WRITTEN TESTIMONY OF
DR. CHRIS LANDSEA
TROPICAL
PREDICTION CENTER/NATIONAL HURRICANE CENTER
NATIONAL WEATHER
SERVICE
NATIONAL OCEANIC
AND ATMOSPHERIC ADMINISTRATION
U. S. DEPARTMENT
OF COMMERCE
OVERSIGHT HEARING
ON
“FEDERAL FLOOD
INSURANCE PROGRAM”
BEFORE THE
COMMITTEE ON
BANKING, HOUSING, AND URBAN AFFAIRS
UNITED STATES
SENATE
OCTOBER 18, 2005
Good morning, Mr. Chairman and members of the
Committee. Thank you for inviting me to
discuss the outlook for hurricane activity in the future and the storm surge
and inland flooding associated with hurricanes.
I am Chris Landsea, with the
The devastation along the
NOAA’s forecasts and warnings for Hurricane Katrina demonstrated the abilities of the state of the art of hurricane prediction. Our continuous research efforts at NOAA, and in partnership with universities and other Federal agencies, have led to our current predictive capabilities and improved ways of describing uncertainty in prediction. Hurricanes pose a major threat to our Nation's coastal communities. The impacts of hurricane winds, storm surge and inland flooding remain major threats to the Nation. Accurate and timely hurricane forecasts provide emergency managers and the public information needed to prepare for an approaching storm, including considering evacuations, if necessary. Understanding the location and severity of hurricane landfall is the key to planning long before the event.
NOAA strives to improve the reliability, accuracy, timeliness, and specificity of predictions of hazardous weather, such as hurricanes, to help society cope with these phenomena. Over the last 15 years, hurricane track forecast errors have decreased by 50%, largely due to advances in hurricane modeling, an increased understanding of hurricane dynamics, improvements in computing and technology, and increased availability of data from the region around the hurricane. Today’s five-day forecasts of a hurricane track are as accurate as three-day predictions were 20 years ago.
Recently there have been questions raised about NOAA’s Hurricane Program. Given the importance to the Nation, NOAA and the Department of Commerce appreciate any insights to improve our forecasts and warnings. NOAA continues to develop new satellite technologies, procure and deploy new buoys, upgrade radiosonde instruments and invest in additional modeling efforts. The result has been that Hurricane predictions are better today than they have ever been and will continue to improve in future.
While the
An active hurricane season does not necessarily mean more
storms make landfall, nor does an inactive period mean no landfalling
hurricanes. In 1992, a relatively quiet
year, Hurricane Andrew became the costliest disaster in
Outlook for Future
Hurricanes
In recent decades, the
The 2005 hurricane season has already been one of the most
active on record. In the last ten years,
we have experienced a higher level of
Based on changes in oceanic and atmospheric conditions, we
believe this increased activity is due to a natural cycle called the Atlantic
Multidecadal Mode, a shift in the surface temperature of the north Atlantic and
Recent research papers by respected scientists have linked
global warming changes to increased hurricane intensity. While these researchers have brought up very
important questions that need to be addressed, it can still be concluded that
the increase in hurricane activity in recent years is due to a natural cycle,
rather than man-made causes.
Inland Flooding and
Storm Surge
Both storm surge and inland flooding pose significant
challenges to both coastal and inland communities. As experienced with Hurricane Katrina, storm
surge can be a deadly aspect of hurricanes for which we need to be
prepared. Storm surge is water pushed
over the shoreline by the force of the winds associated with a hurricane. An advancing storm surge combines with normal
tides to create a hurricane storm tide, which can increase the water level to
as much as 30 feet or more above normal levels.
The direct and indirect effects associated with the massive storm surge
from Katrina were responsible for hundreds of lives lost in
For coastal counties, storm surge has historically represented the primary tropical cyclone threat. The dangers associated with storm surge apply along the coast, bays, sounds, and coastal sections of rivers. The severity of a surge, as measured by the depth and how far inland the water reaches, depends on a number of natural factors, such as cyclone intensity (surface wind speed) and forward speed of motion, local bathymetry, coastal topographic gradients, and barrier (e.g., dune) structure. The level of surge in a particular area is also determined by the slope of the continental shelf. A shallow slope off the coast will allow a greater surge to inundate coastal communities. This rise in water level can cause severe flooding in coastal areas, particularly when the storm surge coincides with the normal high tides. Because much of the densely populated United States Atlantic and Gulf coastlines lie less than 10 feet above mean sea level, the danger from storm surge is tremendous. Communities with a steeper continental shelf will not see as much surge inundation, although large breaking waves can also cause serious damage in those areas. Storm surge, waves, and currents in confined harbors result in severe damage to ships, marinas, and pleasure boats.
