WEBVTT FILE

1
00:00:00.000 --> 00:00:02.190
Hurricane Harvey, Irma, and Maria

2
00:00:02.210 --> 00:00:04.300
wreaked havoc when they made landfall.

3
00:00:04.320 --> 00:00:07.120
They were all categorized as major hurricanes,

4
00:00:07.140 --> 00:00:12.300
but part of what made them so dangerous was how they rapidly intensified before moving inland.

5
00:00:12.320 --> 00:00:16.210
When hurricanes intensify a large amount in a short period,

6
00:00:16.230 --> 00:00:19.290
scientists call this process rapid intensification.

7
00:00:19.310 --> 00:00:24.500
This is the hardest aspect of a storm to forecast and it can be most critical to people’s lives.

8
00:00:24.520 --> 00:00:27.890
While any hurricane can threaten lives and cause damage

9
00:00:27.910 --> 00:00:30.740
with storm surges, floods, and extreme winds,

10
00:00:30.760 --> 00:00:34.810
a rapidly intensifying hurricane can greatly increase these risks

11
00:00:34.830 --> 00:00:38.570
while giving populations limited time to prepare and evacuate.

12
00:00:38.590 --> 00:00:43.030
Rapid intensification occurs when a hurricane’s maximum sustained winds

13
00:00:43.050 --> 00:00:49.280
increase at least 35 miles per hour in 24 hours and often results in major hurricanes.

14
00:00:49.300 --> 00:00:53.530
The latest Atlantic storm to rapidly intensify was Hurricane Maria,

15
00:00:53.550 --> 00:00:58.860
which developed from a Category 1 to a Category 5 hurricane in less than 18 hours.

16
00:00:58.880 --> 00:01:03.560
In the past few decades, forecasting errors for tracking hurricanes have decreased.

17
00:01:03.580 --> 00:01:07.440
While intensity forecast errors have shown recent improvement,

18
00:01:07.460 --> 00:01:11.850
significant errors can still occur because of rapidly intensifying storms.

19
00:01:11.870 --> 00:01:18.090
There are, however, clues to a rapidly intensifying hurricane that can be seen from NASA satellites.

20
00:01:18.110 --> 00:01:22.580
Scientists say ocean water needs to be warm - 80 Degrees Fahrenheit or higher.

21
00:01:22.600 --> 00:01:25.130
There also needs to be low vertical wind shear,

22
00:01:25.150 --> 00:01:27.780
meaning winds that don’t change much with altitude,

23
00:01:27.800 --> 00:01:31.840
so that the central part of the storm doesn’t get tilted over or ripped apart.

24
00:01:31.860 --> 00:01:35.530
A key indicator of a potentially rapidly intensifying storm

25
00:01:35.550 --> 00:01:39.410
storm is a symmetrical, deep ring of precipitation surrounding the eye.

26
00:01:39.430 --> 00:01:44.300
Rapidly intensifying storms typically occur up to twice in a hurricane season.

27
00:01:44.320 --> 00:01:48.350
But in 2017, we have seen four storms rapidly intensify

28
00:01:48.370 --> 00:01:52.910
and scientists attribute this to warmer ocean waters and favorable winds.

29
00:01:52.930 --> 00:01:56.660
But these key ingredients don’t always lead to rapid intensification

30
00:01:56.680 --> 00:01:59.090
-- proving that it’s a much more complex problem.

31
00:01:59.110 --> 00:02:05.460
Researchers say there are many small-scale processes, such as those associated with deep thunderstorms,

32
00:02:05.480 --> 00:02:08.570
that influence how strong a hurricane becomes.

33
00:02:08.590 --> 00:02:11.780
Satellites such as NASA’s Global Precipitation Measurement Mission

34
00:02:11.800 --> 00:02:15.140
can observe precipitation inside evolving storms

35
00:02:15.160 --> 00:02:21.280
and help scientists better understand how these processes come together to intensify hurricanes.

36
00:02:21.300 --> 00:02:33.879