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A mechanism that will continue until the imbalances that created them is corrected.
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Meterologyunnit4
Unit 4
| Questions | Answers |
|---|---|
| Thunderstorms | The product of a very strong convection air current that extends deep into the upper troposphere. It is made visible with billowing cumulus clouds. |
| A mechanism that will continue until the imbalances that created them is corrected. | Thunderstorms |
| found in areas of greatest solar intensity. | Thunderstorms |
| Creates a Thunderstorm | Rising columns of air (Air mass Convection) and convergence of surface air cause thunderstorms, consists of several cells |
| Continuing a Thunderstorm | latent heat is greatest influences of a continuing T-storm. cooling of surrounding air causes the warm moist air to rise faster |
| Thuderstorms sometimes... | extend into the tropopause--- short lived-- mesoscale system |
| T-storms on the earth at any given moment | 2000 T-storms, 15-20 million/year, 10,000 severe storms, 1,000 tornadoes |
| Florida Peninsula | 200 T-storms/year-trig is Daily sea breezes(100 day year) |
| East of the Rockies | Is #2 **SW Mn 40 - 50 per year |
| Parts of South Am. and Africa | average 322 days of T-storms(T Rain Forest) |
| Thunderstorms | produces 80% of seasonal precip. in the midwest and central plains(MCC's) |
| Thunderstorm occur | almost always occur in late afternoon hours*** Temp. will always drop |
| Thunderstorm Cells size= | 1/2 to 25 miles in diameter, Clusters = 7 - 12 miles long |
| most T-storms consist of | 5 - 8 cells to make a line of storms (drawing) |
| Thunderstorms last | about 30 minutes ( most intense last 10 - 15 minutes) but the general storm system last longer because it is part of a T-storm cluster(diagram) |
| 6 Types of thunderstorms | Air mass or Thermal, Orographic, Thermal, Squall Line, MCC, Supercells. |
| Air mass or thermal | least intense. created by intense solar heating of earth |
| Orographic | rising up over a land mass |
| Frontal | cold or warm front -very energetic storms--vigorous uplift-intense |
| Squall line-pseudo(false)front | parallels & in front of a cold front - most intense |
| MCC | Mesoscale Convective Complexes--circular cluster of interacting T-storms, night storms, least intense, slow moving, can be severe(latent heat) |
| Supercells | Long lived intense T-storms, strong-tilted updrafts 150-175 mi/hr. due to this rapid convection, develops strong rotational circulation. Always severe! |
| 3 stages of development of T-storms | 1.)Cumulus 2.)Mature 3.)Anvil Stage |
| Cumulus stage | towering cumulus clouds emerge -uplift of 10-45 mph - cumulus congestus NO ppt.-updraft is so strong, all moisture is suspended in the air, 3-5 mile wide |
| Cumulus Congestus | significant vertical growth of a cloud, abundant latent heat and updrafts |
| Mature Stage | Rain drops or ice pellets gain mass to fall faster than the updraft rises Falling rain or snow cause adjacent air to be dragged down (downdraft) The downdraft drags part of the cloud with it creating a roll cloud |
| (rotating slowly) | rarely severe!!! |
| Mature thunderstorms Creates a gust of wind before the rain arrives | |
| gust front | cool rush of air from the evaporation of rain, miniature cold front, can create a 2nd line of T-storms *This creates an outflow boundary |
| A shelf cloud (wall cloud) | is when a low elongated cloud is wedged shaped. moves in front of the storm. signals damaging winds |
| violent stage of the storm | Hail, rain, tornadoes, strong winds *lasts 10-20 min |
| clouds can exceed | 60,000 feet ~ 12 miles, 5-10 miles wide |
| late mature stage creates | an Anvil cloud |
| Anvil cloud | strong updraft causes the water vapor to hit the tropopause and level off. *jet stream cause the clouds to be flat and pointed in a certain direction. |
| Mammatus clouds | pouch like clouds that appear on the bottom side of an anvil cloud *air rushes upward, runs into jet stream, and is deflect back down creating holes in the cloud deck(not always associated with severe wx) |
