2C-1-S190-EP Lesson 2C - Weather. 2C-2-S190-EP Lesson Objectives 1.Describe the affect of...

2C-1-S190-EP

Lesson 2C - Weather

2C-2-S190-EP

Lesson Objectives

1. Describe the affect of temperature and relative humidity has on wildland fire behavior.

2. Describe the affect of precipitation on wildland fire behavior.

3. Describe the differences between a stable and unstable atmosphere.

4. Describe general and local winds.

5. Describe critical fire weather conditions.

6. List the different types of fire weather forecasts and outlooks available.

2C-3-S190-EP

Fire Weather

*Click on image to play video

2C-4-S190-EP

Air Temperature

In weather we refer to this as air temperature or

dry bulb temperature.

The degree of hotness or coldness of a substance.

An average of the thermal energy of a group of

particles in a substance (does not depend on # of

particles)

2C-5-S190-EP

Temperature is measured with a thermometer

calibrated either to the FAHRENHEIT scale

or the CELSIUS or centigrade scale.

What influences air temperature?•Time of day•Season•Elevation•Topography•Latitude•Weather systems•Bodies of water

Why does air temperature matter in wildland fires?

2C-6-S190-EP

Relative Humidity

For a given air temperature, relative humidity (%) is the amount of moisture in the air divided by the amount the air could hold when saturated; usually expressed in percent.

•Ranges from 1-100%...what does 100% mean?

2C-7-S190-EP

3 grams of H2O3 grams

3 grams

Temperature and RH Relationships

50ºF 70ºF90ºF100%

(saturated)50%

(unsaturated) 25%(unsaturated)

2C-8-S190-EP

ThermographTemperature and RH Relationship

2C-9-S190-EP

Temperature vs. RH (general) for a given volume of air

Temperature

Rel

ativ

e H

um

idit

y

A

Temp. = 60 FRH = X

B

Temp. = 80 FRH = X/2

2C-10-S190-EP

So what?• Think of the fire triangles…what does RH

affect? – Does this differ between fine/large fuels?

• Why does this matter for wildland fire suppression?

• Why does this matter for prescribed burning?– Small changes in RH that aren’t noticed can have

significant impacts• What should you do on a fire?• Monitoring = belt weather kit

2C-11-S190-EP

Precipitation

Precipitation is liquid or solid water particles that originate in the atmosphere, and become large enough to fall to the earth’s surface.

2C-12-S190-EP

PrecipitationAmount vs. Duration

• Fine Fuels– gain and lose moisture

quickly

– react rapidly to precipitation

• Heavy Fuels – gain and lose moisture

slowly

– react slowly to precipitation

• Duration vs. Amount– Precipitation duration has

greater impact on fuel moisture than precipitation amount

2C-13-S190-EP

Atmospheric StabilityThe degree to which vertical motion in the atmosphere is

ENHANCED or SUPPRESSED.


