Information on cloud top heights at different stages in the life cycle of
the rapidly intensifying Hurricane Wilma may prove useful for evaluating
the ability of numerical weather models to predict the intensity changes
of hurricanes. NASA's Multi-angle Imaging SpectroRadiometer (MISR)
acquired this sequence of images and cloud-top height observations for
Hurricane Wilma as it progressed across the Caribbean in October 2005.
Each pair in the sequence has a photo-like view of the storm on the left
and a matching color-coded image of cloud-top height on the right.
Cloud-top heights range from 0 (purple) to 18 (red) kilometers altitude.
Areas where cloud heights could not be determined are shown in dark gray.
The pair on the left show Wilma on Tuesday, October 18, when Hurricane
watches were posted for Cuba and Mexico. The central pair shows the eye
of Hurricane Wilma just hours before the storm began to cross the Yucatan
Peninsula on Friday, October 21. At that time, Wilma was a powerful
Category 4 Hurricane on the Saffir-Simpson scale, and had a minimum
recorded central pressure of 930 millibars. Hurricane Wilma surged from
tropical storm to Category 5 hurricane status in record time, but the
storm slowed and weakened considerably after battering Mexico's Yucatan
Peninsula and the Caribbean. The right-hand image pair displays the
eastern edges of a weakened Wilma, when Wilma had been reduced to
Category 2 status and was just starting to reach southern Florida on the
morning of Sunday, October 23. Wilma gathered speed and strengthened on
Sunday night, crossing Florida as a Category 3 storm on Monday, October
24.
On the 18th, Wilma looked a bit ragged. Its eye is located at the center
of the left edge, and its outer bands of clouds appear to be dominated by
a rather loose collection of thunderstorms. In the photo-like images,
these look like areas of "boiling clouds," and in the cloud-height image,
these appear as orange blobs, sometimes topped with pinkish-red. On
October 21 (center), when Wilma was a Category 4 storm, cloud-top height
on the eastern side of the storm near the eye reached 18 kilometers in
altitude, with lower heights on the western side. The image from the 23rd
shows the eastern edge of Wilma as it approached Florida (upper right)
and Cuba (center right).
MISR has nine different cameras which view the Earth from a variety of
angles. Shifts in the clouds' apparent position from one camera's
perspective to another's allows MISR to measure the height of the
cloud-tops. MISR scientists have programmed computers to compare the
different views, identify features that appear to shift from view to view,
and use that information to calculate cloud height automatically. The
height fields pictured have not been corrected for the effects of cloud
motion. Wind-corrected heights (which have higher accuracy but sparser
spatial coverage) are within about 1 kilometer of the heights shown here.
The Multi-angle Imaging SpectroRadiometer observes the daylit Earth
continuously, viewing the entire globe between 82° north and 82° south
latitude every nine days. Each image covers an area of about 380
kilometers by 1830 kilometers. The data products were generated from a
portion of the imagery acquired during Terra orbits 31037, 31081 and
31110, and utilize data from within blocks 68-83 within World Reference
System-2 paths 13, 16 and 18, respectively.
MISR was built and is managed by NASA's Jet Propulsion Laboratory,
Pasadena, CA, for NASA's Science Mission Directorate, Washington, DC. The
Terra satellite is managed by NASA's Goddard Space Flight Center,
Greenbelt, MD. JPL is managed for NASA by the California Institute of
Technology.