Mid latitude Cyclonic Storm System. 08 _15 ab. jpg

Transcription

1 Mid latitude Cyclonic Storm System 08 _15 ab. jpg

2 Mid Latitude Cyclone Storm System (MLCSS) It has several names. Cyclone, Cyclonic Storm, Cyclonic System, Depression. Cyclonic Storms are the weather maker for mid-latitude locations and create the changeable pattern of weather there. The cyclonic storm consists of a center area of low pressure which anchors the fronts attached to the low. This gives a comma shaped cloud shield on the satellite image. The cyclonic system pulls air masses of very different character together. This results in local thunder storms along the fronts. The cyclonic system can destabilize the atmosphere over a large region of the U.S. causing many areas of thunderstorms that are not located along fronts. The cyclonic systems are short lived (1 week) and migrate moving generally west to east. Cyclonic systems are created by the westerlies and jet stream aloft. The surface low pressure cell is connected to a trof aloft and is created by the trof.

3 Meandering of the Westerlies Creates Areas of Convergence and Divergence Displaced to the East of Corresponding Upper Level Feature

4 Strong Divergence Field from N. Texas to Kansas Strong Convergence Field from IL and WI to MI

5 Divergence Aloft Causes Low in TX Panhandle Convergence Aloft Causes High Over Gt. Lakes

6 Family of Cyclones Associated with Trof Aloft Overrunning Causes Band of Showers in Min & Wi.

7 Stages in Life Cycle of a Cyclonic System 1. Cyclogenesis. Low develops along frontal boundary with winds showing rotation. 2. Mature or Open. Classic fully developed cyclonic system with pronounced warm sector of maritime tropical air wedged between the fronts. 3. Occlusion or Occluded System. Cold front has overtaken the warm front and lifted it off the surface. System is also losing upper air support as it approaches the crest of the next ridge.

8 Stages in the Life Cycle of a Cyclonic Storm System

9 Stages in the Life Cycle of a Cyclonic Storm System

10 Types of Cyclonic Systems 1. Trof Type is the most common. Cyclonic system develops near the base of the trof and moves up the east side. No closed isobars aloft. These often exist as families. 2. Long Wave Type is big and tends to occur during cooler half of year. Key is upper level support showing at least one closed isobar aloft. 3. Short Wave Type is smaller, form rapidly, and move quickly. This is the forecaster's nightmare. Connected to short wave aloft.

11 Strong Cyclonic System over Eastern U.S. With Counterclockwise Pattern of Rotation around Low

12 Family of Cyclones Across Great Plains. Note Counterclockwise Pattern of Circulation.

13 Clockwise Circulation around Anticyclone Centered over Indiana

14 Strong Cyclonic System in Southern Canada Wegded between Two Strong Anticyclones. Hurricane Gustav is over Louisana and Arkansas

15 Upper Air Chart for March 30, 2008

16 Daily Weather Map for March 30, 2008

17 Classic Open Stage of Cyclonic System

18 Upper Air Chart, 500 mb, Showing Deep Trof over Great Plains and Strong Divergence Field from Nebraska to Texas. Surface Cyclone Is in Same Place

19 System Recently Occluded Warm Front Merges with Cold Front South of Low

20 Occluded System Only Different Weather Map

21 Upper Air Pattern, 500 mb Showing 3 Closed Isobars; Therefore, Cyclone at Surface is Longwave Type.

22 Upper Air Chart, 300 mb, Showing One Closed Isobar, Therefore, Cyclone at Surface is Long Wave Type

23 Occluded System in Quebec

24 The Conveyer Belt Model of Cyclonic Storm Flows

25 Upper Level Trof Controlling Family of Cyclones

26 Formation Factors for Severe Thunderstorms 1. Jet Stream Aloft 2. Upper Air Divergence 3. Upper Air Inversion 4. Fronts within a Mid latitude Cyclonic System 5. Proper Wind Shear Profile 6. Moisture Tongue 7. Negative Lifted Index 8. Development of Squall Lines 9. Large Steady State Thunderstorm

27 Lifting Along Cold Front is Under Running Lifting Along Warm Front is Over Running

28 Significant Wind Shear in Severe Thunderstorm Shown by Black Spiral Ladders

29 Current Theory on Formation of Rotating Mesocyclone

30 Most Tornadoes Occur from April to July

31 Has the Number of Tornadoes Really Increased from 200 per year to 1300 per year?

32 Tornado Alley Includes the Great Plains, Midwest and Parts of the South.

33 Tornado Extending to Ground from Wall or Collar Cloud. Note blue green color of cloud.

34 Tornadoes take on the color of the soil they pick up.

35 The Moisture Tongue is the Maritime Tropical Air Flowing into the Open Sector of a Cyclone. Note Dryline is Boundary between Mt and Ct Air

36 Curiously, An Inversion Aids Development of Severe T storms This is often associated with a flow of dry warm air from the southwest and is called the cap. Storm chasers employ black magic to determine where the cap will break