In Haines we trust. But should we? 🤔
Welcome to the first edition of the Wildflyer newsletter.
Despite better judgment, we’re diving straight into nerd mode 🤓 with a miniseries on Fire Indices 🔥. Plus, we’re excited to introduce two new features on the Wildflyer platform.
Every division’s Fire Behaviour Analyst team must answer a critical question: which set of fire risk indicators should we use? Most of the time, the answer is: “the one we’ve been using all along.”
However, with changing fire regimes, firefighting divisions are now revisiting old practices and experimenting with new ones.
The most commonly used Fire Indices today include the Haines Index, the Canadian Fire Weather Index (FWI), and the 30/30/30 rule. All of these are over four decades old. While old doesn’t necessarily mean ineffective, we must ask: are they still up to the task?
In this miniseries, we’ll delve into the most commonly used Fire Indices, such as the Haines Index and FWI. We’ll examine their strengths and weaknesses. Additionally, we’ll explore emerging and lesser-known indicators like HDWI, PFT, CH, and FWIe.
Before we smoke jump into the Haines index, here are two features you can now try on Wildflyer. We’re looking forward to hearing your feedback.
Historical Forecasts - Leverage terabytes of weather data to browse through Forecast and Reanalysis data for every incident. Perfect for learning from past incidents and saving time on reporting ✨
Telegram Integration - Receive incident and weather warnings directly to your existing workflow by securely integrating Wildflyer to your Telegram Groups 💬.
The Haines Index.
Haines 101
Let’s start with a quick refresher on the Haines Index. Originally published as the Lower Atmospheric Severity Index (LASI) by Donald Haines in 1988, it describes the chance a fire, once started, will develop into a big fire.
Donald A. Haines
Born on May 29, 1932 and passed away in December 31, 2022.
The Haines Index consists of two components: atmospheric stability and atmospheric aridity (moisture content in the air). It assigns 1-3 points to each component by comparing the temperature (for stability) and the dew point (for aridity) at two different atmospheric levels. The levels used depend on the terrain elevation, classified into three categories: low, medium, and high elevation.
Pressure levels and threshold values for the Haines Index - Potter 2018
Example: Athens 23 July 2024
Temperature at 950hPa was 27°C, at 850 hPa it was 24 °C = 3°C difference (1) point
Dew point at 850hPa was 1°C. 24°C - 1°C = 23°C. Very dry atmosphere, (3) points.
Haines Index: 1 + 3 = 4/6 indicates a risk large fire growth.
We did warn you about diving straight into nerd mode.
Now that we have a detailed understanding of how the Haines Index works, let's address the question: is it useful, and should we use it?
Spoiler: No, we shouldn’t.
The many problems with Haines
To start with a clue:
‘This is a first effort at constructing a national fire-weather index based on features of the lower atmosphere… it will… undoubtedly require further refinement and/or additional components.’
Thus spoke Mr. Haines himself (the above quote is from an insightful paper by Brian Potter from the US Forest Service).
There are four big problems with the Haines Index.
Misused as generic fire weather indicator
The first problem isn't with the Haines Index itself, but with how it has been used and interpreted. Mr. Haines intended the LASI to be a preliminary step towards a broader Fire Risk Index, but personal circumstances prevented him from developing it further.
Due to optimistic and naive peer reviews that correlated high Haines values with big fires in a limited number of cases, the index was quickly adopted as a generic fire risk indicator.
Every fire behaviour analyst will point out that relying solely on atmospheric stability and aridity as fire indicators is inadequate. It’s like tasting one ingredient and assuming you know the whole recipe. Even though fuel conditions, wind, temperature, orography, to name a few, are also in the mixing bowl.
Overly simplistic
The Haines Index examines only two atmospheric levels. In the example above, it ignores what happens between 950 and 850 hPa, or above 850 hPa. The interactions between the fire and the atmosphere are disregarded, and there is no sub-diurnal detail, among other limitations.
Empirical, thus difficult to adapt to different localities
The Haines Index was empirically derived. In plain terms this means that Haines just thought up different classification values based on his rich experience and understanding.
What makes this problematic is when fire divisions from other countries try to implement this and copy/paste the values, even though atmospheric dryness might be on completely different scales in the south of Italy or mainland Australia.
This problem is not restricted to the Haines Index. It exists in other Fire Indices, including the FWI, and the solution is quite simple. But we’ll save that for a future edition.
Maxing out
A frequently heard problem with the Haines Index is that it just maxes out too often. If Haines is at 6/6 for a full 20 days of August, it loses its predictive skill.
The Continuous Haines Index
One adaptation of the Haines Index that overcomes at least some of the problems of the original Haines index
The same two components are derived, but rather than classified (1/2/3) and then added, (2-6), a continuous scale is used where both components are combined according to slightly more complicated formula.
Very few divisions I spoke to in Europe use the CH, and the exact formula differs. The original Australian version of the CH is this:
Here, CA represents the temperature gradient (at slightly different pressure levels) and the CB the atmospheric aridity.
By using a continuous scale, the problem of maxing out is solved and adapting the index to one’s own region becomes more straightforward.
Conclusion and recommendations
First, do we trust in Haines? In Haines, the person, yes! he completely understood the limitations of his LASI.
In Haines, the Index, however, it is clear that it is a good fire indicator ONLY if convection is the only factor in play. And who knows that that will be so without looking at other factors. And even in those cases its predictive skill is quite low. We must never base our preparedness or response level solely on Haines.
If you’re still using Haines, you might be interested to check out the Continuous Haines Index (CH) if you haven’t done so already.
Keep following this miniseries on fire indices.
Disclaimer: we are NOT seasoned fire meteorologists. The views in this newsletter come from talks with dozens of experts in the field and many scientific studies.
What do you think?
Are we wrong about ditching Haines? What do you think?
Also, should we include the Continuous Haines Index on the Wildflyer platform? Let us know what you think.
Acknowledgements
A lot of information used for this newsletter came from these two fantastic papers by Brian Potter (2018) and Wilson et al. (2023). Thanks!
Thanks to Jay Charney (USFS) and Georgios Papavasileiou (NOA) for proofreading.
Thanks to Mr. Haines for advancing the science of fire weather ❤️🔥.