| Anvil Stage or Dissipating stage | upward air motion is at it's peak - thus creating a downdraft of air to replace the rising air -this air is adiabatically warmed by compression -humidity decreases, air temp cools, ppt stops--- clouds disappear, evaporate |
| ITCZ | is actually a discontinuous line of T-storms on either side of the equator |
| T-storms are created by either | forced convection or free convection (difference?) |
| Free convection | convection triggered by intense solar heating of earth's surface-flat terrain |
| Forced convection | the topography or fronts causes an air mass to rise or surface convergence |
| Severe T-storms | A t-storm with a much higher top-the greater the altitude, greater the risk -rapid convection, extreme temp. gradient--called supercells -updrafts are tilted , the falling precip doesn't drag against the rising air(pict.) |
| Mid latitude jet is important in this process-produces wind shear-tilts updraft -large hail, frequent lightning, strong winds, flooding, tornadoes | |
| Southeast sector of a mid-latitude cyclone(usually) | usually are common in the Central Great Plains -Why is this area prone to severe weather? |
| Wind shear | air moving in different directions or velocities with height. 90 degrees is the key |
| Low level jet stream | warm, moist air that is pumped northward out of the Gulf of Mexico -it is on the west side of the Bermuda High *this is responsible for severe winter storms |
| Upper level jet--cool dry air comes down from the North, the 2 air masses collide-severe wx -Also referred to as the Mid-Latitude jet | |
| Dry line | hot dry air that is compressionally warmed from subsiding air from the (Mid-level jet) advancing cold front, air pulled into a low pressure system on leeward side of mtns. or flows east from the desert southwest (diagram) |
| dry line is found? | found west of the mT air mass and east of the cP air mass(diagram) |
| Dry line moves? | often advances east during the day, and retreats westward at night -often the trigger mechanism for severe wx formation--Central Great Plains |
| T-Storm Hazards | 1. Lightning 2. Downbursts 3. Flash Floods 4. Hail 5. Tornadoes |
| 1.)Lightning | a flash of light produced by an electrical discharge of about 100 million volts -Created because of fast moving air displacing electrons. The electrons build and are discharged to balance out charges.(graupel pellets are neg.) |
| Lighting results in... | #1 killer of people - 200 per year, 90 in the U.S. causes 9000 fires per year *On a clear day, the ground is neg. charged...it changes when clouds form. |
| Lightning Cont. | Air gives up electrons to the bottom of the clouds.(Rubbing feet on carpet) -Air is a very insulator, thus a tremendous potential exists for a discharge -lightning may be discharged to the top of a cloud, to a totally different cloud or to the ground. |
| lightning travels | 31,000 mi/sec - 5 times hotter than the sun, 50,000F |
| Life of a Lightning bolt 1 | Stepped Leader-> 1. surge of electrons travel towards the ground |
| Life of a Lightning bolt 2 | 2.This surge is met by a positively charged return stroke from the ground -it forms a narrow conductive path that is illuminated from the ground to the cloud by a lightning flash! (3-6 cm wide) |
| Life of a Lightning bolt 3 | 3.A dart leader flows from the cloud back to the ground, is met by positive charges moving upward and is illuminated from the ground to the cloud. *a typical lightning bolt may consist of 3-6 dart leaders (return strokes) |
| How fast does it accure | all of these events occur in less than 2 tenths of a second *our eyes can't perceive the different flashes, we just see a flickering light. |
| How do we get the forked lightning | sometimes the dart leaders are met by a new path from return stroke that forges a new path from the ground, the result is forked lightning |
| 4 Different Types of Lightning | 1.)Bolt Lightning 2.)Sheet Lightning 3.)Ball Lightning 4.)Heat Lightning |
| 1.Bolt lightning | cloud to ground- appears in streaks, only 20% of all lightning |
