1.7 Meteorological Information
The surface weather observation taken about 1951 at JFK on July 17, 1996, located 52 nautical miles (nm) west of the accident site, stated the following: Winds 220° at 8 knots; visibility 10 miles; clouds at 6,000 feet scattered, ceiling 7,000 feet broken, 9,000 feet broken; temperature 82° F; dew point 70° F; altimeter setting 30.07 inches of Hg [mercury]; wind shift 1906; rain began 1918 and ended 1929; precipitation 0.00 inch between 1927 and 1951.
The surface weather observation taken about 2051 at JFK stated the following: Winds 240° at 9 knots; visibility 10 miles; few clouds at 10,000 feet; temperature 80° F; dew point 69° F; altimeter setting 30.08 inches of Hg.
The surface weather observation taken about 1945 at Francis S. Gabreski Airport (FOK) Westhampton Beach, New York, located 12 nm north of the accident site (the nearest reporting station to the accident site), stated the following: Winds 240° at 4 knots; visibility 4 miles; haze; clouds at 6,000 feet scattered; temperature 73° F; dew point 66° F; altimeter setting 30.08 inches of Hg; total sky cover 3/8.
The surface weather observation taken about 2045 at FOK stated the following: Winds calm; visibility 6 miles; haze; clouds at 6,000 feet scattered; temperature 72° F; dew point 66° F; altimeter setting 30.09 inches of Hg; total sky cover 3/8. The winds aloft measured by a weather balloon launched from Upton, New York, on July 17, 1996, about 2000, are shown in table 3. (Upton is located about 15 nm from the accident site.)
Table 3. Winds aloft measured by a weather balloon launched from Upton, New York.
Altitude (feet msl)
Wind Direction (degrees) Wind Speed (knots)
1,000 270 12
2,000 280 14
3,000 285 17
4,000 290 17
5,000 303 19
6,000 310 19
7,000 315 17
8,000 320 16
9,000 330 12
10,000 335 12
11,000 320 12
12,000 295 16
13,000 290 16
14,000 300 17
15,000 303 19
16,000 305 21
17,000 315 29
18,000 315 33
These numbers were used during the Safety Board™s trajectory study. 105 Review of the meteorological data revealed no record of significant meteorological conditions in the area or at the time of the accident.
In the interim, the readers may also find the following additional information about the weather balloons interesting.
http://www.erh.noaa.gov/er/okx/upperair.htm
 |
 |
 |
Upper-air Observations Program
Weather Forecast Office, Upton, NY (WFO OKX) is one of the select weather stations in the US that is part of the National Weather Service Upper-air Observations Program. There are only 92 Radiosonde stations in North America and the Pacific islands. Radiosondes provide upper-air data that are essential for weather forecasts and research. A new radiosonde ground system will replace the old system currently in use by September, 2005.
Weather Balloons
 |
 |
 |
 |
 |
 |
Weather balloons are launched from the upper air building which is located in a valley adjacent to the forecast office (pictured, top row left). They are filled with helium inside of the small building (pictured, top row center and right), then taken outside to launch (pictured, bottom row center). The helium, which is a very light gas, allows the balloon to reach heights of 60,000 feet above the earth's surface in about an hour. As the balloon rises, the atmosphere thins and the pressure outside the balloon decreases allowing the balloon to expand and eventually break. This usually happens within two hours of the launch at elevations of 80,000 to 120,000 feet.
An instrument, called a radiosonde, is tethered to the balloon (pictured, bottom row center). As the balloon rises through the air, the radiosonde measures temperature, relative humidity, and pressure. A transmitter within the radiosonde transmits this data back to a receiver located in the shelter (pictured, bottom row right). The receiver tracks the azimuth and range of the balloon as it ascends. From this information, the wind speed at various levels in the atmosphere can be calculated.
After the balloon flight is complete, a technician ensures the data is accurate before it is disseminated. Additional quality control checks are done at one of our national centers before the data is incorporated into computer models which meteorologists use to make their forecasts.
The balloons are launched from hundreds of locations around the world twice a day every day of the year. The launches occur simultaneously worldwide! This gives meteorologists a snapshot of the earth's three-dimensional atmospheric conditions.
Check out our most recent Upper Air Sounding Plot
from the 0000Z or 1200Z (8:00 p.m. or 8:00 a.m. EDT) Weather Balloon launch.
from the 0000Z or 1200Z (8:00 p.m. or 8:00 a.m. EDT) Weather Balloon launch.
But what happens to the radiosonde when the balloon breaks? The radiosonde is protected by a styrofoam container, which cushions the radiosonde upon impact with the ground. However, a small parachute will also pop out as the radiosonde falls, slowing its descent.
Are the radiosondes returned? Frequently, the radiosondes are discovered in a pasture, grove of trees, creek, peoples' backyards and other locations. A self-addressed postage-paid envelope, which is in a compartment of the radiosonde container, can be used to return the radiosonde to a reconditioning center for repair, and eventual reuse. Most of the radiosondes launched from this office follow the prevailing wind and wind up dropping into the North Atlantic Ocean, never to be recovered.