Presentation on theme: "Thunderstorms Florida has more thunderstorms than anywhere else in the US. Florida has more thunderstorms each year than anywhere else in the US."— Presentation transcript:
1 ThunderstormsFlorida has more thunderstorms than anywhere else in the US.Florida has more thunderstorms each year than anywhere else in the US
2 HailThe 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
3 TornadoesAlthough Florida also has lots of tornadoes per square miles most of these are F0 to F2. The central plains have the most tornadoes each year.
4 Normally the upper part of a cloud is positively charged and the bottom is negatively charged.
5 Electrons have negative charge and protons have positive charge.
6 Opposite charges attract each other and similar charges repel each other
7 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.
8 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.
10 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 lighteningElectrification of Clouds: graupel and hailstones fall through supercooled water, ice crystals become negatively chargedUpper cloud positive, bottom cloud negative
12 FIGURE The lightning stroke can travel in a number of directions. It can occur within a cloud, from one cloud to anothercloud, 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 describedas a “bolt from the blue.”
13 FIGURE When the tiny colder ice crystals come in contact with the much larger and warmer hailstone (or graupel), the icecrystal 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.
14 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.
15 Thunderstorms The Lightening Stroke Positive charge typically on ground, cloud to ground lighteningStepped leader, ground stroke, forked lightening, ribbon lightening, bead lightening, corona discharge
16 ACTIVE FIGURE 14. 31 The development of a lightning stroke ACTIVE FIGURE The development of a lightning stroke. (a) When the negative charge near the bottom of thecloud 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, suchas trees, buildings, and even humans. (c) When the downward flow of electrons meets the upward surge of positive charge, astrong electric current — a bright return stroke — carries positive charge upward into the cloud. Visit the Meteorology ResourceCenter to view this and other active figures at academic.cengage.com/login
17 Thunderstorms Observation: Apple tree DO NOT seek shelter during a thunderstorm under an isolated tree.Lightening Detection and SuppressionLightening direction finder detects radiowaves produced by lightening, sphericsNational Lightening Detection NetworkSuppression: seed clouds with aluminum
18 Figure 3A 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
19 Figure 14.32Time 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 , p. 392
20 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.
21 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.
26 Lightning Deaths in the United States Weighted by Population, 1990 to 2003 Death Rate/ MillionRankWyoming2.02 1Utah0.70 2Colorado0.65 3Florida0.56 4Montana0.55 5New Mexico 6South Dakota0.47 7Idaho0.39 8Alabama0.38 9Louisiana0.37 10
27 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.
28 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.
29 "If you can see it, flee it; If you can hear it, clear it.“
30 Thunderstorms Observations: TLEs Transient Luminous Events Blue jets, red sprite, ELVES
31 Figure 2Various electrical phenomena observed in the upper atmosphere.Fig. 2, p. 390