Hurricane Harvey, Irma, and Maria
wreaked havoc when they made landfall.
They were all categorized as major hurricanes,
but part of what made them so dangerous was how they rapidly intensified before moving inland.
When hurricanes intensify a large amount in a short period,
scientists call this process rapid intensification.
This is the hardest aspect of a storm to forecast and it can be most critical to people’s lives.
While any hurricane can threaten lives and cause damage
with storm surges, floods, and extreme winds,
a rapidly intensifying hurricane can greatly increase these risks
while giving populations limited time to prepare and evacuate.
Rapid intensification occurs when a hurricane’s maximum sustained winds
increase at least 35 miles per hour in 24 hours and often results in major hurricanes.
The latest Atlantic storm to rapidly intensify was Hurricane Maria,
which developed from a Category 1 to a Category 5 hurricane in less than 18 hours.
In the past few decades, forecasting errors for tracking hurricanes have decreased.
While intensity forecast errors have shown recent improvement,
significant errors can still occur because of rapidly intensifying storms.
There are, however, clues to a rapidly intensifying hurricane that can be seen from NASA satellites.
Scientists say ocean water needs to be warm - 80 Degrees Fahrenheit or higher.
There also needs to be low vertical wind shear,
meaning winds that don’t change much with altitude,
so that the central part of the storm doesn’t get tilted over or ripped apart.
A key indicator of a potentially rapidly intensifying storm
storm is a symmetrical, deep ring of precipitation surrounding the eye.
Rapidly intensifying storms typically occur up to twice in a hurricane season.
But in 2017, we have seen four storms rapidly intensify
and scientists attribute this to warmer ocean waters and favorable winds.
But these key ingredients don’t always lead to rapid intensification
-- proving that it’s a much more complex problem.
Researchers say there are many small-scale processes, such as those associated with deep thunderstorms,
that influence how strong a hurricane becomes.
Satellites such as NASA’s Global Precipitation Measurement Mission
can observe precipitation inside evolving storms
and help scientists better understand how these processes come together to intensify hurricanes.