Northern California is ablaze with wildfires.
As of Thursday, according to CalFire, 22 wildfires are burning in the Golden State. They have scorched over 190,000 acres and forced the evacuation of entire neighborhoods. Officials say at least 26 people have been killed and more than 400 are missing. In terms of property damage, they conservatively estimate that 3,500 homes and structures have been destroyed.
The smoke and ash from these fires are also causing widespread air quality issues. In the Bay Area, well outside of the burn zone, air quality reached historically poor levels this week.
These huge fires are largely the result of climate whiplash. California has distinct wet and dry seasons, but they have been extreme recently. After years of drought, this winter brought the state record amounts of precipitation that spurred explosive new plant growth. Then during the summer, which was the state’s warmest on record and unusually dry, all that vegetation turned to tinder.
Making matters worse, the region’s seasonal winds known as the Diablo Winds began blowing over the weekend. They reportedly reached speeds as high as 70mph in some areas. Blowing east to west, these winds warm from compression as they flow downslope from the mountains towards the coast and dry out vegetation even further. They also fan the flames of any fire already burning and can cause it to spread very quickly.
The Diablo Winds are essentially the same type of air current as the famous Santa Ana winds in southern California. They only really differ in location and name. The Diablo Winds are named for Mount Diablo in the East Bay area and the Santa Ana Winds are the namesake of Santa Ana Canyon in Orange County.
Wildfires are not unusual in California, but this outbreak is considered one of the worst in state history. The exact cause of the fires is still unknown.
Wildfire burns near Glen Ellen, CA. Credit: The SF Chronicle
Hurricane Nate, the 14th named storm of the 2017 Atlantic Hurricane season, made two landfalls along the US Gulf Coast this weekend. The first was near the mouth of the Mississippi River in Louisiana and the second was near Biloxi, Mississippi.
Coming ashore with 85mph winds, this category-1 hurricane generated a significant storm surge that swamped parts of the region from Louisiana to the Florida Panhandle. One of the hardest hit areas was Pascagoula, MS where a storm surge of 6.3 feet was reported. The storm also downed trees and caused widespread power outages.
Moving inland, Nate was soon downgraded to a tropical depression. However, it still spawned a number of destructive tornados from Alabama to North Carolina. They ranged in strength from EF-0 to EF-2.
Nate was the first hurricane to make landfall in Mississippi since Katrina in 2005.
Credit: NOAA/NASA GOES
There are a number of key indicators, beyond our rising global temperature, that show Earth’s climate is changing. One of these is Arctic sea ice.
Measured via satellite since the late 1970’s, the extent and thickness of sea ice tend to vary from year to year but both have been in an overall decline for decades. According to NASA, the melt season in the Arctic has increased by 37 days since 1979.
Sea ice extent, the area of ocean with at least 15% sea ice, has a strong seasonal cycle. It typically peaks in March as winter ends and then declines during the summer, reaching a minimum in September. In March 2017, it hit a record low maximum for the third year in a row. The record minimum occurred in September 2012.
According to the National Snow and Ice Data Center, the average age of Arctic sea ice is also changing. Thick multi-year ice – the ice that lasts through at least one melt season – has decreased 11% per decade since the satellite era began. That means there is more first-year ice, which tends to be thin and brittle. This is troublesome because it is more vulnerable to warming temperatures and wave action.
Sea ice is frozen ocean water. It forms, grows, and melts in the ocean. In contrast to land ice (glaciers), it does not contribute to sea level rise. However, as it melts it creates a global warming feedback loop. Ice is lighter in color and reflects more sunlight than dark ocean water. So, as more ocean water is exposed, more of the sun’s energy is absorbed. This drives temperatures up even further and causes more ice to melt.
The Arctic is now warming twice as fast as the rest of the planet – a phenomenon known as “Arctic amplification.” At this rate, scientists expect the region to be ice-free in summer by the 2030s.
September 2017 felt like a temperature roller coaster in New York City. Highs ranged from an unseasonably cool 66°F to a record warm 91°F. But with eighteen of the month’s thirty days posting above average readings, the heat won out in the end. The city’s mean temperature for September was 70.5°F, which 2.5°F above average.
In terms of precipitation, the month was mostly dry. Only 2.0 inches of rain was measured in Central Park, marking the third month in a row to deliver below average rainfall. The city usually gets 4.28 inches of rain in September.
Credit: The Weather Gamut
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 season officially changed to autumn over the weekend, but it felt more like summer in New York City.
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.
As always, thank you for reading!
Credit: Maria Elena
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
Hurricane Maria, the 13th named storm of this Atlantic Hurricane season, made landfall in Yabucoa, Puerto Rico on Wednesday morning. It was the strongest storm to hit the US Territory since 1928.
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.