Weather Lingo: Lake Effect Snow

Winter snowstorms have a variety of names, such as Nor’easters and Alberta Clippers. It all depends on where and how they develop. In the Great Lakes region of the US, the vast bodies of fresh water influence the weather and create something known as lake effect snow.

Lake-effect snowstorms, according to NOAA, develop when cold air blows across the warmer waters of a large unfrozen lake. The bottom layer of the air mass is warmed by the water and allows it to evaporate moisture, which forms clouds. When the air mass reaches the leeward side of the lake its temperature drops again, because the land is cooler than the water. This releases the water vapor as precipitation and enormous amounts of snow can accumulate. The effect is enhanced if the air is lifted upward by local topography.

With the clouds typically forming in bands, the snowfall is highly localized. Some places can see the snow come down at a rate of more than 5 inches per hour, while nearby, others will only get a dusting. The shape of the lake and the prevailing wind direction help to determine the size and orientation of these bands.

Fetch, the distance wind travels over a body of water, also plays a key role. A fetch of more than 60 miles is needed to produce lake effect snow. In general, the larger the fetch, the greater the amount of precipitation, as more moisture can be picked up by the moving air.

The impressive depths of the Great Lakes allow them to remain unfrozen longer into the winter season than more shallow bodies of water. This combined with their massive surface area, make them excellent producers of  lake effect snow. With northwesterly winds prevailing in the region, communities along the southeastern shores of the lakes are often referred to as being in the “Snowbelt.”

Credit: NOAA

November 2018: Seventh Wettest and Fourth Snowiest on Record in NYC

November was unusually cold in New York City this year. Highs ranged from a relatively balmy 72°F to a chilly 28°F. But, with 22 days posting below average readings, the cold won out in the end. The city’s mean temperature for the month was 44.5°F, which is 3.3°F below average.

In terms of precipitation, November was a month for the record books. The city received 7.62 inches of rain in Central Park, making it the seventh wettest November on recordSnowfall was also abundant, despite the fact that it all fell during a single storm. Central Park reported 6.4 inches of snow, setting set a new daily record for the date. It was also the earliest 6-inch one-day snowfall on record for the city and the largest one-day November snowfall since 1882. Moreover, that one snow event was enough to make this November the city’s fourth snowiest on record.

New York City, on average, sees 4.02 inches or rain and 0.3 inches of snow for the entire month of November.

 

Destructive 2018 Atlantic Hurricane Season Comes to a Close

The 2018 Atlantic Hurricane Season officially ends today.  It marked the third year in a row with above average activity.

According to NOAA, there were fifteen named storms this season. Of these, eight developed into hurricanes and two 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 season was the first since 2008 to have four named storms active at the same time – Florence, Helene, Isaac, and Joyce.

Officially running from June 1 to November 30, the season got off to an early start with Tropical Storm Alberto forming in May. This was the fourth consecutive year to see a pre-season storm develop. The biggest names of the season, however, were Florence and Michael.

In September, Hurricane Florence made landfall in North Carolina and dumped a massive amount of rain on the area. Traveling inland, it caused catastrophic flooding in parts of both North and South Carolina. In Elizabethtown, NC, 35.93 inches of rain was reported, making the wettest tropical cyclone on record for the state. For the contiguous US, it ranked as the eighth wettest.

A few weeks later, Hurricane Michael hit the Florida panhandle as a cat-4 storm. With winds measured up to 155mph, it was the strongest storm on record to strike the region and the third strongest storm to make landfall in the continental US. Its powerful winds and storm surge flooding decimated the Panama City area.

Causing so much destruction, both Florence and Michel 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 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.

Overall, the season is reported to have claimed the lives of 154 people and caused an estimated $33 billion in damages. The official tally from NOAA will not be available until early 2019.

Source: NOAA

Fourth National Climate Assessment: A Dire Forecast for US if Action is Not Taken

The Fourth National Climate Assessment (NCA4) report was released rather inauspiciously last week on the day after Thanksgiving – a traditionally slow news day. Nevertheless, the report is out and it clearly states, “the evidence of human-caused climate change is overwhelming and continues to strengthen.”

The massive report, considered volume two of NCA4, builds on the Climate Science Special Report issued last year. It gives a detailed account of what the impacts will be across the country and how the worst effects could be avoided.

The U.S average temperature, according to the report, has increased by 1.8°F since 1901, and is projected to continue rising. Over the next few decades, temperatures are projected to rise another 2.5°F.  By the end of the century, our average temperature could soar by as much as 11.9°F if greenhouse gas emissions continue to increase unchecked.

The report also looks at the long-term economic impacts for the country as the average temperature continues to climb. Costs from rising sea levels could reach as high as $118 billion and the projected total for damaged infrastructure is $32 billion. This is in addition to the reduced agricultural productivity expected from high heat and extended drought events. Overall, the report warns that if significant steps are not taken, climate change could slash the US economy’s GDP by 10% by the end of the century.

