Weather by Malcolm RileyOld Weather Forecasts

There has been an explosion in the availability and frequency of weather forecasts over the last 15 years. Much of this content is available only due to the internet, once the domain of the home computer, it is now available on a smart phone over much of Australia’s coastal waters.
Of course this was not always the case and forecasting the weather has been around for thousands of years. Indigenous Australians used various types of watercraft, in Tasmania reed boats and outrigger type dugouts were used.
Given Tasmania’s changeable weather conditions it is likely that there were aborigines lost at sea due to changes in weather conditions. These early Tasmanian mariners would have kept a “weather eye” on the conditions based on their local knowledge.
As Europeans began to arrive in uncharted and unknown Australian waters the mariners relied on their knowledge and wits. Possibly the only advantage these mariners had over the indigenous inhabitants was most would have had a barometer.
Wrecks and groundings were common place. One of the first shipwrecks in eastern Australia was the Sydney Cove in 1797.
At the time the existence of Bass Strait was unknown to European mariners. As the vessel travelled up the east coast of Tasmania it was lashed by storms that increased an existing leak. Turning westward to seek shelter the vessel was run aground on Preservation Island in the Furneaux group.
Ironically one of the vessels (Eliza) sent to rescue the survivors became Australia’s second shipwreck when it was lost without a trace returning to Sydney.
The list of wrecks grew longer each year often with the weather playing the major part.
The Cataraqui an 800 ton emigrant ship in 1845 gives an insight into the perils facing early mariners. She endured a series of northerly to southwesterly gales, a “perfect hurricane” and rain and cloud from mid-July as she crossed the Bight. With only indifferent positions obtained they did not know where they were. At 4am in dark and rainy conditions the vessel struck a reef off (now) Cataraqui Point off the west coast of King Island. There were only nine survivors with 342 bodies buried in mass graves on the Island.
These early shipwrecks led to the establishment of some lighthouses that, as well as warning mariners, also collected meteorological information. This information became the basis of the weather forecast but needed the invention of the telegraph to get the data in a timely manner. By looking at the information at various locations a broad idea of the movement of weather systems could be determined.
Dangerous WindsIn 1860 Admiral Fitzroy began forecasts in The Times newspaper in London and a series of shapes were displayed at some ports to give departing mariners an idea of expected conditions. This innovation reputedly saved thousands of lives.
Clement Wragge a flamboyant early Australian meteorologist, at first based in Queensland, in 1887 produced forecasts for agriculture and shipping. His rainfall forecasts earned him the nickname ‘inclement Wragge’ and accounts from the turn of the century have him equally cursed and praised.
There are reports of steamship Captains swearing by him … but there are also other reports of steamship Captains swearing at him.
Storm SignalsThere was a system of signals similar to the ones Fitzroy used that were displayed at ports, at some lighthouses and suitable vantage points along the coast. Wragge’s forecasts were the basis of these displays. The illustrations at right and on the next page were printed in Wragge’s almanac in 1898.
On the day of the Bureau of Meteorology’s formation (1/1/1908) the following forecast appeared in the Hobart Mercury.
Forecast for January 1:- Fine weather, warmer. Prevailing winds light easterly.
State of adjacent seas slight.
H. C. Kingsmill, Government Meteorologist.
This type of forecast changed little in the ensuing years and by the mid 1920s it started to include information about seas offshore.
Australian storm chartOcean. Rather rough conditions approaching from the Western Bight.
By the 1950s the forecast had expanded to give wind directions and speeds and state of the sea.
Today there is a wealth of information literally at our fingertips. The image above right is from the Bureau of Meteorology website on Monday 31 January, 2011 forecasting for 10pm on Wednesday night 2nd February and is a forecast of cyclone Yasi.
The models actually gave good guidance of Yasi’s formation and landfall nearly a week in advance.
It is important to remember that the myriad of forecasts the mariner can get are just that … forecasts.
radarForecast accuracy is good and it is unlikely that any major system would be missed. However, there are many factors that can alter a forecast, local topography is a good example, and outflows from individual thunderstorms can extend 20 kilometres or more from the storm and be completely different from the daily forecast.
A forecast that for whatever reason is under-forecasting wind speed by 15% would usually not be hazardous. That is unless the original forecast wind speed was at the top of your vessels capabilities and the increased wind speed would then exceed your vessels safe operating wind range.

 

*Malcolm Riley is the Public and Marine Officer for the Bureau of Meteorology in Hobart. He has worked in all States with the exception of Qld and is a Master V. He gives education courses on Marine Meteorology.