Freshwater floods from rain present another great threat to
life and property in tropical cyclones, and these effects occasionally exceed
the coastal impact. While public attention
often shifts away as hurricanes move inland, additional death and property
damage can occur due to inland flooding from excessive rainfall. For example, the devastation experienced
throughout much of eastern
Two types of inland flooding occur from tropical cyclones: flash flooding and river flooding. Flash flooding occurs in creeks, streams, and urban areas within a few minutes or hours of excessive rainfall. Rapidly rising water in confined valleys or canyons can reach heights of 30 feet or more. Streets can become swift moving rivers and underpasses can become death traps. River flooding occurs from heavy rains associated with decaying hurricanes or tropical storms, and in extreme cases, river floods can last a week or more.
Since Hurricane Floyd and Tropical Storm Allison, we have taken steps to improve our forecasts of rainfall amounts, extended those forecasts out to five days, and incorporated those rainfall forecasts into our river and flood predictions. The NWS conveys the magnitude of observed or forecast flooding using flood severity categories. These flood severity categories include minor flooding, moderate flooding, and major flooding. Each category has a definition based on property damage and public threat. Minor Flooding indicates minimal or no property damage, but possibly some public threat or inconvenience. Moderate Flooding indicates some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations may be necessary. Major Flooding is defined as extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations may be necessary. NWS precipitation frequency estimates are used as design standards for civil infrastructure built to cope with rainfall and runoff, such as storm water drainage systems, roads, bridges, culverts, small dams, etc. These precipitation frequency estimates also contribute to computing flood insurance rate maps and support various planning activities. The estimates help ensure an objective assessment of the probability of heavy rainfall in planning and design.
The impacts of a flood vary locally. For each NWS river forecast location, flood stage and the stage associated with each of the NWS flood severity categories are established in cooperation with local public officials. Impacts vary from one river location to another because a certain river stage (height) in one location may have an entirely different impact than the same level above flood stage at another location.
Future Plans
A key
program for increasing our ability to monitor hurricanes, particularly over the
data-sparse ocean areas, will be addressed through the Global Earth Observation
System of Systems (GEOSS), a 10-year international endeavor of which the
Using a
combination of atmospheric and ocean observations from satellites, aircraft,
and all available surface data over the oceans, NOAA, NASA, the National
Science Foundation, other federal agencies, and universities conduct
experiments to better understand internal storm dynamics and interactions
between a hurricane and the surrounding atmosphere and ocean. Much of NOAA’s improvement in tropical
cyclone forecasting is attributed to advances in Numerical Weather Prediction
(NWP). In collaboration with many
scientists and developers in the domestic and international operational NWP
centers, the
Predicting
hurricane intensity, which includes wind structure, storm surge, and rainfall
amounts, remains one of our acute challenges.
For example, even though we knew conditions were favorable for Katrina
and Rita to intensify, and we forecast strengthening, there was some error for
both storms in the intensity forecast for the eastern Gulf due to their rapid
intensification. To advance hurricane
prediction, especially hurricane intensity and size forecasts, NOAA is
developing the Hurricane Weather and Research Forecasting (HWRF) system. The HWRF system uses a collaborative approach
among the research community and will apply advanced model physics as HWRF couples
the atmosphere, land, and ocean into an integrated model. Our goal is to couple an advanced wave model
with a dynamic storm surge model to better predict coastal impacts of waves and
storm surge.
We have
increased our efforts to transfer research into operations. The United States Weather Research Program
(USWRP) Joint Hurricane Testbed (JHT) was formed in late 2000. The mission of the JHT is to facilitate the
transfer of new technology, research results, and observational advances of the
USWRP, its sponsoring agencies, the academic community, and the private sector
for improved operational tropical cyclone analysis and prediction. A large portion of my job at the
Conclusion
Thank you Mr. Chairman and members of the Committee for this opportunity to
discuss the outlook for hurricane activity in the future and the storm surge
and inland flooding associated with hurricanes, and how we are working to
better prepare our country for these changes.
I would be happy to address any questions you may have.