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Cyclone Debbie Made Landfall in Australia

Cyclone Debbie approaching landfall in northeastern Australia on March 28, 2017. Image Credit: SSEC/Google Earth

 
A powerful cyclone came ashore on Australia’s northeastern coast on Tuesday, the most intense storm to strike the country in several years. Cyclone Debbie made landfall on the Queensland coast south of the town of Bowen, which lies about 300 miles southeast of Cairns. The storm hit land with winds in excess of 120 mph, which would make it the equivalent of a major hurricane on the Saffir-Simpson Hurricane Wind Scale used in the United States. Debbie stands out as an intense storm in an unusually quiet cyclone season in this part of the world. A storm of this magnitude hasn’t struck the country since Cyclone Yasi made landfall south of Cairns in February 2011.

Cyclone Debbie made landfall in an area that’s home to nearly 100,000 people, including the towns of Mackay and Bowen. Media reports indicate that local emergency response crews were worried that the town of Bowen, which found itself in the cyclone’s eyewall, would sustain substantial damage from the storm, as many of the town’s homes and businesses were built before more stringent construction standards were introduced in the 1980s [PDF]. The town of Mackay and its suburbs saw less intense winds from the cyclone, but residents along the coast were ordered to evacuate in anticipation of a dangerous storm surge.

Early reports of damage are few and far between, due to power and communications outages with the hardest-hit areas. Videos published online by storm chasers in the area show damage to trees and buildings as the storm came ashore.

An infrared satellite image of Cyclone Debbie on March 28, 2017. Warmer colors indicate higher cloud tops, associated with intense convection in the cyclone. Image Credit: SSEC

 
Cyclone Debbie formed under ideal conditions that allowed the storm to thrive. Sea surface temperatures off the northeastern Australian coast were around 80°F, there was ample tropical moisture to feed the storm, and the cyclone encountered almost no wind shear in the upper levels of the atmosphere to disrupt its development. The storm took advantage of the favorable conditions and underwent rapid intensification as it neared the Australian coast early on Tuesday morning local time. WeatherBELL’s Ryan Maue reported that satellite estimates pegged the cyclone’s peak winds at more than 140 mph at the storm’s strongest point. The storm weakened somewhat as it approached the coast due to an eyewall replacement cycle, a common process in strong tropical cyclones in which a new eyewall develops and chokes off the old eyewall, temporarily weakening the storm until the process is completed.

Tropical cyclones in the southwestern Pacific Ocean are most common between the months of November and April, though cyclones are possible at any point in the year. The peak of the season coincides with the heat of the summer toward the beginning of the year. Australia’s northern coast is vulnerable to major tropical cyclones. The last significant cyclone to strike this region of Queensland was Cyclone Marcia in 2015; the storm caused significant damage but thankfully resulted in no fatalities. Debbie threatens to be the strongest storm to make landfall since Yasi back in February 2011. Cyclone Yasi reached shore with winds of 155 mph, causing billions of dollars in damage.

The term “tropical cyclone” applies to any low-pressure system that develops over the ocean and feeds its energy off of thunderstorms near the center of the system rather than winds high in the atmosphere. Strong tropical cyclones are called “hurricanes” in the Atlantic and eastern Pacific Ocean, “typhoons” in the northwestern Pacific Ocean, and simply “cyclones” everywhere else in the world, including around Australia. All of the storms are structurally the same—the only difference is that they’re classified a little differently based on wind speeds.

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Weather Watch
Thanks to Desert Dust, Eastern Europe Is Covered in Orange Snow
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Certain areas of Eastern Europe are starting to look a bit like Mars. Over the last few days, snowy places like Sochi, Russia have experienced an unusual snowfall that coated mountains in orange powder, according to the BBC.

The orange snow was the result of winds blowing sand from the Sahara east to places like Moldova, Romania, Bulgaria, Ukraine, and Russia. The sand mixes with precipitation to form orange-tinted snow. According to the BBC, the phenomenon occurs semi-regularly, turning snow orange about once every five years, but this year is especially sandy. As a result, skiers are navigating slopes that look like they're from a different world, as you can see in the video below from The Guardian.

The Sahara rarely gets snow, but when it does, the landscape can look somewhat similar, as you can see in this image of the Atlas mountains in Morocco.

Instagram is currently filled with photos and videos from Eastern Europe featuring the odd-looking snow. Check out a few samples below.

[h/t BBC]

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Weather Watch
What Is Thundersnow?
Jessica Kourkounis, Getty Images
Jessica Kourkounis, Getty Images

The northeastern United States is dealing with its second major nor'easter in a week, with rain and heavy snow—and the associated power outages—cutting a path across the Mid-Atlantic and New England. But news of the adverse impacts of the snowstorm is being accompanied by an unusual buzzword: thundersnow. Thundersnow occurs during a thunderstorm that produces snow instead of rain. The mechanisms that produce rainy thunderstorms and snowy thunderstorms are largely the same, even if the air temperature is below freezing.

A band of snow can become strong enough to produce lightning through two processes known as convection and forcing. Convection occurs when an area of warm air quickly rises through cooler air above it. Convective snow is most common during lake effect snow events like those you’d find on Lake Ontario or Lake Erie, since the process requires extreme vertical temperature gradients that can result from bitterly cold air flowing over a warm body of water.

Forcing is slightly different. A strengthening low-pressure system involves fast, dynamic changes in the atmosphere, especially when one of these storm systems quickly gains strength. Such a fast-developing storm can cause large amounts of lift in the atmosphere, a process that forces air to swiftly rise like you’d see during convection. This creates intense bands of snow that can grow so strong that they produce thunder and lightning. This process is responsible for the thundersnow that occurs during blizzards and nor’easters, those powerful storms that regularly hit the eastern coast of the U.S. during the winter. Thundersnow can be pretty exciting—just ask The Weather Channel's Jim Cantore:

The name “thundersnow” can be a bit misleading. One of the most enjoyable things about a snowfall is how silent it is outside when there’s a thick blanket of snow on the ground. Snow absorbs sound waves so efficiently that you can usually only hear ambient noises immediately around where you’re standing. Snow muffles the sound of thunder for the same reason. Thunder that might be audible for many miles during a rainy thunderstorm might only be audible for a few thousand feet away from where the lightning struck. Unless the lightning strikes very close to where you are, you might only see a bright flash during thundersnow without ever hearing the thunder.

While thundersnow is a fascinating phenomenon to encounter, it does involve lightning, after all, and it’s just as dangerous as any other lightning bolt you’d see in a rainy thunderstorm. If you’re ever lucky enough to experience thundersnow, the event is best enjoyed indoors and out of harm’s way.

This piece originally ran in 2017.

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