7/30/2019 FW1 Full Presentation_0
1/173
Ed. 1.0 Sept 2007
Fire Weather 1Meteorological Concepts
7/30/2019 FW1 Full Presentation_0
2/173
Slide 1
Session Goal
This training session introduces several meteorologicalconcepts which will help you to understand weathercharts, forecasts and fire weather
A number of diagrams used in this presentation are takenfrom Bureau of Meteorology publications (copyrightCommonwealth of Australia) and are used with theirpermission. For more details see Fire Weather 1Learning Manual
7/30/2019 FW1 Full Presentation_0
3/173
Slide 2
Learning Outcomes
This training session will cover two learning outcomes
After completing this session you should be able toexplain:
how weather originates in terms of global circulation airmass and frontal characteristics, and how these
may impact fire behaviour
7/30/2019 FW1 Full Presentation_0
4/173
Slide 3
Outline
1. What is weather?
2. Fundamentals of meteorology
3. Global circulation
4. Weather associated with high or low pressure
5. Airmass characteristics
6. Ridges, troughs and fronts
7. Effect of weather on fire behaviour
7/30/2019 FW1 Full Presentation_0
5/173
Slide 4
Scenario
CFA Public Affairs
(used with their permission)
7/30/2019 FW1 Full Presentation_0
6/173
Slide 5
What is Weather and Climate?
Weather describes the state of the atmosphere andhow it varies over short time periods from hours to days
Climate refers to the long term weather conditions at a
location over months or years, or average weather
7/30/2019 FW1 Full Presentation_0
7/173
Slide 6
What is Fire Weather?
Fire weather describes the atmospheric conditions ofweather and climate in which:
(a) a wildfire is likely to be ignited
(b) a wildfire is difficult to suppress
7/30/2019 FW1 Full Presentation_0
8/173
Slide 7
Key Weather Components
Temperature
Humidity
Wind
Precipitation Pressure
7/30/2019 FW1 Full Presentation_0
9/173
Slide 8
Composition of the Atmosphere
Water vapourvaries between0 and 4%
7/30/2019 FW1 Full Presentation_0
10/173
Slide 9
Vertical Structureof the Atmosphere
The Troposphere
Generally the lowest 10-12 km inVictorian latitudes
75% of the overall mass of the
atmosphere Temperature drops with height
Where weather happens!
The Stratosphere
Stable, dry layer above the level ofsurface convective currents
Temperature no longer falls with height
Contains the ozone layer
7/30/2019 FW1 Full Presentation_0
11/173
Slide 10
Global Circulation
Global circulation describes atmospheric motion over theearth but what causes this?
7/30/2019 FW1 Full Presentation_0
12/173
Slide 11
Incoming Solar Radiation
Solar energy combined with the earths geometry drives theweather
7/30/2019 FW1 Full Presentation_0
13/173
Slide 12
Warm Air Rises
Heating air causes it to expand andbecome less dense
A sample of (otherwise identical) air that
is warmer than its surroundingenvironment will rise because it is lessdense and therefore lighter than the airaround it
Warm
7/30/2019 FW1 Full Presentation_0
14/173
Slide 13
Cool Air Sinks
Cooling air causes it to contract andbecome more dense
A sample of (otherwise identical) air that
is cooler than its surroundingenvironment will sink because it is moredense and therefore heavier than the airaround it
Cold
7/30/2019 FW1 Full Presentation_0
15/173
Slide 14
Pressure at the Earths Surface
Variations in surface pressureresult from differential solarheating
Rising air creates a relative void,resulting in low surface pressure
Sinking air creates a pile-up ofmass and high surface pressure
Supporting airflow is needed inthe upper atmosphere to sustainthese changes
7/30/2019 FW1 Full Presentation_0
16/173
Slide 15
Simplified AtmosphericCirculation
A uniform, non-rotating earth,warmed at the equator andcooled at the poles
In reality this does not occurbecause:
The earth spins on its axisonce every 24 hours
There are seasonal variations
in solar heating The earth does not posses a
uniform surface oratmosphere
7/30/2019 FW1 Full Presentation_0
17/173
Slide 16
A Dynamic Earth
Daily and annualvariations in solarheating
Surface featuresmountains, oceans,cities
Variations in thecomposition of the
atmosphere
7/30/2019 FW1 Full Presentation_0
18/173
Slide 17
Coriolis Force
Coriolis force is anapparent deflection of theair from its path asdictated by the pressure
gradient force whenviewed by an observer onthe earths surface
7/30/2019 FW1 Full Presentation_0
19/173
Slide 18
A Real Atmosphere
Real global circulation isdue to:
Variations in solarheating
Variations in the earthssurface features andatmosphere
Coriolis force
7/30/2019 FW1 Full Presentation_0
20/173
Slide 19
Typical Global Conditions -February
Global map ofaverage sea levelpressure showingsubtropical highs
and equatoriallow (ITCZ)
7/30/2019 FW1 Full Presentation_0
21/173
Slide 20
Typical Global Conditions -August
Global map ofaverage sea levelpressure showingsubtropical highs
and equatoriallow (ITCZ)
7/30/2019 FW1 Full Presentation_0
22/173
Slide 21
Pressure Gradient Force
The atmospheretries to push airfrom high to lowpressure
Pressure GradientForce
S i S l Wi d i h
7/30/2019 FW1 Full Presentation_0
23/173
Slide 22
Synoptic Scale Winds in theMid-latitudes
Air moves from high to lowpressure and is deflectedto the left by CoriolisForce. Eventually the two
forces balance and thewind blows parallel to theisobars
If you stand with your
back to the wind inAustralia the low pressurewill be on your right
Wi d St th d P
7/30/2019 FW1 Full Presentation_0
24/173
Slide 23
Wind Strength and PressureGradient
The closer togetherthe isobars, thestronger the wind!
