I hear these are formed when the water temperature in the clouds is below freezing but the water has not frozen yet due to the lack of ice nucleation particles but Wikipedia says it better
http://en.wikipedia.org/wiki/Fallstreak_hole
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCkdgfQ6FRpHeBbOOQei94Zr61OYnvPVVbViJiOds4p_klST8MvhFmJ1xdvd2NRs_jmcA3PV00ONw3_J-lXjRIcBTzGVrHYpbojfmYuRqdfUiX0Fl_e4QAaG17QAxAUbtK4XWZb_Mk-TmA/s640/26-10-2009_016.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCqw2zWlUSTkSKlTKkiKRBYKdKgzes85T874b14weQ471XEi6DH9DiaNTHo01-WBq6YZm3UnGcrrmwXKm_IZ3PD5xrMeU3FgPJYluZhXODiPqJRGpR-TwlIu2XAINb1nuYlGU6G6w7UxDP/s640/26-10-2009_025.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqCdL6cupWcS0fF0_7wXpnsFiaGC-GjkY2NS2tMGqpV5o99Lehjjuf2Muigeb8dsPxCKtGCgsgOu2kmJZ4XaOkc_ISlRGtAVL8kXAx2tvMJgF7FE3zXH9zyvPzTOtD0oAnfM9DrnLRdGcq/s640/26-10-2009_031.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZb1wKVSrbuovt0bUWSUn1iAFEgg5jEDC0WSyKuA9Bekzl2cR6WneEDP5byrl3HYx-Aa8YmNuo0X1I7VHRwcTSByX4tpDrcHDDdL2jqE0NvESiJwsoQlo0eMdbsu7EsPWgb6Is_iUYcyiO/s640/26-10-2009_034.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKC1hSnhjoQIBEguyZiATADlVi8rqAQ6ouF_arODciwMqKOoanW8Cxqdl7DfoJSEYnum8CH8yzR7U6z7vCOzPSEHqXssaZ_ujzluQU2ri647y9bEnDpfuqqw7tPSKHd8TAqJv37V0fWQuw/s640/26-10-2009_045.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxZ2jx1hdL3OTL-QgczMVpIAsh0BiOYRKUYGhJiltfurkM4HqiNVdxkL_ppGTC-s0JwQ_p2FuLPv7pJdW22XGp4vFXG4hVa4qLoFyMhchPVNDl9uZ3z_ErftVUUzs7Bn2YaYnbIGnqrj5V/s640/26-10-2009_054.jpg)
http://en.wikipedia.org/wiki/Fallstreak_hole
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCkdgfQ6FRpHeBbOOQei94Zr61OYnvPVVbViJiOds4p_klST8MvhFmJ1xdvd2NRs_jmcA3PV00ONw3_J-lXjRIcBTzGVrHYpbojfmYuRqdfUiX0Fl_e4QAaG17QAxAUbtK4XWZb_Mk-TmA/s640/26-10-2009_016.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCqw2zWlUSTkSKlTKkiKRBYKdKgzes85T874b14weQ471XEi6DH9DiaNTHo01-WBq6YZm3UnGcrrmwXKm_IZ3PD5xrMeU3FgPJYluZhXODiPqJRGpR-TwlIu2XAINb1nuYlGU6G6w7UxDP/s640/26-10-2009_025.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqCdL6cupWcS0fF0_7wXpnsFiaGC-GjkY2NS2tMGqpV5o99Lehjjuf2Muigeb8dsPxCKtGCgsgOu2kmJZ4XaOkc_ISlRGtAVL8kXAx2tvMJgF7FE3zXH9zyvPzTOtD0oAnfM9DrnLRdGcq/s640/26-10-2009_031.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZb1wKVSrbuovt0bUWSUn1iAFEgg5jEDC0WSyKuA9Bekzl2cR6WneEDP5byrl3HYx-Aa8YmNuo0X1I7VHRwcTSByX4tpDrcHDDdL2jqE0NvESiJwsoQlo0eMdbsu7EsPWgb6Is_iUYcyiO/s640/26-10-2009_034.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKC1hSnhjoQIBEguyZiATADlVi8rqAQ6ouF_arODciwMqKOoanW8Cxqdl7DfoJSEYnum8CH8yzR7U6z7vCOzPSEHqXssaZ_ujzluQU2ri647y9bEnDpfuqqw7tPSKHd8TAqJv37V0fWQuw/s640/26-10-2009_045.jpg)
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxZ2jx1hdL3OTL-QgczMVpIAsh0BiOYRKUYGhJiltfurkM4HqiNVdxkL_ppGTC-s0JwQ_p2FuLPv7pJdW22XGp4vFXG4hVa4qLoFyMhchPVNDl9uZ3z_ErftVUUzs7Bn2YaYnbIGnqrj5V/s640/26-10-2009_054.jpg)