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Category Archives: Severe Weather
How does hail get its shape?
Hail is precipitation in the form of balls or chunks of ice.
Hailstones begin as small ice particles that grow primarily by accretion; to grow large, they require abundant water droplets. As the hailstone moves up and down through a storm, it collides with water droplets and ice crystals, growing larger with each collision. Hailstones can be smaller than peas or as large as oranges and grapefruits. The small hailstones are roughly spherical in shape, while large ones can take on jagged shapes. Continue reading
Has there been a sudden stratospheric warming this year?
The stratosphere, which begins approximately 6 miles above the cold poles and 10 miles above the tropics, is where the temperature increases with altitude. Temperatures increase because ozone molecules in the stratospheric ozone layer absorb solar ultraviolet energy within the stratosphere. Air flow in the stratosphere is much less turbulent than in the troposphere. For this reason, jet aircraft pilots like to cruise at stratospheric altitudes so the flight is less bumpy. In polar regions, the top of the stratosphere extends upward to around 30 miles.
The polar vortex is a band of strong winds high in the atmosphere that spins counterclockwise around the North Pole. At the southern edge of the vortex is the polar jet stream, which separates warm air to its south from increasingly colder air to its north. Continue reading
Category: Phenomena, Severe Weather
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Are drones used in meteorology?
Unmanned aerial vehicles, or UAVs, have been used to make weather observations for half a century. Over the past decade there has been a wider application of drones in meteorology due in part to technological developments.
Drones can provide critical research observations of weather systems. For about a decade, NOAA has partnered with NASA to fly the Global Hawk high-altitude unmanned aircraft to observe and study how hurricanes form and intensify. High-resolution photographs from low-flying drones are used to understand and document wind and flood damage associated with severe weather. They also help to better assess storm intensity based on the damage. Continue reading
What is the National Climate Assessment?
The U.S. National Climate Assessment is mandated by the Global Change Research Act of 1990. The assessment is conducted about every four years and is an authoritative scientific analysis of climate change risks, impacts and responses in the U.S.
The nation this month completed the Fifth National Climate Assessment, or NCA5. The National Oceanic and Atmospheric Administration is the administrative agency for NCA5 and certifies that the report meets Information Quality Act and Evidence Act standards. The assessment is an extensive process that includes internal and external review from federal agencies, the general public and external peer review by a panel of experts. Continue reading
Category: Climate, History, Seasons, Severe Weather
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What is a gale wind?
A gale is a strong, sustained wind impacting maritime weather.