2C-14-S190-EP

Stable AtmosphereStable atmosphere resists upward vertical motion


2C-15-S190-EP

Stable AtmosphereVisual Indicators

• Visual Indicators– Clouds form in

layers– Smoke drifts apart

after limited rise– Poor visibility due

to smoke or haze– Fog layers– Steady winds

2C-16-S190-EP

Stable AtmosphereVisual Indicator Examples

• Clouds form in layers

2C-17-S190-EP


• Smoke drifts apart after limited rise

2C-18-S190-EP


• Poor visibility due to smoke or haze

2C-19-S190-EP


• Fog Layers

2C-20-S190-EP


• Steady Winds

2C-21-S190-EP

Stable Atmosphere Inversion


2C-22-S190-EP

Stable Atmosphere Inversion Types

• Four Inversion Types– Nighttime (Radiation)– Frontal– Marine– Subsidence

• Two most common types– Nighttime (Radiation)– Subsidence

2C-23-S190-EP

Stable Atmosphere Nighttime Inversion


2C-24-S190-EP

Stable Atmosphere Thermal Belt

• Thermal Belt– Nighttime inversions in

mountainous regions– The warm layer

typically found on the middle third of the slope

– Characterized by the highest minimum temperature and lowest minimum RH

– Fire can be very active within the thermal belt

2C-25-S190-EP

Stable AtmosphereSubsidence Inversion


2C-26-S190-EP

• Subsidence Inversion– May persist for several

days– May reach the surface

further enhancing fire activity

– Typically results in• clear or cloudless

skies• above average

temperatures• low relative humidity• drying of fuels

Stable AtmosphereSubsidence Inversion Facts

2C-27-S190-EP

Unstable AtmosphereEncouraging upward vertical motion

2C-28-S190-EP

Unstable AtmosphereVisual Indicators

• Visual Indicators– Clouds grow vertically

and smoke rises to great heights

– Cumulus clouds– Good visibility– Gusty winds– Dust devils and

firewhirls

2C-29-S190-EP

Unstable AtmosphereVisual Indicator Examples

• Clouds grow vertically and smoke rises to great heights

2C-30-S190-EP


• Cumulus Clouds• Good Visibility

2C-31-S190-EP


• Gusty Winds• Dust devils and

firewhirls


2C-32-S190-EP

WindsHorizontal movement of air


2C-33-S190-EP

• Wind impacts the fire environment by:– Increasing the supply of oxygen to the fire.– Determining the direction of fire spread.– Increasing the drying of the fuels.– Carrying sparks and firebrands ahead of the main fire causing

new spot fires.– Bending flames, which results in the preheating of fuels ahead of

the fire.– Influencing the amount of fuel consumed by affecting the

residence time of the flaming front of the fire. The stronger the wind, the shorter the residence time and the less fuel is consumed.

WindsWind’s Effect on Wildland Fire

2C-34-S190-EP

General Winds


2C-35-S190-EP

Local Winds


2C-36-S190-EP

Local WindsSlope Winds

• Upslope Winds– A result of differential

heating and convective processes along the slope

– Average speeds range from 3 to 8 mph

– Develop along east facing slope first and south and west facing slope by late morning

• Downslope Winds– Air along the slope cools

and sinks producing the downslope wind

– Average speeds range from 2 to 5 mph

– Develop on east facing aspects first and south and west facing aspects after sunset

2C-37-S190-EP

Local WindsValley Winds

• Upvalley Winds– As the air warm, temperature

and pressure differences within the valley or adjacent valleys result in upvalley wind flow.

– Strongest mid to late afternoon.

– Average speeds range from 10 to 15 mph.

• Downvalley Winds– As the valley loses solar

heating, the air in the valley cools.

– The cool air drains downvalley.

– Average downvalley wind speeds range from 5 to 10 mph.

– Typically develop a few hours after sunset.

2C-38-S190-EP

Local WindsSea/Land Breeze

2C-39-S190-EP

Sea Breeze1998 Perry Fire

Sea breeze interacting with Perry fire. Fire activity increases when sea breeze front penetrates fire.

2C-40-S190-EP

Used in Rx prescriptions• LVORI- Low Visibility Occurrence

Risk Index• “Smog” index- risk of low visibility

(vehicles)• Increases with RH, and low DI

– From operational experience, one should be VERY CAUTIOUS ABOUT BURNING if one of the following situations occurs:

– When LVORI for a nighttime forecast period is 8,9 or 10

– When ACTIVE SMOKE from stumps logs, etc. is present during the night

– When there is a roadway within three miles of a burn site with open fields, logging roads, or open streams that can provide an easy transit of the smoke from the burn site to the roadway

Table 1: Low Visibility Occurrence Risk Index (LVORI)

LVORI Category Interpretation

1 Lowest proportion of accidents with smoke and/or fog reported (130 of 127,604 accidents, or just over 0.0010 accidents.)

2 Physical or statistical reasons for not including in category 1, but proportion of accidents not significantly higher.

3 Higher proportion of accidents than category 1, by about 30% to 50%, but of marginal significance (1%-5%).

4 Significantly higher than category 1, by a factor of 2.

5 Significantly higher than category 1, by a factor of 3 to 10.





10 Significantly higher than category 1, by a factor of 150.

2C-41-S190-EP

• Dispersion Index – Estimates daytime and nightime stability of the

atmosphere. Higher DI = greater mixing, but very high = potential fire control problems

– Doubling of the DI results in a doubling of the amount of smoke the airshed can hold

– RX : 41-70– Under 30, could be OK…if small unit with little smoke,

or stagnant if winds are low– Over 71: very good dispersion…but hazardous to

burn

Used in Rx prescriptions

2C-42-S190-EP

Those who know how to read and heed weather!

