The hurricane array is composed of nine drifting buoys provided by AOML, deployed northeast of Brazil by the Navy, from a US Navy aircraft in May 2000 (buoy id.s 18905-18913) and eight drifting buoys provided by the Navy, deployed northeast of the Bahamas in August 2000 (id.s 12860, 28840, and 26965-26970). The buoys are WOCE BP/WSD drifters produced by Metocean Data Systems, Ltd. Translated, this means they meet the accuracy requirements for the World Meteorological Organization's (WMO) WOCE program, and in addition to measuring sea surface temperature (SST) they also measure barometric pressure (BP) and wind speed and direction (WSD). Funding for first nine buoys buoys was provided by the NOAA Office of Global Programs. The second eight buoys were contributed by the Naval Meteorology and Oceanography Command (NMOC). NMOC performed both deployments.
The purpose of the annual deployment of the hurricane array is to provide forecasters with surface meteorological data in the region of hurricane development. Normally, weather data over the oceans is observed and sent by merchant ships, but obviously these ships will divert from their normal tracks to avoid areas of rough weather so there is a dearth of data where and when it is needed most. Thus, the buoy data (and data collected by satellites and special research aircraft) are very important. They are input into the computer weather models from which forecasts are made. Additionally, local forecasters use the buoy data to make better regional assessments of the impact of a storm. Fanally, the data helps researchers improve the models, resulting in better forecasts in future hurricane seasons.
Each buoy is a 14 inch sphere which floats partially submerged. A "holey sock" drogue centered at 15 meters depth reduces the effect of the wind pushing the buoy through the water. Sensors measure SST and BP. A wind vane mounted atop the sphere and an internal compass are used to measure the direction from which the wind blows. Two acoustical devices, one listening at 2 KHz and one at 8 KHz, are used to estimate wind speed. Data are acquired continuously and then an average for each sensor is calculated at the top of the hour. When a satellite passes overhead (roughly every six hours), the past four hourly sets of averaged data are transmitted. The satellite also measures the location of the buoy.
The hurricane buoy data files available at this site are RAW. No quality control has been applied. Barometric pressure (BP) is presented in millibars (mB); sea surface temperature (SST) is presented in degrees Celsius (C); wind direction is in degrees clockwise from north and is the direction from which the wind is blowing; wind speed is presented in meters per second (m/s). The maximum value for wind speed the buoy can measure is 63 m/s (122 knots). The min/max BP is 850 mB/1054.7 mB. The min/max SST is -5 C/35.88 C. A wind direction of "999" means no wind direction data was available.
There are 3 data files created daily: P_dd-mmm-yy.dat, S_dd-mmm-yy.dat and
BW_dd-mmm-yy.dat. dd-mmm-yy is the creation day, month, and year of the file.
Each of these files contains data for the previous day.
The P_ file contains latitude, longitude, and the time of the position.
The S_ file contains SST, drogue presence, and time these were measured. A
nonzero value for drogue presence means it is still attached to the buoy,
which is important to know if you are using the change in position of the buoy
to determine the ocean currents. To determine drogue presense, it is important
to examine the entire time series of the drifter.
The BW_ file contains barometric pressure, wind direction, wind speed
estimated from 8 KHZ acoustic sensor, wind speed from the 2 Khz sensor, and
the time these were measured.
There is one file, P_may_jul00.dat, containing all data since deployment in
May through July 31. Refer to the daily files for data since August 1.