Hydrometeorological Hazards

Meteorology

is the study of the atmosphere, atmospheric phenomena, and atmospheric effects on weather.

Hydrometeorological hazards

are processes that involve the interaction of the atmosphere, bodies of water, and land which pose a threat to lives and human properties.

Northeast Monsoon

Amihan

Southwest Monsoon

Habagat

Intertropical Convergence Zone

ITCZ

Typhoons

Powerful storm systems characterized by strong winds, heavy rain, and storm surges.

Thunderstorms

Localized storms featuring lightning, thunder, heavy rain, and sometimes hail.

Floods/Flash Floods

Overflow of water onto land that is normally dry, which can occur rapidly and cause widespread damage.

Storm Surges

Rising of the sea as a result of atmospheric pressure changes and wind associated with a storm. They mostly affect coastal areas.

El Nino

Warmer than average sea surface temperatures, weaker than normal trade winds; causes droughts and dry spells in the Philippines.

La Nina

Cooler than average sea surface temperatures, stronger than normal trade winds; increases the likelihood of above-normal rainfall in the Philippines.

Typhoon

is a severe weather disturbance characterized by strong winds and heavy rains which revolve around a central low-pressure area.

Northwest Pacific

Where typhoons usually take place, hitting countries like the Philippines and Japan

Atlantic and Northeast Pacific

where hurricanes take place, hits the East and West coasts of North America, as well as western parts of Europe and and Africa, and the Eastern Coast of South America

Cyclones

are the disturbances that take place in the South Pacific and Indian Ocean, hitting areas such as Australia, India, and East Africa.

550, 2000

A typhoon, on the average, has a total diameter of _____ km but can have a diameter more than ______ km wide. Its basic structure is composed of an eye, an eye wall, and surrounding rain bands.

Eye

The area of lowest atmospheric pressure in the structure of a tropical cyclone

Eye

With a diameter that may span 20–65 km wide

Eye

Where winds are weak, the temperature is warm, and the sky is clear

Eye Wall

The region immediately surrounding the tropical cyclone’s center

Eye Wall

Can reach as high as 15 km above mean sea level

Eye Wall

Brings the strongest winds, heavy rains, and turbulence shortly after the passage of the eye

Rain Bands

Spiraling strips of clouds in the fringes of tropical cyclones which are associated with rainfall

1. Formative Stage

2. Immature Stage

3. Mature Stage

4. Decay Stage

Stages of Typhoon Development

Formative Stage

The initial stage where the system forms from pre-existing disturbances, with winds usually below typhoon force.

Immature Stage

The system starts to organize and intensify but has not yet reached its peak intensity.

Mature Stage

The typhoon has fully developed, featuring a well-defined eye, and reaches its maximum wind speed and lowest central pressure.

Decay Stage

The typhoon weakens, typically due to land interaction, cooler water, or wind shear, eventually dissipating.

4,5

Damage assessment revealed that the resulting impacts on the ground of meteorological conditions commonly associated with the Wind Signal Nos. ___ and ____ of the old TCWS system are indistinguishable from each other.

Wind Signal no. 2

spans a wide range of wind speeds thus, it means that its coverage will have a wide range of impact severity.

Thunderstorms

are violent, transient type of weather disturbance associated with thousands of meters of tall cumulonimbus clouds and which usually involve lightning, thunder, strong winds, intense rainfall, and occasionally tornadoes and hail. Thunderstorms need the following to form: moisture, rising unstable air, and a lifting mechanism.

1. Developing Stage

2. Mature Stage

3. Dissipating Stage

Thunderstorm Life Cycle

Developing Stage

When air is lifted upward due to heat that makes it lighter, it becomes cooled through expansion.

Developing Stage

Cooling forms the cumulus cloud through the process of condensation.

Mature Stage

Accumulation of clouds, spreading, and formation of cumulonimbus clouds

Mature Stage

Turbulent current still exists within the cloud creating the constant association and dissociation of raindrops

Mature Stage

Buildup of strong electric charges that result in lighting

Dissipating Stage

Hail, heavy rains, frequent bolts of lightning, strong winds, and tornadoes

Dissipating Stage

Results in large amounts of precipitation and halts the upward movement of air

1. Thunderstorm Advisory

2. Thunderstorm Watch

3. Thunderstorm Information

Thunderstorm warning icons

Thunderstorm Advisory

• This will be issued when there is an indication that a thunderstorm is threatening a specific area/s within the next 2 hours

• Updates will be issued as frequent as necessary

• This will be disseminated via SMS, Social Media, and website

• ‘yung may exclamation mark

Thunderstorm watch

• this will inform the public that TSTM formation is likely within the next twelve hours

• this is more general than a warning

• this will be disseminated thru socmed and website

• may mata

Thunderstorm information

• issued when TSTM is less likely within the next twelve hours

• this will be disseminated thru twitter, fb, and website

• may letter (i)

Flooding

is the abnormal rise of water level in rivers, coastal areas, plains, and in highly urbanized centers which may be a result of natural phenomena, human activities, or both. Flooding duration can be as short as a few minutes but can take as long as several days or even weeks to subside. Some areas, due to their location, land configuration, and climactic setting, are naturally susceptible to flooding.

