Categorized | Environment, Featured, Sci-Tech

Hurricane Season 2009: Blanca (Eastern Pacific)

Video courtesy of NOAA-NASA GOES Project

Blanca Moving Out to Sea and Into Cooler Waters

By Rob Gutro with Hal Pierce, NASA’s Goddard Space Flight Center

Tropical Storm Blanca has made the move away from the western Mexican coast, and is heading out to sea in a west-northwest direction near 9 mph. Blanca’s course will take her further out to sea and into cooler waters which will weaken the storm.

The TRMM satellite shows heavy rain, falling at about 2 inches per hour in Tropical Storm Blanca. Credit: NASA/SSAI, Hal Pierce

The TRMM satellite shows heavy rain, falling at about 2 inches per hour in Tropical Storm Blanca. Credit: NASA/SSAI, Hal Pierce

As a tropical storm, Blanca is generating a good amount of rainfall over the open ocean. NASA and the Japanese Space Agency’s Tropical Rainfall Measuring Mission (TRMM) Satellite acts like a “rain gauge in space” and can estimate rainfall in storms. On July 6 at 12:09 a.m. EDT (0409 UTC) TRMM flew directly above Blanca and captured an image of rainfall happening throughout the storm.

Creating an image of TRMM’s rainfall in a storm takes some doing. Hal Pierce at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where TRMM is managed, assembles images from various TRMM instruments.

To create an image of rainfall analysis, Hal uses data from the TRMM Microwave Imager and Precipitation Radar instruments and overlays it on a TRMM infrared image. The analysis shows heavy rainfall of over 50 millimeters per hour (~2 inches) in an area east of the center of circulation.

Meanwhile, an instrument on another NASA satellite analyzed cloud temperatures. The Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite captured an infrared image of Blanca on July 6 at 5:17 a.m. EDT (0917 UTC). In the AIRS infrared image, Blanca’s clouds appear to resemble a comma-shape.

The AIRS infrared images are false-colored to show Blanca’s highest, cold clouds in purple and blue. Those temperatures are as cold as or colder than 220 degrees Kelvin or minus 63 degrees Fahrenheit (F). The blue areas are around 240 degrees Kelvin, or minus 27F. The colder the clouds are, the higher they are, and the more powerful the thunderstorms are that make up the tropical storm.

During the morning hours of July 7, Blanca had sustained winds near 50 mph with higher gusts. Because she’s moving into cooler waters, and it takes water temperatures of 80 F to maintain a tropical cyclone, Blanca is expected to weaken over the next two days. At 5 a.m. EDT on July 7, Blanca was about 425 miles southwest of the southern tip of Baja California. That puts the center of the storm near latitude 18.5 north and 114.5 west.

Blanca started out as an area of low pressure southwest of Mexico was upgraded to tropical storm Blanca during the morning of July 6. Blanca is the second named tropical storm in the eastern Pacific this hurricane season and isn’t expected to become a hurricane.

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