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Accumulated rainfall models

You may come across posts with images like this, which might suggest rainfall totals of over 250mm. However, these images represent the accumulation of potential rainfall over time, not a guarantee of actual totals.


While some areas might experience significant rainfall exceeding 250mm, it’s important to note that much of this comes from storms, which are highly localized and depend on the shifting position of weather systems, like troughs.




To get a clearer picture, focus on the 24-hour accumulated rainfall images, as I provided in below, as these provide a more accurate day-by-day outlook. Remember to check updates regularly to stay informed about any changes.



Queensland Weather Outlook: Focus on Storms and Rainfall

From Tuesday through Friday, expect significant rainfall and storms across central and southeastern Queensland. Storms are likely to intensify midweek, with widespread showers and moderate falls in areas like Rockhampton, Bundaberg, and the Central Coast. Rainfall totals could exceed 40mm in some regions, particularly along the east coast, with Townsville and Innisfail seeing heavy showers. Keep an eye on the skies, and don't forget to check the detailed 4-day forecast supported by Bold Shout!


Who Can Expect the Most Rain

  • Innisfail: Up to 50mm on Thursday, with consistent rainfall across the week.

  • Ayr: Heavy falls of up to 40.9mm on Thursday.

  • Emerald: Significant rain on Tuesday (20.3mm) and Wednesday (9.9mm).

  • Mackay: Periods of moderate rain, peaking at 14.4mm on Wednesday.

  • Brisbane and Gatton: Moderate to heavy falls on Tuesday (31.2mm and 26.4mm respectively).


Who Can Expect Something

  • Townsville: Light rain overall, with 24.1mm on Thursday being the highlight.

  • Cairns: A mix of light to moderate showers, with 24.1mm expected Thursday.

  • Bundaberg and Rockhampton: Scattered rain, ranging from 5–13mm, particularly midweek.

  • Charleville: Patchy rain, peaking at 17.4mm on Wednesday.


Who Can Expect No Rain

  • Birdsville: Minimal rainfall, with only 0.1mm across the week.

  • Tully: Nearly dry, with less than 1mm expected most days.

  • Gold Coast: Dry conditions with only 17.7mm on Tuesday and minimal rain thereafter.

  • Make sure to prepare for the rain if you're in areas expecting heavy falls!



Forecasts for accumulated rainfall 10 to 16 days in advance are often highly unreliable due to the inherent limitations in weather modeling and the chaotic nature of atmospheric systems. Here's an educational breakdown of why these models can be misleading and how much error they might include:


1. Chaos in Weather Systems

Weather is a chaotic system, meaning small changes in initial conditions can lead to significant differences over time (the "butterfly effect"). While short-term forecasts (1–5 days) are increasingly accurate, models struggle to maintain precision over longer periods. By 10 to 16 days, small errors in the initial state can amplify dramatically, rendering long-term rainfall predictions speculative at best.


2. Model Limitations

Forecast models rely on complex equations and assumptions to predict future weather. These models are updated with real-time data, but their ability to simulate precipitation accurately diminishes with time. Factors like small-scale convective storms, localized temperature variations, and topography often deviate significantly in predictions beyond a week.


3. Verification of Model Accuracy

Studies and real-world data show that long-range precipitation forecasts have much lower skill scores than short-term forecasts. For example:

  • The skill of 10-day precipitation forecasts is about 20% lower than 5-day forecasts in terms of accuracy.

  • Extreme rainfall events (e.g., localized heavy storms) are particularly challenging to predict far in advance​ https://content.meteoblue.com/en/research-education/weather-data-accuracy/precipitation

    Practical Implications Long-term forecasts are best used as guidance for general trends rather than specific outcomes. For example, a 10-day forecast might suggest "above-average rainfall potential" but should not be interpreted as precise rainfall amounts for a specific location.


Example Data Showing Errors

Comparisons between forecasted and observed rainfall for long-term models often reveal significant deviations. For instance:



Conclusion

10-16 day rainfall models are not inherently "bad," but they should be understood as low-confidence tools. Their purpose is to provide general trends, not precise outcomes. Meteorologists often emphasize the probabilistic nature of these forecasts and encourage users to stay updated as the forecast period shortens.


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