section 9 tb meteorology

7/28/2019 Section 9 TB meteorology

1/181

Sectie9 TB 1

Section 9 FLIGHT HAZARD

1. Icing

2. Turbulence

3. Windshear4. Thunderstorms

5. Hazards in mountainous areas


2/181

Sectie9 TB 2

Welke Hazards zijn hier eventueel aanwezig?

shear

fog (vis)

Icing

MTI


3/181

Sectie9 TB 3


4/181

Sectie9 TB 4

1. Icing

loss of performance

large increase in fuel consumption

difficulty with aircraft control


5/181

Sectie9 TB 5


6/181

Sectie9 TB 6


7/181

Sectie9 TB 7

Conditions for ice accretion

Meteorological factors

Aerodynamic factors

on the ground and during the flight


8/181

Sectie9 TB 8

Meteorological factors

1. temperature of the outside air in clouds < 0 C

2. supercooled water content of the cloud

3. duration of the flight in the clouds where there is a risk of icing

4. droplet and crystal size distribution*


9/181

Sectie9 TB 9

droplet and crystal size distribution

Smaller drops easely follow stream lines

Bigger drops dont. (and hit the surface!)*


10/181

Sectie9 TB 10

The formation of ice accretion in clouds depends on

the quantity and on the size of the supercooled water drops

above the freezing level

the temperature.

the lower the temperature, the smaller the droplet that can

exist in supercooled form


11/181

Sectie9 TB 11

The supercooled water content depends on the temperature.

Between 0C and -13C *:almost only supercooled water drops (large and small).

Between -13C and -23C:

the large supercooled water drops freeze on ice nuclei(= ice) small supercooled water drops dont. Mix*

Between -23C and -40C:

Only small supercooled water drops can exist

Below -40C

there is no more supercooled water available for ice accretion*


12/181

Sectie9 TB 12

Aerodynamic factors

speed of the aircraft

the faster the aircraft, the greater the risk of ice deposit*.

temperature of the aircraft's surface

shape (thickness) of the aircraft cell part (wings, antenna,.)

the smaller the curvature, the greater the risk of ice deposit

angle of attack*


13/181

Sectie9 TB 13


14/181

Sectie9 TB 14

Carburettor icing *

caused by

1. the sudden temperature drop as

latent heat is absorbed when fuel

evaporates

2. due to adiabatic cooling following

the pressure reduction as air is

accelerated through the carburettor

venturi

in cloud or in clear air

most critical range of temperature is from3C and +15C

(warm air can contain more moist)


15/181

Sectie9 TB 15

The supercooled water drops in different clouds

stratiform cloudsonly light icing between 0C / -13C

Except:

- Sc formed by convetion over sea in winter (Old Sc)

- Sc formed by spreading out of CU below subsidence inversion

- in an active front

- in orographic clouds

cumuliform clouds TCU/CB mod/sev icing between 0C / -23C


16/181

Sectie9 TB 16

The types of ice accretion

The formation of a deposit of ice on objects:

directly from water vapour, by sublimation* (deposition)

( gas ice)

by the freezing of liquid water drops ( liquid ice)

Types: 1. Clear ice or glaze (IJzel)

2. Rime ice (Ruige Rijp)

3. Mixed ice or cloudy ice (Mixed ijs)

4. Hoar frost (Rijp)


17/181

Sectie9 TB 17

1. Clear ice or glaze (IJzel*)

Conditions of formation: - large, supercooled water drops (mainlyprecipitation)

- temperatures between FZL* and -18CAspect of clear ice: - transparent, translucent, glassy appearance

- high weight- great adhesion to the frame,

cannot be broken away easily

Formation of clear ice: - CU, CB and NS at temperatures just below

freezing

- in supercooled rain (T < 0C)


18/181

Sectie9 TB 18

Clear ice


19/181

Sectie9 TB 19

extremely dangerous form of clear ice occurs in the so-called

ice triangle => rain ice caused by freezing rain

usually ahead of a warm front

sev icing in only a few minutes


20/181

Sectie9 TB 20


21/181

Sectie9 TB 21


22/181

Sectie9 TB 22


23/181

Sectie9 TB 23

Remarks:

Cold layer at sfc 2 FZLs

(Ice triangle at sfc)

Cold layer 2500` thick

Supercooled drops and/or snow

Becoming warm rain

FZRA

Ca 2000ft

Ca 5000ft


24/181

Sectie9 TB 24

Main dangers of clear ice

can grow rapidly and it is difficult to remove

if shaken off it flies away in large lumps, which may damage

the surface or may strike the fan and compressor blades

when it occurs on the propeller, may lead to serious vibration.


25/181

Sectie9 TB 25

Conditions of formation: - small supercooled water dropsCloud drops! (clouds withlow LWC)

- low temperatures (well below 0C)

2. Rime ice (Ruige Rijp)

Aspect of rime ice: - white opaque deposit- little weight

- low density, easy to remove

Formation of rime ice : - in top of CB or in Ns

- in freezing fog (with wind!)


