1 For automobiles a taxpayer uses for business purposes, the portion of the business standard mileage rate treated as depreciation is 23 cents per mile for 2013, the same as in 2012. 2  The IRS also publishes a standard mileage rate for the use of a vehicle for medical or moving purposes.
What causes continuous rolling thunder when no lightning visible? Thunder is caused by the rapid expansion of super-heated air as electrical spark passes through. What causes the long (ie some several seconds) of rumbling when no lightning is visible even at night during tropical downpours?
What causes thunderstorms? Thunderstorms form when an air mass becomes so unstable that it overturns (convects) violently. Thunderstorms are most common in the afternoon over land, when daytime heating of the land by the sun causes the lower part of the troposphere to become unstable from higher temperatures and more water vapor in the air.