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NASA Satellites Record a Month for the Hurricane
History Books |
09.06.05
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Image to right: Five named tropical cyclones in the month of
July 2005 broke the record for the highest number of storms during
that month. Cindy (top left) made landfall in Louisiana. Dennis (top
center) hit Cuba and landed in the Florida Panhandle. Emily (top
right) landed in northeastern Mexico. Franklin (bottom left) swept
by the Bahamas and into the north Atlantic Ocean. Gert made landfall
on Mexico's east coast. Click on image to enlarge. Credit:
NASA (4 images) and NOAA (1 image)
Satellites from NASA and the National Oceanic and Atmospheric
Administration (NOAA) had a busy month in July following the five
named storms in July: Cindy, Dennis, Emily, Franklin and Gert.
During July, 2005 NASA and NOAA investigators flew sophisticated
research aircraft within and above several of these storms, as part
of NASA's Tropical Cloud Systems and Processes (TCSP). TCSP was
undertaken to better understand the processes that lead to the birth
and intensification of hurricanes.
"Hurricane Emily was the most powerful hurricane that NASA has ever
flown over," stated Dr. Jeffrey Halverson, Severe Weather
Meteorologist, at NASA's Goddard Space Flight Center, Greenbelt, Md.
"Emily and Dennis were both strong hurricanes, meaning Category 3 or
higher; it is highly unusual for two strong storms to develop in
close succession as early as July in the Atlantic hurricane season."
Image to left: This image shows sea surface temperatures
averaged during the month of July 2005. It was compiled by data from
the Advanced Microwave Scanning Radiometer (AMSR-E) aboard NASA's
Aqua satellite. Click on image to enlarge. Credit: Remote
Sensing Systems
NASA provides researchers and forecasters with space-based
observations, data assimilation, and computer climate modeling. NASA
also provides measurements and modeling of global sea surface
temperature, precipitation, winds and sea surface height, all
ingredients that contribute to the formation of tropical cyclones
(which is the general name for typhoons, tropical storms and
hurricanes).
What was the reason for this record setting number of named storms?
According to NASA satellite data, the winds and sea surface
temperatures were perfect during the month of July to help these
five tropical cyclones form.
Winds can help storms form, or tear them apart (wind shear). Several
times during July, NASA satellites detected rotating winds over the
ocean's surface, precursors to tropical cyclone development. From
those winds the five storms were born.
Image to right: Tropical Storm Cindy was preparing to make
landfall over southeastern Louisiana on July 5, 2005, when the
Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua
satellite captured this image. At the time, the National Hurricane
Center reported the storm to have winds of 70 miles per hour, just 4
miles per hour under hurricane status. After coming ashore near the
mouth of the Mississippi River, Cindy moved northeast, drenching
Alabama with rain. Though the storm left thousands without power and
triggered some flooding, though no serious damage has been reported.
Credit: NASA
Wind shear is simply a change with the wind in height. When wind
shear is present, the warm moist air that needs to rise high in the
atmosphere is blown in varying directions depending how high in the
atmosphere you are. Hurricane development requires that the rising
air remain stacked vertically to produce very deep thunderstorm
activity.
During July, the amount of wind shear in the Atlantic was minimal.
The NASA-provided SeaWinds instruments aboard Japan's Midori 2 and
NASA's QuikSCAT satellites can detect these winds before other
instruments, providing early notice of developing storms to
forecasters and scientists.
Warmer-than-normal sea-surface temperatures were also a key player
in the record number of storms. Tropical cyclones need ocean surface
water temperatures of 82 degrees Fahrenheit (F) or greater to fuel
the evaporation and rising air that helps create the thunderstorms
in a tropical cyclone.
