Thunderstorms Florida has more thunderstorms than anywhere else in the US. Florida has more thunderstorms each year than anywhere else in the US

Hail The western side of the central plains have the most hail each year. The western great Plains has more Hail storms each year than anywhere else in the US

Tornadoes Although Florida also has lots of tornadoes per 10000 square miles most of these are F0 to F2. The central plains have the most tornadoes each year.

Normally the upper part of a cloud is positively charged and the bottom is negatively charged.

Electrons have negative charge and protons have positive charge.

Opposite charges attract each other and similar charges repel each other

Pick up a piece of paper with a comb Pick up a piece of paper with a comb. Although the paper does not have a total positive or negative charge the charges on it are shifted around so that the + charge on the paper is closer to the – charge on the comb. The paper is attracted to the comb.

A balloon sticks to the wall A balloon sticks to the wall. Although the wall does not have a total positive or negative charge the charges on it are shifted around so that the + charge on the wall is closer to the – charge on the balloon. The Balloon is attracted to the wall.

Polarization of a molecule in the bottom figure

Thunderstorms Lightening and Thunder Lightening: discharge of electricity in mature storms (within cloud, cloud to cloud, cloud to ground) Thunder: explosive expansion of air due to heat from lightening Electrification of Clouds: graupel and hailstones fall through supercooled water, ice crystals become negatively charged Upper cloud positive, bottom cloud negative

FIGURE 14.28 The lightning stroke can travel in a number of directions. It can occur within a cloud, from one cloud to another cloud, from a cloud to the air, or from a cloud to the ground. Notice that the cloud-to-ground lightning can travel out away from the cloud, then turn downward, striking the ground many miles from the thunderstorm. When lightning behaves in this manner, it is often described as a “bolt from the blue.”

FIGURE 14.29 When the tiny colder ice crystals come in contact with the much larger and warmer hailstone (or graupel), the ice crystal becomes positively charged and the hailstone negatively charged. Updrafts carry the tiny positively charged ice crystal into the upper reaches of the cloud, while the heavier hailstone falls through the updraft toward the lower region of the cloud.

FIGURE 14.30 The generalized charge distribution in a mature thunderstorm. Normally the upper part of a cloud is positively charged and the bottom is negatively charged.

Thunderstorms The Lightening Stroke Positive charge typically on ground, cloud to ground lightening Stepped leader, ground stroke, forked lightening, ribbon lightening, bead lightening, corona discharge

ACTIVE FIGURE 14. 31 The development of a lightning stroke ACTIVE FIGURE 14.31 The development of a lightning stroke. (a) When the negative charge near the bottom of the cloud becomes large enough to overcome the air’s resistance, a flow of electrons — the stepped leader — rushes toward the earth. (b) As the electrons approach the ground, a region of positive charge moves up into the air through any conducting object, such as trees, buildings, and even humans. (c) When the downward flow of electrons meets the upward surge of positive charge, a strong electric current — a bright return stroke — carries positive charge upward into the cloud. Visit the Meteorology Resource Center to view this and other active figures at academic.cengage.com/login

Thunderstorms Observation: Apple tree DO NOT seek shelter during a thunderstorm under an isolated tree. Lightening Detection and Suppression Lightening direction finder detects radiowaves produced by lightening, spherics National Lightening Detection Network Suppression: seed clouds with aluminum

Figure 3 A cloud-to-ground lightning flash hitting a 65-foot sycamore tree. It should be apparent why one should not seek shelter under a tree during a thunderstorm. Fig. 3, p. 395

Figure 14.32 Time exposure of an evening thunderstorm with an intense lightning display near Denver, Colorado. The bright flashes are return strokes. The lighter forked flashes are probably stepped leaders that did not make it to the ground. Fig. 14-32, p. 392

A lightning rod (invented by Benjamin Franklin) “encourages” lightning to hit it (as opposed to the house) allowing current to flow safely along a wire to the ground.

A car is a very safe place to be during a lightning storm because being inside a metal container shields one from outside electric fields. The rubber tires do nothing to protect you.

Fulgurite (lightning fusing sand)

Sferics Electromagnetic waves given off by lightning (Sferics) allows scientists to determine the source location.

http://www.lightningsafety.com/nlsi_lls/fatalities_us.html

Lightning Deaths in the United States Weighted by Population, 1990 to 2003 Death Rate/ Million Rank Wyoming 2.02     1 Utah 0.70     2 Colorado 0.65     3 Florida 0.56     4 Montana 0.55     5 New Mexico     6 South Dakota 0.47     7 Idaho 0.39     8 Alabama 0.38     9 Louisiana 0.37   10

Location of Incident: 40% Unreported. 27% Open fields & recreation areas (not golf). 14% Under trees (not golf). 8% Water-related (boating, fishing, swimming…). 5% Golf/golf under trees. 3% Heavy equipment and machinery-related. 2.4% Telephone-related. 0.7% Radio, transmitter & antenna-related.

2. Gender of victims = 84% male; 16% female. 3. Months of most incidents = June 21%, July 30%, Aug 22%. 4. Days of week of most incidents = Sun./Wed./Sat. 5. Time of day of most incidents = 2 PM to 6 PM. 6. Number of victims = One (91%), two or more (9%). 7. Deaths by State, Top Five = FL, MI, TX, NY, TN. 8. Injuries by State, Top Five = FL, MI, PA, NC, NY.

"If you can see it, flee it; If you can hear it, clear it.“ http://www.lightningsafety.com/nlsi_pls/decision_tree_people.html

Thunderstorms Observations: TLEs Transient Luminous Events Blue jets, red sprite, ELVES

Figure 2 Various electrical phenomena observed in the upper atmosphere. Fig. 2, p. 390