Hydrometeorological Hazards
Global Impacts of El Nino
- Suppress tropical storms and hurricanes in Atlantic - Increase tropical storms over eastern and central pacific ocean - Increase rainfall in southern tier of US and Peru, destructive flooding, drought in west pacific, monsoon failure in India, sometimes associated with brush fires in Australia
Types of Thunderstorms (Frontal Thunderstorms)
- Usually produced by advancing cold-front - Result in line of thunderstorms hundreds of KMs long - Or (rarely) advancing warm front - Result in a relatively mild thunderstorm
Thunderstorm (Moisture)
- Require a lot of moisture in lower atmosphere - Humid air is less dense than dry air and is lifted - Humid air cools and forms water droplets and clouds
Precautions for Thunderstorms and Lightning (Inside precautions)
- Stay away from open windows, sinks, toilets, tubs, showers, electric boxes, outlets, and appliances. Lightning can flow through these systems and "jump" to person - Don't use water - Avoid wired telephone, except in emergency. If lightning hits telephone lines, it could flow through phone. Cell or cordless phones, not connected to building's wiring, are safe
Types of Flooding (Esturine and Coastal)
- When seawater encroaches low-lying land above sea level due to storm surges or unusual high tide - Salt and fresh water meet
Thunderstorms Develop in 3 Stages (Cumulus stage)
- air starts to rise vertically creating updrafts which transport water vapor to cooler upper regions in the cloud - as water condenses, clouds become larger and heavier until updrafts can't sustain them and they rain
Eye
- area of lower atm pressure - diameter of 20-65km wide - weak winds - warm temperature - clear sky - safest zone
Return Stroke
- branch channel of positively charged ions that rushes upwards from ground to meet stepped leader
Stepped Leader
- channel of partially charged air - path of ionized air which extends downward from cloud during initial stages of lightning strike
Storm Surge Factors (Storm approach angle)
Perpendicular (down towards coastal area) = higher surge Parallel (flat along coastal area) = very weak surge
Types of Flooding (Catastrophic Flooding)
Result of ground failure, weakening of rock or soil (ex. Subsidence, liquefaction, landslide) and infrastructure failure
Types of Flooding (Riverine)
Rise of water level in rivers beyond average
Storm Surge Factors (Slope of ocean floor)
Steep - higher sea level needed to reach it so not as affected Wide - not that high sea level needed so more dangerous
Storm Surge Factors (Wind speed)
Stronger wind = higher surge
Thunderstorm Warning Icons
Thunderstorm Advisory - TSTM threaten specific area in next 2 hrs. - updates will be issued when necessary (via SMS, social media, and website) Thunderstorm Watch - TSTM formation is likely within next 12 hrs. - more general than warning - disseminated via social media and website Thunderstorm Information - TSTM is less likely within next 12 hrs. - disseminated via Twitter, FB, and website
Classification of Tropical Cyclone based on Intensity
Tropical Depression - 61KPH or less Tropical Storm - 62-88KPH Severe Tropical Storm - 89-117KPH Typhoon - 118-220KPH Super Typhoon - 220KPH and above
Low Pressure Area
region where atmospheric pressure is lower than surrounding locations
Mitigating Typhoons (Revised Public Storm Warning System - PSWS)
#1 - 36 hrs lead time - 30-60KPH winds - impacts of winds: no damage to very light damage #2 - 24 hours lead time - 61-120KPH winds - impact of winds: light to moderate damage #3 - 18 hours lead time -121-170KPH winds - moderate to heavy damage #4 - 12 hours lead time - 171-220KPH winds - impact of winds: heavy to very heavy damage #5 - 12 hours lead time - more that 220KPH winds - very heavy to widespread damage
El Nino
- "little boy" - Unusually warm ocean surface temperature in eastern central pacific (US) - Change in atmospheric conditions and rainfall patterns - Weak trade winds or easterlies - Bring cold air, dry weather to PH (drought) - Temperature rises 0.5°C for 3 months
La Nina
- "little girl" - Strong easterlies - Abnormal lowering of temperature of surface water - Periods of below average sea surface temperature across east-central equatorial pacific - Western (PH) - wet season (evaporation of water etc.) - Neutral area = cold since warm water is accumulated in western - Similar to neutral (so El Nino = extreme one) - Result to heavy rain, floods and flash floods