7/30/2019 FW1 Full Presentation_0
25/173
Slide 24
High and Low Pressure Centres
In the southernhemisphere, windsblow anticlockwisearound highs and
clockwise around lowsbecause of the balancebetween PressureGradient Force,Coriolis Force and
Centrifugal Force
7/30/2019 FW1 Full Presentation_0
26/173
Slide 25
The Influence of Friction
Friction acts in theopposite direction tosurface winds thisreduces the wind
speed
A force balance isreached where windvelocity is seen to
veer towards thedirection of lowerpressure
Hi h d L P C t
7/30/2019 FW1 Full Presentation_0
27/173
Slide 26
High and Low Pressure CentresUnder the Influence of Friction
The balance offorces causes air tobe deflected awayfrom the centre of
highs and deflectedtowards the centreof lows
7/30/2019 FW1 Full Presentation_0
28/173
Slide 27
Wind and the Weather Map
7/30/2019 FW1 Full Presentation_0
29/173
Slide 28
Weather and High Pressure
Subsiding air tends to create more stable conditions asubsidence inversion can occur
Temperature:
Dependent upon upstream airmass Tends to increase, especially if the high pressure centre
moves to the east of Victoria
Cloud:
Low likelihood of cloud and precipitation Low cloud may become trapped under a subsidence
inversion
7/30/2019 FW1 Full Presentation_0
30/173
Slide 29
Weather and Low Pressure
Rising air tends to create less stable conditions asubsidence inversion will erode
Temperature:
Dependent upon upstream airmass Tends to decrease, especially following the passage of a
cold front or low pressure trough
Cloud:
High chance of mid-level and convective cloud High chance of precipitation
7/30/2019 FW1 Full Presentation_0
31/173
Slide 30
Airmasses
Airmasses are classified according to their sourceorigin. Consider the air upstream:
Is it continental, maritime, polar or tropical?
Is it dry or moist, warm or cool? In some instances air from the Southern Ocean can be
very dry
Consider how rapidly or slowly the airmass is moving
Consider whether the air will be modified: How will diurnal changes influence the air?
Will the air be moving from water to land?
7/30/2019 FW1 Full Presentation_0
32/173
Slide 31
Summer Airmass Characteristics
Tropical
Maritime Tropical
MaritimeTropical
Continental
Southern
MaritimeSouthern
Maritime
Southern
Maritimemodifiedby
TasmanSea
7/30/2019 FW1 Full Presentation_0
33/173
Slide 32
Winter Airmass Characteristics
Tropical
Maritime
Southern
Maritime
Southern
MaritimePolar
MaritimePolar
Maritime
Southern
Maritime
7/30/2019 FW1 Full Presentation_0
34/173
Slide 33
Ridges and Troughs
Ridge:
An elongated area of relatively higher pressure associatedwith anticyclonic flow
Commonly extend from a high pressure system
Typically bring light winds and warm, clear weather
Trough:
An elongated area of relatively lower pressure associatedwith cyclonic flow
Commonly extend from a low pressure system
Typically bring cool, unsettled weather and precipitation
7/30/2019 FW1 Full Presentation_0
35/173
Slide 34
Fronts
The boundary between airmasses of different densitiesis referred to as a front
Four types of front are evident:
Cold Warm
Occluded
Stationary
Cold fronts are most common in SE Australia
7/30/2019 FW1 Full Presentation_0
36/173
Slide 35
Cold Front
A cold front is the boundary between a cold airmassmoving towards a region of warmer air
A backward sloping face forms as the cool, dense airslides underneath the warmer, lighter air ahead
Warm air retains more moisture than cold air so as it israpidly forced upwards, any moisture condenses out toform cloud and precipitation
Strong and gusty winds, cloud, rainfall, thunderstormsand falling temperatures are typically experiencedduring the passage of a cold front
7/30/2019 FW1 Full Presentation_0
37/173
Slide 36
Profile of a Cold Front
7/30/2019 FW1 Full Presentation_0
38/173
Slide 37
Cold Fronts in Victoria
The typical weather changes associated with thepassage of a cold front in Victoria are:
Strengthening and gusty northeasterly to northwesterlywinds before the front
Increasing evidence of instability such as cumulus cloud ordeveloping thunderstorms
A west to southwesterly wind change which can be quiteabrupt and bring severe squalls
A moderation of the wind speed and a clearing of theweather behind the front
7/30/2019 FW1 Full Presentation_0
39/173
Slide 38
Wind Changes
A wind change refers to a distinct shift of winddirection, greater than 30, where wind speeds beforeor after the change are 10 km/h or more
In Victoria, the passage of a cold front is often referredto as a wind change or just a change because theseconditions are generally met
Cold Fronts Wind Changes and
7/30/2019 FW1 Full Presentation_0
40/173
Slide 39
Cold Fronts, Wind Changes andFire Behaviour
Cold fronts, or changes, have a major impact on firebehaviour:
Strong, gusty, hot and dry north to northwesterly windsprior to the change promote fast moving intense fires
Lighting may ignite new fires
It might be a dry change i.e. precipitation is not expected
The west to southwesterly wind change may turn the eastflank of the fire into the main fire front
Effect of a Wind Change on Fire
7/30/2019 FW1 Full Presentation_0
41/173
Slide 40
Effect of a Wind Change on FireBehaviour
7/30/2019 FW1 Full Presentation_0
42/173
Slide 41
Summary
The sun is the driving force behind the worlds weather
Changes in air density create regions of high and lowpressure
Air will tend to move from high to low pressure Air flows anticlockwise around highs (anticyclones) and
clockwise around lows (cyclones)
7/30/2019 FW1 Full Presentation_0
43/173
Slide 42
Air will rise:
As it converges towards low pressure
If it is less dense than the surrounding air
If it is forced by a barrier or another airmass Airmass characteristics can be determined from
examination of the weather map.
