This is common during high wind storms. It is caused by a failure of the tar or the sealant (called a tab) located under the shingle. This tab is the glue that adheres the top shingle to the base layer. There are two main reasons why this seal fails:
Old Roof: While shingles can blow off from older roofs without indication that there is a serious condition. That is not always the case. If a roof has aged and is over 15 years to 40 years old it could be cooked or fried. This is an industry term for failing. As the shingles age they loose their elasticity and their ability to stay sealed together. They also become hard and brittle which keeps them from lifting. But strong wind will lift them up and snap them back creating a visible clean shear cut. When a roof is in this condition it becomes difficult to repair. When a roofer attempts to replace this missing or damaged shingle and has to lift the top shingle just enough to get the new shingle under it; it too may snap making you a candidate for a new roof.
New Roof: If your roof was installed in the winter and the shingles were not exposed to enough heat to seal properly they may dry up or freeze making them susceptible to blow off. Can this be repaired? Yes. You can hire a roofing contractor to physically go on the roof and lift each shingle and install 6 dabs of carnack (roof cement) from a caulking gun and then press the shingle back in place,. You would want to do this on a warm day of at least 55 degrees, I would avoid doing this in an extremely hot day because the roofer could accidently damage the roof by walking around and doing his work.
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