Image to left: Hurricane Dennis was bearing down on the Gulf
Coast of the United States on July 10, 2005, at 12:15 p.m. (16:15
UTC) when the Moderate Resolution Imaging Spectroradiometer on
NASA’s Terra satellite captured this image. With winds of 135 miles
per hour (217 kph), Dennis was a powerful Category 4 storm just
hours away from making landfall. At the time this image was taken,
the eye of the storm was about 55 miles (90 kilometers) south,
southeast of Pensacola, Florida, and the storm was moving northwest
at about 18 miles per hour (29 kph). The size of the storm put
clouds of rain over most of the southeastern United States well
before the storm came ashore. In this image, Dennis covers all of
Florida, Alabama, Mississippi, and stretches over parts of
Louisiana. The northern fringes of the storm appear to be over
Tennessee and North Carolina. Credit: NASA
Sea surface temperatures (SST) in the tropical Atlantic and Gulf of
Mexico easily surpassed the "hurricane threshold" beginning in July
2005 and continued to climb into the mid- to high 80's through
August. These sea surface temperatures are 1 to 3 degrees F above
normal. "Hurricane-wise, we are in an incendiary situation," said
Bill Patzert, oceanographer at NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "These toasty SSTs are high octane fuel for
September's hurricanes." September is usually the busiest month for
Atlantic hurricanes.
Unlike traditional infrared satellite instruments, the Aqua
satellite's Advanced Microwave Scanning Radiometer (AMSR-E) and the
Tropical Rainfall Measuring Mission's (TRMM) Microwave Imager can
detect sea surface temperatures through clouds. This valuable
information can help determine if a tropical cyclone is likely to
strengthen or weaken. The Jason-1 satellite altimeter provides data
on sea surface height, a key measurement of ocean energy available
to encourage and sustain hurricanes.
Air temperature and humidity are also important factors. The
Atmospheric Infrared Sounder (AIRS) experiment suite aboard the Aqua
satellite obtains measurements of global temperature and humidity
throughout the atmosphere. This may lead to improve weather
forecasts, improved determination of cyclone intensity, location and
tracks, and the severe weather associated with storms, such as
damaging winds.
Image to right: The Tropical Rainfall Measuring Mission (TRMM)
satellite captured this remarkable image of a rejuvenated Hurricane
Emily in the western Gulf of Mexico. The image was taken at 17:36
UTC (1:36 pm EDT) on 19 July 2005 as Emily was bearing down on the
northern coast of Mexico. The image shows a top-down perspective of
the rain intensity within Emily as obtained from TRMM's sensors.
Rain rates in the center of the swath are from the TRMM
Precipitation Radar (PR), a radar that can measure precipitation
from space. Rain rates in the outer swath are from the TRMM
Microwave Imager (TMI). The eye of Emily is clearly visible in the
center of the storm as a red semicircle indicating heavy rain
intensities. At the time of this image, Emily was classified as a
strong Category 1 hurricane with maximum sustained winds reported at
95 mph by the National Hurricane Center. The storm was moving
west-northwest at 14 mph and was located 210 miles southeast of
Brownsville, Texas. Credit: NASA
The TRMM satellite's Precipitation Radar (PR) instrument provided by
Japan for the TRMM satellite provides CAT scan-like views of
rainfall in the massive thunderstorms of hurricanes. TRMM
instruments look at rainfall intensity for the likelihood of storm
development. TRMM also sees "hot towers" or vertical columns of
rapidly rising air that indicate very strong thunderstorms. These
towers are like powerful pistons that convert energy from water
vapor into a powerful wind and rain-producing engine. Once a storm
develops, TRMM provides an inside view of how organized and tightly
spiraled rain bands are, key indicators of storm intensity.
The TRMM PR got a good workout with Tropical Storms Cindy and Dennis
as they both formed in early July, and both packed heavy rains.
After Cindy formed on July 3 in the extreme western Caribbean Sea
just east of the Yucatan-Belize border. After crossing the Yucatan
peninsula and re-entering the Gulf, she became a tropical storm on
July 5. She moved northward, making landfall near Grand Isle, La.
Just under hurricane strength. She brought heavy rains and inland
flooding as she moved northeastward across the eastern U.S.