Fronts are the boundaries between airmasses of
different densities Fire behaviour can alter dramatically during a wind
change event
7/30/2019 FW1 Full Presentation_0
44/173
Ed. 1.0 Sept 2007
Fire Weather 1Understanding Weather Charts
7/30/2019 FW1 Full Presentation_0
45/173
Slide 44
Session Goal
This training session will introduce and describe weathercharts and their application
A number of diagrams used in this presentation are takenfrom Bureau of Meteorology publications (copyrightCommonwealth of Australia) and are used by permission.For more details see Fire Weather 1 Learning Manual
7/30/2019 FW1 Full Presentation_0
46/173
Slide 45
Learning Outcomes
This training session will cover five learning outcomes
After completing this session you should understand:
the basic features depicted in a weather chart
how to interpret a weather chart typical summer and winter weather patterns in Australia
how to identify a day of severe fire danger from thesynoptic map
the three-dimensional nature of the atmosphere
7/30/2019 FW1 Full Presentation_0
47/173
Slide 46
Outline
1. Typical features of a weather chart
2. Interpreting a weather chart
3. Typical summer and winter weather patterns in
Australia4. Severe fire weather on the synoptic map
5. Three-dimensional nature of atmosphere
7/30/2019 FW1 Full Presentation_0
48/173
Slide 47
The Value of a Weather Chart
Weather charts or synoptic charts are veryrecognisable to most people
Weather charts display past, current and forecastinformation for a particular region
A large amount of material is contained within aweather map
7/30/2019 FW1 Full Presentation_0
49/173
Slide 48
Typical Features of a Weather Map
7/30/2019 FW1 Full Presentation_0
50/173
Slide 49
Isobars
Isobars indicate areasof constantatmospheric pressurein the same way that
contours indicateareas of constantaltitude on a landmap
Rid d Hi h P
7/30/2019 FW1 Full Presentation_0
51/173
Slide 50
Ridges and High Pressure
High pressure zonesare clearly visible
Ridge axes areidentified by a wavy
line
T h d L P
7/30/2019 FW1 Full Presentation_0
52/173
Slide 51
Troughs and Low Pressure
Low pressure zonesare clearly visible
Trough axes areidentified by a
dashed line theseare less clearlydefined than ridgeaxes
F t W th M
7/30/2019 FW1 Full Presentation_0
53/173
Slide 52
Fronts on a Weather Map
Cold fronts are indicated by a solid triangle (blue on acoloured map) in the direction of the movement
Warm fronts are indicated by a solid semicircle (red ona coloured map) in the direction of the movement
Occluded fronts are indicated by alternating solidsemicircles and triangles (purple on a coloured map) inthe direction of movement
Stationary fronts are indicated by a solid line alternated
with triangles (blue on a coloured map) towards thewarmer air and semicircles (red on a coloured map)towards the colder air
Examples of Fronts on a
7/30/2019 FW1 Full Presentation_0
54/173
Slide 53
Examples of Fronts on aWeather Map
Typical Summer Weather
7/30/2019 FW1 Full Presentation_0
55/173
Slide 54
Typical Summer WeatherPatterns in Australia
The mean path ofsummer high pressurecentres across southern
Australia as a result of
global circulation
Summer Weather Pattern 1:
7/30/2019 FW1 Full Presentation_0
56/173
Slide 55
Summer Weather Pattern 1:Easterly Dip
A high pressure centreover the Bight directssoutheasterly windsover Victoria and NSW,
whilst a low overQueensland reinforcesthose easterlies
Victoria is likely toexperience cool andmoist conditions
Summer Weather Pattern 2:
7/30/2019 FW1 Full Presentation_0
57/173
Slide 56
Summer Weather Pattern 2:Summer Heatwave
The SummerHeatwave results froma ridge associated witha blocking high
pressure system overthe Tasman Sea
Victoria is likely toexperience fine and hotweather
Typical Winter Weather
7/30/2019 FW1 Full Presentation_0
58/173
Slide 57
Typical Winter WeatherPatterns in Australia
The mean path of winterhigh pressure centresacross southern Australiaas a result of global
circulation
Winter Weather Pattern:
7/30/2019 FW1 Full Presentation_0
59/173
Slide 58
Winter Weather Pattern:Winter High
A high pressure centreover eastern Australiawith an associated ridgeextending westwards
Stable, cold and clearconditions would beexperienced as frontalactivity is restricted
Fire Weather and the Synoptic
7/30/2019 FW1 Full Presentation_0
60/173
Slide 59
Fire Weather and the SynopticMap
A day in which severe firedanger may occur can bepredicted when specificsynoptic patterns are
known and identified onthe forecast weather chart
A Th Di i l At h
7/30/2019 FW1 Full Presentation_0
61/173
Slide 60
A Three-Dimensional Atmosphere
Most weather mapsdisplay sea levelpressure when in realitythe atmosphere is three-
dimensional Upper level charts are
available that showmeteorologicalinformation aboveground level
300 hPa map
Atmospheric Thickness
7/30/2019 FW1 Full Presentation_0
62/173
Slide 61
Atmospheric Thickness
Thickness refers to theheight of the layer between1000 hPa (~sea level) and500 hPa in metres or
decametres If the column of air is
heated, it expands andthe height increases
If the column of air iscooled, it contracts andthe height decreases
7/30/2019 FW1 Full Presentation_0
63/173
Slide 62
Thickness is therefore a measure of how warm or coldthe atmosphere is between 1000 hPa and 500 hPa thiscan be related to ground level conditions
The warmer the 1000 hPa to 500 hPa layer, the higherthe temperature is likely to be at ground level
Thickness on a Weather Chart
7/30/2019 FW1 Full Presentation_0
64/173
Slide 63
Thickness on a Weather Chart
Thickness is indicated
by dashed lines in
metres
Summary
7/30/2019 FW1 Full Presentation_0
65/173
Slide 64
Summary
Features of a weather map include areas of high andlow pressure, ridges, troughs, and fronts
Synoptic charts give an indication of the weatherthrough applying the concepts of global circulation and
airmass characteristics
Typical seasonal weather patterns exist in Australia
An day of severe fire weather can often be predictedfrom a synoptic map
Atmospheric thickness gives an indication of theexpected temperature at the earths surface
7/30/2019 FW1 Full Presentation_0
66/173
Ed. 1.0 Sept 2007
Fire Weather 1Satellite and Radar Interpretation
Session Goal
7/30/2019 FW1 Full Presentation_0
67/173
Slide 66
Session Goal
This session will introduce the use of satellite and radarimagery in meteorology and discuss its interpretation
A number of diagrams used in this presentation are takenfrom Bureau of Meteorology publications (copyright
Commonwealth of Australia) and are used with theirpermission
Satellite images are credited where appropriate
Learning Outcomes
7/30/2019 FW1 Full Presentation_0
68/173
Slide 67
Learning Outcomes
This training session will cover two learning outcomes
After completing this session you should understand:
the different types of satellite and radar images
what meteorological features are present on a satellite orradar image
Outline
7/30/2019 FW1 Full Presentation_0
69/173
Slide 68
Outline
1. Introduction to remote sensing
2. Satellite imagery:
Infrared
Visible Water vapour
3. Other uses of satellite technology
4. Radar imagery
Remote Sensing in Meteorology
7/30/2019 FW1 Full Presentation_0
70/173
Slide 69
Remote Sensing in Meteorology
Remote sensing is the art of obtaining informationabout an object without physical contact
Remote sensing techniques:
Allow data to be obtained from gaps between the fixedAutomatic Weather Stations
Provide data about the upper atmosphere
Provide holistic information i.e. complete weathersystems can be seen on a single image
Passive and active remote sensing is available
Satellite Imagery
7/30/2019 FW1 Full Presentation_0
71/173
Slide 70
Satellite Imagery
Passive satellite imagery is available in three forms:
Infrared
Visible
Water vapourThese are viewable as a single image or as a continuousloop
Infrared Satellite Imagery
7/30/2019 FW1 Full Presentation_0
72/173
Slide 71
Infrared Satellite Imagery
Infrared images are pictures of the earth andatmosphere taken in the infrared part of theelectromagnetic spectrum they measure heat leavingthe earth and atmosphere
In an infrared image, brighter areas represent colderfeatures - higher cloud is colder than lower cloud andwill therefore appear brighter
Colour enhancements aid interpretation
Infrared images are available 24 hours a day
Example of Infrared Satellite
7/30/2019 FW1 Full Presentation_0
73/173
Slide 72
pImagery
Images originally processed by the Bureau ofMeteorology from a geostationary satellite operated bythe Japan Meteorological Agency
Visible Satellite Imagery
7/30/2019 FW1 Full Presentation_0
74/173
Slide 73
Visible Satellite Imagery
Visible images are created by measuring the reflectedsolar radiation from the earth and atmosphere in thevisible spectrum i.e. like a normal photograph
Land and water are generally dark grey to black
whereas clouds are typically white or light grey
Greater reflection is evident for thicker clouds and theyappear brighter on visible satellite images
It can be difficult to discern between clouds at different
altitudes
Visible images are unavailable during the night
Example of Visible Satellite
7/30/2019 FW1 Full Presentation_0
75/173
Slide 74
pImagery
Image originally
processed by the Bureau
of Meteorology from a
geostationary satellite
operated by the JapanMeteorological Agency
Water Vapour Satellite Imagery
7/30/2019 FW1 Full Presentation_0
76/173
Slide 75
Water Vapour Satellite Imagery
Water vapour images indicate moisture in the upperatmosphere (mainly upwards of 4 km above sea level)
They also provide information on upper level circulationthat may not be apparent on other satellite imagery
Dry air is typically shown by darker colours whereasmore moist conditions are lighter and brighter
Example of Water Vapour
7/30/2019 FW1 Full Presentation_0
77/173
Slide 76
Satellite Imagery
Image originally processed
by the Bureau of
Meteorology from a
geostationary satellite
operated by the JapanMeteorological Agency
Other Uses of Satellite
7/30/2019 FW1 Full Presentation_0
78/173
Slide 77
Technology
Satellites can detect morethan just meteorologicalinformation:
smoke plumes
dust storms
Victorian Alpine Fires 2003 smoke plume image
originally processed by the Bureau of Meteorology
from a polar orbiting satellite operated by the US
NOAA
7/30/2019 FW1 Full Presentation_0
79/173
Slide 78
Visible dust storm over eastern Australiaon 23rd October 2002 image originally
processed by the Bureau of Meteorology
from a polar orbiting satellite operated by
the Chinese Meteorological Administration
Radar Imagery
7/30/2019 FW1 Full Presentation_0
80/173
Slide 79
Radar Imagery
Radar works by a transmitter emitting a pulse of radiowaves into the atmosphere, part of which is scatteredback by rain droplets and other debris
The location and intensity of precipitation is determined
by the time taken for the scattered pulses to return tothe receiver and the power with which they return:quicker and more intensely returned pulses indicateheavier precipitation
A horizontal map is produced of where rain is fallingand an indication of how heavily it is falling
Example of Radar Imagery
7/30/2019 FW1 Full Presentation_0
81/173
Slide 80
Example of Radar Imagery
Radar Interpretation
7/30/2019 FW1 Full Presentation_0
82/173
Slide 81
Radar Interpretation
Radar interpretation can be difficult:
The radar beam widens and increases in altitude with increasingdistance from the source, and therefore echo intensity is reducedand it can miss rainfall at increasing distances from the radarinstallation. Rainfall detected at a high level may evaporate
before hitting the ground Radar reflectivity is strongly dependent on the diameter of
raindrops rather than the amount of raindrops
A shadow effect can occur e.g. a thunderstorm cell close to theinstallation can shield the area of atmosphere in its wake
A lack of large droplets may result in the underestimation of
drizzle intensity It is possible for the radar to pick up insect swarms or smoke
plumes from major fires
Summary
7/30/2019 FW1 Full Presentation_0
83/173
Slide 82
Summary
Remotely sensed imagery fills the gaps between fixedAutomatic Weather Stations and is holistic
Infrared, visible and water vapour satellite imagery isavailable in single image or continuous loop format
Radar images are useful in identifying precipitation interms of location and intensity, however a number oflimitations can reduce the accuracy
Remotely sensed imagery assists in the identification of
features such as cold fronts, dry air, rainbands,showers and thunderstorms
7/30/2019 FW1 Full Presentation_0
84/173
Ed. 1.0 Sept 2007
Fire Weather 1Local Weather Effects
Session Goal
7/30/2019 FW1 Full Presentation_0
85/173
Slide 84
Session Goal
This session will introduce several local weather effectsthat need to be considered in conjunction with thesynoptic weather situation when analysing fire behaviour
A number of diagrams used in this presentation are taken
or adapted from Bureau of Meteorology publications(copyright Commonwealth of Australia) and are used withtheir permission. For more details see Fire Weather 1Learning Manual
Learning outcomes
7/30/2019 FW1 Full Presentation_0
86/173
Slide 85
Learning outcomes
This training session will cover three learning outcomes
After completing this session you should be able toexplain:
several local weather effects
situations in which local weather effects may develop
how local weather effects may affect a fire
Outline
7/30/2019 FW1 Full Presentation_0
87/173
Slide 86
Outline
1. Sea/land influenced winds
2. Mountain and valley winds
3. Thunderstorm outflow
4. Fire induced effects5. Synoptic weather influences
Weather on a Local Scale
7/30/2019 FW1 Full Presentation_0
88/173
Slide 87
Weather on a Local Scale
Small-scale meteorological phenomena that impact aparticular area in isolation are referred to as localweather effects
In many instances local weather effects can dominate
over large-scale conditions e.g. during light synopticwinds
Local weather effects can have a significant impact onfire behaviour wildfires often become erratic andunpredictable
Sea Breeze
7/30/2019 FW1 Full Presentation_0
89/173
Slide 88
Sea Breeze
During the day the landwarms more quickly thanthe water
Air above the land
warms, expands andrises causing surface lowpressure
Cooler and more moist
air in the high pressureregion over the waterflows onshore
Land Breeze
7/30/2019 FW1 Full Presentation_0
90/173
Slide 89
Land Breeze
At night the land coolsmore quickly than thewater
Air above the land cools,
and the dense air sinkscreating a surface highpressure region
Air flows from the land to
the low pressure regionover the water
Mountain and Valley Winds
7/30/2019 FW1 Full Presentation_0
91/173
Slide 90
