make summary for each lucture

NOAA Ocean Today video: “The Hurricane Hunters”

https://www.youtube.com/watch?v=JulJhamN7d8

Aircraft Reconnaissance (Hurricane Hunters) 15

Aircraft Reconnaissance (Hurricane Hunters)

Hurricane hunting is born on a bet: Major Joe Duckworth, highly regarded creator of instrument-flying program, established a school in Bryan, Texas, in Feb 1943 to teach young pilots to fly by instruments in all kind of weather.

On the morning of July 27, 1943, a hurricane was approaching Galveston, about 120 miles southeast of Bryan. Taunted by British Royal Air Force pilots about the airworthiness of the American AT-6 Texan Trainer aircraft, Duckworth (along with reluctant Lieutenant, Ralph O’Hair) flew into the hurricane to prove the toughness of the AT-6.

While in the eye (when the storm was already ashore), they radioed to the Houston weather office the exact location of the center of storm.

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Aircraft Reconnaissance (Hurricane Hunters)

In Feb 1944, the Army Air Corps, the Navy, and the Weather Bureau established a plan for airborne hurricane reconnaissance. Today, Hurricane Hunters stop at the coastline because of severe turbulence than can develop over land (this was not known in 1943).

Before the advent of meteorological satellites in 1960s, forecasters relied on reconnaissance aircrafts for locating the storms in the ocean.

In early days, Hurricane Hunters had to fly only a few hundred feet above surface to estimate wind direction and speed by observing the ocean surface.

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Dangers with Hurricane Hunting

The turbulence in the Atmospheric Boundary Layer (ABL) flow caused several aircraft losses during low-level penetrations (mid 1940s-late 1950s).

Storm’s Eyewall: Strong updrafts can give way to equally strong downdrafts in a few hundred feet. Horizontal wind speed can change by more than 100 mph in a few seconds as the aircraft flies across the eyewall.

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Dangers with Hurricane Hunting

(Ref: ‘Divine Wind’ by Kerry Emanuel)

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Dangers with Hurricane Hunting

Hurricane Hunters: Bumpy Ride

(Ref: ‘Divine Wind’ by Kerry Emanuel)

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http://www.youtube.com/watch?v=qpUMOsmCebI

Advancement in Aircraft Reconnaissance

In late 1950s, several technical advances made it feasible to make useful measurements from higher altitudes.

Doppler radars (carried on aircrafts), sending pulses of electromagnetic radiation to ocean surface and measuring the intensity and time of return of backscattered radiation, were able to obtain precise measure of altitude.

Doppler radars also measure Doppler shift to show how fast the aircraft is moving over ground. The speed of the aircraft through air is also measured and the vector difference between these two measurements yields the speed and direction of the wind relative to the ground. [No longer pilots need to fly low to see the ocean to estimate wind speed.]

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Advancement in Aircraft Reconnaissance

In late 1960s, ‘inertial navigation systems’ based on precisely manufactured gyroscopes (measuring accelerations to determine velocity and position of aircraft) were being used in aircrafts to determine (1) their precise position, and (2) speed and direction of the wind in which they were flying.

In the 1990s, ‘inertial navigation systems’ were supplemented by Global Positioning System (GPS) to pinpoint location using signals from a constellation of satellites.

The top of a hurricane can be over 50,000 feet high, and reconnaissance aircrafts could only go up to 30,000 feet. Also, we are interested in the weather down at the bottom of the storm which will affect the coastline. For this reason, reconnaissance aircrafts fly in as low as safely possible. These days Hurricane Hunters normally stay at 10,000 feet.

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Advancement in Aircraft Reconnaissance

Dropwindsonde or Dropsonde It’s a small tube with instruments in it that has a parachute attached. It also has a radio transmitter to send data back up to the airplane. When reconnaissance aircraft gets to the center of a hurricane at 10,000 feet, the dropsonde operator releases the “sonde” into the exact center of the eye.

Atmospheric sensors on the sonde measure temperature, humidity, and pressure. Onboard GPS chip keeps track of the sonde’s exact location and drift from which the wind direction and speed can be deduced.

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Dropwindsonde or Dropsonde Just before it splashes into the water, it sends the most important data: the pressure in millibars. This is the information the hurricane forecasters use to decide if the storm is getting stronger or weaker.

Data collected from the aircraft and sondes are immediately transmitted back to mainland United States and used in computer models to substantially improve forecasts of the storm’s motion.

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Radars send radio waves that are reflected back from airplanes and ships. During WWII scientists learned that raindrops, snowflakes, hail, sleet, and cloud drops reflect radio waves, which interfered with spotting enemy airplanes and ships – thus they realized that radar can help detect dangerous storms such as thunderstorms, hurricanes, typhoons.

September 14, 1944: Lakehurst (New Jersey) Naval Air Station’s radar showed Great Atlantic Hurricane of 1944’s structure with an eye wall and rain bands. This first view of a hurricane’s structure, which until then had gone unrecognized, was an important step in better scientific understanding of hurricanes.

In 1950s, Doppler radars were carried on aircrafts to obtain precise measure of altitude, wind speed and wind direction.

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