| 2.Sheet lightning | bright flashes across the sky-lightning within the clouds(cloud to cloud) |
| 3.Ball lightning | when 2 or more discharges occur in the same area or path |
| 4.Heat lightning | light reflected by clouds from thunderstorms occurring beyond the horizon |
| St. Emo's Fire | glowing of the outline of an object due to a lightning strike at or behind it. |
| Thunder | lightning heats up the air in a narrow path 50,000 degrees Fahrenheit *the intense heating of the air causes it to expand violently, greatly increasing pressure, which initiates a sound wave that we hear as thunder. |
| how fast does the air move for thunder | The air moves faster than the speed of sound, thus crashing through the sound waves creating a Sonic Boom (subsequent waves creates rumbling) |
| Lighting distance measuring | (5 secs. for 1 mile) |
| We cant hear the tunder if | When T-storms are greater than 12 mi away! General rule "if you can hear thunder, you could be struck, Your too close!!! |
| 2.)Downbursts | strong downdraft of air created by precip. Upon striking the earth's surface, diverges horizontally to create destructive surface winds *Discovered by Dr. Ted Fujita *can be created with/out precip(then under virga)-Outflow Boundaries |
| How fast does the air move? | Air sinks at 60-80 mph striking the earth and moving outward in every direct -classified based on size--Macro or Micro bursts |
| Macroburst | Destructive path greater than 2.5 miles, 130 mi/hr., lasts up to 30 min. |
| Microburst | smaller and short lived, less than 2.5 mi, 170 mi/hr., lasts less than 15 min. -very intense downdrafts in a small region--creates localized wind shear -deadly at airports because the small size defies detection |
| Derecho | Family of straightline downbursts, long line of sustained winds of 58 mi/hr or more -causes considerable damaged in a small area "The Invisible Tornado" -caused considerable damage in Boundary Water/MN, July 4, 1999 |
| Wind Shear | abrupt change in wind speed or direction over a short distance -induces the production of mesocyclones--tornadic activity -1 destroyer of aircraft.-invisible cause to dramatic loss of altitude of planes |
| 3.)Flash Floods | when the rain is falling at a faster rate than ground can absorb.~ .5 in/hr. -sudden overflow of river or drainage channels -Hazardous in mountains. regions-erosion |
| What causes flash flooding? | slow moving or stationary storm that continues to build, or "training" cells (stagnot mid level/steering jet or persistent influx of moisture laden air) |
| Where has the biggest problem with flooding? | Deserts, how is that possible? |
| what is the number one killer | flashfloods, since 1993!!! |
| 4.Hail | precipitation in the form of balls or lumps of ice-Colorado is #1 in hail events -hail region is very similar to tornado alley -hail streak within cloud shows descending hail column -.75 inch hail=70 mi/hr updraft, 3.0 inch hail-100 mi/hr updrafts |
| Hait is chariterized by what? | from storms that reach near the tropopause-(diagram) |
| What keeps hail up? | strong updrafts, keep ice crystals suspended while adding water to its size |
| Larger the hail, the greater...? | potential for tornadoes. (Why and how?) |
| Large hail events | 18 in. of hail in Kansas on July 8, 1980**6 ft drifts of hail in Iowa, 1980 |
| 5.Tornadoes | a violently rotating column of air with extreme surface convergence. -extreme horizontal air pressure gradient creates vigorous circulation/centripetal fc -most violent of all severe storm hazards. Product of high velocity wind shear |
| What makes a tornado visable? | made visible by condensation funnel. produced by 10% of severe storms |
| Tornadoes that don't tuch the ground are called? | -called a funnel cloud when not touching ground, still dangerous |
| Death's per year, world wide Lightning | 200 + |
| Death's per year, world wide Tornadoes | 100 |
| Death's per year, world wide Down bursts | less than 50 |
| Death's per year, world wide Flash Floods | around 250+ |
| Death's per year, world wide Hailstorms | less than 50 |
Created by:
nwolter
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