MET 4300/5355 Severe Weather

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1 MET 4300/5355 Severe Weather Lecture 1 Introduction

2 Course Organization Tu/Th 11:00AM-12:15 PM, AHC5 Rm357 Haiyan Jiang, , AHC5 Rm371, Office Hours Tu 12:15-1:15 PM, or by appointment Previous General or Introduction to MET course. On-line course materials at: WxChallenge (Local manager Alannah Irwin will stop by on Thursday Jan 22 after class )

3 Grades: Grading Factors Participation 10% Term-paper (Graduate) 10% Exam #1 20% Exam #2 20% Final 50%(Under) 40% (Graduate) Total 100%

4 Absence: Need a valid excuse (in-class exercises are counted toward your grade)

5 Text:

6 Textbook: 27 chapters: we ll cover 22 of them Website: weather links and animations/photos (for 3 rd edition); (for 4 th edition, access code comes with the book) Special sections: 1). List of learning Objectives 2). Check your understanding 3). Test your understanding 4). Test your problem solving skills 5). Use the website (animations don t work in my laptop??) 6). Focus box (case, advanced topics, etc.)

7 Suggestions Preview the chapter Read the text, start with learning objectives Pay attention to check your understanning questions while reading Answer Test your understanding questions after reading the chapter Test your problem-solving skills

8 Class Activities: From Active Learning Exercises book or textbook test your problem solving skill questions Due in class, counting 10% of your total grade No Make-ups

9 Exams: Total 3 exams: Exam 1, 2, and final Final exam on Apr. 30 (Thursday) 9:45am-11:45am (same on pathersoft) Your input about exam time?

10 Course Focus: Severe & Hazardous Weather

11 Course Topics 1/3 of the whole course will cover some very basic meteorology concept (lec 1-11; textbook CH1-9) The rest: different types of severe & hazardous weather including lee cyclone, northeasters, ice storms, lake-effect snow, cold waves, blizzards, mountain snowstorms, mountain windstorms, thunderstorms, tornadoes, hailstorms, lightning, and downbursts.

12 What is severe weather? Large, damaging hail (20 mm, or ¾ in) Damaging winds (60 mph, 50 kt, or 25 m s -1 ) Tornado Or all of the above Strong updrafts!

13 Severe Weather = MESOSCALE Weather Meso = Middle, between Macro- and Microscale Or between Synoptic and Convective Actually includes Convective scale, too. Horizontal scale is determined by surface properties or natural scales of convective systems Vertical scale is defined by the depth of the troposphere.

14 What is Hazardous Weather? The definition is much broader than severe weather. Hazardous weather includes all types of weather that has hazardous impacts. It includes almost all scales of weather systems, not only mesoscale.

15 MET SCALES

16 Scales of Atmospheric Motion Scale Length Time Planetary ~6000 km (R e ) Weeks Synoptic ~ 2000 km days to a week Meso-α km A day or two Meso-β km A day-hours Meso-γ 20-2 km Hours-minutes Convective 5 km 500m Minutes Micro < 2 km Minutes-seconds Orlanski, 1975

17 Planetary Waves

18 Synoptic-Scale Weather in 1863

19 Synoptic-Scale Weather

20 Meso- Radar, which maps hydrometeors (primarily rainfall) is a key instrument for understanding the mesoscale

21 Meso-Antiyclone

22 Gust Front

23 Gust front: the leading edge of cool air rushing down and out from a thunderstorm.

24 Downslope wind (Chinook, snow eater) is a wind directed down a slope, often used to describe winds produced by processes larger in scale than the slope.

25 Suction vortex are really substructures of many, perhaps all, tornadoes but are not always easily visible. These occur, usually, at the base of the tornado vortex where the tornado makes contact with the surface.

26 Dust devil is a strong, well-formed, and relatively long-lived whirlwind, ranging from small (half a metre wide and a few metres tall) to large (more than 10 metres wide and more than 1000 metres tall). The primary vertical motion is upward. Dust devils are usually harmless.

27 Summary Severe weather Large, damaging hail (20 mm, or ¾ in) Damaging winds (50 kt, or 25 m s -1 ) Tornado Or all of the above Hazardous weather: include all scales of weather Scales of motion Planetary & synoptic balanced > 2000 km Mesoscale---nonbalanced, km Convective buoyant motions, km (scale height) Microscale---near surface < 1 km

EOS-310 Severe & Unusual Weather Spring, 2009 Associate Prof. Zafer Boybeyi 1/20/09

EOS-310 Severe & Unusual Weather Spring, 2009 Associate Prof. Zafer Boybeyi 1/20/09 EOS-310 Spring, 2009 Associate Prof. Zafer Boybeyi 1/20/09 1 Instructor and Contact information Associate Prof. Zafer Boybeyi Research I, Room 217 Mail Stop 6A2 Email: zboybeyi@gmu.edu Phone: (703) 993-1560