1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot...

63
1 BASIC CONVECTION By: Ken Harding NWS ABR

Transcript of 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot...

Page 1: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

1

BASIC CONVECTION

By:Ken HardingNWS ABR

Page 2: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

2

Who am I?• NWS meteorologist – 20 years• Private pilot – 13 years• In Aberdeen since 1996

Page 3: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

3

What do I talk about?• I know a lot about:

– The NWS– Aviation weather

• TAF/METAR• ARTCC Weather Support

• I know a little about:– ASOS– Aviation Weather Center Products

• I’d like to learn from you:– Weather concerns– ‘War stories’

Page 4: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

4

Page 5: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

5

Page 6: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

6

Page 7: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

7

Page 8: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

8

Page 9: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

9

Page 10: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

10

Page 11: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

11

Some days, the sky is very inviting…..

Page 12: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

12

Some days…not

Page 13: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

13

Subject Overview

• What is Convection• Initiating Convection• Some “Rules of Thumb”

Page 14: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

14

What is Convection?• The transport of heat (and

moisture) by the movement of a fluid.

• In meteorology, describes vertical transport of heat/moisture...– by updrafts/downdrafts – in an unstable atmosphere

Page 15: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

15

Convection

• Air in the free atmosphere will continue rising…– until it reaches a level where it is no

longer buoyant.

• The more unstable the atmosphere…– the greater the convection.

Page 16: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

16

Initiating Convection• Atmospheric stability

– Is determined by the way temperature varies with altitude

• The ‘stability’ of a layer of air…– is the resistance to vertical

displacement.

• “Unstable” air promotes convection• “Stable” air inhibits convection

Page 17: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

17

Altering StabilityThree ways to decrease stability:

UpperLevelCooling

LowLevel

Warming

Increase inAtmosphericMoisture

Page 18: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

18

Air Mass Boundaries

• Are ‘Favored’ areas for convection and Thunderstorm growth

• Often subtle differences between air masses…– have large impacts on convection.

Page 19: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

19

Air Mass Boundaries

• Types– Fronts– Dry lines– Sea-Breeze fronts (Lake Breeze?)– Convergence Zone

Page 20: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

20

“Triggering” Mechanism

• Starts the convection– Low pressure systems– Fronts– Thunderstorm ‘outflow boundaries’– Orographic lift

Page 21: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

21

Low Pressure Systems

• An upper low gives cooling aloft– This reduces stability

• Surface lows give low-level convergence– this supplies ‘Lift’ from

below

Page 22: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

22

Fronts• Provide lift - Convection is likely

– if air is unstable

Cold Air

Page 23: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

23

Thunderstorm Outflow Boundaries

• Colliding outflow boundaries often provide lift for additional convection.

Page 24: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

24

Page 25: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

25

Page 26: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

26

Page 27: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

27

Page 28: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

28

Page 29: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

29

Rules of Thumb for Convection - 1

• If cumulus tops are ‘crisp’ and ‘well defined’...– the cloud

will continue to grow.

Page 30: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

30

Rules of Thumb for Convection - 2

• If cumulus tops are ‘ragged’ and ‘ill-defined’...

– the cloud will not continue to grow.

Page 31: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

31

Page 32: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

32

Rules of Thumb for Convection - 3

• The taller the cloud..– The stronger the convection, and…– The greater likelihood of turbulence– The greater likelihood of micro/down

bursts

Page 33: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

33

Supercell Thunderstorms

Page 34: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

34

Wind Shear

Page 35: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

35

Page 36: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

36

Page 37: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

37

Page 38: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

38

Page 39: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

39

Convection Vs TurbulenceStrength

of ConvectionCloudType

Type ofTurbulence

Weak Fair Wx Cu Lgt Chop

Moderate ToweringCu (Tcu)

Mod chopMod Turbc

Strong Tcu andCb

Sev ChopSev Turbc

Pilot reports in thunderstorms indicate +/- 4000 fpm UDDF

Page 40: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

40

Convective Turbulence

• Avoid convective turbulence by flying above cloud tops…When possible.

