Natural Hazards Exam 2

Heat

most fatalities of all severe weather in the US over the last 40 years

Heat Wave

a period of abnormally and uncomfortably hot and unusually humid weather, typically lasts two or more days

Heat Index

an accurate measure of how hot it really feels when relative humidity is added to the actual air temperature

Wet Bulb Globe Temperature

a parameter that estimates the effects of temperature, relative humidity, wind, and solar radiation on humans, good indicator of heat stress for active populations like outdoor workers and athletes

Extreme Heat Outlooks

issued when the potential exists for an excessive heat event in the next 3-7 days

Extreme Heat Watch

conditions are favorable for an excessive heat event in the next 24 to 72 hours, heat wave risk is increased but still uncertain

Heat Advisory

issued within 12 hours of the onset of dangerous heat conditions, 100 degrees or higher for at least two days and nighttime temps will not go below 75 degrees

Extreme Heat Warning

issued within 12 hours, max temperatures to be 105 degrees or higher for more than 3 hours per day for at least 2 days, nighttime temps will not go below 75 degrees

NWS HeatRisk Prototype

color-numeric based index that provides forecast risk of heat-related impacts, takes into account how unusual the heat is for the time of year, duration of heat, and if the temperatures pose an elevated risk of heat impacts, categories: Green → Yellow → Orange → Red → Magenta

Hyperthermia

body temperature above 40 degrees C (104 F)

Hyperthermia Warning Signs

high body temp, mental confusion, fainting, dry skin with rapid or slow pulse

Urban Heat Island

urban areas significantly warmer due to increased heat absorption, temperature difference larger at night, store more heat than rural areas

Heat and Air Pollution

heat waves can lead to poor air quality, increased ozone and particulate pollution

Changes in Heat Waves

frequency, duration, length of season, and intensity of heat waves have all gone up since the 1960s

Drought

period of abnormally dry weather long enough to cause a hydrologic imbalance in the affected area

Meteorological Drought

precipitation deficiency, reduced infiltration, high temp, greater sunshine, increased evaporation, and transpiration

Agricultural Drought

soil water deficiency, plant water stress, reduced biomass and yield

Hydrological drought

reduced streamflow, inflow to reservoirs, lakes, and ponds, reduced wetlands

Drought Characteristics

it is difficult to recognize, relative to normal amounts of water, government response to drought is lacking

What Causes Drought?

drought is a function of scale, and can be caused by various different things, like teleconnections, high pressure systems, climate change, or even human use of water

Why is Calculating Drought Hard?

finding the supply or the amount of rain and snow melt is easy, but the demand or evapotranspiration and soil moisture is more difficult to measure

Palmer Drought Severity Index

meteorological drought, uses precipitation, temp, and soil moisture to determine severity, does not take into account lag between precip and runoff/infiltration

Drought and Agriculture

U.S. farms contributed $164.7 billion to the economy, drought can cause crop failure and pasture losses and expand distribution of pests and diseases

Teleconnections

recurring and persistent, large-scale pattern of pressure and circulation anomalies that span vast geographical areas

ENSO

El Nino Southern Oscillation, fluctuation in sea surface temperatures (El Nino) and atmospheric pressure (Southern Oscillation), pressure differences between Darwin, Australia and Tahiti used to generate Southern Oscillation Index, lasts 6-18 months

Sustained Negative SOI Values

higher pressure than normal at Darwin, lower than normal at Tahiti, trade winds weaken, El Nino (warm phase)

Sustained Positive SOI Values

lower than normal pressure at Darwin, Higher than normal pressure at Tahiti, pacific trade winds strengthen, La Nina (cool phase)

El Nino

warm phase of ENSO (-SOI), five consecutive 3-month mean warmer than normal sea-surface temperatures in the eastern pacific, weaker trade winds, typically occurs around N.H. winter

La Nina

cool phase of ENSO (+SOI), five consecutive 3- month mean cooler than normal sea-surface temperatures in the eastern Pacific, stronger trade winds, upwelling on the Coast of South America