Flash Floods

are rapid, short-lived, and violent arrival of a large volume of water. It can be caused by intense localized rainfall on land that is saturated or unable to absorb water. It may also occur due to the collapse of infrastructure such as dams. Floods that take place within six hours of intense rainfall are classified as flash floods.

1. Flood hazard assessment and mapping

2. Flood prediction

3. Flood forecasting and warning

4. Flood-control engineering measures

Mitigation of flood hazards

Dams

• are barriers that hold back water and can regulate water flow rates.

• In the Philippines, ___ operations are closely monitored by PAGASA together with agencies like the National Power Corporation (NPC) and the National Irrigation Administration (NIA).

Diversion Canals

Diversion canals are artificial waterways utilized to reroute the excessive storm water to an area with lower risk or impact to flooding such as the open sea or in a reservoir intended for floodwater containment.

Artificial Levees (or dikes)

A levee or a dike is a permanently fixed barrier which is constructed parallel to the channel and built to be sufficiently higher than the estimated maximum flood levels in the area.

Self Closing Flood Barriers (SCFB)

are designed to prevent foods due to overflow of natural and artificial waterways from entering property.

Sea Walls

are constructed along coasts to protect communities from being destroyed by flooding during high tide, by storm surge, and by tsunamis.

Storm Surges

is a localized unusual increase of sea water level beyond usual high tide levels primarily due to intense winds and lowered atmospheric pressure during the passage of an intense tropical cyclone from the sea to the land.

Storm Surges

are the primary cause of about 90% of casualties and damage to properties in coastal areas during a tropical cyclone.

El Niño Southern Oscillation (ENSO)

is a natural climatic phenomenon characterized mainly by cyclic fluctuation of warm and cold sea surface temperatures and atmospheric pressure in the central and eastern equatorial Pacific.

El Niño Southern Oscillation (ENSO)

causes extreme regional-scale weather and climate pattern changes (i.e., temperature and rainfall) which can result either in droughts or floods in various regions of the earth, making it the most powerful climatic force on earth.

El Niño Southern Oscillation (ENSO)

Opposite extremes of this phenomenon are the El Niño (warm phase) and the La Niña (cold phase).

El Nino

is a Spanish term which literally means “Christ child” or Jesus. The term was coined by fishermen in Ecuador and Peru who noticed unusual inter-annual warming of ocean waters in their fishing areas off the west coast of South America that peaked around Christmas time.

El Nino

is a prolonged unusual warming of sea surface temperatures in the central equatorial Pacific and the eastern equatorial Pacific. It entails a 3-month, greater-than-usual warming in a specific portion of the east-central tropical Pacific Ocean. This phenomenon usually lasts for 9 months up to 2 years. It causes droughts and dry spells in the

Philippines.

La Nina

Niña involves prolonged unusual cooling (of at least -0.5 °C) of sea surface temperatures in central and eastern equatorial Pacific that may last for 1-3 years. A La Niña can follow an El Niño but historical records show that El Niños occur twice as frequent as La Niñas. The term is Spanish for “the girl” and this event is the exact opposite of El Niño.

La Nina

is caused by the strengthening of the easterly trade winds which blows more warm water toward the west and allows the upwelling of cold water in the east (near west coast of South America).

Automatic Weather Station (AWS)

have built in weather instruments with electronic sensors for measuring surface level air temperature, pressure, solar radiation, rainfall amount, and wind speed

Automatic Rain Gauge (ARG)

intended to catch rainfall through a tipping bucket mechanism that gauges and registers amount of rainfall

Automatic Aviation Weather Observation System (AWOS)

helps pilots and aviation personnel make critical decisions by providing continuous, real time information and reports on airport weather conditions

Radio Detection and Ranging (RADAR)

useful in locating precipitation and estimating its intensity and in determining the location, speed, and direction of objects like tropical cyclones

Upper-Air Observation

provide a vertical profile of the atmosphere; measures air temperature, humidity, and pressure to altitudes of approximately 30 km