26/181

Sectie9 TB 26

Main dangers of rime ice:

little weight but it alters the aerodynamic characteristics of the

wings and it may block the air intakes.
http://upload.wikimedia.org/wikipedia/commons/9/95/Windbuchencom.jpg


27/181

Sectie9 TB 27
http://upload.wikimedia.org/wikipedia/commons/9/95/Windbuchencom.jpghttp://upload.wikimedia.org/wikipedia/commons/9/95/Windbuchencom.jpg


28/181

Sectie9 TB 28

Eventueel Weerplaatjes/ sneeuw en rijp dec 2007


29/181

Sectie9 TB 29

FZFG

FZBR

FZRA


30/181

Sectie9 TB 30

3. Cloudy ice or mixed ice

mixed ice - formed when supercooled water

droplets are of various sizes or are intermingledwith snow or ice particles.

large range of drop sizes at any temperatures between 0 and -40C

difficult to remove and, because of its roughness, may seriously

increase the drag of the aircraft


31/181


32/181

Sectie9 TB 32


33/181

Sectie9 TB 33

4. Hoar frost (Rijp)

Conditions of formation: - in clear air

- T sfc < frost point of the air

Aspect of hoar frost: - white, crystalline deposit

- little weight

Formation of hoar frost:

by deposition of water vapour directly in ice.

the only icing where no liquid water is involved..!

occurs frequently on parked aircraft during a clear night

when the temperature ofairframe surface falls below 0C*

in flight, if the aircraft moves rapidly into a warmer and

damp layer of air by descent or from ascent into an inversion May occur on bottom sfc of wings holding fuel T


34/181

Sectie9 TB 34


35/181

Sectie9 TB 35

Main dangers of hoar frost: some loss of radio facilities,

frost on the windscreen before landing.

frost on the airframe may increase the stalling speed.

hoar frost


36/181

Sectie9 TB 36

Martinair kist op Tunis bij T=28 en Td=22

Rijp?


37/181

Sectie9 TB 37

Intensity of Icing

Light. ( ) problem if flight is prolonged more than one hour in the

environment, usede-icing/anti-icing equipment

Moderate. ( ) short encounter becomes potentially hazardous

and use of de-icing/anti-icing equipment is

necessary or a diversion is necessary to escape

the icing conditions.

Severe. ( ) rate of accumulation is such that de-icing/anti-icingequipment fails to remove or control the hazard.

Immediate diversion is necessary


38/181

Sectie9 TB 38

Dangers of aircraft icing

1. Increase in weight2. Loss of lift, deformation of aerodynamic characteristics.

3. Increase in drag. The stall speed of an ice covered aircraft

may be 20 to 30 percent higher than normal.

4. Loss of power, carburettor icing

5. Loss of control, icing on control surface hinges

6. Loss of thrust, propeller icing

7. Loss of vision, windscreen freezing

8. Loss of communication, icing of aerials

9. Pitot tube icing10. Unbalance of aircraft, unbalance of propellers


39/181

Sectie9 TB 39

Dangerous zones of icing in clouds and fronts

Convective cloudsBetween FZL and -23oC moderate or severe icing - clear ice/ cloudy ice

Between -23oC and -40oC light icing - rime ice

Below -40C small risk of light icing

Non-frontal stratified clouds, St, Sc, Ac

Between FZL and -10oC moderate icing

Below -10oC light icing


40/181

Sectie9 TB 40

Frontal clouds

Warm front Cold front

non-active 0 to -10C

< -10C

risk of mod icing

risk of light icing

0 to -10C

< -10C

risk of mod icing

risk of light icing

with embd CB

active 0 to -15C

< -15C

risk of mod (sev) icing

risk of light icing

0 to -23C

-23 to -40C

risk of mod to sev icing

risk of light icing

Icing at above 0 C

tanks of an aeroplane on the ground contain fuel that has a

temperature below zero, moisture condensation


41/181

Sectie9 TB 41

Ground de-icing and anti-icing

de-icing:removing ice formations

anti-icing:preventing new accretions from forming

freezing point depressant (FPD) fluids

take care of holdover time*


42/181

Sectie9 TB 42


43/181

Sectie9 TB 43

Recommendations

Know the level of icing for which your airplane is certified

and never intentionally exceed that level.

Never leave the ground with ice or snow adhering to any part

of the airframe.

Never fly in known icing conditions with any anti-icing or de-

icing components inoperable.

When you observe ice on the wings, assume that there is even

more ice on the tail and that it will have a more profound

effect.

Use de-icing and anti-icing components strictly according to

manufacturer's recommendations.


44/181

Sectie9 TB 44

Use signif icant weather chart(SWC).


45/181

Sectie9 TB 45

Use signif icant weather chart(SWC).

Mod Icing btn FL180en XXX

onderkant SWC !!


46/181

Sectie9 TB 46

2. Turbulence

Definition:

Turbulence isshort-period and small-scale oscillations in wind.

