What is NASA's Anvil Rule for Thunderstorms?

Question: What is NASA's Anvil Rule for Thunderstorms?

The launch of any shuttle is directed by strict protocol. With most flight delays caused by weather, NASA set forth a series of rules for clearing a shuttle launch. In fact, not only are there launch rules, but emergency landing rules, alternate landing rules, and flight return rules. One of the protocols for launch involves sky conditions and specifically refers to anvil clouds.

Answer:
Where Can I See an Anvil Cloud?
Anvil clouds are the icy upper portions of cumulonimbus thunderstorm clouds that are caused by a rising of air in the lower portions of the atmosphere. When the rising air reaches 40,000-60,000 or more feet, it tends to spread out in a characteristic anvil shape. Generally, the taller the cumulonimbus cloud, the more severe the storm will be.

Damage by Lightning Could be Disastrous to the Shuttle.
Lightning is dangerous to sensitive electronic equipment aboard the space shuttle. Specifically, the shuttle and the plume from the engines can actually increase or trigger lightning to occur. The weather launch rules specifically state that no launches will occur if an anvil cloud is located within 10 nautical miles.

Can I Make Lightning?
Lightning occurs when the potential for a charge difference occurs between two objects. For example, perhaps at one point in your life you rubbed a balloon on your head at a party and laughed as it stuck to your head. Your hair stands up and you feel the static charges. Those charges are caused by a transfer of electrons. If you were to complete this little trick in a very dark room, you would actually see the charge differences in the form of a spark. It is a tiny little lightning bolt!

The Shuttle can CAUSE more Lightning
When the space shuttle goes high into the atmosphere, the long plume from the exhaust gives a pathway through which lightning can flow. In addition, the plume will reduce the electrical field necessary to trigger natural lightning.