About Esperance Meteorological Office

The Esperance Meteorological Office (MO) opened on 28 June 1969. Synoptic observations had previously been taken at the Esperance Post Office beginning in 1883.

The Esperance MO is one of 14 Bureau staffed stations in Western Australia providing a vital role in Australia's surface and upper-air measurement network. Weather balloons are released 4 times per day at 12:15am, 7:15am, 1:15pm and 7:15pm. Information about temperature, humidity, pressure and wind profiles from the surface to a height of about 27kms (90,000ft) is gathered from these balloon flights. Surface observations of wind, pressure, temperatures, visibility, precipitation, weather phenomena, evaporation, etc, are recorded at regular intervals throughout the day and night. Limited observations are recorded and transmitted by an automatic weather station when staff are not present.

Meteorological Technical Officers (Observers) staff the office seven days a week and provide coverage for most of the day. At times the hours of coverage are reduced to cater for leave and training requirements.

Radar
The radar is used to automatically track a target suspended under a balloon and compute the wind speed, wind direction and the height of the balloon as it ascends through the atmosphere. Typical balloon flights last about 90 minutes, reach heights up to 27 km and the balloon can often travel 200 km downwind before it bursts. Balloons are normally released four times each day.

Apart from tracking weather balloons, the radar is used to detect precipitation (rain, snow and hail). It estimates precipitation intensity from the strength of the returned echoes. It can detect light rain to a distance of about 200km and severe thunderstorms to over 300km, limited mainly by the earth's curvature. The radar displays a map of colour graded precipitation distribution and intensity on a PC monitor in the MO. This image is updated every 10 minutes when the radar is not being used for balloon tracking.

Radiosonde
Radiosondes are small battery powered radio transmitters that are carried through the atmosphere under a weather balloon. The radiosonde contains a small aneroid barometer and temperature & humidity sensing elements. When operating, the radiosonde transmits radio signals indicating pressure, temperature and humidity to a receiver in the MO. Radiosondes are released world wide at scheduled times. In WA, radiosondes are released daily at 7.15am. At Esperance, additional radiosonde flights are also released on Sunday and Thursday evenings at 7.15pm. The signals that the radiosonde transmits back to the MO are processed by a computer and displayed graphically on the computer screen. The data received from the radiosonde enables a temperature and moisture profile of the atmosphere to be calculated. As the data is displayed it is manually scrutinised and modified if necessary before being encoded and transmitted to the Bureau's communications network for national and international distribution.

Weather Balloons
Meteorological balloons are inflated with hydrogen. They are filled with sufficient gas to cause them to ascend through the atmosphere at about 300m (1,000ft) per minute. As air pressure decreases with height, the balloon expands in size until it finally bursts. During the hours of darkness balloons are released with a small torch attached under the target to allow visual tracking for the first few minutes before the radar acquires and automatically tracks the reflective target suspended under the balloon. The hydrogen used to inflate the balloon is a highly flammable gas and safety precautions must be strictly followed when inflating and handling weather balloons. These precautions include the wearing of an anti-flash coat, goggles, gloves and antistatic boots. As the balloon is inflated, overhead sprinklers ensure the balloon and surrounds are wet in order to reduce the chance of static electricity build-up.

Marine Radio Broadcast ( 27 Meg & VHF Radio )
"Esperance Whr" is a limited coastal radio station.

• 27 Meg Radio - calling ch 88, working ch 96.
• VHF Radio - calling ch 16, working ch 72.

Coastal waters forecasts (Bremer Bay to Israelite Bay) & current weather conditions are transmitted from the MO by duty staff daily at 0635, 1235 & 1635 WST. Warnings are transmitted upon receipt.

Feedback or suggestions are welcomed.