It is very unorganised atmospheric motion including gusts and

lulls in the wind

Aviation definition of the turbulence:

Variations in the wind along the aircraft flight path of apattern, intensity and duration that disturb the aircrafts

attitude about its major axis but do not significantly alter its

flight path.


47/181

Sectie9 TB 47

The ICAO turbulence definition

Very low below 0.05g Light oscillations

Low 0.05 to 0.2g Choppy; slight, rapid, rhythmic bumps or

cobblestoning

nothing spoiled

Moderate 0.2 to 0.5g Strong intermittent joltscoffee spoiled

Severe 0.5 to 1.5g Aircraft handling made difficult

stewardess spoiled

Very severe above 1.5g Increasing handling difficulty, structuraldamage possible.

aircraft spoiled *


48/181

Sectie9 TB 48

Types of turbulence:

Convective turbulence

Mechanical or frictional turbulence

Orographic turbulence

Wake turbulence

Clear air turbulence

Frontal turbulence


49/181

Sectie9 TB 49

1. Convective turbulence

results from convection

dry thermals or CU

CB severe turbulance under, in and above


50/181

Sectie9 TB 50

2. Mechanical or frictional turbulence

due to obstructions such as steep hills, ridges, buildings,

trees or cliffs along the seashore or inland waters

expected when wind speeds are higher than 20kts

SCHUIFSPANNINGSTURBULENTIE DOOR HWS


51/181

Sectie9 TB 51

SCHUIFSPANNINGSTURBULENTIE DOOR HWS

DE STRUCTUUR VAN DE WIND


52/181

Sectie9 TB 52

DE STRUCTUUR VAN DE WIND

TIJD

Hoe dichter bij de grond:

Hoe meer variatie in

richting en snelheid.

De ruwheid* is

zichtbaar aan het

karakter van de wind.

i d


53/181

Sectie9 TB 53

wind

G

E

B

O

U

W

Op afstand 30 x H nog 25% verstoring op hoogte H


54/181

Sectie9 TB 54

3. Orographic turbulence

mountainous areas are often turbulent

in areas with marked mountain waves (MTW)Ac

lenticularis

Ac lenticuaris

Rotor cloud

Stable!!!*


55/181

Sectie9 TB 55

4. wake turbulence

wing-tip vortices

very hazardous, especially during take-offs and landings*

persistent for 5 minutes or even more


56/181

Sectie9 TB 56

Wing-tip vortices

Walk away from generating aircraft with wind

Hazards:

In flight: possible sudden roll over!

On ground: mainly small aircraft too close behind

big one (wide body)*


57/181

Sectie9 TB 57


58/181

Sectie9 TB 58


59/181

Sectie9 TB 59

5. Clear air turbulence: CAT

clear air turbulence occurs in the free atmosphere away

from any visible convective activity

mostly associated with a jet stream

in the dense cirrus clouds along jet streams CAT may also occur*


60/181

Sectie9 TB 60

CAT with upper level

trough and ridge

CAT ith CB clo ds*


61/181

Sectie9 TB 61

CAT with CB clouds*

USA: keep clear of CB 30 miles.

i ( )


62/181

Sectie9 TB 62

Mountain waves (MTW)

Alsowithout Ac lenticularis (clear air)

Height of

MTW up to

20 km! *

Effect of MTW up to > 1000 km downwind


63/181

Sectie9 TB 63

6. Frontal turbulence


64/181

Sectie9 TB 64

Intensities of turbulence

LIGHT - slight erratic changes in altitude and/or attitude

- slight strain against seat belts or shoulder straps- no difficulty is encountered in walking

MODERATE- changes in altitude and/or attitude

- definite strain against seat belts or shoulder straps

- unsecured objects are dislodged

- food service and walking are difficult

SEVERE - large, abrupt changes in altitude and/or attitude

- aircraft momentarily out of control

- forced violently against seat belts or shoulder straps

- unsecured objects are tossed about

- food service and walking are impossible

EXTREME - aircraft is violently tossed and is practically impossible

to control

- may cause structural damage *


65/181

Sectie9 TB 65

WINDSHEAR

Definition:

change in windspeed and/or wind direction over short distance

VERTICALE WINDSCHERING (VWS)


66/181

Sectie9 TB 66

is de verandering van dehorizontalewindsnelheid en/of -richting per lengte-eenheid tussen tweeverticaal bovenelkaar staandepunten.

Horizontaal vlakHorizontaal vlak

H

O

O

G

TE

VWS is dus een snelle verandering over een korte afstand

van de horizontale wind in een verticaal vlak.

D d i d h i l i d lh id / fHORIZONTALE WINDSCHERING (HWS)


67/181

Sectie9 TB 67

De verandering van dehorizontalewindsnelheid en/of -richting per lengte-eenheid tussen twee punten, die beideninhetzelfde horizontale vlakliggen.