Mountain and Valley Winds
Mountain and valley winds are caused by threeprocesses:
Wind flow around and between obstacles
Wind flow over obstacles
Surface heating and cooling
Wind flow is very sensitive to topography and localweather effects in upland terrain can have a significantimpact on fire behaviour
Wind Flow Around and BetweenObstacles
7/30/2019 FW1 Full Presentation_0
92/173
Slide 91
Obstacles
Air will attempt to flow around isolated obstacles ratherthan over them this is especially the case in stableatmospheric conditions as the air is unable to rise
Under such conditions the wind is strongest and most
turbulent on the lower mountain sides and is alsofunnelled through gaps in the ranges
Eddy Formation
7/30/2019 FW1 Full Presentation_0
93/173
Slide 92
ddy o at o
If the terrain or obstacleis rough, airflowdownwind near groundlevel can become more
turbulent and a wakemay be created whereairflow is lighter butgustier in nature
An eddy can form in the
lee side of the hill, withflows opposite to thegeneral wind direction
Plan view
Plan view
Wind Channelling
7/30/2019 FW1 Full Presentation_0
94/173
Slide 93
g
Wind can becomedirectionally channelledby ridges and valleysunder both light and
strong wind conditions Wind speed increases
due to funnelling
Plan view
Wind Flow Over Obstacles
7/30/2019 FW1 Full Presentation_0
95/173
Slide 94
If air is unable to flow around an obstacle or theatmosphere is unstable it will be forced to rise andcross the obstacle in its path
Top acceleration and mountain waves can occur when
airflow passes over a region of steep topography If airflow encounters a large obstacle in its path (such
as a mountain):
1.The flow can remain as a single airflow (laminar flow) as
it passes over the obstacle, or2.The flow can become turbulent
Top Acceleration
7/30/2019 FW1 Full Presentation_0
96/173
Slide 95
p
If the flow remainslaminar, and there is astable layer of air abovethe obstacle, wind speed
increases as the top ofthe obstacle isapproached this is topacceleration
Side view
Mountain Waves
7/30/2019 FW1 Full Presentation_0
97/173
Slide 96
If airflow becomes turbulent, eddies and mountain wavescan form
Mountain waves typically occur when the wind forced overa mountain increases in speed with height in a mildly
unstable atmosphere In such cases, the air is forced up and the disturbance on
the lee side forms a series of wavelike troughs and peaksthat are sometimes recognisable by lenticular clouds
Rotors also occur due to mountain waves and are a closedparcel of air rotating along an axis parallel to the mountainrange but somewhat downwind
7/30/2019 FW1 Full Presentation_0
98/173
Slide 97
In complex terrain, adecoupling between theair within and above thevalley rim can occur two
separate flow systemscan become evident
Side view
Up-Slope and Down-Slope Winds
7/30/2019 FW1 Full Presentation_0
99/173
Slide 98
p p p
A number of up-slope and down-slope local weathereffects can occur in regions of undulating terrain due toheating or cooling of the air
These include:
Foehn
Katabatic
Anabatic
Under these conditions erratic and unpredictable fire
behaviour is likely, especially for up-slope winds wherepreheating effects to fuel upstream can increase fireintensity and rate of spread
Foehn Wind
7/30/2019 FW1 Full Presentation_0
100/173
Slide 99
As a moist air parcel movesup-slope it cools andcontracts
Water vapour will condense
and is released. This processadds heat to the environment latent heat of condensation
Air that descends is warmerand drier a Foehn wind
Typically requires moist windsthat increase in speed withheight
Side view
Katabatic Wind
7/30/2019 FW1 Full Presentation_0
101/173
Slide 100
The earth cools at night as it emitslongwave radiation
The layer of air directly above the groundalso cools and is then cooler than a layerof air at higher altitudes or a layer at the
same altitude but away from the slope This cooler and denser slab of air moves
down-slope under the influence of gravityforming a katabatic wind or drainage flow
Katabatic winds are strongest when the
sky is clear, in steep terrain wherevegetation is sparse, and when synopticwinds are light
Anabatic Winds
7/30/2019 FW1 Full Presentation_0
102/173
Slide 101
During the day incoming solar radiationwarms the earths surface
The layer of air directly above this warmsmore than a layer of air at higher altitudes ora layer at a similar altitude but further fromthe slope
The warmer and less dense air rises andcreates a void that tends to draw in air fromlower down the slope
Anabatic winds are strongest when the sky isclear, in steep terrain where vegetation is
sparse, in areas that receive greater amountsof sunlight and when synoptic winds are light
Anabatic winds are typically stronger thanKatabatic flows
Anabatic/Katabatic ValleySystems
7/30/2019 FW1 Full Presentation_0
103/173
Slide 102
Systems
A decoupling betweenthe air within and abovethe valley can occur
In some instances up-
valley anabatic winds candominate during the dayand down-valleykatabatic winds candominate during the
evening despite a strongsynoptic flow above
The Influence of Cloud on LocalWeather Effects
7/30/2019 FW1 Full Presentation_0
104/173
Slide 103
Weather Effects
Many local weather effects result from differential solarheating
Increased daytime cloud density will reduce theintensity of incoming solar radiation, and will impede
the development of local weather effects driven byheating such as the sea breeze or anabatic wind
Increased nocturnal cloud levels will reduce thepotential for katabatic and land breeze effects to occur
as the earths surface will cool at a lower rate
Thunderstorm Outflow
7/30/2019 FW1 Full Presentation_0
105/173
Slide 104
If moist air rises to great heightsin an unstable atmosphere dueto convection, it will condense.If it continues to rise, toweringcumulonimbus clouds will formcreating a thunderstorm cell
Accompanying the columnformation is strong up and downdrafts
Cool dense air that sinks out of
a thunderstorm (a down draft)diverges rapidly when it hits theground thunderstorm outflow
Exercise I
7/30/2019 FW1 Full Presentation_0
106/173
Slide 105
Consider what local effects maytake place here:
Morwell
Yarram
McAllister River Valley
Mt Baw Baw
Exercise II
7/30/2019 FW1 Full Presentation_0
107/173
Slide 106
Topographic maps canbe used to identifypossible local effects
What local effects might
take place around theGrampians?
Fire Induced Effects
7/30/2019 FW1 Full Presentation_0
108/173
Slide 107
A fire itself can impact on the local weather if it is ofsufficient size. Smoke columns typically carry moremoisture than the surrounding air and this is mainly dueto the effects of combustion
The rising plume of smoke can act as an immoveableobject to the synoptic wind flow and this can causeerratic fire behaviour in its wake
Fires can also generate thunderstorms and lightning onsome occasions lightning activity can cause newstarts downwind, making suppression even moredifficult
Synoptic Weather InfluencesWeak Pressure Gradients
7/30/2019 FW1 Full Presentation_0
109/173
Slide 108
Weak Pressure Gradients
A weak pressuregradient with clearskies will allow whichlocal effects todevelop?
Synoptic Weather InfluencesStrong Pressure Gradients
7/30/2019 FW1 Full Presentation_0
110/173
Slide 109
Strong Pressure Gradients
A strong pressuregradient will allowwhich local effects todevelop?
