Stowing for storms

High winds and electrical storms present a real danger to the ATCA, so you should monitor the weather and be prepared to stow the array in the event of bad weather. The state of the weather is not always obvious from the comfort of the Control Room, and people are asked to be alert for problems (go outside occasionally, and keep an eye on the various web weather links and the lightning detectors).

Stow when any of these conditions is met:

• the primary monitor alarm sounds due to a high wind indication on the controller,
• you otherwise notice that the wind exceeds 40km/hr,
• close lightning or the approach of a storm front.

There are two independent systems checking whether the array should be stowed because of high winds. The software is monitoring the weather station that is in the paddock east of the control building. CAOBS will issue a stow command if two consecutive readings are above 40km/h or one above 45km/h. Weather station wind speed and direction is plotted in yellow in the winds display.

The PMON rack monitors the anemometer on the Control Building Roof and the PMON rack will issue a stow command to the array if wind speeds are greater that 50km/hr. (Note: a PMON wind stow only stows in elevation - not azimuth.) PMON speeds are plotted in brown in the `WINDS' display.

Consult the Duty Astronomer about when to re-commence observing after a stow. You should normally wait at least 20 minutes after the error condition that initiated the stow desists.

You may like to monitor weather using these websites:
http://fringes.org/weather/
http://www.narrabri.atnf.csiro.au/astronomy/weather.html

Check the time of the most recent images to ensure you are getting up to date information.