|PAGASA Yellow, Orange and RED Color Code Warning System|
PAGASA releases new advisory for the implementation of new color coded warning signal system as of August 9, 2012. GREEN warning signal was changed to ORANGE warning signal which means preparedness and alert for possible evacuation in your area.
PAGASA Color Coded Warning Signal Alert System
New alert system is created by PAGASA to warn public (NCR only) of incoming rainfall volume brought by weather disturbance. Unlike for Storm signal number 1, 2 and 3 during Typhoons that measures the strength of wind, the new system is color coded which means possible rainfall volume within 2 hours in a certain area.
YELLOW Warning Signal
Rainfall Volume: 7.5 - 15mm per hour (Heavy)
Effects: Flooding is possible
What to do: Awareness - Monitor the weather condition in 2 hours and wait for next PAGASA weather advisory
ORANGE Warning Signal
Rainfall Volume: 15 - 30mm per hour (Intense rains)
Effects: Flooding is threatening
What to do: Preparedness - Alert for possible evacuation
RED Warning Signal
Rainfall Volume: 30+ mm per hour (Torrential)
Effects: Flooding is expected in low lying areas
What to do: Emergency - Evacuation
What Does mm/hr or millimeter per hour of Rain Means?
Rain or Rainfall is measured in length per unit time. PAGASA uses mm/hr or millimeter per hour in it's color code warning signal alert system and what does it mean?
1 mm/hr of rainfall means 1 millimeter of rainfall height in 1 m2 area per hour. To fully understand, I draw a figure in the above page showing 30+ mm/hr in a box with length = 1 meter, width = 1 meter and height = 1 meter. For a volume of 1 m3, it takes 33 hours to fully filled it with rainfall 30+ mm (RED warning signal). In addition, lets see the equivalence of 1mm to liters of water.
1 mm/h = 1 Liter of water in 1 m2 area per hour
15mm/h = 15 Liters of water in 1 m2 area per hour
30mm/h = 30 Liters of water in 1 m2 area per hour
So, for Yellow warning, people can experience 7.5 - 15 Liters per hour of rainfall volume per 1 m2 area, for Orange warning 15 - 30 Liters per hour of rainfall volume per 1 m2 area and 30+ Liters per hour for RED warning alert.
Rainfall Volume Conversion to Liters
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