Heat Load Indices Forecast Season 2011‐2012

Summary

The 2011/12 heat load forecasting season heralded the launch of the Cattle Heat Load Toolbox web site. The new website provided forecast weather and heat load information to users for a seven day period. The first four days were derived from hourly forecast generated by the WRF modelling system and the final 3 days were extracted from the Global Forecasting System (GFS). The WRF modelling domain was extended to encompass a larger area of the surrounding oceans to better resolve the generation of tropical weather systems. The forecast was also updated with observed daily sea surface temperatures. The forecast was generated every 12 hours (twice daily) and uploaded to the website at 0600 and 1800 daily.

A new innovation developed for the 2011/12 forecasting system was an email and SMS alert system. Registered feedlot operators specified Accumulated Heat Load Unit (AHLU) thresholds that triggered a warning message to be sent to nominated recipients when the threshold was forecast to be exceeded, and the site was likely to experience adverse conditions. Operators could also nominate several sites to monitor; this option was popular with regional veterinarians, nominated by feedlot operators to receive the alerts. A weather outlook service was also provided by a Katestone meteorologist, updating visitors to the site on the current regional weather conditions and the likelihood of adverse conditions for the outlook period of 7 days.

There were only a small number of high heat load events this season. At the broad scale, it appears that the movement of warm and moist tropical air masses to southern parts of the country for extended periods of time resulted in increased temperature and relative humidity, especially during the night-time, thereby maintaining a high HLI and restricting recovery.

The synoptic patterns exhibited during these high heat load events indicate that fluctuations in the position of the monsoon trough and relative position of the sub-tropical ridge could play a significant role in the development of heat load events at both the regional and continental scale.

The relationship between high heat load events and the various scales of motion in the atmosphere provides a new approach to the management of heat load at feedlots. Analysing the climatic drivers of high heat load events will enhance our understanding of the dynamic relationship between large circulation patterns, meso-scale features, such as tropical cyclones, and local influences. To accurately predict the evolution of these dynamic systems and their influence on the HLI and AHLU a better understanding of their development, interactions and ultimately their predictability is required.

The forecasting system performed well at forecasting the location and magnitude of the synoptic features and weather patterns that influenced the development of high heat load events at the regional and local scale.

There was a steady increase in the number of registered users over the season. As of 19 March 2012 there were 57 feedlots registered, with approximately 500,000 head of cattle or just over 40% percent of industry capacity covered by the service.

Other MLA Cattle Heat Load Toolbox projects

• B.FLT.4011 – summer 2019-2020 and 2020-2021
• B.FLT.4004 – summer 2018-2019
• B.FLT.4001 – summer 2017-2018
• B.FLT.0365 – summer 2010-2011
• B.FLT.0357 – summer 2009-2010
• B.FLT.0352 – summer 2008-2009
• B.FLT.0346 – summer 2007-2008
• B.FLT.0340 – summer 2006-2007
• FLOT.334 – summer 2005-2006
• FLOT.329 – summer 2004-2005
• FLOT.324 – summer 2003-2004
• FLOT.320 – summer 2002-2003
• FLOT.313 – summer 2001-2002