This Week’s Roundup of Interesting Weather Stories

A massive plume of dust from the Sahara Desert has made its way all the way across the Atlantic Ocean into the Caribbean and the southeast United States! Known as the Saharan Air Layer (SAL), this very dry mass of dusty air normally forms over the Sahara Desert between late spring through early fall and moves out over the North Atlantic Ocean every 3-5 days. The SAL can cover an area as large as the size of the continental United States (!), and extends between ~5,000-20,000 feet in the atmosphere.

This geocolor enhanced imagery was created by NOAA’s partners at the Cooperative Institute for Research in the Atmosphere.  Its multi-band imaging capabilities provide high-resolution visible and infrared imaging of atmospheric aerosols, such as dust and sand. Photo courtesy NOAA Environmental Visualization Laboratory.

While the dust can exacerbate respiratory issues with people with pre-existing allergies and lead to hazier days, there are positive effects from this intrusion – one of the most immediate effects you’ll notice are the more radiant sunsets. Additionally, the dry air associated with the SAL often suppresses hurricane and tropical storm development. Massive quantities of dust entering the Atlantic during the summer hurricane season create a stable layer of dry, sinking air, which prevents storms from spinning up or gaining strength.

Every year, over one hundred million tons of Saharan dust gets blown across the Atlantic, often causing spectacular sunsets like the one seen here. Photo courtesy James Spann

Raikoke Eruption

Nestled within the Kuril Islands (a volcanic archipelago made up of at least 9 islands off the eastern coast of Russia and south of the Kamchatka Peninsula) lies Raikoke. Raikoke is one of the smaller islands and is located near the center of the chain of islands, and although many of its neighbors have their share of eruptions, the Raikoke Volcano rarely erupts. In fact, the small island’s two most recent explosions occurred in 1924 and 1778! However, the dormant period ended at approximately 4:00 AM on June 22, 2019, when a massive plume of ash and volcanic gasses exploded from the 700-meter-wide crater.

Several satellites—as well as astronauts on the International Space Station—observed as a thick plume rose and then streamed east as it was pulled into the circulation of a storm in the North Pacific. Astronauts shot the photograph above on the morning of June 22, 2019. Credit NASA Earth Observatory.

After an initial surge of activity that included several distinct explosive pulses, activity subsided and strong winds spread the ash across the Pacific. By the next day, just a faint remnant of the ash remained visible to MODIS. Since ash contains sharp fragments of rock and volcanic glass, it poses a serious hazard to aircraft.
The Tokyo and Anchorage Volcanic Ash Advisory Centers have been tracking the plume closely and have issued several notes to aviators indicating that ash had reached an altitude of 13 kilometers (8 miles).  Meanwhile, data from the CALIPSO satellite indicate that parts of the plume may have reached 17 kilometers (10 miles).

A composite views from the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP shows the plume a few hours after eruption. Credit NOAA NASA.

“Radiosonde data from the region indicate a tropopause altitude of about 11 kilometers, so altitudes of 13 to 17 kilometers suggest that the eruption cloud is mostly in the stratosphere,” said Simon Carn, a volcanologist at Michigan Tech. “The persistence of large SO2 amounts over the last two days also indicates stratospheric injection.” Volcanologists watch closely for plumes that reach the stratosphere because they tend to stay aloft for longer than those that remain within the troposphere. That is why plumes that reaches the stratosphere typically have the greatest effects on aviation and climate.

Summer Has Arrived – At Least in Some Places!

We are almost a full week into the summer season, and people from Spain to France are already in the middle of a dangerous heat wave that has already crushed June temperature records in three countries (Germany, Poland, and the Czech Republic)! Local officials in France have taken precautionary measures to ensure the safety of both residents and tourists since the combination of heat and humidity is capable of causing heat-related illnesses and worsening pre-existing conditions. For example, the government has installed more than 1,000 new drinking fountains and charities have been passing out water bottles to the homeless. The city has also extended the hours at local parks and swimming pools, giving people more time to cool off. Dozens of schools have closed because they lack adequate air conditioning, and national school exams have been postponed until next week. Authorities warned early summer heat waves are especially dangerous because people have not had to adapt to the higher temperatures. Heat waves are becoming more common across Europe and are expected to double in frequency by 2050, the French  meteorological agency says.

Meanwhile, people in other places across the world were seeing snow! Two days before the official start of summer, snow fell across an Okanagan highway while wildfires were being fought nearby. According to Environment Canada, snow blanketed the Okanagan Connector on Wednesday morning, with flakes continuing to fall between Aspen Grove and Brenda Mines. The low freezing levels combined with an unstable air mass paved the way for “thundersnow” according to the weather agency.

The snow wasn’t just in Canada though! Some mountainous areas of Colorado celebrated the first day of summer with nearly two feet of snow.

While a winter weather advisory was in effect until Sunday morning, sunshine and more seasonable weather soon returned to the area. As we look forward to the coming week, NOAA NWS Climate Prediction Center has begun to highlight the concern for excessive heat for the upcoming July 4th holiday from the southeast into the midatlantic.

Heat indices will reach values of 105-110+ degrees Fahrenheit in the areas highlighted, with the hot weather potentially lingering across parts of the Southeast into the weekend. To ensure your safety this week, or during any heat wave, stay tuned to the local weather service, drink plenty of water, and wear appropriate clothing. 

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