| TROPICAL STORM ISIDORE PROVES THE PERFECT CANDIDATE FOR
NOAA’s RAPID INTENSIFICATION STUDY
The season’s second tropical cyclone to reach hurricane strength
gave the Commerce Department’s National Oceanic and Atmospheric
Administration’s (NOAA) hurricane hunters the opportunity
to monitor and measure a tropical storm undergoing rapid intensification
before making landfall in the Yucatan peninsula. Isidore,
now moving north from the southern Gulf of Mexico, is poised
to hit the Louisiana and Mississippi coast by Thursday morning.
“The key ingredient that NOAA scientists and colleagues are
watching is the warm ocean temperature profile below the sea
surface, that provides the primary source of energy that fuels
storms during the height of hurricane season from August through
October,” said Frank Marks, acting director of NOAA’s Hurricane
Research Division at the Atlantic Oceanographic and Meteorological
Laboratory in Miami.
Since 1998, Peter Black of NOAA’s Hurricane
Research Division and Lynn K. Shay of the University of Miami
have studied how areas of the ocean that have a deep layer
of warm water near the surface play a significant role in
allowing hurricanes to rapidly intensify, one of the most
difficult situations to forecast and one of the most dangerous
to residents along the coast. Their previous work focused
on specific sources of deep warm water found in the Loop Current
and large-scale eddies that spin off from this source and
traverse the Gulf of Mexico.
On Sept. 19, the scientists dropped
a series of ocean probes known as AXBTs and AXCPs (airborne
expendable bathyothermographs and current probes, respectively)
from the two NOAA WP-3D hurricane hunter aircraft. The probes
were released in the projected path of Isidore in the southern
Gulf of Mexico. The probes measured the ocean temperature
and currents down to 200 meters (about 600 feet), the depth
at which hurricane winds usually churn up colder water and
cool the overall temperature of water below the storm.
significance of Isidore being over the Gulf Stream loop current
is that the warm water below extends to great depths, not
allowing Isidore’s winds to cool the surface temperature thereby
keeping the heat reservoir intact and allowing further intensification
of the hurricane,” said Shay.
During the second phase of the
study ocean probes were deployed both as Isidore passed over
the same region, and then immediately afterwards. Black and
Shay will measure the difference in the ocean temperature
structure during all three of these phases. During the time
Isidore passed over the array of ocean probes dropped the
day before, NOAA and University of Miami scientists collected
data that describes both the complete structure of Isidore
and the ocean beneath the storm.
“These data will allow for
a much more analytical analysis of the ocean's role in intensification,
the eventual goal being a greater ability to predict when
and how much a storm may intensify, a challenge considered
to be the next key step in hurricane forecasting,” said Black
Marks notes that the ocean is not the only factor
in hurricane intensity change. NOAA hurricane researchers
also consider environmental data gathered around the storm
by NOAA's Gulfstream-IV jet (G-IV), a surveillance aircraft
operated by NOAA's Aircraft Operations Center. Though the
G-IV missions are designed to improved track forecasts for
landfalling hurricanes, an added benefit is measurement of
the wind shear and environmental moisture and stability that
can affect intensity. Wind shear is the difference in wind
velocity at upper and low levels in the atmosphere. High wind
shear, dry air, and low stability are associated with weakening
of tropical storms. Direct measurements of these variables
are unavailable over the Gulf of Mexico without use of the
“We hope to discover the relative importance
of the loop current and environmental wind shear in determining
hurricane intensity change,” Black says.
Black and Shay hope
that data gathered during this study will enhance knowledge
and predictability of major hurricanes, which translates into
improved intensity forecast, increased warning time, and better
preparedness in coastal regions.
The mission of NOAA’s Hurricane
Research Division is to advance the understanding and prediction
of hurricanes and other tropical weather. Their research is
based on a combination of models, theories, and observations,
with particular emphasis on data obtained with the NOAA research
aircraft. A key goal of this research is to advance the prediction
of tropical cyclone intensity change by improving understanding
of the processes that modulate internal storm dynamics and
interactions of a storm with the atmosphere and ocean.
Commerce Department’s National Oceanic and Atmospheric Administration
(NOAA) is dedicated to enhancing economic security and national
safety through the prediction and research of weather and
climate-related events and providing environmental stewardship
of our nation’s coastal and marine resources. To learn more
about NOAA, please visit http://www.noaa.gov.
To learn more
about hurricane research, visit: http://www.aoml.noaa.gov/hrd.
To learn about NOAA’s Aircraft Operation Center, visit:
To learn about the University of Miami’s Rosenstiel School
for Marine and Atmospheric Science, visit: http://www.rsmas.miami.edu.