Summary
7/30/2019 FW1 Full Presentation_0
111/173
Slide 110
A number of different local weather effects exist thatencourage unpredictable fire behaviour
Fires can influence the local environment by generatingtheir own weather
Understanding the relationship between synopticconditions and local weather effects is essential tosuccessful fire management
7/30/2019 FW1 Full Presentation_0
112/173
Ed. 1.0 Sept 2007
Fire Weather 1Weather and Fire Danger Indices
Session Goal
7/30/2019 FW1 Full Presentation_0
113/173
Slide 112
This session will discuss how to interpret the fire dangerrating system used in Bureau of Meteorology fire weatherforecasts
A number of diagrams used in this presentation are taken
from Bureau of Meteorology publications (copyrightCommonwealth of Australia) and are used by permission.For more details see Fire Weather 1 Learning Manual
Learning Outcomes
7/30/2019 FW1 Full Presentation_0
114/173
Slide 113
This training session will cover two learning outcomes
After completing this session you should be able toexplain:
the inputs into the Fire Danger Index (FDI)
the FDI / Fire Danger Rating (FDR) system and how it isused
Outline
7/30/2019 FW1 Full Presentation_0
115/173
Slide 114
1. What is fire danger?
2. Forest Fire Danger Index
3. Grassland Fire Danger Index
4. Weather associated with an extreme FDI day
What is Fire Danger?
7/30/2019 FW1 Full Presentation_0
116/173
Slide 115
Fire danger is a measure of the difficulty in controllingor suppressing a wildfire and is a function of fuel stateand weather
Fire danger is quantified using a numerical FDI to
which a descriptive FDR is attached, where highervalues represent a higher level of danger
FDI values are typically calculated in two situations:
As part of routine fire weather forecasting
To predict the behaviour of a going wildfire
Fire Danger Index
7/30/2019 FW1 Full Presentation_0
117/173
Slide 116
FDI is calculated with the following input variables:
Fuel state
Temperature
Humidity
Wind speed
For the following environments:
Forests
Grassland
McArthur Forest Fire DangerIndex (FFDI)
7/30/2019 FW1 Full Presentation_0
118/173
Slide 117
Index (FFDI)
McArthur FFDI determines the difficulty of firesuppression due to:
Drought Factor (a measure of forest fuel availability)
Temperature
Relative humidity
Average wind speed (at 10m height)
Drought Factor
7/30/2019 FW1 Full Presentation_0
119/173
Slide 118
DF estimates the proportion (in tenths) of the fine fuels(
7/30/2019 FW1 Full Presentation_0
120/173
Slide 119
The descriptive forest fire danger system is defined as follows:
FDR FFDI
Low 0 4
Moderate 5 11
High 12 23
Very high 24 49
Extreme 50 +
The value for FFDI is capped at 100, however higher values arepossible on rare occasions
Fires with an FFDI above 50 typically become weather dominated
How Variables Impact FFDI
7/30/2019 FW1 Full Presentation_0
121/173
Slide 120
Drought Factor = FFDI
Temperature = FFDI
Relative humidity = FFDI
Wind speed = FFDI
Diurnal Variation of FFDI
7/30/2019 FW1 Full Presentation_0
122/173
Slide 121
FFDI Assumptions
7/30/2019 FW1 Full Presentation_0
123/173
Slide 122
Terrain aspect or slope is not taken into account
An available fuel amount of 12.5 tonnes per hectare isassumed (indicated on the back of the meter) and fuelloads can be heavier than this
The FFDI model assumes moderate instability. Firebehaviour in elevated fuels may be underestimated, andextreme days will often be more unstable than the modelassumes
The FFDI model assumes a uniform canopy interceptionof sunlight
The FFDI model assumes full sunlight
McArthur Grassland FireDanger Index (GFDI)
7/30/2019 FW1 Full Presentation_0
124/173
Slide 123
g ( )
McArthur GFDI determines the difficulty of fire suppressiondue to:
Curing (a measure of forest fuel availability)
Temperature
Relative humidity
Average wind speed (at 10m height)
Curing
7/30/2019 FW1 Full Presentation_0
125/173
Slide 124
Most grasses have a natural life cycle in which plantsmature annually, and die or become dormant
The moisture content of the grass is lost seasonally inthe drying or curing process
Values for curing are expressed as the percentage ofdry (dead) grass 0% cured (completely green) to100% cured (completely dead)
GFDI System
7/30/2019 FW1 Full Presentation_0
126/173
Slide 125
The descriptive grassland fire danger system is as follows:
FDR GFDI
Low 0 2
Moderate 3 7
High 8 19
Very high 20 49
Extreme 50 +
GFDI values can reach over 100 on rare occasions, particularlyif wind speed and curing is high
Fires with an GFDI above 50 typically become weather dominated
How Variables Impact GFDI
7/30/2019 FW1 Full Presentation_0
127/173
Slide 126
Curing = GFDI
Temperature = GFDI
Relative humidity = GFDI
Wind speed = GFDI
Diurnal Variation of GFDI
7/30/2019 FW1 Full Presentation_0
128/173
Slide 127
GFDI Assumptions
7/30/2019 FW1 Full Presentation_0
129/173
Slide 128
Aspect or slope is not taken into account
Atmospheric instability is not taken into account
Extreme FDI Conditions
7/30/2019 FW1 Full Presentation_0
130/173
Slide 129
In many instances, days where fire danger is severewill experience FFDI or GFDI values of 50 or more i.e.fire danger will reach extreme on the McArthur scale
If the synoptic chart implies a day of severe or
extreme fire danger, then this will often be confirmedupon examination of the FDI values
Forecast values of extreme FDI are the strongestreason for a Total Fire Ban declaration
Weather Associated With anExtreme FDI Day
7/30/2019 FW1 Full Presentation_0
131/173
Slide 130
y
Extreme FDI values are associated with a number ofsynoptic situations including:
A dry low pressure system directing strong and gustynorth, west or northwesterly winds across the state
A high pressure system directing hot and dry northerlywinds over the state
A vigorous cold front approaching a strong high pressureregion directing hot and dry northerly winds across thestate before a gusty southwesterly wind change
Summary
7/30/2019 FW1 Full Presentation_0
132/173
Slide 131
Fire danger is a measure of the difficulty in controllingor suppressing a fire
There are two fire danger indices used in Victoria:
FFDI and GFDI
Fire danger is used as a basis for fire agencypreparedness, fire behaviour prediction, and publicsafety awareness
FDI / FDR varies hourly and daily
An extreme FDI day can occur under a number ofsynoptic conditions
7/30/2019 FW1 Full Presentation_0
133/173
Ed. 1.0 Sept 2007
Fire Weather 1
Bureau of Meteorology Productsand Services
Session Goal
7/30/2019 FW1 Full Presentation_0
134/173
Slide 133
This session will discuss how to access and interpretBureau of Meteorology fire weather products andservices
A number of diagrams used in this presentation are taken
from Bureau of Meteorology publications (copyrightCommonwealth of Australia) and are used with theirpermission. For more details see Fire Weather 1Learning Manual
Learning Outcomes
7/30/2019 FW1 Full Presentation_0
135/173
Slide 134
This training session will cover three learning outcomes.
