NASA's CloudSat Captures A Sideways Look At Fading Tropical Depression Lana

As Lana passed south of the Hawaiian Islands this past weekend, its maximum sustained winds peaked around 65 knots (74 mph), making it a Category One hurricane for a brief period before it ran into adverse atmospheric conditions that weakened the storm quickly.

By Monday, August 3, 2009 at 5 a.m. EDT, Lana's sustained winds were down to 30 knots and her minimum central pressure had gone up to 1010 millibars. Weakening winds and rising air pressure are signs of a weakening storm. Lana was located near 14.5 degrees north latitude and 162.0 west longitude and headed west near 13 knots (15 mph).

When NASA's CloudSat satellite's Cloud Profiling Radar captured a sideways look across Lana the day before, Sunday, August 2, it was still a tropical storm with high clouds higher than 14 kilometers (8.7 miles) high. CloudSat measured the highest, coldest cloud temperatures near minus 60 degrees Celsius (minus 76 degrees Fahrenheit)! Those high clouds indicated that there were some strong thunderstorms still occurring on Sunday, August 2. At the time when CloudSat swept over Lana, its maximum sustained winds were near 45 knots (52 mph) and pressure was 1008 millibars.

Less than 24 hours later, satellite data showed that Lana lacked "deep convection" – that is, rapid rising air that helps to build the powerful thunderstorms that fuel the tropical storm. Thus, Lana was re-classified as a weaker tropical depression. Forecasters believe that by August 4, Lana will start dissipating, and by August 5, she'll be a remnant low pressure area in the Central Pacific.