This satellite image shows how cold ocean water (in dark blue) is drawn to the surface in the wake of Hurricane Fabian, positioned off the Carolina coast.

When hurricanes are far from land, satellites are the best way to gather information about them. Hurricane hunter aircraft can also fly through an approaching storm to collect firsthand observations. When a hurricane gets closer to land, ground-based Doppler radar and weather stations record valuable information.

 

Satellites are important data-gathering tools. They can show large portions of Earth’s surface at one time and can also gather huge amounts of data very quickly. Specially equipped satellites detect parts of the electromagnetic spectrum that human eyes cannot see. This capability allows satellites to measure many different properties of hurricanes at the same time. Some satellite images show the locations of storms, sea- surface temperature, and wind speed and direction. Some satellite images are photographs taken with visible light. Infrared satellite images show temperature data. These image scan be collected during the day or night.

Watch the NASA video “Birth of a Hurricane” in the JASON Mission Center

GOES satellites provide weather data on a global scale.

 
Satellites are great for collecting large amounts of data over wide regions. But better yet, a hurricane hunter airplane can get data directly from within a hurricane. Researchers fly these specially equipped planes right through hurricanes to collect a variety of weather data. Another purpose for the flights is to determine the exact location of the hurricane’s eye, which is difficult to track from a satellite. Jason Dunion participates in these flights so that he can gain a better understanding of hurricanes.

 

In addition to the battery of instruments located on the airplane, scientists also release probes called dropsondes into the storm. A dropsonde is an instrument package designed to be dropped from an aircraft by a parachute. Many dropsondes are launched during a hurricanehunter flight. When released from an airplane, the dropsonde descends on its parachute through the storm to the ocean below, taking a series of measurements as it falls. Sensors measure wind speed and direction, temperature, humidity, and air pressure. Its radio transmitter sends a stream of data, including its location, to a computer back onboard the airplane. In this way, the data collected by a dropsonde helps researchers produce a vertical profile of the features of a storm and build 3-D models of the event.

Ground-based instruments, including Doppler radar, also collect hurricane data. Doppler radar stations, positioned in a grid system that covers the continental United States, use radar to “see” through clouds, locate areas of precipitation, and estimate rates of precipitation. This radar also measures the motion of water droplets toward or away from the radar. Scientists use this information to calculate wind speed and direction within the storm. Doppler radar provides detailed data about a hurricane’s wind, rain, and the direction of its path. Unfortunately, the range of a Doppler radar unit is only about 400 km (250 mi). Because these systems are land-based and not at sea, a hurricane must be close to land before a Doppler radar unit can collect data on it.

   

Hundreds of weather observatories across the United States collect local weather data, including temperature, wind speed and direction, and precipitation. The observatories are useful for tracking and monitoring a hurricane after it comes ashore.

 

Forecasters analyze the data collected by all of these instruments and feed it into computer models. These models use math to simulate weather conditions in the atmosphere and help predict how hurricanes will move and change. Accuracy in predicting the probable path of a hurricane has improved dramatically, although predicting storm intensity remains difficult. The National Hurricane Center uses the computer model results and forecasters’ analyses to issue hurricane watches and warnings.