set by Super Typhoon Haiyan in the northwest Pacific in 2013. Furthermore, Irma remained a Category 5 hurricane for three consecutive days, the longest such measurement since the satellite era began in 1966.
August was unusually mild in New York City this year. Of the month’s thirty-one days, nineteen posted below average readings, including an unseasonably cool 68°F on August 29. Furthermore, the month typically produces four days with readings in the 90s, but this year we only had one. In the end, the city’s mean temperature for the month was 74°F, which is 1.2°F below average.
In terms of precipitation, August was mostly dry. Overall, 3.34 inches was recorded in Central Park, marking the fourth month this year and second in a row to deliver below average rainfall. The city usually gets 4.44 inches of rain for the month.
August 2017 was unusually mild in NYC. Credit: The Weather Gamut