HORIZONTALE BREEDTE HORIZONTALE BREEDTE

HORI

ZONTALE

LENGTE

HORI

ZONTALE

LENGTE

HWS is dus een snelle verandering over korte afstand van de

horizontale wind in een horizontaal vlak.

Voetbalveld.

SCHERING VAN DE VERTICALE WIND (SVW)


68/181

Sectie9 TB 68

De verandering van deverticalewindsnelheid en/of -richtingper lengte-eenheid tussen twee punten, die inhetzelfde

horizontale vlakliggen.

HOOGT

E HOOGT

E

BODEM BODEM

SVW is dus een snelle verandering over korte afstand

van de verticale windcomponent in een horizontaal vlak.

WINDSCHERINGSVARIATIES TOEGEPASTOP DE LUCHTVAART


69/181

Sectie9 TB 69

OP DE LUCHTVAART

Windschering (windshear)is de variatie in grootte van dewindvector of zijn componenten langs en dwars op devliegroute.

Men onderscheidt: Head- of tailwindshear, de variatie in sterkte van de

neus- of staartwind-component;

Crosswindshear, de variatie van de dwarswind-

component en Vertical windshear, de variatie van de verticale

windcomponenten.


70/181

Sectie9 TB 70

Types of windshear

1. Nocturnal type; occurs during the night and in the early morning

in undisturbed radiation weather

2. Synoptic type; usually associated with fronts, but they also occur

otherwise

3. Orographic type; caused by orographic influences

4. Thunderstorm type; in and near thunderstorms associated with gust

fronts, downbursts, microbursts, macrobursts,

outbursts


71/181

Sectie9 TB 71

http://www.youtube.com/watch?v=OtnL4KYVtD

E&feature=related

Sh I i !


72/181

Sectie9 TB 72

Shear on Inversions!

T Wind

21008 kt

25018 kt

NACHTELIJK WINDMAXIMUM een voorbeeld van vws


73/181

Sectie9 TB 73

NACHTELIJK WINDMAXIMUM, een voorbeeld van vws

x 1000 ftx 100 ftX 1000 ft

Top inversie

DAG


74/181

Sectie9 TB 74

http://www.metacafe.com/watch/30410/boeing_747_extreme_landing/
http://www.metacafe.com/watch/30410/boeing_747_extreme_landing/http://www.metacafe.com/watch/30410/boeing_747_extreme_landing/


75/181

Sectie9 TB 75

Synoptic type

associated with cold and warm fronts

FRONTALE WINDSCHERING, een ander voorbeeld van


76/181

Sectie9 TB 76

VWS


77/181

Sectie9 TB 77

the sea-breeze front

What shear?


78/181

Sectie9 TB 78

Orographic type

mountain waves may lead to severe turbulence and windshear

Thunderstorm type

thunderstorms and cumulonimbus can cause the most severe

windshears

all kinds of windshear can happen


79/181

GEBIED MET BERGGOLVEN


80/181

Sectie9 TB 80

Strong winds (>30 kts)Perpendicular to mountains

Stable atmosphere

DRY ROTOR


81/181

Sectie9 TB 81

DRY ROTOR

Axis?

STERKTE VAN DE WINDSCHERING


82/181

Sectie9 TB 82

De ICAO geeft de volgende kwalificatie van de sterktevan windschering:

Zwakke windschering bij 0 - 4 kt /100 ft

Matige windschering bij 5 - 8 kt /100 ft

Sterke windschering bij 9 - 12 kt /100 ft

Zware windschering bij 12 kt /100 ft

Thunderstorm type


83/181

Sectie9 TB 83

yp

thunderstorms and cumulonimbus can cause the most severe

windshears

all kinds of windshear can happen

Downdrafts, microbursts, macroburst, gustfront, rollcloud etc

DE DOWNDRAUGHT ( Amerikaans: downdraft)


84/181

Sectie9 TB 84

DE DOWNDRAUGH ( Amer kaans downdraft)

In de onderste helft en onder de bui kan een krachtigeneerwaartse stroming ontstaan.

De algemene term ervoor is downdraught.

De algemene term van de voor de luchtvaart gevaarlijkevorm heet downburst.

ONTSTAANSOORZAKEN VAN DEDOWNDRAUGHT


85/181

Sectie9 TB 85

DOWNDRAUGHT

In de wolk : Afkoeling van de lucht door het smelten van ijsvormige

neerslagelementen onder het 0 0c-niveau. Meesleuren van de lucht tussen de neerslag-elementen.

Onder de wolk: Afkoeling van de lucht door het verdampen van de

vloeibare neerslagelementen. Meesleuren (drag) van de lucht tussen de neerslag-

elementen.

SOORTEN DOWNDRAUGHT


86/181

Sectie9 TB 86

MACROBURST:Een krachtige neerwaartse stroming met eendoorsnede > 4 km.

Komt voor in het gebied met de zwaarste neerslag.

Kan in een groot gebied tornado-achtige schadeaanbrengen.

Aan de grond kan de windsnelheid oplopen tot 130 kt.