Types of Thunderstorms (Air-mass Thunderstorms)
- Air rises because of unequal heating of Earth's surface with single air mass - Most common during afternoon and evening - two types: mountain and sea-breeze
Formation of Typhoon (Tropical Cyclone)
- All stages in a continuous process and not separate stages -each stage may occur more than once during cycle as strength of cyclone rises and falls
Mitigation for Storm Surge
- Construct seawalls along coastal section depending on usual height of storm surges reach coast - Mangroves can help equalize waves that come to land like a natural sea wall - Formulate land-use regulation
Preparedness Measures
- Develop/adopt a community disaster contingency plan, consistent with the NDRRM plan - Community evacuation plan - Delineate storm surge risk zones - Stay off beaches when tropical cyclone is brewing at coast
Mitigating Typhoons (Project NOAH)
- Distributes hydrometeorological devices, "Hydromet" in hard-hit areas - Enhances geohazard mapping through Light-Detection and Ranging or LIDAR (landslides) - Provides timely and accurate information for flood early warning system through Flood Information Network (FloodNet)
Effects of Thunderstorms
- Each year lightning causes: > 7,500 forest fires > 300 injuries > 93 human deaths
ENSO Cycle
- El Nino Southern Oscillation - Fluctuations in atmosphere occurring in area between International Date Line and 120° west referred to us East-Central Equatorial Pacific - Extreme weather conditions - El Nino is different for every country - Climate weather and ocean (Pacific ocean mostly and Indian ocean)
Global Impacts of La Nina
- Favor hurricane formation in western Atlantic - Brings colder winters to Canadian west and Alaska - Drier weather to American southeast
Mitigation of Flood Hazards
- Flood assessment and mapping - Flood forecasting and warning
Thunderstorms (Unstable Atmosphere)
- If air remains cooler than rising air mass, unstable conditions can produce clouds that grow upwards - when density of rising air mass and surrounding air are nearly same, clouds stop growing.
Precautions for Thunderstorms and Lightning (Outside precautions)
- If possible, get inside a building - If shelter is not available, lie in a ditch or low-lying area or crouch near a strong building. Be aware of potential flooding - Use arms to protect head and neck
Importance of Tropical Cyclones
- It replenishes groundwater and surface water - Flora and fauna in Philippines are heavily reliant on tropical cyclones for water
Thunder
- Lightning heats air to 30,000 degrees Celsius - Thunder is the sound produced by this super heating of air expanding and contracting - because sound travels more slowly than light you see lightning before you hear thunder
What causes lightning?
- Lightning is transfer of electricity generated by rapid rushes of air in a cloud - clouds become charged when friction between updrafts and downdrafts cause atoms to lose or gain electrons
Disadvantages of Thunderstorms
- Lightning strikes creates fires - Excessive rainfall cause flash flooding - High speed winds from tornadoes destroy homes
Types of Air-mass Thunderstorms (Sea-breeze Thunderstorms)
- Local air-mass thunderstorm that commonly occurs along a coastal area because land and water store and release thermal energy differently
Effects of Typhoons
- Lost of lives and properties - sever flooding - changed topography
Thunderstorms (Lifting)
- Mechanism is needed to lift air into cooler regions in the atmosphere - Ex. > Cold fronts push up warmer air > Cities or bodies of water can create a heat source to push up air - Only when water vapor condenses can it release latent heat and keep cloud rising
Precautions for Thunderstorms and Lightning (Inside a car)
- Never try to out-drive tornado - Get out of car immediately (except for hard topped vehicle) and take shelter in building - avoid open anything - avoid open vehicles such as convertibles, motorcycles, and golf carts - avoid open structures such as porches, gazebos, baseball dugouts, and sports arenas. - avoid open spaces such as golf courses, parks, playgrounds, ponds, lakes, swimming pools, and beaches
How often is the cycle?