After completing this session you should understand:
how to access the Bureau of Meteorology Registered Userwebpage
how to access numerous weather products and servicesavailable on the Bureau of Meteorology Registered Userwebpage
the information contained in the various fire weatherproducts issued by the Bureau of Meteorology
Outline
7/30/2019 FW1 Full Presentation_0
136/173
Slide 135
1. Accessing the Bureau of Meteorology public website
2. Registered User page
3. Fire weather products
4. Other information available on the website
Weather on the Web
7/30/2019 FW1 Full Presentation_0
137/173
Slide 136
The Bureau ofMeteorology (Bureau)public website isaccessed throughwww.bom.gov.au
To access theRegistered Userwebpage click on thelink.
Login to the Registered UserWebpage
http://www.bom.gov.au/http://www.bom.gov.au/7/30/2019 FW1 Full Presentation_0
138/173
Slide 137
Enter Username and Password
7/30/2019 FW1 Full Presentation_0
139/173
Slide 138
Four different RegisteredUser pages exist:
Username bomw0025:CFA HQ and regions
Username bomw0026:CFA volunteers
Username bomw0027:DSE HQ and regions
Username bomw0028:
General fire weather
Registered User webpage
7/30/2019 FW1 Full Presentation_0
140/173
Slide 139
The Registered User webpage contains a large amountof data under the following headings:
Synoptic Charts
Forecasts and Warnings
Observations Satellite Imagery
Radar
Computer Model Diagnostics
Climate InformationForecasts and Warnings includes products prepared forfire management agencies.
Fire Weather Products
7/30/2019 FW1 Full Presentation_0
141/173
Slide 140
The Bureau produces a number of fire weather productsspecifically for fire management agencies:
Fire Weather Estimates
Extended Fire Weather Estimates
Fire Weather Briefing Fire Weather Outlook
Spot Fire Forecast / Prescribed Burn Forecast
Wind Change Chart
Thunderstorm Forecast
Fire Weather Estimates
7/30/2019 FW1 Full Presentation_0
142/173
Slide 141
Fire Weather Estimates areissued twice daily during the fireseason at:
0630h for the current dayand,
1645h for the following day
Fire Weather Estimates areissued for 25 representativelocations around Victoria in nine
weather districts
7/30/2019 FW1 Full Presentation_0
143/173
Slide 142
For each of the 25 locations the following fields arepredicted for maximum temperature time:
Maximum temperature (C)
Relative humidity (%)
Wind direction Wind speed and gust (km/h)
FFDI (using a calculated Drought Factor)
GFDI (using an observed Curing value)
Wind change time and wind strength (if appropriate)
7/30/2019 FW1 Full Presentation_0
144/173
Slide 143
For each of the nine districts the following fields are predicted formaximum temperature time:
Lightning Activity Level (LAL; 0 = nil, 1 = one or two, 2 = a few, 3= numerous strikes over a district)
Rain (No = less than 5mm, Yes = greater than 5mm over an
entire district during the 24 hour period from 0900h on theforecast day)
Height of the mixing depth above sea level (mix, metres)
Upper level wind direction and strength (at 1000 to 2000 metresabove mean sea level; km/h)
FDI above 35 (approximate time when FDI is above 35, for *locations if occurring four hours or more before or after maximumtemperature time)
7/30/2019 FW1 Full Presentation_0
145/173
Slide 144
Summary comments are also provided to complementthe numerical predictions
Mallee district sample
Extended Fire WeatherEstimates
7/30/2019 FW1 Full Presentation_0
146/173
Slide 145
At 1715h each day during the fire season a set ofExtended Fire Weather Estimates (with a reducednumber of locations and meteorological parameters) isissued for an additional three days beyond the next-dayforecast
Fire Weather Briefing
7/30/2019 FW1 Full Presentation_0
147/173
Slide 146
At 1045h each day during the fire season a written FireWeather Briefing is issued
The Fire Weather Briefing:
Outlines any variations to the estimates issued earlier that
day at 0630hrs Provides more detail about the days weather
Gives a summary of the expected weather over the nextfew days
Fire Weather Outlook
7/30/2019 FW1 Full Presentation_0
148/173
Slide 147
At 1650h each day during the fire season the FireWeather Outlook is issued which provides synopticcharts and comments regarding the expected weatherconditions for the following four days
Spot Fire / Prescribed BurnForecast
7/30/2019 FW1 Full Presentation_0
149/173
Slide 148
A Spot Fire / Prescribed Burn Forecast for the localweather conditions associated with a fire can berequested at any time during the year
Spot Fire/Prescribed Burn Forecasts cover a short-term
forecast period and include: Predictions for temperature, RH and wind speed at ground
and upper levels in three hourly time steps for a nine hourperiod, and an outlook for the following 12 hours
A written description and alternative scenarios
Spot Fire/Prescribed Burn Forecasts have the highestpriority behind Wind Change Charts
Thunderstorm Forecast
7/30/2019 FW1 Full Presentation_0
150/173
Slide 149
A Thunderstorm Forecast isissued for the state ofVictoria by 1130h each dayindicating areasof likely thunderstorm activity
This chart is updated whenapplicable
Wind Change Chart
7/30/2019 FW1 Full Presentation_0
151/173
Slide 150
A Wind Change Chart is issued on days where asignificant wind change is expected to cross the stateand the fire danger is expected to be very high orextreme
This chart plots the current position of the wind changeand the predicted position in three-hour increments,and indicates the wind speed and direction before andbehind the change
The chart is updated every three hours until the change
either moves out of the state or has weakened, to suchan extent, that it is no longer considered to be a threat
Additional website information
7/30/2019 FW1 Full Presentation_0
152/173
Slide 151
The Registered User webpage also containssupplementary weather information, including:
Synoptic charts
Observations
Satellite imagery Radar
Computer Model Diagnostics (model data and predictedmeteograms for selected locations across Victoria)
Climate information Links
Summary
7/30/2019 FW1 Full Presentation_0
153/173
Slide 152
The Bureau public website provides access to a range ofweather products and services:
Detailed products for fire management agencies can beaccessed from the Registered User section
A number of products are regularly issued to firemanagement agencies during the fire season
Wind Change Charts and Spot Fire Forecasts assume thehighest priority
Spot Fire / Prescribed Burn Forecasts and Thunderstorm
Forecasts are issued all year
7/30/2019 FW1 Full Presentation_0
154/173
Ed. 1.0 Sept 2007
Fire Weather 1Weather Observations on the FireGround
Session Goal
7/30/2019 FW1 Full Presentation_0
155/173
Slide 154
This training session will introduce the importance ofbeing aware of local weather conditions as well asproviding guidance on how to obtain a simple weatherobservation