Those who think they can “weather it all”

2C-43-S190-EP

2008 burnWinter Annual

ACMF

2C-44-S190-EP

2C-45-S190-EP

2C-46-S190-EP

2C-47-S190-EP

Review Lesson Objectives

1. Describe the affect of temperature and relative humidity has on wildland fire behavior.

2. Describe the affect of precipitation on wildland fire behavior.

3. Describe the differences between a stable and unstable atmosphere.

4. Describe general and local winds.

5. Describe critical fire weather conditions.

6. List the different types of fire weather forecasts and outlooks available.

2C-48-S190-EP

Critical Fire Weather


2C-49-S190-EP

Critical Fire WeatherCold Fronts


2C-50-S190-EP

Critical Fire WeatherFoehn Winds


2C-51-S190-EP

• Meteorology• Santa Ana winds are a type of drainage wind, an offshore wind that results from the buildup of

air pressure in the high-altitude Great Basin between the Sierra Nevada and the Rocky Mountains. When upper level winds are favorable, this high altitude air mass spills out of the Great Basin and is propelled gravitationally towards the southern California coastline, generally as a northeasterly wind.

• It is often said that the air is heated and dried as it passes through the Mojave and Sonoran deserts, but according to meteorologists this is a popular misconception. The Santa Ana winds usually form during autumn and early spring when the surface air in the elevated regions of the Great Basin and Mojave Desert (the "high desert") becomes cool or even cold, although they may form at virtually any time of year. The air heats up due to adiabatic heating during its descent. While the air has already been dried by orographic lift before reaching the Great Basin as well as by subsidence from the upper atmosphere, the relative humidity of the air is further decreased as it descends from the high desert toward the coast, often falling below 10 percent.

• The air from the high desert is initially relatively dense owing to its coolness and aridity, and thus tends to channel down the valleys and canyons in gusts which can attain hurricane force at times. As it descends, the air not only becomes drier, but also warms adiabatically by compression. The southern California coastal region gets some of its hottest weather of the year during autumn while Santa Ana winds are blowing. During Santa Ana conditions it is typically hotter along the coast than in the deserts.

• • • QuikSCAT image showing the speed of the Santa Ana winds (m/s).• Note that while the Santa Ana Winds are an adiabatic wind, they are not a Föhn wind. A Föhn wind

results from precipitation on the windward side of a mountain range which releases latent heat into the atmosphere which is then warmer on the leeward side (e.g. the Chinook or the original Föhn). The Santa Ana winds do not originate in precipitation, but in the bone-dry high deserts.

• The combination of wind, heat, and dryness accompanying the Santa Ana winds turns the chaparral into explosive fuel feeding the infamous wildfires for which the region is known. Wildfires fanned by Santa Ana winds burned 721,791 acres (2,921 km²) in two weeks during October 2003.[1] These same winds have contributed to the fires that have burned some 426,000 acres (1,720 km2) as of late October 2007.[2]

• Although the winds often have a destructive nature, they have some positive benefits as well. They cause cold water to rise from below the surface layer of the ocean, bringing with it many nutrients that ultimately benefit local fisheries. As the winds blow over the ocean, sea surface temperatures drop about 4°C (7°F), indicating the upwelling. Chlorophyll concentrations in the surface water go from negligible, in the absence of winds, to very active at more than 1.5 milligrams per cubic meter in the presence of the winds.

http://en.wikipedia.org/wiki/Katabatic_wind

http://en.wikipedia.org/wiki/Atmospheric_pressure

http://en.wikipedia.org/wiki/High_altitude

http://en.wikipedia.org/wiki/Great_Basin

http://en.wikipedia.org/wiki/Sierra_Nevada_(U.S.)

http://en.wikipedia.org/wiki/Rocky_Mountains

http://en.wikipedia.org/wiki/Mojave_Desert

http://en.wikipedia.org/wiki/Sonoran_Desert

http://en.wikipedia.org/wiki/Desert

http://en.wikipedia.org/wiki/Lapse_rate#Dry_adiabatic_lapse_rate

http://en.wikipedia.org/wiki/Orographic_lift

2C-52-S190-EP

Critical Fire WeatherFoehn Winds

• Common Foehn Winds– Chinook– Wasatch– North– East– Santa Ana

2C-53-S190-EP

San Diego, Oct. 2007Californias love the Santa Ana winds

2C-54-S190-EP

Critical Fire WeatherThunderstorms

2C-55-S190-EP

Critical Fire WeatherDust Devils and Firewhirls


2C-56-S190-EP

Complete Exercise 4

2C-57-S190-EP

Predictive Services

• Predictive Services– Products Produce By:

