Grandma sez, based on observation – and so do forensic engineers

Cindy Day’s grandmother predicted the weather the same way forensic engineers initially hypothesize the cause of a failure or accident – by ‘accumulated wisdom and careful observation‘. (Ref. 1)

I was struck by this as I read Cindy’s book, ‘Grandma Says’ – and the fact the two of them get their predictions and hypotheses right a lot of the time based on little evidence. This as confirmed by science in weather forecasting and more detailed forensic investigation in engineering.

‘Grandma Says is a collection of 80 weather-related sayings and prognostications about the weather based on traditional sayings and experience’. Most weather lore is based on careful observation of nature’s cycles or of animal behaviour. (Ref. 1)

I’m reading the book and noting which of Grandma’s 80 sayings are based on simple observation but well supported by science – so far, many.

For example:

  • Morning dew on the grass, rain will never come to pass. That’s because the air temperature drops on a clear, windless night to the dew point – the point when the air is saturated with moisture. Condensation then occurs and appears as dew on the grass. These conditions exist in the centre of a fair weather system.
  • If the dog is acting up, there’ll be thunder before long. This is because they can smell increased concentrations of chemicals in the air associated with a storm, like ozone which has a metallic scent. They can also hear thunder long before we do. My two dogs do that.
  • It’s not snow, it’s poor man’s fertilizer. That’s because snow contains a lot of nutrients, like nitrogen, for example, and a lot of moisture. If the snow falls on unfrozen ground in the spring, the nutrients penetrate the soil and do some good, like fertilizer.

I’ve mentioned different times how an expert’s initial hypothesis – an educated guess – on the cause of an accident or failure is based on a (1) visual assessment of a site, (2) preliminary data and (3) experience. I’ve even ventured to estimate the percent probability that the hypothesis will be borne out by additional forensic investigation. (Ref. 2) This is the approach in both science and applied science (engineering).

For example, as mentioned in the following blogs:

  • A Bundle of Blogs: Using visual site assessment. Posted January 25, 2021
  • What can you get from a virtual visual site assessment of a retaining wall on the verge of failure? Posted November 13, 2020
  • “Calibrating” a forensic expert. Posted June 23, 2020
  • “Technical” visual site assessment. Posted September 4, 2012

I’ve demonstrated the application of experience and observation by hypothesizing the cause of failures reported in the news, and noted the potential for failures in the future – see the following list.

I study these failures to get more experience. The correctness of my educated guessing has been endorsed by local colleagues in engineering, and others away and overseas. We’re getting it right most of the time based on experience and observation – like Cindy’s Grandma.

For example:

  • Condo collapse, Miami, Posted July 14, 2021
  • Cost overruns, Ottawa Posted June 22, 2021
  • Building collapse, London, Posted December 31, 2020
  • Retaining wall failure, Ottawa, Posted November 13, 2020
  • The potential for failure, Everywhere, Posted July 23, 2020
  • Bridge failure, Edmonton, Posted March 25, 2020
  • Crane collapse, Halifax, Posted September 20, 20019
  • Bridge collapse, Italy, Posted October 5, 2018

Farmers, gardeners, outdoor people, dog owners and forensic engineers are all doing it – forecasting the weather and the cause of problems. If truth be told, I can imagine the young farm girl is alive and well inside Cindy Day, the meteorologist, and that she is still forecasting the weather, like Grandma did, on her drive to work each day.

For sure, Cindy’s checking the charts and hard data before going public with the weather forecast. But still having fun on the drive observing, estimating and learning based on wisdom and experience – like engineers do – and getting it right often enough.


  1. Day, Cindy, Grandma Says, Weather Lore from a Meteorologist, Nimbus Publishing, Halifax 2012, 2013
  2. The reliability of an educated guess on the cause of a failure or accident. Posted October 22, 2020

(Eric E. Jorden, M.Sc., P.Eng. Consulting Professional Engineer, Forensic Engineer, Geotechnology Ltd., Halifax, Nova Scotia, Canada Posted July 28, 2021

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