THE ANSWER IS VISUALLY SIMPLE
You see it all the time. The trees that break are typically imbalanced or diseased. Observe these photos for example:
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| THIS TREE WILL SPLIT RIGHT DOWN THE MIDDLE DURING A BAD STORM SUMMER OR WINTER |
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| THIS TREE WILL COMPLETELY UPROOT IN A BAD STORM SUMMER OR WINTER |
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| THIS TREE'S DEAD FROM DISEASE LIMBS WILL BREAK OFF IN EVEN A MILD STORM |
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| THIS TREES LEFT LIMB IS WEAK IN CALIBER AND IT COULD VERY WELL BREAK IN AN ICE STORM |
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| THIS TREE WILL LOSE THE LOWER RIGHT BRANCHES FROM WEIGHT IN A SNOW OR ICE STORM |
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| THIS TREE WILL LOSE THE VERY BRANCH THE ARBORIST IS BEGINING TO PRUNE IN A WINTER STORM OF SNOW, ICE AND HIGH WINDS |