Not all doom and gloom, the report’s authors emphasize, “These impacts are projected to intensify—but how much they intensify will depend on actions taken to reduce global greenhouse gas emissions and to adapt to the risks from climate change now and in the coming decades.”

While similar in theme to the IPCC report from the UN, this assessment focuses solely on the United States. Emphasizing the fact that rising temperatures will affect different parts of our vast country in different ways, the NCA breaks the nation down into specific regions. It details the current and future impacts of climate change in each one:

The report also includes a supplemental set of State Climate Summaries that give a clear idea of what to expect in each of the 50 states as well as the US territories.

Mandated by Congress under the Global Change Research Act, this exhaustive 1600 page peer-reviewed report was produced by 300 scientists from 13 different government agencies. Published every four years, it is considered this country’s most authoritative statement on climate change.

Annual average temperatures across the United States are projected to increase over this century, with greater changes at higher latitudes as compared to lower latitudes, and greater changes under a higher scenario (RCP8.5; right) than under a lower one (RCP4.5; left). This figure shows projected differences in annual average temperatures for mid-century (2036–2065; top) and end of century (2071–2100; bottom) relative to the near present (1986–2015). Image credit: Fourth NCA, Vol II, figure 2.4.

Cold and Windy Conditions Expected for the Macy’s Thanksgiving Day Parade in NYC

The Macy’s Thanksgiving Day Parade is a long-standing holiday tradition in New York City.  For 92 years, it has marched rain or shine. Nevertheless, the weather has been a factor in the event several times over the years.

Famous for its giant character balloons, high winds are the main weather challenge for the parade. According to city guidelines, the multi-story balloons cannot fly if there are sustained winds in excess of 23 mph or gusts higher than 34 mph. These regulations were put in place following a 1997 incident where gusty winds sent the “Cat in the Hat” balloon careening into a light post, which caused debris to fall on and injure spectators.

The only time the balloons were grounded for the entire parade was in 1971, when torrential rain swept across the city. In 1989, a snowstorm brought the Big Apple a white Thanksgiving and the “Snoopy” and “Bugs Bunny” balloons had to be pulled from the parade because of damage from high winds.

This year, the wind could potentially be a problem again. Gusts are forecast to be between 20 and 30 mph during the parade hours. Temperatures are also expected to be a challenge. They are forecast to hover near record cold levels, with readings not getting out of the 20s. When the wind chill is factored  in, it will feel more like the single digits to low teens. This extreme cold will be more than a nuisance for holiday revelers, it will be dangerous. Frostbite is a real threat for anyone with exposed skin. So, bundle up if you are planning to be outside along the parade route.

Marching from West 77th Street to West 34th Street in Manhattan, the 92nd Annual Macy’s Thanksgiving Day Parade is scheduled to begin at 9 AM on Thursday morning.

Happy Thanksgiving!

Paddington Bear Balloon floats down 6th Ave in the Macy’s Thanksgiving Day Parade. Credit: Macy’s

October 2018: Earth’s Second Warmest October on Record

Our global temperature continued its upward trend last month with October 2018 marking the second warmest October ever recorded on this planet. Only October 2015 was warmer.

According to the State of the Climate report by NOAA’s National Centers for Environmental Information, Earth’s combined average temperature for the month – over both land and sea surfaces – was 58.65°F, which is 1.55°F above the 20th-century average. October also marked the 406th 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.

While heat dominated most of the planet this October, some places were particularly warm. These included eastern Russia, northern Australia, Alaska, and most of the east coast of the United States. These soaring temperatures are largely attributed to the long-term trend of human-caused climate change. ENSO-neutral conditions prevailed in October, which means there was neither a warm El Niño nor a cool La Niña in the Pacific to influence global weather patterns.

For many people in the central US, however, October was relatively cold. These chilly temperatures, driven by a deep dip in the jet stream, helped cool the national average to 0.3°F below normal for the month. To put this disparity into context, consider that the contiguous United States constitutes less than 2% of the total surface of the Earth. This detail highlights the fact that climate change is a complex global phenomenon that involves much more than the short-term weather that is happening in our own backyards.

Year to date, the first ten months of 2018 were the fourth warmest such period of any year on record. Global temperature records date back to 1880.

October 2018 was the second warmest October ever recorded on this planet. Credit: NOAA

First Snow of the Season in NYC Breaks Several Records

New York City saw its first snow of the season on Thursday and it was one for the record books.

According to the NWS, 6.4 inches of snow was measured in Central Park, setting a new daily record for the date. The previous record of 1 inch had been in place since 1906. It was also the earliest 6-inch one-day snowfall on record for the city and the largest one-day November snowfall since 1882.