De levensduur varieert, vanaf het moment dat de grond isbereikt, van 5 tot 20 minuten.

SOORTEN DOWNDRAUGHT (vervolg 1)


87/181

Sectie9 TB 87

MICROBURST:Een zeer krachtige neerwaartse stroming met eendoorsnede 4 km.

Komt voor in het gebied met de zwaarste neerslag.

De verticale snelheid kan 30-60 ft boven de grond 1000-2000 ft/min (5-10 m/s) bereiken.

Aan de grond kan de windsnelheid oplopen tot >160 kt.

De levensduur varieert, vanaf het moment dat de grond isbereikt, van 2 tot 5 minuten.



88/181

Sectie9 TB 88


MIDAIR MICROBURST:Een microburst die het aardoppervlak niet bereikt en deluchtstroming daar niet benvloedt.

DROGE MICROBURST:Een microburst uit een bui met een hoge basis, waarvande regen verdampt voordat die het aardoppervlak kanbereiken. De microburst bereikt het aardoppervlak

echter wel.


89/181

Sectie9 TB 89


90/181

Sectie9 TB 90

FOOTPRINT VAN EEN DOWNBURST UITEEN STATIONAIRE BUI


91/181

Sectie9 TB 91

EEN STATIONAIRE BUI

Gustfront van de horizontaal

uitstromende koude lucht

Omtrek bui

Centrum

downburst

FOOTPRINT VAN EEN DOWNBURST UITEEN BEWEGENDE BUI


92/181

Sectie9 TB 92

EEN BEWEGENDE BUI

Bewegingsrichting

Omtrek bui

Gustfront van de horizontaal

uitstromende koude lucht

Downburst

centrum

EVOLUTIE VAN EEN DOWNBURST


93/181

Sectie9 TB 93

0 3 5 10 15

Verlopen tijd in minuten

Onderkant van de bui


94/181

Sectie9 TB 94

WINDSCHERINGSDETECTIE


95/181

Sectie9 TB 95

Er zijn drie operationele windscherings-systemen ingebruik op de grond:

Low Level Windshear Alert System( LLWAS)

De windprofiler,een Doppler-radar

SODAR,een akoestische radar

In gebruik of in ontwikkeling voor airborne systemen:

Doppler-radar

Infrarood detectiesysteem

Laser detectie systeem


96/181

Sectie9 TB 96


97/181

Sectie9 TB 97

horizontal windshear

vertical windshear

shear of the vertical wind


98/181

Sectie9 TB 98

GET OUT !!!!

Effect of windshear on flight:


99/181

Sectie9 TB 99

Effect of windshear on flight:

Windshear is the variation of the components of the wind

vector along and perpendicular to the flight route.

Head windshear / tail windshear: variation of the windspeed of the

head/tail wind.

Shearing of vertical wind: variation of the vertical wind.

Cross windshear: variation of the wind component perpendicular to

the flight route.

Windshear in practice:


100/181

Sectie9 TB 100

Windshear in practice:

Often simplified to Negative or Positive Shear

Positive: performance increase, more lift, greater IAS

Negative: performance decrease, less lift, smaller IAS.

THUNDERSTORMS (onweersBUI*)

USA STORM i BUI !!!!!


101/181

Sectie9 TB 101

USA STORM is een BUI !!!!!

Conditions for thunderstorm development

a thunderstorm is a CB accompanied by thunder and lightning.

1. Most of cloud must be above the FZL => WBF

2. atmosphere must be unstable , at least 10.000 ft, strongupdraft, 10-35 m/s

3. top of the clouds above the level of -20C (not necessary in

the tropics)

4. Sufficient lifting forces

5. adequate supply of moisture from below

lifting forces can be caused by:


102/181

Sectie9 TB 102

g y

- local differential heating over land, solar insolation and formation

of thermal lows

- night time radiation cooling from the top

- orographic effects (lifting)

- frontal activity (frontal lifting)

- low level convergence, along a trough for example

- due to differential advections: cold air advection aloft and warm air

advection in low levels.

Life cycle of an individual thunderstorm cell


103/181

Sectie9 TB 103

Life cycle of an individual thunderstorm cell

Single Cumulonimbus cells rarely exceed a few km in diameter

In the individual cell three stages of development can be recognised:

1. Cumulus stage

2. Mature stage3. Dissipating stage

The life cycle of an individual cell is in the order of 30 minutes
http://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpg


104/181

Sectie9 TB 104

1 C l t
http://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpg


105/181

Sectie9 TB 105

1. Cumulus stage

only updrafts

no precipitation

10-15min duration

1. Cumulus stage


106/181

Sectie9 TB 106

CU and TCU

Only updrafts

No precip.

