1 / 25

Wet and Dry Microbursts

Wet and Dry Microbursts. Daniel R. Adriaansen & Baylee A. Balschmiter. SUNY Brockport Department of the Earth Sciences ESC 452 Mesoscale Meteorology 20 April 2006. What is a microburst?.

wyoming-duke
Download Presentation

Wet and Dry Microbursts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wet and Dry Microbursts Daniel R. Adriaansen & Baylee A. Balschmiter SUNY Brockport Department of the Earth Sciences ESC 452 Mesoscale Meteorology 20 April 2006

  2. What is a microburst? Downburst: Strong downdraft which induces an outburst of damaging winds on or near the ground. (Fujita 1985) - 2 types: Macroburst: A large downburst with its outburst winds extending in excess of 4km (2.5 mi) in the horizontal with maximum wind speeds of 60 m/s (134 mph). (Fujita 1985) Microburst: A small downburst with its outburst, damaging winds extending only 4 km (2.5 miles) or less with maximum wind speeds of up to 75 m/s (168 mph). (Fujita 1985)

  3. Conceptual Model - Vortex ring model - Meso Low on either side of meso High http://www.cimms.ou.edu/~doswell/microbursts/Figure_04.JPG

  4. Two (three) varieties http://www.cimms.ou.edu/~doswell/microbursts/Figure_08.JPG (Intermediate?)

  5. Dry Microburst A microburst that is accompanied by little or no rain between the onset and the end of the high winds. (Wakimoto 1985) http://www.cimms.ou.edu/~doswell/microbursts/Figure_08.JPG

  6. Dry Microbursts - JAWS (Joint Airport Weather Studies, 1982) - Further defined microburst characteristics, particularly involving dry microbursts. - Denver, CO

  7. Physical Characteristics - Time scale 2-5 minutes - Peak wind speeds exceeding 30 m/s (67 mph) - Reflectivities of ≤ 30 dBz - Precipitation ≤ 0.25 mm (0.01 inches) - Lightning often limited - Limited synoptic forcing/influence - Sometimes associated with fair weather

  8. Thermodynamic environment - Morning Inversion - Inverted V signature - Nearly dry-adiabatic ABL - Large Dew-point depressions in ABL - Moist layer located ~ 500mb (DPD  0) - Light ABL winds

  9. http://www.cimms.ou.edu/~doswell/microbursts/Figure_09b.JPG

  10. http://www.cimms.ou.edu/~doswell/microbursts/Figure_09a.JPG

  11. Visual Identification - Virga is defined as wisps or streaks of water or ice particles falling out of a cloud but evaporating before reaching the earth's surface as precipitation. (NOAA 2001) - Blowing dust/dust rings at surface - Very good indicators of dry microburst potential

  12. http://www.cimms.ou.edu/~doswell/microbursts/Figure_17a.JPG

  13. http://www.cimms.ou.edu/~doswell/microbursts/Figure_17b.JPG

  14. http://www.cimms.ou.edu/~doswell/microbursts/Figure_13.JPG

  15. http://www.cimms.ou.edu/~doswell/microbursts/Figure_14.JPG

  16. http://www.cimms.ou.edu/~doswell/microbursts/Figure_16.JPG

  17. Wet microburst • A microburst accompanied by heavy precipitation at the surface. A rain foot may be a visible sign of a wet microburst. http://www.cimms.ou.edu/~doswell/chasesums/chase97_18.JPG

  18. Wet Microburst Formation • There is a layer of nearly saturated air that is close to Γm • Above this layer is an elevated dry layer • When Tw is brought to saturation and mixed with warm air, it creates a negatively buoyant atmosphere that leads to a severe downdraft

  19. http://www-frd.fsl.noaa.gov/~caracena/micro/FACEsons.gif

  20. Characteristics • Little or no capping inversion. • A moist mid-tropospheric layer between 5000 ft and 15,000 ft. • An elevated dry layer above 15,000 ft. • When combined there is a high potential for a wet microburst

  21. http://www.cimms.ou.edu/~doswell/microbursts/SW_Texas_rainfoot_c.JPGhttp://www.cimms.ou.edu/~doswell/microbursts/SW_Texas_rainfoot_c.JPG

  22. http://www.nssl.noaa.gov/~doswell/microbursts/SW_Texas_virga_sm.JPG&imgrefurlhttp://www.nssl.noaa.gov/~doswell/microbursts/SW_Texas_virga_sm.JPG&imgrefurl

  23. References 1. Caracena, F., Holle, R. L., & Doswell III, C. A. (2001, June). Microbursts: A Handbook for Visual Identification. Retreived April 10th, 2006, from http://www.cimms.ou.edu/~doswell/microbursts/Handbook.html 2. Fujita, T. (1985). The Downburst: Microburst and Macroburst. Chicago: The University of Chicago. 3. NOAA. (2001). Question of the Month. Retreived April10th, 2006, from http://www.noaa.gov/questions/question_081701.html 4. Wakimoto, R. M. (1985). Forecasting Dry Microburst Activity over the High Plains. Monthly Weather Review, 113, (1131-1143).

  24. Questions? Comments? Rude Gestures?

More Related