A number of diagrams used in this presentation are takenfrom Bureau of Meteorology publications (copyrightCommonwealth of Australia) and are used by permission.For more details see Fire Weather 1 Learning Manual
Learning Outcomes
7/30/2019 FW1 Full Presentation_0
156/173
Slide 155
This training session will cover three learning outcomes
After completing this session you should be able toexplain:
the suitable environmental conditions in which to take
weather observations how to undertake and interpret basic sky observations
how to undertake and interpret observations of wind speedand direction
Outline
7/30/2019 FW1 Full Presentation_0
157/173
Slide 156
1. Being aware of the weather
2. Taking a weather observation cloud
3. Taking a weather observation visibility
4. Taking a weather observation wind speed anddirection
5. Taking a weather observation precipitation andhumidity
6. Weather Observation Activity assessed componentof Fire Weather 1
Being Aware of the Weather
7/30/2019 FW1 Full Presentation_0
158/173
Slide 157
Weather has a major impact on fire behaviour, and fireground safety can be dependent on interpreting visualweather clues
A lack of awareness of the weather can have a serious
and detrimental effect on fire management andsuppression activities, and can jeopardise firefightersafety
Taking a Weather Observation
7/30/2019 FW1 Full Presentation_0
159/173
Slide 158
Local weather observations need to be taken of thegeneral environmental conditions unaffected by a fireotherwise the data recorded may not be representativeof the surrounding area
Weather observations must be taken to a set standardin order for them to be referenced and compared topast and future observations
7/30/2019 FW1 Full Presentation_0
160/173
Slide 159
When taking a weather observation on a fire ground: Take the observation away from the fire line
Take the observation upwind of the fire and smoke plumein an unburnt area
Take the observation in a clear and well exposed areaaway from trees or the forest canopy
Ideally take the observation in an elevated location
However, the observation site should reflect the type ofterrain in which the fire is currently burning
A fire ground weather observation should include cloud,wind and visibility
Cloud Observations
7/30/2019 FW1 Full Presentation_0
161/173
Slide 160
Cloud observations should include the cloud type andamount as a minimum
Cloud type:
Stratiform or Cumuliform
Stratiform Clouds
7/30/2019 FW1 Full Presentation_0
162/173
Slide 161
Stratiform clouds: Are generally flat in appearance
and of low to medium height
Typically display extensivehorizontal rather than vertical
development
Can give rise to precipitation thatis more continuous rather thanshowery
Stratiform clouds can be a precursorto a coming weather change e.g. anapproaching frontal passage
Cumuliform Clouds
7/30/2019 FW1 Full Presentation_0
163/173
Slide 162
Cumuliform clouds: Are generally heaped in
appearance and of low to mediumheight; however cumulonimbus canstretch the height of the
troposphere Display greater vertical rather than
horizontal development indicatingconvective activity and an unstableatmosphere
Showers and thunderstormsare more likely to occur fromcumuliform clouds
Cloud Amount
7/30/2019 FW1 Full Presentation_0
164/173
Slide 163
Cloud amount is estimated in eighths (or oktas) althoughit is perhaps simpler to record on the fire ground as:
Clear (no cloud)
Partly cloudy (cloud cover of less than 50%)
Mostly cloudy (50% to less than full cloud cover) Overcast (full cloud cover)
Visibility
7/30/2019 FW1 Full Presentation_0
165/173
Slide 164
Visibility can be determined by comparing visualestimations with a map indicating the distance to knownpoints
Wind Speed Observations -Mechanical
7/30/2019 FW1 Full Presentation_0
166/173
Slide 165
1. Obtaining wind speedobservations with ananemometer is typicallydone at about two metres,with the anemometer held
into the wind it can thenbe converted to a 10m windspeed
2. The anemometer should be
held for ten minutes to getan average wind speed andalso a maximum gust
Wind Speed Observations -Visual
7/30/2019 FW1 Full Presentation_0
167/173
Slide 166
Wind speed is typically measured using an instrumentsuch as an anemometer, however visual indicators canalso be used if instrumentation is not available
Visual indicators include:
Watching cloud movement as the behaviour of cloudswill give an indication of wind conditions at that particularaltitude
Noting the speed of fire / smoke movement
Watching the movement of trees and vegetation usethe Beaufort Scale
Beaufort scale
7/30/2019 FW1 Full Presentation_0
168/173
Slide 167
Wind Direction
7/30/2019 FW1 Full Presentation_0
169/173
Slide 168
Wind direction can be estimated using a vane Without using specialist equipment wind direction can be
obtained using a compass or map and the followingmethods:
Analysing the direction of fire, smoke or cloud movement Analysing the directional movement of trees and other
foliage
Factors to Consider WhenTaking Wind Observations
7/30/2019 FW1 Full Presentation_0
170/173
Slide 169
Convection: Any high based cumuliform cloud has the potential to
produce gusty and erratic wind behaviour
Inversion:
A dramatic increase in wind speed can result from thebreakdown of the overnight inversion
Diurnal variations in wind speed behaviour:
Wind speed and direction fluctuates significantlythroughout the day - take an observation over a ten
minute time period Height of observation:
Try and take the observation at a height of 10m
Precipitation and Humidity
7/30/2019 FW1 Full Presentation_0
171/173
Slide 170
It is quite straightforward to detect precipitation but itmust not be assumed that the presence of rain meansthat relative humidity has reached 100%
Relative humidity only reaches 100% in clouds, and the
presence of fog is the only clear indicator that humidityat ground level has reached 100%
Weather Observation Activity
7/30/2019 FW1 Full Presentation_0
172/173
Slide 171
This is an assessed component of the FW1 course1. Use the Bureau Registered User webpage to access
the forecast and current weather conditions, and anycurrent warnings for the local area
2. Go outside and take a local weather observationusing the assessment sheet estimate:
Temperature and humidity
Wind direction and speed using the Beaufort scale
Height, amount and type
Evidence of an approaching wind change
3. Complete the worksheet
Summary
7/30/2019 FW1 Full Presentation_0
173/173
The safety of fire management personnel on the fireground is dependent on an awareness andunderstanding of the local weather conditions
Fire behaviour can be predicted through understanding
local meteorological conditions by taking a weatherobservation
Top Related