• Agency Fire Meteorologists• Intelligence Coordinator• FBAN• Fuels Specialists

– Monitors, analyzes and predicts • Fire weather• Fire danger• Interagency fire management

resource impact

2C-58-S190-EP

Predictive Services (national, regional websites)

• Predictive Services– 7 Day Significant Fire

Potential• Produced Weekly• Daily in 2006

– 30 Day Fire Potential• Produced Monthly

– Season Fire Potential• Produced Annually

– Spring– Fire Season Update

• Southern Area Coordination Center

2C-59-S190-EP

DOF Website: http://www.fl-dof.com/fire_weather/forecast/seasonal_forecast.html

Seasonal Fire Weather Outlook: Updated January 4, 2008 January-March 2008• Current Conditions Around Florida:• The state began 2007 under neutral ENSO conditions but La Niña conditions

formed later in the year. Dry conditions persisted through the fall due to the La Niña and positive Pacific North American (PNA) pattern…According to the U.S. Drought Monitor, most of the state is experiencing abnormally dry conditions with the south central part of the state seeing moderate to severe drought conditions.

• Long-range Outlook:• The outlook for the next three months is for the current La Niña pattern to

continue. Drought conditions are expected to worsen…Rainfall amounts are forecast to be near average by June and above average toward the end of the summer when we approach peak hurricane season. Summary:

• Drought conditions are expected to worsen over the spring months as the La Niña in the eastern Pacific Ocean persists. The potential will be high for another active wildfire season this spring once again. Longer term outlooks suggest summer rainfall could be influenced by another active hurricane season.

• The next forecast will be the first week in April, 2008. Should there be any questions, please contact Deborah Hanley at [email protected].

2C-60-S190-EP

National Weather Service

• National Weather Service– Products produced for:

• Fire Weather Zones– Products produced by:

• Meteorologists– Products geared

toward:• Tactical planning

2C-61-S190-EP

NWS: Fire Weather Planning Forecast

• A narrative or tabular zone-type product

• Here, will most likely be for JAX

• Elements include:– Sky/weather– Temperature– Relative humidity

FNUS52 KJAX 171939FWFJAXFIRE WEATHER PLANNING FORECAST FOR NORTHEAST FLORIDA/SOUTHEAST GEORGIANATIONAL WEATHER SERVICE JACKSONVILLE FL239 PM

EST THU JAN 17 2008DISCUSSION...

LOW PRESSURE WILL TRACK ACROSS THE FORECAST AREATHIS EVENING AND PUSH NORTHEAST OF THE REGION TONIGHT. SCATTEREDSHOWERS WILL DISSIPATE

THROUGH THE EVENING HOURS. WEAK HIGH PRESSUREWILL BUILD INTO THE REGION ON FRIDAY. ANOTHER LOW WILL DEVELOP INTHE GULF OF MEXICO SATURDAY AND

TRACK NORTHEAST OF THE REGIONSETTING THE STAGE FOR A COLD...BRISK AND DRY SUNDAY WITH HIGHPRESSURE SETTING UP OVER THE REGION EARLY NEXT WEEK.

RELATIVE HUMIDITIES WILL REMAIN ABOVE CRITICAL LEVELS THROUGH THE PERIODEXCEPT FOR SUNDAY WHEN RH VALUES WILL BOTTOM OUT IN THE 15-25

PERCENTRANGE OVER THE INLAND SECTIONS AND RED FLAG WARNINGS MAY BE REQUIRED.WINDS LESS THAN 15 MPH ARE EXPECTED ON FRIDAY. NORTHWEST WINDS OF15 TO 20 MPH ARE EXPECTED ON SATURDAY. NORTH WINDS OF 15 TO 20 MPHARE

EXPECTED ON SUNDAY. NORTHEAST WINDS OF 15 TO 20 MPH WILLCONTINUE ON MONDAY AND SLOWLY DECREASE TO LESS THAN 15 MPH ONTUESDAY AND

WEDNESDAY.GAZ153-154-165-166-181045-INLAND GLYNN-COASTAL GLYNN-INLAND CAMDEN-COASTAL CAMDEN-239 PM EST THU JAN 17 2008 TONIGHT FRI FRI NIGHT SATCLOUD COVER PCLDY PCLDY MCLDY MCLDYCHANCE

PRECIP (%) 0 0 80 80WEATHER TYPE NONE SHOWERS SHOWERS SHOWERSTEMP 43 59 45 55RH (%) 97 60 100 7020FT WND MPH (AM) N 6 N 8 G2120FT WND MPH (PM) NW 8 N 4 NE 4 NW 14 G26PRECIP DURATION 11 11PRECIP BEGIN 7 PM CONTINUINGPRECIP END

