Chapter 1 Introduction

It was hazy, hot, and humid that day in early July.The hay, cut two days ago and bailed this morning, was in the barn, the bales stacked and ready for winter. I sat in the old green Adirondack chair in the shade of a maple which had graciously volunteered to grow along the edge of the lawn, drinking lemonade and watching the cumulus clouds build to the northwest.The first indication of any action was a faint, low pitched rumble, almost felt. Clouds started to gather, and the sky got darker.

The rumbles became more distinct and longer as the storm headed my way.  I finished the lemonade and went to the barn to close doors and windows where needed and started for the car and truck when the wind shifted direction. The temperature dropped noticeably as I closed the car windows and headed to the house.

A nearby flash and the accompanying thunder announced the arrival of the first giant drops of rain. I counted it off starting with one thousand when I saw the flash and continued with “two thousand, three thousand, four thousand, five thousand” and then heard the first thunder.Since sound travels about 1,000 feet in a second, five seconds is about 5,000 feet, about one mile.  The bolt started roughly 5,000 feet away, roughly a mile. If you keep counting until the end of the thunder and assume the lightning bolt was vertical, you can estimate the length of the bolt. The time from the flash to the end of the thunder gives the distance which is the hypotenuse of a right triangle so you need to do some squaring and square roots. Of course, lightning rarely moves in a straight line.

Watching the huge drops splatter on the pavement, the gusty winds sent spray all over and tried to wrest the screen door. Time to close the windows.

Sheets of rain come down. The willow tree in the front yard whipped back and forth as one side of it got wet in a gust of rain. The other side is spared only to be doused a few seconds later in another gust. Out on the back porch, sheltered from the gusts by the glass on the end, the bursts of wind and rain move the grass in the field next door in serpentine patterns like ocean whitecaps.

The rate of lightning bolts can tell you something about the storm.  This thunderstorm produced lightning bolts about every 15 seconds and was a reasonably vigorous storm. This, coupled with the fact that the raindrops were large, indicated that there was considerable ice up in the cloud which melted as it came down.

Most people are surprised that snow forms during the heat of summer. But, the sun heats the atmosphere by shining on the surface; the surface heats the air just above it and that hot air bubbles upward. On the average, the temperature of the atmosphere decreases 3.5 degrees Fahrenheit for every thousand feet. For a surface temperature of 72 F any cloud material over about 11,500 feet has a temperature below 32 F.

Then the rain gusts stop, tailing off into a gentle patter singing on the pools and rivulets caused by the earlier inundation. The rain stops almost as suddenly as it started. Looking out of the back porch the clouds once again appear to have defined edges. The clean smelling breezes are cool and the sun is starting to peek out from behind the cloud. The departing thunderstorm glides onward looking like cotton sails leaving the air smelling like it had been scrubbed clean.  

From the ground, the thunderstorm was a refreshing break, as long as the hay was in and didn’t get wet and you’re under cover.

City dwellers rarely give a thought to agriculture. After college, I taught school and married a dairy farmer’s daughter. While dairy farming is relatively free from weather worries during most of the year, it gets intense around hay season, usually June in the Catskills of New York. When the hay is ripe for cutting, a heavy windstorm or rain can “lodge” the hay, crushing it down so it is almost impossible to cut. Once cut, the hay needs to cure in the sun for around two days. Curing is more than drying as the diatoms in the hay convert the starch to sugars. Should it rain, the sugar and some of the starch dissolves and heads down the brook. A thunderstorm on cut hay is a disaster. 

Other crops have their own weather problems. Too much rain at the wrong time can ruin almost any crop No rain during the time corn tassels can ruin a corn crop. The list goes on. It is little wonder why farmers have been concerned with the weather, probably since humans came out of Africa.

Chapter 2 Types of Thunderstorms

The early people probably developed a healthy respect for thunderstorms. In the ages before writing, it would only be natural for tribes to have some explanation of these fearsome manifestations of nature. It should not be surprising that Zeus wielded the lightning bolts. Further north among the Vikings, Oden delegated the thunder to Thor who, with Loki, had numerous adventures featuring lightning and thunder.  Whether religion or mythology, these entities controlled the weather as did around fifty other deities or demigods in other cultures around the world.

Judaism, Christianity and Islam being mono-theological, do not have separate gods for lightning, so other ideas sprang up to deal with weather events.  Borrowing from the small gods where river meets road and the like, the folk “under the hill” became likely candidates. Stories whiled away the quiet nights, perhaps in the pubs or around a peat fire in the hearth. Titania, the summer queen of the fairies, shows up in Shakespeare’s Midsummer Night’s Dream. Stories are told which hold that the Winter Queen counterbalances her, presumably defeating Summer in the weather battles during the fall while Titania starts winning sometime just after the Winter Solstice. One of Titania’s favorite weapons, the thunderstorm, predominates in temperate climates during spring and summer.

Somewhere between four and their teens, children enjoy looking for the animals and such in clouds. It is easy to watch growing cumulus and imagine Titania’s minions with bibulous ears and big white eyes marching across the blue sky.   Some days, a shepherd watching the flock might see a whole array of cloud warriors with dragons marching from horizon to horizon. It is also said that King Arthur fought under the symbol of the red dragon implying that he held the battlefield after sunset. It might be easy to believe they are from the Unseelie court under the hill marching off to battle with the summer queen and her hosts. Whatever the myths or religion, people recognized that lightning could really do damage. Whole or parts of herds were killed by lightning. Barns, houses and forests were set on fire. People were struck down and killed by lightning and still are. Florida has a very high death rate due to lightning.  Lightning is nothing to mess with.

Modern ideas about thunderstorms start with recognizing the different sizes and organizations of thunderstorms which grow in the atmosphere.  

• The thunderstorm on the farm discussed earlier was an isolated thunderstorm, perhaps the most common of them. The thunderstorm cell is the visible outside of the cumulus cloud and the thermals which drive the cloud move upward inside, often breaking through the cell to enlarge the cell.  Most isolated thunderstorms last an average of a half an hour.

          

• A study of the effects on houses, trees and other things produced a classification of Severe Thunderstorms which had winds greater than 50 knots and/or hail larger than one inch. The category seems to be one which can produce some damage in most of the presently used building codes.

          

• Supercell Thunderstorms are more intense thunderstorms and seem to have fairly complex circulations than their weaker brethren.   They are typically long lived and produce hail and frequently tornadoes. They sometimes split into two cells which move in somewhat different directions, right moving and left moving cells. One or both of the cells may have a weak radar echo region.

   

          

• With the caveat that many cumulonimbus clouds do not have lightning and thunder, there are a number of organized groupings of thunderstorms. These are convergence zones such as Hurricanes, Squall Lines, Mesoscale Convective Systems, and Sea Breezes and other similar convergence situations.

          

• Winter thunderstorms occur, although most people have never seen one as they occur where population is sparse. Lake Effect storms produce the most thunder and lightning in the continental USA, mostly from storms from Lake Ontario in New York and Salt Lake, Utah. Similar thunderstorms occur over the Sea of Japan and may occur elsewhere. These thunderstorms are small, rarely with tops around 10,000 feet.

          

• Another type of winter thunderstorm is the occasional “thundersnow” near the center of an extratropical cyclone. These storms usually produce very rapid snowfalls.

Table 1 Calendarof Phenomena for Northern Hemisphere