PROJECT NOAH – ClimateX: Accurate Rain Forecasting for the Philippines

CP David( a,b,c), BA Racoma (a,b,c), Irene Crisologo (a,b,c)

(a) FloodNet (ClimateX)
(b) Nationwide Operational Assessment of Hazards
(c) National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City

Fig, 1 ClimateX provides the 4-hour rainfall forecast in the Project NOAH website. It can be accessed at www.climatex.ph

Fig. 1 ClimateX provides the 4-hour rainfall forecast in the Project NOAH website. It also provides “nowcast” via its Twitter account @climatexph.  It can be accessed at www.climatex.ph.

What is a ClimateX forecast?

Fig. 1 ClimateX website screenshot of percent chance of rain

Fig. 2 ClimateX website screenshot of percentage chance of rain of a particular area.

ClimateX forecasts both the chance of rain, and the amount of rain that comes along with it whenever applicable.

The chance and amount can be in 2 formats:

  • Number: 80% chance of 3.5mm
  • Interpreted: HIGH chance of MODERATE rain

What is the source of ClimateX forecasts?

Fig. 3 PAGASA Doppler images can also be viewed in the ClimateX website.

Fig. 3 PAGASA Doppler images can also be viewed on the ClimateX website.

The forecasts mainly come from Doppler Weather Radar data. Different Weather Radars located around the country detect the location of rainclouds, as well as the amount of rain they bring.

Besides the Doppler Weather Radar data, the following data sources are also considered:

  • Historical data
  • Time of day
  • Nearby rain gauges
  • Location of ITCZ

How far in the future can these forecasts be?

Fig. 4 Image of Mactan Doppler station. The color scale shows the probability of rainfall in a particular area.

Fig. 4 Image from the Mactan Doppler station. The color scale shows the probability of rainfall in a particular area.

Forecasts are made for up to four (4) hours into the future for all major cities and municipalities that are covered by the PAGASA RADAR network. This is particularly applicable for thunderstorms which can appear within an hour and last anywhere from 1 to 4 hours

How accurate are the forecasts?

An independent accuracy assessment was done by the COGNOS team of IBM Philippines.

Two accuracy measures were made: accuracy and success ratio.

Accuracy is the total number of correct forecasts over the total number of forecasts. By saying correct forecasts, we have two types of correct forecasts: (1) Forecasted YES rain, and upon observation it did RAIN, (2) Forecasted NO rain, and upon observation it did NOT RAIN. This accuracy metric is biased since it is very easy to forecast NO rain with a high degree of accuracy. Using this method we get a total of 84% accuracy.

Success ratio is the total number of correct Forecast YES rain (forecast YES, upon observation it did rain) over the total number of Forecast YES rain. This metric only checks the accuracy for the times we forecast that it will rain, disregarding the NO rain forecasts. Using this metric, we get an 80% success ratio.

Where was ClimateX developed?

It was developed in house in the Environment Monitoring Laboratory in the National Institute of Geological Sciences, UP Diliman. It is one of the component projects of DOST PROJECT NOAH. Most data is provided by PAGASA, while software and hardware support is provided by DOST-ASTI (Advanced Science and Technology Institute).

It is the first of its kind in the country. Continuous development is being undertaken to extend the forecasting and make it even more accurate.

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