Smooth Ride

Bumpy Ride

Page 41: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

41

Weak Convection ?• No problem

– Except sometimesNormal

ApproachAffects of

Convection

Page 42: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

42

Rules of Thumb forConvective Turbulence

• Expect light turbulence in areas where dust devils are occurring.

• Expect light/Mod turbulence under areas of developing cumulus clouds.

• Thermals rarely exceed 10,000 feet AGL without forming clouds.

Page 43: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

43

• Expect moderate turbulence…– in areas where extreme heating and

low humidity are expected or..– where exceptionally large dust devils

are occurring.– In areas of Virga

Rules of Thumb forConvective Turbulence

Page 44: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

44

Convection vs. Icing

• Convective clouds tend towards clear icing

• Moderately growing cumulus can have mod/svr clear/mixed icing

• If the cloud is raining, it has supercooled water – clear icing

• Supercooled water can extend to great heights (>20,000 ft AGL) and temps < -15 C.

Page 45: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

45

Page 46: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

46

A thunderstorm is never as bad on the inside as it appears from the outside…it’s worse.

Page 47: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

47

Convective SIGMETS

• For Severe Thunderstorms (50 Kts, ¾” hail, tornadoes)

• Embedded Thunderstorms• Lines of Thunderstorms• Over 40% coverage in an area >

3000 mi2 of VIP level 4 Thunderstoms.

Page 48: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

48

Convective SIGMETS

Page 49: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

49

CCFP

Page 50: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

50

Lightning Facts

• About 100 strikes per second worldwide• Carries approximately 100,000,000 Volts• Bolts over 110 miles long have been

measured• Both negative and positive lightning• 50,000 degrees C.• Approximately 1” in diameter

Page 51: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

51

Page 52: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

52

Page 53: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

53

Lightning Sequence

Page 54: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

54

Page 55: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

55

ASOS Thunderstorm

Reporting

Page 56: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

56

KEFC – 330/1690kts

Page 57: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

57

National Lightning Detection Network

Near Selby, SD

Near Morris, MN

Near Rapid City, SD

Near Minot, ND

Page 58: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

58

How it Works

1. Sensors transmit lightning data to satellite; 2. Satellite relays information to earth station; 3. Data is transmitted to NCC via land-lines; 4. NCC processes data; 5. Processed data is relayed back to satellite; 6. Lightning data is displayed within seconds of occurrence 7. Accurate within +/- 1/2 mile

Page 59: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

59

How it Detects

• Detects ONLY Cloud to Ground (CG) • 30 mile range• Provides info for 30-10 miles, 10-5

miles, and 5-0 miles.• Reports once per minute• Detection Efficiency

– 90% of CG within 10 miles– 100% of thunderstorms after the 3rd CG

Page 60: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

60

How It’s Reported• Detection 10 - 30 miles:

– LTGDSNT DIR • Detection 5 – 10 miles:

– VCTS• Detection 0 – 5 miles:

– TS reported as present weather• TSNO remark: NLDN down, or no

ALDARS• KMBG 201855Z AUTO 08011KT 10SM

SCT048 28/17 A2992 RMK AO2 SLP122 T02830167 TSNO

Page 61: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

61

Thunderstorms in TAFs

• 12-24 hours out– VCTS or SCT030CB

• 06-12 hours out– Shorter duration of thunder– PROB30 beyond 9 hours

• 00-06 hours– TEMPO Thunder (less than 4 hours)– Prevailing Thunder (less than 2 hours)

Page 62: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

62

New Resources

• 24-hour TAF for Mobridge• Pilot resources CD

– Sign up if you want one mailed to you• Web Log (Blog) of aviation links

– http://pilotweather.blogspot.com• Us

[email protected]– 605-225-0519– We’re always open – Visit us or bring your

students by. Come and hanger fly with us.

Page 63: 1 BASIC CONVECTION By: Ken Harding NWS ABR. 2 Who am I? NWS meteorologist – 20 years Private pilot – 13 years In Aberdeen since 1996.

63