PHYSCI M5: Weather DisturbancesPrepared by: Emmanuel C. RevillaInstructor: Mr. Tan Bicomong

Weather DisturbancesWeather Disturbances A weather disturbance is a general term that describes any pulse of energy moving through the atmosphere. They are important in that they can act as focusing mechanisms for storm formation, or even to intensify low pressure systems. They are typically mid or upper atmospheric troughs of low pressure that are embedded in the general wind flow of the atmosphere.Different Weather Disturbances1. Tropical Cyclonea. Tropical depressionb. Tropical stormc. Typhoons2. Tornado*Intertropical Convergence Zone*Monsoons

Tropical Cyclone

Originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds and heavy rains. Draws energy from the sea surface and maintaining its strength as long as it remains over warm water. Accompanied by torrential rains.

A. Tropical DepressionOnce a group of thunderstorms has come together under the right atmospheric conditions for a long enough time, they may organize into a tropical depression. Winds near the center are constantly between 20 and 34 knots (23 - 39 mph).

B. Tropical StormAtropical stormis an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds between 17 and 33 meters per second (34 to 63 knots, 39 to 73 mph, or 62 to 117 km/h). At this point, the distinctive cyclonic shape starts to develop, though an eye is usually not present. This generally forms from Low-Pressure Area (LPA)

C. Typhoons.A Typhoon is a name used in east Asia for a Hurricane. It is a type of cyclone occurring in the western regions of the Pacific Ocean. A typhoon is similar to a hurricane in levels of destructiveness. The word typhoon comes from the Chinese term tai-fung meaning great wind.Tornado Tornado is a small-diameter column of violently rotating air developed within a convective cloud and in contact with the ground. Tornadoes that hit a populated area causes fantastic destruction and great loss of life, mainly from flying debris and collapsing structures. These strong winds occur in all continents except Antarctica.

Intertropical Convergent Zone TheIntertropical Convergence Zone(ITCZ), known by sailors asThe Doldrums, is the area encircling the earth near theequatorwhere winds originating in the northern and southern hemispheres come together. The ITCZ was originally identified from the 1920s to the 1940s as the "Intertropical Front" (ITF), but after the recognition in the 1940s and 1950s of the significance ofwind field convergenceintropicalweather production, the term "ITCZ" was then applied.Monsoon Monsoonis traditionally defined as a seasonal reversingwindaccompanied by corresponding changes inprecipitationbut is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea. Usually, the term monsoon is used to refer to the rainy phase of a seasonally-changing pattern, although technically there is also a dry phase.Public Storm SignalPSWS #1 - Tropical cyclone winds of 30km/h (19mph) to 60km/h (37mph) are expected within the next 36hours. (Note: If a tropical cyclone forms very close to the area, then a shorter lead time is seen on the warning bulletin.)PSWS #2 - Tropical cyclone winds of 60km/h (37mph) to 100km/h (62mph) are expected within the next 24hoursPSWS #3 - Tropical cyclone winds of 100km/h (62mph) to 185km/h (115mph) are expected within the next 18hours.PSWS #4 - Tropical cyclone winds of greater than 185km/h (115mph) are expected within 12hours.

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