Jet Stream During El Nino

lower than usual, southern US experiences wet conditions, while northern US experiences warm and dry conditions

Jet Stream During El Nina

pushed northward, southern US experiences dry conditions, Pacific Northwest and Canada experience heavy rains

Fire

combination of oxygen with carbon, hydrogen, and other elements of organic material that produces flames, heat, and light

Fire Reaction

photosynthesis in reverse, oxygen combines with organic material, bonds between carbon and hydrogen are broke, chemical bonds form between carbon and oxygen and hydrogen and oxygen, energy given off as heat

Human Caused Fires

make up 85% of all fires

Natural Fires

make up 15% of all fires

Points of the Fire Behavior Triangle

fuels, topography, and weather

Weather

highest degree of variability in fire behavior triangle, high temperatures decrease moisture content in fuel source, low relative humidity increases risk for fires

Weather Elements that Influence Fire

stability: limits vertical transport of air

wind speed and direction: most important variable for spreading fire, hardest variable to predict

precipitation: increases relative humidity and adds to moisture content of fuels

Topography

most constant variable in fire behavior triangle

Topographic Features that Contribute to Fires

elevation: lowest ½ of slope is the hottest, upper ½ is the coldest

position on slope: know where the fire is located and where best fuels are present

aspect: direction a slope is facing

shape of terrain: can limit or enhance spread

steepness: stepper leads to greater heating and quicker spread, fire spreads most effectively uphill

Fuels

any combustible material, divided into four groups

Aerial Fuels

upper portion of trees, tree branches, tall shrubs

Ladder Fuels

surface fuel, small trees or shrubs, low branches, moss or lichen on tree trunks

Surface Fuels

needles or leaves, duff, grass, low shrubs

Ground Fuels

deep duff, roots, rotten buried logs, peat

Horizontal Continuity of Fuels

occurs when fuel source is continuous and has no patches, allows fire to spread easily as opposed to a patchy fuel source

Vertical Continuity of Fuels

allows the fire to climb vertically due to a continuous vertical fuel source

Moisture Content of Fuels

can deter the spread of fire temporarily

Chemical Content of Fuels

can limit or enhance spread of fire

Ignition

a temperature of 600 degrees F is required to ignite wildland fuels

Low Intensity Fire

weak indraft at fire’s edge, limited updraft and smoke column, environment controls the fire

High Intensity Fire

strong indrafts at fire’s edge, strong updraft and smoke column, fire controls the environment, alters weather elements

Factors Affecting Rate of Spread

wind speed, steepness of slope, changes in fuel type

Fire Weather Watch

means critical fire weather conditions are possible but not imminent or occurring

Red Flag Warning

issued when fire conditions are ongoing or expected to occur shortly

Amarillo Red Flag Criteria

minimum relative humidities equal to or less than 15%, 20ft winds of 20 mph or higher and/or gusts of 35 mph or higher, NFDRS adjective fire rating of High or higher

St Louis Red Flag Criteria

sustained 20ft winds >15mph, relative humidity <25%, 10 hr dead fuel moisture <9%

Extreme Fires

one or more criteria must be met: moving fast, prolific crowing and/or spotting, presence of fire whirls, strong convection column

Backfire

starting a fire separate from the wildfire to burn up potential fuels to prevent the fire from spreading further

Annual Average Acres Burned

has gone down since 1920 but has begun to rise since 2000

Prescribed Fires

acres burned and cost have gone up since 1995, as we have realized their importance

Change in Wildfire Patterns

megafires have become more frequent, more destructive, and more deadly, warmer climate causes drier conditions and longer wildfire season

Areas at Risk

western U.S. wildfires increasing in area, number of homes built in wildfire prone areas has increased

States most at Risk of Wildfires

California has the most houses in wildfire prone areas and had the most fires and acres burned in 2023 with Texas and North Carolina ranking highly as well