Higher FZL in

CLD

2 Mature stage


107/181

Sectie9 TB 107

2. Mature stage

up- and downdrafts

precipitation

downburst and outburst

gust front

hail, turbulence,

lightning and gusts

greatest activity of the stormsand thunderstorms

Max vertical speeds 3040 m/s

2. Mature stage


108/181

Sectie9 TB 108

both down and updrafts

often tilted!*

FZL higher in updrafts

1) Warm air updraft

2) Release of latent heat

FZL lower in downdrafts

1) Drag of cold upper air

2) Melting and evaporation

need energy

3. Dissipating stage


109/181

Sectie9 TB 109

3. Dissipating stage

downdrafts dominate

precipitation decreases

and finally stops

no more lightning

turbulence inside the

cloud will rapidly decrease

Clouds dissolve

Anvil- Ci clouds often remain

longtime

Classification of thunderstorms


110/181

Sectie9 TB 110

Classification of thunderstorms

Air mass thunderstorms

Thermal thunderstorms, a result of irregular local heating of

the surface. Uplift due to solar radiation.

Cold mass thunderstorms:thunderstorms or night/ winter

thunderstorms over sea and coastal areas. They often occur at

the rear of a cold front. The temperature in the higher layers islow, causing a steep environmental lapse rate.

Orographic thunderstorms: when moist potentially unstable

air is forced to rise against a mountain range, it becomes

statically unstable.

Prefrontal thunderstorms: in unstable airmass ahead of a kata

cold front (fast running front), generally organised along a

squall line.

Example Pre-frontal TS

Sly warm flow


111/181

Sectie9 TB 111

Often Thermal

Low beforeColdfront arrives

y

over W Eur

Very hightemperatures

over France

F t l th d t


112/181

Sectie9 TB 112

Frontal thunderstorms

When the warm air in the warm sector is unstable, the forced lifting along

the frontal surface may lead to the formation of embedded cumulonimbusin the frontal clouds along the front at the surface. They are not random

but organised along a line along the surface front. They are associated

with active cold fronts.

Convergence thunderstorms

These thunderstorms are observed along the ITCZ, an E-ly wave, a

trough and if the airmass is potentially unstable there is also a risk of

thunderstorms along the sea-breeze front.*

Frontal thunderstorms


113/181

Sectie9 TB 113

Mostly on Coldfronts

stratiform



114/181

Sectie9 TB 114

Trough

L

surfaceTrough

CB



115/181

Sectie9 TB 115

May develop near/in:

1. ITCZ

2. Troughs

3. Lows

4. Easterly Waves

5. Cyclonic cols

6. Etc

Frequency of thunderstorms


116/181

Sectie9 TB 116

Thunderstorms are wide spread, around 50 000 thunderstorms

per day !! The frequency of thunderstorms over land is highest in

summer during daytime; over sea the frequency is highest in

winter during the late night.*

The frequency of occurrence changes from one region to another

- In Polar areas: nearly no thunderstorms

- Between latitudes 70-80: 1 day a year with thundery weather.- In mid-latitude: 32 days with thundery weather.

- In subtropical areas: only 10 days

- Near equator: 136 days with thundery weather.

Thunderstorm Classification


117/181

Sectie9 TB 117

Single cell/ Airmass

Multi cell

Super cell

Squall lines
http://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpg


118/181

Sectie9 TB 118

Single cell or Airmass TS

Lifetime to 1 hour

3 to 8 km diameter

Multi cell TSUpper wind
http://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpghttp://upload.wikimedia.org/wikipedia/commons/3/39/Cumulonimbus_NOAA_gov.jpg


119/181

Sectie9 TB 119

By growing new cells on forward right side, system moves

to the right of upper winds!

Upper wind

Movement

New cells

Oldest Cell


120/181

Sectie9 TB 120

Multi cell TS

Often called MCC or MCS (depending on size)

(Mesoscale Convective Complex or System)

Anvils up to 100 km away

Up to 300 x 300 km!

Lifetimes up to 12 hours


121/181

Sectie9 TB 121


122/181

Sectie9 TB 122

Fig. 8.49 Schematic of an idealized multicell storm developing in an

environment

with strong vertical shear in the direction of the vertically averaged wind. The

vertical profile of equivalent potential temperature e in the environment is

shown at the left, together with the wind profile. Arrows in the right panel

denote motion relative to the moving storm.

Super cell


123/181

Sectie9 TB 123

Acts as a Low

Rotation

Very big

Very active

ONE CELL

Tornados

Rare in Europe


124/181

Sectie9 TB 124

Fig. 8.56 Structure of a typical tornadic supercell storm. Motion of the warm air is

relative to the ground. [Based on NOAA National Severe Storm Laboratory

publications and an unpublished manuscript by H. B. Bluestein. From R. A.

Houze, Cloud Dynamics, Academic Press (1993) p. 279.]

Supercell 26 juli 1983

moving NNE


125/181

Sectie9 TB 125

Developing MCC

Bigger than the

NetherlandsHail at 07.00 Lt Den

Helder golfball size

Well developed Low

on sfc charts

2,5 m water upset

Harlingen*

Squall lines

Squall= sudden wind


126/181

Sectie9 TB 126

More or less closed LINE

of active CBs moving in

one direction

>200 km long Gustfront up to max 32

km in front of Squall line!!

