WASHINGTON, Aug 31, 2019 (BSS/AFP) – The path of Hurricane Dorian, which is
currently over the Atlantic and heading for the state of Florida, is closely
monitored by US weather services with powerful forecasting tools.
– Planes and satellites –
The priority is to collect as much information as possible about the
hurricane itself, which is mainly done by sending planes into the storm —
rough missions flown by specialized pilots.
On Friday, for example, seven flights by the National Oceanic and
Atmospheric Administration (NOAA) and the US Air Force with aircraft known as
“hurricane hunters” were planned in and around Dorian.
They record temperature, humidity, atmospheric pressure and wind speeds,
and also drop probes that take measurements down to the surface of the ocean.
Buoys and weather balloons can also be scattered before and during the
hurricane.
Such field data is supplemented by information from above that is gathered
via satellites and NASA.
The US space agency has a number of satellites oriented toward the earth.
One of them, Suomi NPP, has its instruments focused on Dorian and gives
information on its structure and strength, the temperature at the top of the
clouds and the volume of rain.
– Models and forecasts –
This mass of data is then made available to all global weather services,
feeding hundreds of forecasting models.
The European model, developed by the European Centre for Medium-Range
Weather Forecasts, is recognized as the most accurate.
In Miami, a team of 10 forecasters from the National Hurricane Center (NHC)
produce detailed forecasts predicting the path and intensity of emerging
storms.
At any given moment, two of these forecasters are on duty, working eight-
hour shifts. They produce their own predictions based on what the various
models they use indicate.
“You need to know what’s going on all over the world in order to forecast,”
because what happens in the Atlantic depends on weather elsewhere, said Sim
Aberson, a meteorologist at NOAA’s Atlantic Oceanographic and Meteorological
Lab.
– How precise? –
On the trajectory of a storm, which is the number one priority, forecasts
have improved significantly since the 1970s.
“The expected forecast accuracy for a hurricane three days from now, right
now is about the same as it was for a one and a half day forecast just about
10 to 15 years ago,” said Aberson.
But models have made less progress when it comes to hurricane intensity,
which is classified on a five-level scale.
On average, the error at three days was about a category, or 25 kilometers
per hour (15 miles per hour) of wind speed, according to Aberson.
It is for this reason that the NHC publishes probabilities — for example,
55 percent risk that West Palm Beach will be hit by winds exceeding 118
kilometers per hour (74 miles per hour) — and a cone of uncertainty
illustrating the possible course of the storm.
The animations seen on television channels come directly from the forecasts
of the team of 10 experts in Miami.