- Occurs every 2-7 years - Last for 9-12 months, sometimes more than 1 year - El Nino occurs more often than La Nina
Types of Flooding (Urban Flooding)
- Occurs in highly populated and developed area on low-lying areas due to intense rainfall and as "catch-basin" Causes - garbage, too much population
Flooding
- Overflowing of water that submerges usually dry land - Short duration of occurrence but has long duration to subside
Thunderstorms (National Geographic)
- Rain showers with lightning and thunder - 2,000 at any moment worldwide
Effects of ENSO Cycle
- hard to grow crops - coral bleaching (too much sun) - more fishes in some parts - too much phytoplankton in water - soil erosion - flood damage - water replenished in eastern (la nina) - less water so rotational stop of water in western (el nino) - water contamination in flood - food scarcity - less diseases (malaria) in dry weather - more mosquito diseases (La Nina) - leptospirosis (La Nina or flood)
Advantages of thunderstorms
- helps maintain energy and electricity balance > When energy (heat) causes water to evaporate, heat is carried upward with water vapor. > As vapor condenses (warm air rises, cools and can't hold water vapor, condensation occurs) and forms water droplets, it releases heat into higher altitudes of atmosphere and cools earth's surface. - Thunderstorms help regulate electrical balance btwn atmosphere and planet. > As clouds in thunderstorm develop, excess positive and negative charges form within them. This buildup of opposite charges leads to transfer of electrons in form of lightning. > This occurs so quickly that it breaks sound barrier which produces thunder.
Thunderstorms
- intensity and duration of thunderstorms depend on local conditions - generates lightning and thunder, wind gusts and hail - can cover small area (single cloud) or large area; cluster of clouds - have strong up and down (not spiraling counter clockwise) movement of gust, variable winds. - forms in unstable air
Types of Air-mass Thunderstorms (Mountain Thunderstorms)
- occurs when air mass rises from low elevation to high elevation - involves air moving up the side of mountain (mountain barrier)
Eye Wall
- region surrounding cyclone's center - can reach 15km above mean sea level - strongest winds, heavy rains - turbulence shortly after passage of eye
Storm Surge
- rise in sea level during tropical cyclones, intense storms aka typhoons or hurricanes - associated with super typhoons and typhoons and some severe tropical storm - usually single wave (like tsunami) - no wave shoaling - last for several hrs. depending of cyclone size and speed
Rain Bands
- spiraling strips of clouds in the fringes of tropical cyclones - safer to be at outside part of bands than inside
Typhoon (Tropical Cyclone)
- storms formed in NORTHWEST Pacific Ocean - average of 20 typhoons each year enter Philippine Area of Responsibility (PAR)
Thunderstorms Develop in 3 Stages (Mature stage)
- updrafts and downdrafts exist side by side - precipitation cools air, new cool air sinks rapidly causing downdrafts - updrafts and downdrafts form convection cells which cause winds to develop
How do thunderstorms form? (National Geographic)
- warm air in lowest layers of atmosphere rises (updraft) and causes water from earth's surface to evaporate and carries moisture upward for clouds. - clouds build and grow (as tall as 10 miles high) - clouds darken as they fill and become heavy with water - cool, dry air from upper layers of atmosphere (downdraft) pulls moisture downward causing rain
Thunderstorms Develop in Three Stages (Dissipation stage)
- when warm air is finished, convection stops - cool downdrafts spread out and eventually stop - storm dissipates or dies out
Storm Surge Factors
1. Central pressure 2. Storm forward speed 3. Wind speed 4. Storm size 5. Storm approach angle 6. Shape of coastline 7. Slope of ocean floor
Thunderstorms Develop in 3 Stages
1. Developing/Cumulus stage 2. Mature stage 3. Dissipation stage
Tertiary Effects of Flooding
1. Economic hardships 2. Destruction of production and services-based business 3. Decline in additional government expenditures and rehabilitation 4. Destruction of wildlife habitat in rural areas
Parts of a Tropical Cyclone
1. Eye Wall 2. Eye 3. Rainbands
Primary Effects of Flooding
1. Loss of lives 2. No access to basic needs & necessities 3. Health risk 4. Difficulty of mobilization (traffic)
Secondary Effects of Flooding
1. Power loss 2. Water loss and shortage
Process Influencing Storm Surge