Rotor/Arcus cloud

Sand or dust rotor

Next cross section A-B

icrease to >16 kts lasting

1 min at least

cross section A-B


127/181

Sectie9 TB 127

Cold air from shower giving gustfront

Warm air to shower to feed CB

09024

24032G46Gustfront

Squall lines


128/181

Sectie9 TB 128

formed near:

1. cold fronts

2. troughs

3. ITCZ

Squall lines develop mostly in hot summer weather along

lines of convergence or pre-frontal convergence.

When all active TS condition are met.*

The gust front


129/181

Sectie9 TB 129

Outflow of cold air in a (thunder)shower

dangerous for aircraft on takeoffs and landings

HWS and VWS

24 to 32km

ahead of the

storm centre


130/181

Sectie9 TB 130

Rolwolk!


131/181

Sectie9 TB 131

GET OUT!


132/181

Sectie9 TB 132


133/181

Sectie9 TB 133

Hail

H il i f f i i i hi h i f b ll i l
http://en.wikipedia.org/wiki/Precipitation_%28meteorology%29http://en.wikipedia.org/wiki/Precipitation_%28meteorology%29


134/181

Sectie9 TB 134

Hail is a form ofprecipitation which consists of balls or irregular

lumps of ice (hailstones). Hailstones on Earth usually consist mostly

ofwater ice and measure between 5 and 50 millimetres in diameter,with the larger stones coming from severe thunderstorms.[1] Hail is

always produced by cumulonimbi (thunderclouds), usually at the

front of the storm system, and is composed of transparent ice or

alternating layers of transparent and translucent ice at least 1 mmthick. Small hailstones are less than 5 mm in diameter, and are

reported as SHGS. Unlike ice pellets, they are layered and can be

irregular and clumped together.

Wikipedia

Hail development:

1) Precip partical
http://en.wikipedia.org/wiki/Precipitation_%28meteorology%29http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Millimetrehttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Cumulonimbushttp://en.wikipedia.org/wiki/Snow_pelletshttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Snow_pelletshttp://en.wikipedia.org/wiki/Cumulonimbushttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Millimetrehttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Precipitation_%28meteorology%29


135/181

Sectie9 TB 135

) p p

enters updraft

2) Riming startsabove FZL

3) Heavier particle

falls down, melts

partialy below FZL

4) Enters updrafts

againriming

5) Etc etc

Second posibility:

Riming hailstone stays at same level

Updraft = fallspeed growing by riming

Hail development:


136/181

Sectie9 TB 136

Melting and freezing,

Melting and freezing

Thats why a hailstone is layered..!

Hail


137/181

Sectie9 TB 137

due to strong updraft a melting snowflake will go up and down

for several times and freeze due to riming proces

Hailstones can achieve a large size and can be met at any height

in the cloud(45.000 ft) and outside the cloud!!!!
http://www.stormgasm.com/4-17-02LPday/tom%20pics/hail.jpg


138/181

Sectie9 TB 138

Flying below anvil close to CB dangerous for hail!!

Hail

F t f it !!!
http://en.wikipedia.org/wiki/Image:Granizo.jpg


139/181

Sectie9 TB 139

From a pea to a grapefruit !!!

6 cm

Nederland

17 cm

Max ca. 20 cm.USA

Hagelfeiten.De grootste hagelsteen die in de wereld viel had een doorsnedevan 17,8 centimeter. De hagelsteen viel op 22 juni 2003 in Aurora(N b k ) D t k t lh id 160 kil t
http://en.wikipedia.org/wiki/Image:Granizo.jpg


140/181

Sectie9 TB 140

(Nebraska). De steen kwam met een snelheid van 160 kilometerper uur neer.

De zwaarste hagelsteen viel op 3 september 1970 in Coffeyville(Kansas) en woog 757 gram. Het ijsblok wordt bewaard in eenvriezer in Boulder en staat vermeld in het Guinness Book of WorldRecords. Van de hagelsteen is een plastic replica gemaakt, zodat

iedereen het kan zien.

Ook een grote hagelsteen viel in Potter (Nebraska) op 6 juli 1928en was 13,7 centimeter.Ooggetuigen zeiden dat tussen de individuele hagelstenen 3 tot4.5 meter ruimte zat.In juli 1990 werd Denver (Colorado) door zware hagel getroffen.Hier was voor $625 miljoen recordschade.Idem ca. 15 jaar geleden in Munchen

Large hailstones can cause enormous damage to aircraft


141/181

Sectie9 TB 141


142/181

Sectie9 TB 142


143/181

Sectie9 TB 143


144/181

Sectie9 TB 144


145/181

Sectie9 TB 145


146/181

Sectie9 TB 146


147/181

Sectie9 TB 147


148/181

Sectie9 TB 148


149/181

Sectie9 TB 149

http://www.youtube.com/watch?v=wZr8jXo1Uso

The anvil
http://www.youtube.com/watch?v=wZr8jXo1Usohttp://www.youtube.com/watch?v=wZr8jXo1Uso


