Weather Forecast Scales

Beaufort Scale

Hurricane Scale.

 Tropical Storm
 Category One
 Category Two
 Category Three
 Category Four
 Category Five

Tornado scale

## Gusts

A **gust** or **wind gust** is a brief increase in the speed of the wind, usually less than 20 seconds. It is of a more transient character than a squall, which lasts minutes, and is followed by a lull or slackening in the wind speed. Generally, winds are least gusty over large water surfaces and most gusty over rough land and near high buildings.

### Definition

The wind is measured using an anemometer or estimated with a windsock. The average value of the latter is generally measured over a period of 2 minutes before the meteorological observation according to the World Meteorological Organization. Any significant variation at this mean wind during the ten minutes preceding the observation are noted as gusts in messages such as METAR.

It is generally reported in METAR when the peak wind speed reaches at least 16 knots and the variation in wind speed between the peaks and average wind is at least 9 to 10 knots. In marine meteorology, the top speed of a burst is expressed in meters per second (m/s) or in knots, while the Beaufort scale is used for reporting the mean speed. When the maximum speed exceeds the average speed by 10 to 15 knots, the term *gusts* is used while *strong gusts* is used for departure of 15 to 25 knots, and *violent gusts* when it exceeds 25 knots.

### Max wind gusts in Canberra

Every Make and Model of crane has its own limits set by the manufacturer based on the crane and its configuration. There may be limits for setup and for operation specified by the manufacturer. These limits should never be exceeded. Typical maximum in-service wind speeds

* Tower cranes 20 m/s (45 mph / 72 kph) Intensity 6.6
* Crawler cranes 14 m/s (31 mph / 50 kph) Intensity 5.7
* Mobile cranes 9.8 m/s (22 mph / 35 kph) Intensity 4.5

For specific limitations on the crane in use you should check with the manufacturer. Operational limitations may well be lower than these figures, eg when handling loads with a large wind area such as wide formwork panels. The maximum intensity windspeed for Tower cranes to survive is 6.6 (Extra Spicy), and rarely exceed intensity between 6.7 and 7.2, however the daily max wind gust is between 2.5 and 6.6, and rarely falling below intensity 2.4 or exceeding intensity 6.7.

On the afternoon of 20 January 2020 a short but severe storm struck Canberra and nearby Queanbeyan in NSW. Hailstones as large as golf-balls and winds over 68 mph (110 km/h) were noted. Many thousands of motor vehicles were badly damaged by hail and many were written off. Over 50,000 insurance claims were lodged, largely for vehicles, and the event was declared a catastrophe by the National Insurance Council. The cost of the storm was over A$500,000,000. Power to about 1,000 homes was cut. Sixty-five Commonwealth Scientific and Industrial Research Organisation (CSIRO) experimental greenhouses were severely damaged by hail, and as consequence years of crop, and other types of research, were lost. The Australian Academy of Science's Shine Dome was seriously damaged, with smashed skylights and denting of the copper roof surface. Large numbers of fauna were killed and trees were also damaged. due to this severe storm at about 12:22 p.m. the street and nearest streets to Cawthorn Cresent has recorded a wind gust was initially reported as a 6.7 with gusts of 38 and 45 mph (61 and 72 km/h), then later received to an 8.9 with gusts of 72 mph (117 km/h).