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NASA 'Bisects' Tropical Storm Amanda

By Stephanie Pappas, Senior Writer
6/2/2014 8:30:33 AM

NASA has sliced and diced the first named storm of the 2014 hurricane season, capturing a bisected view of Hurricane Amanda at its strongest.

Amanda formed over Memorial Day weekend and reached Category 4 hurricane strength, with winds reaching 155 mph (250 km/h). Those wind speeds made the storm the strongest May hurricane ever seen. Fortunately, Amanda remained far out to sea in the eastern Pacific and never threatened land. After turning north over cooler waters this week, the storm weakened, its winds receding to tropical-storm level. On May 29, Amanda was a mere tropical depression, with maximum sustained winds of only about 35 mph (56 km/h), according to the National Hurricane Center.

NASA's CloudSat satellite caught a detailed glimpse of the storm when it was still a hurricane. On May 25, the storm's winds were blowing at around 150 mph (240 km/h) when the satellite passed over about 25 miles (40 km) from the center of the storm. [Hurricanes from Above: See Nature's Biggest Storms]

The first named storm of the 2014 Eastern Pacific hurricane season, Amanda, is seen as a Category 4 hurricane on May 25, 2014. Credit: NASA image courtesy Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team at NASA GSFC

Inside a hurricane

CloudSat uses ultrasensitive radar to measure clouds and their moisture. In Amanda's eastern half, the satellite detected moderate and heavy-moderate precipitation deep in the storm, below the altitude at which precipitation turns from solid into liquid. The profile of the storm revealed an expansive, anvil-shaped cloud extending northward, as well as smaller cumulus clouds underneath, NASA reported today (May 29).

Tropical storms, hurricanes and typhoons form when warm, moist ocean air rises, creating an area of low pressure where cooler air can rush in, and then be warmed and rise in turn. Amanda's strength was at its greatest on May 25, when the storm was over warm equatorial waters. As the storm tracked north, it traveled over cooler waters that could no longer fuel its fury. Shear winds also contributed to weakening the storm.

Tropical storms are defined as storms in which winds reach 39 mph (63 km/h). To qualify as a hurricane, a storm must have wind speeds of 74 mph (119 km/h) or more.

CloudSat's profile of Hurricane Amanda on May 25, 2014, showing precipitation and an anvil-shaped cloud. Credit: Colorado State University

Hurricane season 2014

Amanda was the first named storm of the 2014 eastern Pacific hurricane season, which begins May 15 and ends Nov. 30. Atlantic hurricane season starts shortly thereafter, on June 1, and also runs through Nov. 30.

Storms are named based on an alphabetical list that changes every year. (There are six lists that meteorologists rotate, but the names of extremely deadly or destructive storms are retired, leading to tweaks in the lists.)

The 2013 Atlantic hurricane season was the quietest since 1982, according to AccuWeather. The weather agency predicts a relatively calm 2014 hurricane season as well, particularly if a robust El Niño weather pattern sets up and increases wind shears across the Atlantic, which tends to decrease the number of tropical storms.

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