Weather word: "Feedback"

Feedback: A relationship between two components of a weather system such that changes in one component cause changes in the other which, in turn, affect further change in the first component.  

Here’s an example: Higher temperatures over the icecap on the Arctic Ocean cause Arctic sea ice to melt, allowing sunlight to warm the water, furthering ice melt. Over the Arctic Ocean, air over open water is warmer than air over the icecap, but as the amount of ice diminishes, the average temperature of air in the Arctic region rises, and the entire process repeats itself.

Debunking the myth that rubber insulation offers protection from lightning

The following is excerpted from “All About Lightning” by Dr. Martin A. Uman, University of Florida (Gainesville) Department of Electrical Engineering:

“To be safe from lightning really means being certain that none of the lightning current can flow through you. If lightning is occurring nearby, this can only be ensured by providing the lightning current with paths to ground more preferred (paths which provide much less resistance) than your body. Lightning does not respect token levels of insulation. It is therefore suicidal to suppose that, for instance, the wearing of rubber shoes will protect you from a direct lightning strike. Lightning which travels many miles through insulating air is not about to be halted by half an inch or even a yard of insulating rubber. The rubber tires on a car do not serve to insulate it from being struck by lightning, as is commonly believed.”

This is not to imply that cars do not offer protection from lightning — they do offer protection. However, the protection is afforded not because a car sits on rubber tires but because the electric charge from a direct lightning strike to the vehicle will be conducted safely to ground through the metal exterior of the car, leaving the passenger compartment untouched.

The Australian cool change

Cool change: In Australia, the passage of a vigorous cold front (usually from a southerly direction) that breaks a summertime heat wave. It introduces cool, moist oceanic air that replaces intensely hot, dry continental air from the interior of Australia. As in the United States and elsewhere, the cool change (cold front) is often accompanied by thunderstorms.

Weather Terms: Tropical cyclone

Tropical cyclone: The generic term for a low pressure system, not associated with warm or cold fronts, that forms over warm (at least 80 degrees) tropical or sub-tropical ocean waters, and with precipitation organized in counterclockwise-curving spiral bands. Tropical cyclones are classified according to their highest sustained winds.

Tropical disturbance: A poorly organized area of low pressure. There may be gusty winds associated with scattered showers and thunderstorms, but tropical disturbances bring little or no organized wind.  

Tropical depression: An organized area of low pressure with sustained winds 38 mph or less.

Tropical storm: Sustained winds 39-73 mph.

Sustained winds 74 mph or higher.

Chicago climatology

Chicago temperature surprise: Based on Midway Airport temperature data from the 82-year period of 1928 through 2009, daily high temperatures in the 60s occur more often in the city during December than during July. High temperatures in the 60s were logged on 51 days in December during those 82 years, whereas highs in July during that same period occurred on only 47 days.