Weather Forecast and Advisory Terms

DEFINITION OF TERMS

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Following are definitions of some common terms used in various issuances such as forecasts and advisories.

Weather		the specific conditions of the atmosphere at a particular place and time. It is measured in terms of such parameters as wind, temperature, humidity, atmospheric pressure, cloudiness and precipitation. In most places, weather can change from hour to hour and season to season.
Climate		the average weather and its long term variability over a particular place and time (say a month, a season, a year or several years).
Climate Variability		refers to the fluctuations / variations of climate observed since the instrumental period (i.e., 1860 to present). These fluctuations are due to natural causes and to human activities.
Season		a division of the year according to some regularly recurent phenomena, usually astronomical or climatic. In the tropics, precipitation is the primary factor; thus, nearly all regions have their rainy season and dry season.
Normal  (climatological normal)		the average value of a meteorological element over any fixed period of years that is recognized as standard for a country and element concerned; usually a 30-year period as recommended by the World Meteorological Organization (WMO).
Anomaly  (departure from normal)		the deviation of (usually) temperature or precipitation from the normal values in a given region over a specified period.
NE Monsoon		locally known as "Amihan". It affects the eastern portions of the country from October up to late March, starts over Siberia as a cold, dry air mass but gathers moisture as it travels across the Pacific Ocean before reaching the eastern sections of the Philippines is characterized by widespread cloudiness with rains and showers. The North Pacific Trades gradually replaces the NE Monsoon in March, appears in all seasons and blows dominantly from March to April, giving strong convective activity.
SW Monsoon		locally known as "Habagat", it affects the country from July to September, is very warm and humid, occurs when warm moist air flows over the country from the southwest direction, is characterized by heavy rainfall that may last for a week. It brings the rainy season to the western portion of the country.

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Linear Systems	Description	Associated Weather	Period
Intertropical Convergence Zone (ITCZ)	Result of the northern hemisphere and southern hemisphere tradewind convergence	Widespread cloudiness, occasional thunder-storms, precipitation, moderate to strong surface winds	Migratory, depending on the time of the year
Tail-end of Cold Front	Front boundary of 2 air masses, found in mid-latitudes	Rainfall and cloudiness over affected areas	Northern portion of the country during the Northern Hemisphere winter season
Easterly Waves	Wavelike perturbations embedded in the easterly current	cloudiness and precipitation in eastern coastal portions	More frequent during the transition period

Tropical Cyclone Intensity / Category

Intensity / Category	Maximum Winds
Tropical Depression	Between 35 KPH and 64 KPH near the center
Tropical Storm	Between 65 KPH and 118 KPH near the center
Typhoon	119 to 200 KPH near the center
Super Typhoon	Maximum winds greater that 200KPH

Reference: http://kidlat.pagasa.dost.gov.ph/cab/define.htm

Date of Download: Jan. 22, 2013