Thursday, June 23, 2011

Doing something about the weather

Everyone talks about the weather, but no one does anything about it. - Mark Twain

On the evening of June 21, 2011, Knoxville, Tennessee experienced a strange onslaught from Mother Nature. A relatively small thunder shower moved through the area and left in its wake thousands of downed trees and limbs. The storm did not seem that intense except for a few seconds of hard wind, but its aftermath left 2/3rd of the Knoxville Utility Board's electrical customers without electricity. Over half of the KUB customers experienced an outage during the evening of were still without electricity the next morning. In addition many Knoxville, Knox County streets and roads were blocked by downed trees and power lines. As of this morning some 25 streets and roads are still closed as work crews struggle to restore order from the storm damage.

My wife Becky and I took a brief tour of north west Knoxville during the next morning and saw downed trees and tree limbs everywhere, some still in streets and roads. Two houses in our neighborhood, next door to each other, both had large trees blown onto their roofs. Downed trees and limbs were still tangled with utility lines that came precariously close to the roadway. Businesses, still without electricity, were closed.

What is most amazing about this storm was that on April 26 a seemingly more powerful, more intense storm, had knocked out some 50,000 KUB customers, and that had been the largest previous outage in KUB history. Thus the June 21 storm, because of its consequences qualifies as an extreme climate event.

Microburst are common in East Tennessee. I recall witnessing several as a young man. These were truly memorable experiences, which included driving between Jacksboro and Caryville, Tennessee in a torential downpour, that was coming so hard that I could not see the road in front of the hood of my car. I could not pull off the road, because I could not see the edge of the road, and thus could not tell whether it was safe to pull off, or even where the edge of the road was. I still do not know how I survived the experience. On another occasion I stood at a window in the Old Oak Ridge, Tennessee Public Library and watched the rain flow off the ridge on Kentucky Avenue several inches deep. Water flowing off the ridge pooled at the old tennis Courts, where my father use to play on summer evenings. A garbage can had somehow floated into the pond that the tennis courts had become. That day the Oak Ridge did not go to press, because its basement located printing press got flooded. My mother use to call the weather pattern that produced East Tennessee microburst "Florida weather." She was not mistaken.

Only recently did I come to realize that these memorable experiences were examples of Wet Microburst. WCTV of Tallahassee described a Wet Microburst
Seven-thousand people went to bed in the dark Sunday evening, and some area traffic lights were out of commission Monday morning, all thanks to a small, but powerful storm that rolled through Tallahassee Sunday afternoon.

In a matter of seconds, sheets of rain, bursts of high wind, and chunks of ice descended upon the Tallahassee landscape shortly after 4 o'clock Sunday afternoon. described a microburst
A microburst is a brief, powerful gust of wind that appears to radiate from a central point on the ground. It is caused by strong downdrafts that form in the central part of a congestus or cumulonimbus cloud. . . .

The wet microburst is usually associated with heavy rain and, again, evaporation is the vital ingredient producing strong surface winds. However, in this case, the precipitation reaches the land below. Often, the wind and rain meet the ground with such force that they spread outward and upward, forming a distinctive curl.
The Airline pilots account added,
The dry microburst occurs in dry conditions, when a column of rain falls into a layer of dry air beneath the cloud, and immediately begins to evaporate. Since evaporation produces cooling, this accelerates the downward motion of the air column, producing a powerful gust of wind that spreads in all directions. Where there is warm air near the ground, this will tend to rise and counter the downdraft. However, the descending air may still reach the surface with some velocity. Because the precipitation usually evaporates completely, the only visible sign of a dry microburst will be raised dust.
The WCTV story also covered the origin of a dry Microburst
There are special things that favor the formation of microbursts. These include a warm, moist environment near the ground, with some dry air a few thousand feet above us. As rain falls through the dry air, it cools through evaporation. The cool air descends from the storm and spreads out violently as it reaches the ground.
Knoxville got clobbered with an unusual microburst, one which the Weather Bureau says was supercharged with winds from a second weather front.

Microbursts are dangerous, they can cause floods, and they can and have most assuredly have killed people. If we are sane, we don't want to see them more frequently.

Not just Knoxville but most of the Southeast has had an unusually wet spring. In fact the news staff of a Knoxville TV station took off time from reporting the latest rampage of mother nature to not how unhappy they were with the abnormal weather and to wish that the weather would return to normal. Of course if we are undergoing climate change, the abnormal will become the new normal.

Knoxville is not the only area of the country to see abnormal spring weather. The middle part of the country has seen unusual flooding with floods on the Mississippi, the Missouri, and now the Souris River in the Dakotas and Canada. In the Southwest, from Texas to California, a drought has lead to record forrest fires. Now this might all be simply coincidence, of it all could be harbingers pf climate change.

How will we know if climate change is upon us? If the climate does not turn back to the old norm we will have witnessed climate change. Climate change skeptics claim that CO2 emissions will not change the climate, and that no undesirable climate changes are taking place.

We have been in a period of confusion about our climate and remedies for climate change. The time of that confusion is almost over. The confusion involves both the acknowledgement of the reality of climate change, and its danger, and the choice of practical steps to bring the forces that are changing our climate under control. As Pogo said,

We need to quickly find paths to post carbon energy, and set out to make those changes. Extreme weather events, which may be signs of climate change, are happening now, and they appear to be happening with increased frequency. We can do something about the weather if we want to act, and not simply talk about it, and the time to act is now.

1 comment:

Joel Riddle said...

My power (near the western edge of KUB's electric service territory) was out for a full 22-24 hours before being restored last night sometime between 6:30 and 8:30. Ironically, KUB's outage map was in an outage as of about 8:30 am yesterday morning.


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