Image to left: This image of
Tropical Storm Franklin was captured on July 25th, 2005 by the
Moderate Imaging Spectroradiometer instrument on NASA's Terra
satellite. At 11 a.m. on 7/25, the center of Tropical Storm Franklin
was located near latitude 31.1 north, longitude 69.6 west, or about
295 miles west-southwest of Bermuda. Franklin was moving toward the
east-northeast near 5 miles per hour, and was expected to continue
with a gradual turn toward the northeast and away from the U.S.
mainland. Maximum sustained winds were near 40 mph at the time of
this image. Credit: NASA
After Cindy formed on July 3 in the extreme western Caribbean Sea
just east of the Yucatan-Belize border. After crossing the Yucatan
peninsula and re-entering the Gulf, she became a tropical storm on
July 5. She moved northward, making landfall near Grand Isle, La.
Just under hurricane strength. She brought heavy rains and inland
flooding as she moved northeastward across the eastern U.S.
Tropical Depression Dennis formed on July 4 near the southern
Windward Islands and moved west-northwestward across the Caribbean
Sea. When he became a tropical storm on July 5, it was the earliest
date on record for a fourth named storm. On July 8, just south of
central Cuba, Dennis became the earliest category 4 hurricane on
record with 150 mph winds. Dennis made landfall along the
south-central coast of Cuba with 145 mph winds, causing considerable
damage, widespread utility and communications outages.
Dennis weakened to a category 2 storm before making landfall along
the western Florida panhandle near Navarre Beach late July 10.
Considerable storm surge related damage occurred near St. Marks
Florida, well east of the landfall location. Heavy rainfall and
flooding occurred across much of Florida and extended well inland
over portions of the southeastern U.S. at least thirty-two deaths
were reported with most occurring in the Caribbean region.
Image above:
Warm ocean waters
fuel hurricanes, and there was plenty of warm water for Katrina to
build up strength once she crossed over Florida and moved into the
Gulf of Mexico. This image depicts a 3-day average of actual sea
surface temperatures (SSTs) for the Caribbean Sea and the Atlantic
Ocean, from August 25-27, 2005. Every area in yellow, orange or red
represents 82 degrees Fahrenheit or above. A hurricane needs SSTs at
82 degrees or warmer to strengthen. The data came from the Advanced
Microwave Scanning Radiometer (AMSR-E) instrument on NASA's Aqua
satellite. Click on image above to view an animation which
depicts the sea surface temperatures for the period June 9 through
August 9, 2005. Also note the different tracks of Hurricanes
Dennis, Emily, and at the very end Katrina. Credit: NASA/SVS
Emily formed July 11, 1300 miles east-southeast of the Lesser
Antilles. She moved west, and became a tropical storm on the 12. In
two days she was a major hurricane (just below a category 5) with
winds of 155 mph, south of Hispanola. On July 18, Emily struck
Cozumel and crossed Mexico's Yucatan Peninsula with 135 mph winds.
After a brief regeneration in the Gulf of Mexico, she made final
landfall with winds near 125 mph in northeastern Mexico.
On July 21, Franklin grew from a depression to a tropical storm near
the central Bahamas. His peak winds of 70 mph occurred on July 23,
as he turned north and northeast in the Atlantic. Franklin merged
with a frontal zone while passing south of Newfoundland, Canada on
July 31.
Tropical Storm Gert set the month's record, forming in the Bay of
Campeche on July 23. Late on July 24, Gert made landfall with 45 mph
winds near Cabo Rojo on Mexico's east coast. She brought locally
heavy rainfall to those areas that had been affected by Hurricane
Emily less than a week earlier. Gert dissipated well inland over
central Mexico on July 26.
Scientists rely on information gathered by NOAA and the U.S. Air
Force Reserve personnel who fly directly into storms in hurricane
hunter aircraft; NOAA, NASA and the U.S. Department of Defense
satellites; NOAA data buoys, weather radars and partners among the
international meteorological services.
Rob Gutro
Goddard Space Flight Center
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