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Observations and thoughts on all things weather and climate

Weather Lingo: ACE

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.

Source: CSU

(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.)

Today is the Autumnal Equinox – Here’s What That Means

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

Climate Week NYC 2017

Climate Week NYC begins on Monday.

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.

Credit: The Climate Group

The Great American Solar Eclipse of 2017

The Great American Solar Eclipse will take place on Monday, August 21. It will be the first time that a total solar eclipse has been visible anywhere in the contiguous US since 1979 and the first event of its kind to travel across the entire continent since 1918.

A solar eclipse occurs when the moon passes between the Earth and the Sun, casting a shadow on the planet’s surface. Communities that are located in the large, but lighter penumbral shadow will see a partial eclipse. Those in the smaller, but darker umbral shadow will experience a total solar eclipse. Moving across the Earth, the umbral shadow creates what is known as a path of totality.

Credit: NASA

On Monday, this path will cross through fourteen states, from Oregon to South Carolina. However, every state in the Lower 48, as well as parts of Mexico and Canada, will see some degree of a partial eclipse.

This celestial event is also expected to affect the weather across the country. As the moon briefly obscures the Sun, temperatures are forecast to drop a few degrees. This, in turn, will also cause the winds to slacken.

When viewing this historic event, do not look directly at the Sun. Doing so will cause serious eye damage. Use special eclipse viewing glasses or a method of indirect viewing, such as a pinhole projector.

Path of Totality for Solar Eclipse 2017. Credit: GreatAmericanEclipse

Weather History: Ten Year Anniversary of NYC’s Strongest Tornado

Ten years ago today, an EF2 tornado roared through New York City. It was the strongest twister on record to hit the Big Apple.

NYC Tornado of 2007. Credit: NYT

With winds measured up to 135 mph, it left a trail of destruction nine miles long from Staten Island to Brooklyn with the hardest hit neighborhoods being Bay Ridge and Sunset Park. The storm toppled trees and knocked out power to more than 4,000 customers. It damaged hundreds of cars and dozens of homes, including five that had their roofs ripped off. The storm also dumped 1.91 inches of rain in just one hour, which caused flash floods and the temporary suspension of subway service during the morning commute.

Historically, tornadoes have been rare events in NYC. In recent years, however, they have been happening more frequently. Of the eleven twisters that have touched down in the city since 1950, seven have occurred since 2003.

Note: Tornado ratings moved from the Fujita Scale (F) to the Enhanced Fujita Scale (EF) in 2007.

What are the Dog Days of Summer?

The “Dog Days” of summer have arrived. This popular saying refers to what are traditionally the hottest and most oppressive days of the season.

Rooted in astronomy, the phrase is linked to Sirius, the brightest star seen from Earth. As part of the constellation Canis Major, it is known as the Dog Star.  During most of July and August, Sirius rises and sets with our Sun. Ancient Greeks and Romans believed it acted like a second Sun, adding extra heat to summer days. Today, we know that light from this distant star does not affect our weather, but the name has endured.

Varying by latitude around the globe, the so-called “Dog Days” of summer typically run from July 3 to August 11 in the United States.

Sirius, the “Dog Star”.  Credit: EarthSky/Tom Wildoner

Tropical Storm Cindy Batters Gulf Coast

Tropical Storm Cindy, the third named storm of the 2017 Atlantic Hurricane Season, made landfall between Cameron, LA and Port Arthur, TX early Thursday morning. It battered the area with heavy rain and winds measured up to 40 mph.

With rainbands spreading out across the Gulf Coast, flash floods were reported from New Orleans, LA to Pensacola, FL. The storm also downed trees and knocked out power to more than 32,000 customers across six states.

Moving inland, the storm was soon downgraded to a tropical depression. However, it still spawned a destructive tornado in Fairfield, AL. The NWS has given the twister a preliminary rating of EF-2.

The remnants of Cindy are expected to travel northeast over the next several days, unleashing even more torrential rain as it moves along.

Tropical Storm Cindy in the Gulf of Mexico. Credit: NOAA/NWS

Severe Thunderstorms: Watches vs Warnings

A severe thunderstorm is forecast for the New York City area on Monday afternoon. In addition to lightning, it could bring strong winds, heavy rain, hail, and the possibility of a tornado. Simply put, this is the type of weather that can cause property damage and loss of life. Therefore, it is important to understand the difference between the various alerts issued by the National Weather Service. They include advisories, watches, and warnings.  All should be taken seriously.

  • Advisory: Issued when significant, but not necessarily hazardous, weather conditions are likely to occur. Residents should exercise caution.
  • Watch: Issued when dangerous weather conditions are possible over the next several hours.  They generally cover a large geographic area.  Residents should be prepared to take action.
  • Warning: Issued when dangerous weather is imminent or already occurring.  They cover a smaller, more specific geographic area.  Residents should take action immediately.

Earth Muse: Art and the Environment at the Heckscher Museum

Nature has inspired artists for centuries, and today the subject seems more relevant than ever. In Earth Muse: Art and the Environment, an exhibition at The Heckscher Museum of Art, contemporary artists explore the natural world from a variety of perspectives.

Curated by Lisa Chalif, the exhibit offers a new experience of familiar landscapes and reflects on society’s impact on the environment. Artists include: Brandon Ballengée, Peter Beard, Alex Ferrone, Melissa Fleming, Winn Rea, Barbara Roux, and Michelle Stuart.

The show runs through July 30, 2017. For a full list of events during the course of the exhibition, including a gallery talk with some of the artists on April 30, please click here.

The Heckscher Museum of Art is located at 2 Prime Avenue, Huntington, NY 11743

Credit: The Heckscher Museum of Art

When to Expect the Final Freeze of the Season

Most people associate spring with flowers and mild weather. But as a transitional season, it can also produce a rollercoaster of temperatures, including serious cold spells. Wearing a short sleeved shirt one day and a parka the next, you may start to wonder when the cold will finally fade away.

The answer to that question largely depends on location. Below is a map from NOAA that shows the typical final freeze dates across the continental US. While actual weather conditions vary from year to year, the dates shown are based on climatology – a thirty-year average of temperature data.

Here in New York City, our last freeze of the season usually comes in mid-April.

Credit: NOAA