Hurricanes: Their Nature and Impacts on Society - Climate Science ...

SOCIETAL RESPONSES
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warning changes every year due to advances <strong>and</strong> refinements in the process.
Thus the following discussion overviews the production <strong>and</strong> dissemination of
forecast products as it existed in the early 1990s in order to provide a general
sense of short-term hurricane response.
A number of models are used to forecast hurricane tracks because experience
has shown that each has particular strengths <strong>and</strong> weaknesses that have been
systematically documented <strong>and</strong> can be compensated for in the development of
an official forecast. The forecaster's subjective judgment is necessary because
"these models often provide conflicting information" (DeMaria, Lawrence <strong>and</strong>
Kroll 1990). The result of the marriage of forecaster judgment <strong>and</strong> the various
models' output is an "Official Forecast" for public dissemination.
As an example, Table 7.1 shows for Hurricane Andrew (1992) average
forecast track errors for a number of models <strong>and</strong> the official forecast for
various time horizons. Post-forecast assessments have judged the forecasts of
Andrew's movement to be very accurate. For instance, the 24-hour average
forecast error of 65 nautical miles was considerably less than the (1979-1988)
contemporary 10-year average of 109 nm, <strong>and</strong> the 72-hour average error of 243
nm is significantly less than the 10-year average of 342 nm (DOC 1990). Note
that in some instances individual models performed better that the official
forecast, but that in general the official forecast out-performed the models.
The NHC forecasts hurricane intensity in addition to storm movement.
Scientists analyze each storm in great detail as it approaches the US coast.
They use data from satellites, reconnaissance aircraft, buoys, ship observations,
radar, etc. to determine trends in storm motion, winds, <strong>and</strong> pressures.
However, data such as surface wind observations are obtained infrequently
because of the sparse information-gathering infrastructure in the vast Atlantic
Ocean <strong>and</strong> Gulf of Mexico (Burpee et al. 1994). Data are gathered if a storm's
path happens to pass over a National Data Buoy Center's moored buoy
station, a Coastal-Marine Automated Network station, or a conveniently
located ship (convenient for the forecaster, not the ship!). In past years, oil
platforms in the Gulf have also hosted meteorological instruments (DOC
1993). The information gathered from such instruments is used in the
production of forecasts of the storm intensification (Gray, Neumann <strong>and</strong> Tsui
1991; DeMaria <strong>and</strong> Kaplan 1994; DeMaria 1995).
To arrive at an official forecast of a hurricane's track <strong>and</strong> intensity, a
number of officials participate in a conference call on the National Weather
Service (NWS) Hurricane Hotline to arrive at the official forecast. Participating
officials include: a National Meteorological Center (NMC) forecaster
(expert on large models), forecasters at relevant NWS field offices (experts on
local conditions), <strong>and</strong> the NHC hurricane specialist (expert on hurricanes). In
addition, forecasters from the NMC Heavy Precipitation Branch <strong>and</strong> National
Severe Storms Forecast Center (tornado expertise), officials from NWS
National, Southern, <strong>and</strong>/or Eastern headquarters, <strong>and</strong> US Navy personnel
may participate or listen in as appropriate. The tropical cyclone track <strong>and</strong>