Evacuation Problem

too many houses in wildlands, traffic builds up on two lane roads

Smoke Effects

ash and particulate matter in smoke poses most risk to those in affected areas, painted surfaces, pipes, plastics, etc contribute to the dangerous smoke

Pyrocumulonimbus Clouds

fires produce updrafts, causing air to cool into clouds potentially causing thunderstorms, lightning can cause more fires

Tropical Cyclone Direction

counterclockwise in NH and clockwise in SH

Tropical Cyclone Ingredients

sea surface temp of at least 27C (80F)

warm, humid, unstable air

significant distance from the equator

weak wind shear

Tropical Cyclone Life Cycle

tropical disturbance → tropical depression → tropical storm → hurricane

Tropical Depression Criteria

cyclone with maximum 1-minute sustained surface winds of 33 knots (38 mph) or less

Tropical Storm Criteria

cyclone with maximum 1-minute sustained surface winds of 34-63 knots (39-71 mph)

Hurricane Criteria

sustained surface winds of 64 knots (74 mph) or greater

Tropical Cyclones

converging winds cause warm, moist air to rise rapidly, and rising air cools to the dew point temperature starting condensation (warming process), warmer air leads to stronger updrafts

Surface Air Pressure in Cyclone

highest air pressure at outer edge of cyclone, lowest in the eye

Wind Speed in Cyclone

highest in eye wall, lowest in eye

Eyewall

strong storms surrounding eye of the cyclone

Eyewall Replacement Cycle

outer rain band strengthen into band of thunderstorms, becoming the outer eyewall, replacing inner eyewall as it narrows

Saffir-Simpson Scale

classifies hurricanes into 5 categories based strictly on sustained wind speed, does not measure anything else

Tropical Cyclone Severity Scale (TCSS)

provides a category for each hazard (wind, surge, and rain), combined score for final category

States that Experience most Hurricanes

florida, texas, and louisiana

El Nino Effect on Hurricanes

less common when el nino is present, more frequent when its absent

North Atlantic Basin Season

June 1 to Nov 30

Eastern Pacific Basin Season

May 15 to Nov 30

Deadliest Hurricane to hit the US

1900 galveston storm, cat 4, 8,000 deaths, predates satellites

Tropical Cyclone Fatalities

outside of large events, number of deaths is decreasing

US Hurricane Deaths

1970-1999 inland floodings accounts for the most deaths, 1963-2012 storm surge accounts for most deaths

Storm Surge

abnormal rise of water generated by a storm, affected by maximum winds, speed of hurricane, size of storm, coastal features

Strongest Quadrant of Cyclone

front right quadrant of the storm, most tornadoes that form in TC form here as well

Flooding

determined by how fast the TC is moving, terrain, hydrology, land use

Forecast Cone

represents probable track of center of tropical cyclone, expected to remain within the cone 60-70% of the time

Hurricane Mitigation

reinforce buildings, covered windows, remove debris, emergency kit, have a plan

Ganges-Brahmaputra Delta Cyclone

east pakistan, most deadly tropical cyclone ever, estimated 400,000 dead, peak winds of 115 mph

Flood Fatalities

top three in deaths due to severe weather, most caused by flash floods, less caused by river floods, 52% caused by vehicles driven into water

US Flood Fatalities

highly variable year to year, not decreasing, younger than 20s and older than 60 more vulnerable

Flood Impacts on Human Health

transport debris and other contaminants, contaminate drinking water, leave mold, disrupt access to health care, injuries and deaths

State with Highest Flood Fatalities

texas, specifically in San Antonio and Houston

Cause of Kentucky Floods

areas of steep terrain development in low-lying areas, increase in rainfall events, deforested areas from past coal mining

Flash Flooding

local and sudden flood, lasts for short time after a few hours of rainfall, causes many deaths, thunderstorms far away can cause flash flooding in canyon areas

Regional Floods

huge, long lasting floods due to prolonged heavy rains over an extensive region