7 AM CONTINUINGPRECIP AMOUNT 0.00 0.00 0.69 0.87LAL 1 1 1 1MIXING HEIGHT(FT-AGL) 500 2200 400 1600TRANSPORT WND (MPH) N 13 N 7 NE 7 NW 30DISPERSION

INDEX 7 15 5 27MAX LVORI 6 9REMARKS...NONE..FORECAST FOR DAYS 3 THROUGH 7....SUNDAY...PARTLY CLOUDY. A

20 PERCENT CHANCE OF RAIN SHOWERS.LOWS IN THE UPPER 20S. HIGHS IN THE LOWER 50S. NORTHEAST WINDS15 TO 20 MPH..MONDAY...PARTLY CLOUDY. LOWS IN THE

LOWER 30S. HIGHS IN THEUPPER 50S. NORTHEAST WINDS 10 TO 15 MPH..TUESDAY...MOSTLY CLOUDY. A 50 PERCENT CHANCE OF RAIN SHOWERS.LOWS IN

THE MID 40S. HIGHS IN THE LOWER 60S. EAST WINDS 5 TO10 MPH..WEDNESDAY THROUGH THURSDAY...MOSTLY CLOUDY WITH A 50 PERCENTCHANCE OF RAIN

SHOWERS. LOWS IN THE LOWER 50S. HIGHS IN THE UPPER 60S. SOUTHWEST WINDS 5 TO 15 MPH.

2C-62-S190-EP

• Issued when the combination of dry fuels and weather conditions support extreme fire behavior or ignition is occurring or expected to occur.

• Can prevent prescribed burning

NWS: Fire Weather Watches / Red Flag

Warnings

2C-63-S190-EP

• Issued when there is a high potential for the development of a Red Flag Event.

• Normally issued 24 to 72 hours in advance.

Fire Weather Watches

FIRE WEATHER WATCH NATIONAL WEATHER SERVICE MIDLAND/ODESSA TX 946 AM CST FRI JAN 27 2006

...FIRE WEATHER WATCH IN EFFECT SATURDAY FOR THE GUADALUPE MOUNTAINS FOR RELATIVE HUMIDITIES OF 15 PERCENT OR LESS...SUSTAINED 20 FOOT WINDS OF 20 MPH OR GREATER AND HIGH FIRE DANGER...

2C-64-S190-EP

• Used to warn of an impending, or occurring Red Flag event.

Red Flag Warnings

Red Flag Warning/Fire Weather Watch Information

...RED FLAG WARNING IN EFFECT ACROSS THE SUWANNEE VALLEY REGION OF NORTH FLORIDA FROM NOON TO 5 PM EST

THIS AFTERNOON FOR LONG DURATIONS OF LOW RELATIVE HUMIDITY...

2C-65-S190-EP

• Site specific forecasts that are issued to fit time, topography and weather of a specific location.

Spot Weather Forecast– DOF in Florida– must have local information and location

Forecast Time Temp HumidityWind Speed

DirectionCloud Cover

Precip

5:00 76-79 85-90% 3-6 WNW BK

6:00 77-80 84-89% 3-6 WNW BK

7:00 77-80 83-88% 4-7 WNW BK

8:00 78-81 83-88% 4-7 WNW BK

9:00 80-83 78-83% 4-7 WNW BK

10:00 82-85 74-79% 4-7 WNW BK

11:00 83-86 70-75% 4-7 NW SC

12:00 84-87 68-73% 4-7 SSW SC

13:00 85-88 66-71% 5-8 ESE SC12%

Chance (Trace)

14:00 86-89 64-69% 5-8 N BK15%

Chance (Trace)

15:00 85-88 65-70% 5-8 NNE BK12%

Chance (Trace)

Florida Division of Forestry - Spot Forecast

Forecast ID: 1185873416 Date Issued: Tue Jul 31, 2007 at 05:16

Name: Leda Kobziar Company: University of Florida

Location: 29.74 / -82.21

2C-66-S190-EP

Complete Exercise 5

2C-1-S190-EP Lesson 2C - Weather. 2C-2-S190-EP Lesson Objectives 1.Describe the affect of...

Documents

Transcript of 2C-1-S190-EP Lesson 2C - Weather. 2C-2-S190-EP Lesson Objectives 1.Describe the affect of...