VO: In order improve hurricane forecasts, scientists model storms of the past.
Braun: We model old storms because it gives a way to
compare the simulations to observations and try to assess the
physical processes within storms and also how well those
processes are represented in the forecast models. Because that's key to
improving forecasts in the future. VO: With improvements in computing power,
researchers have been running ensemble forecasts.
Braun: Instead of a single forecast, we run a whole series of forecasts where you make slight
variations to the initial information that goes into the models and then see how much
spread you get within those forecasts. Running ensembles gives us a visual description
of the level of uncertainty associated with forecasting tropical storms.
Braun: And the average over all those ensembles usually gives you a better forecast
than if you ran just a single forecast model. VO: One way to test forecast models is to
reanalyze past storms. Reale: It's very important to study the
worst possible storms in history because those are the ones that really put the
system to a challenge. VO: NASA and NOAA cooperate in satellite
systems and sharing data, as well as experiments and modeling research, all of
which enable NOAA and other agencies to provide better forecasts of tropical cylones.
Reale: When NOAA and National Hurricane Center issues a forecast, the better the
forecast is historically, the more likely it is that people would trust the
forecast, and decision makers will make the right decisions and
they will tell what place has to be evacuated and what place can stay.
VO: To get a clearer look at the processes inside the hurricane, NASA's Global
Precipitation Measurement Microwave Imager, or GMI, gives us an
X-ray beneath the clouds. Braun: If you have a storm that maybe isn't well defined, doesn't have
a visible eye, with the GMI and similar instruments
you're able to see the rainfall structure underneath those clouds
So you can see the ring of heavy precipitation in the eye wall, as well as
several of the rain bands. And that really helps to tell us a lot about how the storm is evolving,
and how that might relate to the intensity of the storm.
VO: Representing those small-scale eye processes in global models has been an ongoing
area of research. Reale: By increasing resolution and increasing, of course, the quality of
the physical processes that are represented inside the model,
global models have been getting better and better. They make hurricanes
smaller, more compact, closer to the real size,
and the eye becomes smaller and smaller and they become more intense.