1. Pressure effect - low pressure, higher water 2. Direct wind effect - wind move it to shore 3. Effect of earth's rotation - direction of water follows rotation 4. Effect of waves - wave push too much water to shore 5. Rainfall effect - more rain, more water
Types of Flooding
1. Riverine 2. Estuarine and Coastal 3. Urban Flooding 4. Catastrophic Flooding
4 major types of thunderstorms (National Geographic)
1. Single-cell - small, weak, isolated storms 2. Multi-cell - common type that includes cluster of thunderstorms 3. Squall Line - collection of storms that form a line hundreds of miles long 4. Supercell - most intense storm that produce tornadoes
Three Conditions that must exist for a Thunderstorm to form
1. Source of moisture 2. Lifting of air mass 3. Unstable atmosphere
Factors for Formation of Typhoon (Tropical Cyclone)
1. sea temp. of above 26C (only happens in tropical regions) 2. low altitude winds blowing from different directions 3. thunderstorm clusters (disparate first but organizes to bigger storm system) 4. earth's rotation (generates spin of storm and storm rotates in that direction) 5. light wind shear moves typhoon (winds that are too strong can destroy typhoon)
Types of Thunderstorms
2 Major Types: 1. Air-mass Thunderstorms 2. Frontal Thunderstorms
Dissipation Stage of Cyclone Formation
> Once formed, cyclones movement follows pathway away from its source driven by global wind circulation > As warm ocean waters feed it heat and moisture, cyclone continues to enlarge > If all water content was released in land rainfall, cloud will dissipate because it didn't reach ocean
Mature Stage of Cyclone Formation
> Winds spiral to create cylinder and makes eye (whirling cylinder) > As air rises and cools, some dense air descends to form eye as cyclone rages around it > Lowest air pressure in tropical cyclone at center (950 millibars or less) > tropical cyclones have much less air pressure than surrounding air > bigger pressure difference, stronger wind force > low pressure in eye = surrounding area outside eye is super strong
Origin Stage of Cyclone Formation
> body of warm air develop above ocean surface (26.5°C temp.) > low altitude wind form tropical cyclone > as air warms, it expands, becomes lighter, and rises. Other local winds blow in to replace air that has risen, then warms and rises > rising air cools, and condenses into clouds > More warm air rushes in and rises drawn by draft above. > Rising drafts of air carry moisture high into atmosphere so clouds become thick and heavy. > Condensation releases latent heat energy stored in water vapor, providing cyclone with more power to create self-sustaining heat cycle. > Drawn further upwards by new release of energy, clouds can grow to 12-15km high. > Force created by earth's rotation (Coriolis Effect) causes rising currents of air to spiral around center of tropical cyclone.
Direction of Cyclone Rotation
CLOCKWISE - Southern Hemisphere ANTI-CLOCKWISE - Northern Hemisphere
Storm Surge Factors (Shape of coastline)
Concave - accumulated water in smaller area so higher wave Convex - water goes around landform and spreads out so lower wave Straight - allows some water to penetrate but more dispersal
Storm Surge Factors (Storm size)
Greater size = higher surge
Storm Surge Factors (Storm forward speed)
Higher speed = higher storm surge
Effects of Storm Surge
In Ph, usually result in casualties of more than 100 persons - Deaths and injuries of human beings and livestock - Destruction of houses and other civil structures - Disruption of utility services - Damage of farmlands by intrusion of saline water - Pollution of water supply with sea water - Alteration of natural coastal landscape by erosion
Storm Surge Factors (Central Pressure)
Lower central pressure = bigger wave
Mitigating Typhoons (Seasonal Variability of Tropical Cyclone Activity)
May - lowest June - increases gradually July to Sept. - great increase August - highest November - eventually dies off
Stages of Tropical Cyclone Formation
Origin Mature Dissipation
Conditions during ENSO Cycling
Warm water will evaporate then upwelling of cold water (cold replace the warm water) Hot = more tropical cyclones = western pacific Warm water evaporate and create clouds for tropical cyclones Cold = dry conditions = eastern pacific
Mitigating Typhoons (Rainfall Advisories)
YELLOW - flooding is possible - MONITOR the weather condition ORANGE - flooding is threatening - ALERT for possible evacuation RED - serious flooding expected in low-lying areas - EVACUATION
