DRRR 11: Hydrometeorological Hazards

Hydrometeorological Hazards

These are processes or phenomena of atmospheric, hydrological, or oceanographic in nature that can cause loss of life, damage to properties, socio-economic disruption, and environmental damage.

ITCZ

An acronym that stands for the Intertropical Convergence Zone. It is an area in complete contact with the trade winds, which are culprits for the generation of typhoons across the globe.

Typhoons

A powerful weather system originating mainly near the equator over a body of water that is at least 27°C. It is characterized by low pressure, cyclonic circulation, and the upward movement of warm, moist air.

• These are also known as tropical cyclones.

LPA

An acronym that stands for Low Pressure Area. This refers to a region where warm air is lifted upward from the ocean, creating a center that draws in surrounding winds to begin a cyclonic circulation. Its detection in weather reports serves as a primary warning sign that a typhoon is likely forming.

Formative Stage

The incipient phase of a typhoon where waves and shear lines of pre-existing disturbances begin to develop, but winds remain below gale force.

Immature Stage

The deepening phase of a cyclone where the lowest central pressure is reached and wind intensity continues to increase toward its maximum.

Mature Stage

The period of a typhoon where the area of circulation expands, surface pressure stops falling, and no further increase in maximum wind speed is observed.

Decaying Stage

The dissipating phase of a typhoon where surface pressure rises and the affected area diminishes as the system moves toward land, colder air, or drier environments.

Eyewall

The ring of clouds surrounding the center where the most severe winds and heaviest rainfall are concentrated, making this the strongest part of a typhoon/

Eye

It is the calm, circular center of a typhoon. While the most violent winds and rain swirl around it (in the eyewall), this by itself has clear skies, light winds, and the lowest air pressure.

Tropical Depression

Sustained winds of 61 kph or less

Tropical Storm

Sustained winds of 62–88 kph

Severe Tropical Storm

Sustained winds of 89–117 kph

Typhoon

Sustained winds of 118–220 kph

Super Typhoon

Sustained winds of more than 220 kph

Thunderstorm

It is a localized weather disturbance characterized by the presence of thunder and lightning, which is commonly associated with the formation of dense cumulonimbus clouds. It requires moisture, unstable air, and a lifting mechanism, like heat from the sun, to drive the upward motion of air that creates the storm's intensity. These systems progress through three distinct life stages (developing, mature, and dissipating), bringing heavy rain, gusty winds, and sometimes hail.

Cumulonimbus Clouds

Dense, towering vertical clouds associated with atmospheric instability that produce heavy rain, lightning, and occasionally hail or tornadoes.

Flood

An abnormal progressive rise in the water level of a stream or body of water that results in the overflowing of areas not normally submerged.

Flash Flood

A rapid nature of flowing water covering areas with little to no absorption capability, typically occurring in less than six hours.

Storm Surge

An abnormal rise and outflow of water into coastal areas caused by enormous forces from the sea (often from a cyclone or seaquake), pushing water beyond the normal high tide level.

El Niño

A global climate pattern involving the weakening of trade winds, causing warmer waters to move toward the west coast of the Americas and shifting the jet stream south.

La Niña

A phenomenon characterized by the strengthening of trade winds, which brings more warm water toward Asia and causes colder water to upwell to the surface in the eastern Pacific.

RADAR

An acronym that stands for Radio Detection and Ranging. It is a weather surveillance radar that is useful in locating precipitation, eliminating its intensity, and determining the center of tropical cyclones.

ENSO

An acronym that stands for El Niño Southern Oscillation.

PAGASA

An acronym that stands for the Philippine Atmospheric Geophysical and Astronomical Services Administration. It is the national government agency responsible for providing flood and typhoon warnings, public weather forecasts, and other specialized astronomical and climatological information.

PSWS

An acronym that stands for Public Storm Warning Signal. These are levels of warnings issued by PAGASA to inform the public about the incoming strength of a tropical cyclone and its expected impact on a specific locality.

PAR

An acronym that stands for the Philippine Area of Responsibility. It is a specific area in the Northwestern Pacific where the national weather agency, PAGASA, is assigned to monitor tropical cyclone activity.