150/181

Sectie9 TB 150

Top of CB

Anvil points in the direction of the winds in the top of theCBs, and so indicates the direction of the cell motion

anvil

Electricity in the atmosphere


151/181

Sectie9 TB 151

There is always some weak electrical charge in

atmosphere

In clouds the ice particles make the difference

Electricity in the atmosphere PRINCIPLE*


152/181

Sectie9 TB 152

*collides with

* *Large negativefall

* Small positive rise

- - - -- - - -

+ + + +

+ + + +


153/181

Sectie9 TB 153


154/181

Sectie9 TB 154

Sometimes an aircraft is a bridge/trigger for

discharge to the ground:

Selftriggering effect *


155/181

Sectie9 TB 155


156/181

Sectie9 TB 156


157/181

Sectie9 TB 157

Words to know

1) Stepped leader2) Leader

3) Streamer

4) Return strokeBlz 9-42


158/181

Sectie9 TB 158

Lightning damage on propellor tip


159/181

Sectie9 TB 159

(Airborne) Radar To high


160/181

Sectie9 TB 160

Proper tilt is essential

To high

To low


161/181

Sectie9 TB 161

Shadowing


162/181

Sectie9 TB 162

radar CB1 CB2

On the scope:

Only CB1

CB1

Attenuation


163/181

Sectie9 TB 163

radar

By absorbtion of radar energy, false backside


164/181

Sectie9 TB 164

Turbulence: in and close to Rotors*in and close to Lenticularis

in waves

Downbursts, micro- and macro


165/181

Sectie9 TB 165

Famous:


166/181

Sectie9 TB 166

Famous:

Fujita and Caracena 1977

1) Eastern 902

2) Eastern 66


167/181

Sectie9 TB 167


168/181

Sectie9 TB 168

Tornados


169/181

Sectie9 TB 169

Tornados Neerslaggebied

Groen/geel


170/181

Sectie9 TB 170

Let op: echos in

de vorm vanboog of

komma (Eng

Hook Echo)

Tornado

mogelijk

GET OUT!!!

Tornados

Twister, wervelwind,

zware windhoos etc


171/181

Sectie9 TB 171

A tornado is defined as aviolently rotating column

of air extending from a

thunderstorm to the

ground.

zware windhoos etc

Diameter 10 to 100 m normaly

Max around 2 km!!

Rotating windspeed:100 to 150 m/s (550 km uur)

Damaging path: 10 km average

Low pressure inside (900 hPa avg)*

Waterspout (little

tornado over

warm water)

Warm air moves UP !!!

Tornados


172/181

Sectie9 TB 172

Whole CB system rotates

Most Tornados rotate (99%) Cyclonic (Coriolis)*

Whole world knows Tornados

Mostly in the Tornado Alley USA

Tornados


173/181

Sectie9 TB 173

Tornado Alley


174/181

Sectie9 TB 174


175/181

Sectie9 TB 175

CBs need moisture and heat, so mainly form over agricultural areas

Tropical jungles are not hot enough.

Desserts are not moist enough.

Tornado from Tornado

Alley


176/181

Sectie9 TB 176

Let op schuine stand !

Moerdijk F28*

Tornadoes in Nederland?

1) Borculo augustus 1925 de cycloon van Borculo 3 doden

2) N d 1927 10 d d


177/181

Sectie9 TB 177

2) Neede 1927 10 doden

3) Tricht 1967 7 doden

4) Ameland 1972 4 doden

5) Moerdijk ongeluk 1981 F28 verongelukt 2 slurven onder bui

6) Ameland 1992 1 dode*

7) Plus nog ca. 25 kleinere windhozen, waterhozen, downbursts

etc. met schade per jaar!


178/181

Sectie9 TB 178

Bron KNMI

Tornado van Tricht

Rotation speed of air defines Fujita scale: (for Tornados)Fujita

schaal

F064-117 Schade aan schoorstenen, takken


179/181

Sectie9 TB 179

F0km/u breken af

F1118-180

km/u

Schade aan daken, autos worden van

weg afgeduwd

F2

181-

251

km/u

Bomen worden ontworteld, caravans

vernield

F3

252-

330

km/u

Daken en muren worden weggerukt,

autos worden opgetild

F4

331-

417

km/u

Huizen worden vernield en autos

gegooid

F5

418-

509

km/u

Huizen worden van fundamenten

gelicht

Dustdevils

(Wind- of stofhoos)

A li


180/181

Sectie9 TB 180

In Australia:

Willy Willy

Only Thermals (often Dry thermals = no cloud)

( droge thermiek of Blau thermiek)

Dustdevils can cause gusts up to 35 kt ! *

Dustdevil boven verbrande aardeLet op: altijd mooi weer

F t T A d B


181/181

Foto: T.A. de Boer.

section 9 tb meteorology

Documents