These superlatives came as a bit of a surprise. The forecast originally called for a wintry mix with only a dusting of snow at the onset. However, the temperature was colder than expected and the snow hung on longer. This was largely the result of an area of high pressure to the north being stronger than forecast and therefore able to funnel air toward the city that was colder than anticipated. Closer to home, evaporative cooling also played a part.  The air near the surface was very dry as the storm moved into the area. This allowed some of the snow to evaporate as it fell, cooling the air even further. As result, the change over to rain was delayed by several hours.

While pretty to see, the snow caused a number of problems around the city. Widespread travel delays and falling trees were reported across the five boroughs. As it is only mid-November, many of the trees still had their leaves. The combination of the heavy, wet, snow piling up on the foliage, weighing down the branches, and high winds was too much to bear for many trees, even the healthily ones. Many fell across streets and sidewalks as well as on top of parked cars. The city’s Parks Department has reported receiving over 2000 service requests for downed trees and dangling limbs.

This storm clearly outperformed expectations and caught the city off-guard. On average, New York City sees 0.3 inches of snow for the entire month of November.

Record breaking November snowfall topples trees in NYC. Credit: Melissa Fleming

Deadly Wildfires Blaze in Northern and Southern California

California, once again, is ablaze with wildfires.

As of Tuesday, three major wildfires – defined as 100 acres or more – are burning in the Golden State.  Collectively, according to National Interagency Fire Center (NIFC), they have burned more than 200,000 acres and claimed the lives of 44 people. In terms of property damage, close to 8,000 homes and business have been destroyed and at least another 50,000 are at risk.

Sweeping through the wooded northern California town of Paradise, the death toll from the Camp Fire currently stands at 42. That makes it the deadliest wildfire in the state’s history. It surpasses the Griffith Park Fire, which killed 29 people in 1933. Sadly, with 200 people listed as missing, the death toll from this fire is expected to climb even higher in the coming days. It is currently only 30% contained.

At the southern end of the state, the Woolsey and Hill Fires have forced massive evacuations. Raging west of Los Angeles near Malibu and only 30% contained, the Woolsey Fire has charred more than 93,000 acres and destroyed more than 400 structures. The Hill Fire, currently at 85% containment, has scorched upwards of 4,500 acres.

Air quality issues are another concern with these wildfires. Well outside of the burn areas, many people are wearing masks to protect themselves from the smoke and ash carried in the wind.

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, the state saw increased precipitation over the past two winters that spurred explosive plant growth. Then during this past summer, which was unusually dry, all that vegetation turned to tinder.

Making matters worse, the region’s seasonal winds, known as the Diablo Winds in the north and the Santa Ana Winds in the south, kicked into high gear. Flowing from east to west, downslope from the mountains toward the coast, these winds warm from compression and dry out vegetation even further. They also fan the flames of any fire already burning and can cause it to spread very quickly.

To date, according to NIFC, 1.5 million acres in California have been burned by wildfires in 2018. That number, however, is expected to go up as these fires continue to spread.

The Camp Fire in Northern California seen from space. Credit: NASA

Film Looks at Climate Change as a National Security Issue

Today is Veterans Day, a day to honor the men and women who have served in the armed forces. As such, it seems an appropriate time to highlight “The Age of Consequences” – a film that looks at climate change through the lens of national security and global stability.

Directed by Jared Scott, the film features a number of interviews with members of the military. While quick to point out that climate change is not the sole cause of any particular conflict, they discuss how it acts as a “threat multiplier” or “accelerant of instability”.

More specifically, the film shows how water and food shortages, drought, extreme weather, and sea-level rise have stressed social tensions to the point of armed conflict and/or mass migration in some of the more volatile regions of the world. Released in 2016, the war in Syria, the rise of ISIS, and the European refugee crisis are prominently featured.

Watch the trailer here:

How the Santa Ana Winds Help Wildfires Spread

The Santa Ana winds are notorious for exacerbating wildfires in southern California.

These strong winds blow warm, dry air across the region at different times of the year, but mainly occur in the late autumn. They form when a large pressure difference builds up between the Great Basin – a desert that covers most of Nevada and parts of Utah – and the coastal region around Los Angeles. This pressure gradient funnels air downhill and through the passes of the San Gabriel and San Bernardino mountains toward the Pacific. Squeezing through these narrow canyons, the wind is forced to speed up. The Santa Anas, according to the NWS, can easily exceed 40 mph.

Originating in the high desert, the air starts off cool and dry. But as it travels downslope, the air compresses and warms. In fact, it warms about 5°F for every 1000 feet it descends. This dries out the region’s vegetation, leaving it susceptible to any type of spark. The fast-moving winds then fan the flames of any wildfires that ignite.

The Santa Ana winds are named for Santa Ana Canyon in Orange County, CA.

Credit: NOAA/NWS