Seasonal Performance Probability (SPP)

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Seasonal Performance Probability (SPP)

•Goal of Product = To statistically determine categorical probabilities for seasonal rainfall to finish at defined percent of normals .

• Below Average (< 80% of Normal)

• Average (80- 120% of Normal)

• Above-Average (> 120% of Normal)

•Methods based on computing bounded PDF/CDF’s from a 30-yr ARC2 rainfall climatology via Kernel Density Estimation (KDE) methods. No NWP component is used.

•The input for the PDF/CDF is an array (n=30) of precipitation rate’s (prate’s) that occurred from a given/current point in the season (t) to the end of the season (tf).

•The PDF then determines the probability of occurrence for an array of projected prates pertaining to outlook categories.

It is anticipated that SPP will be more insightful to the evolution of seasonal rainfall, and a probabilistic outlook will provide additional guidance for famine early warning scenarios within FEWS-NET.

• Example:

• For a given pixel (j,i) during OND rains season in East Africa, suppose the observed 3-month total rainfall is 25mm by Nov 15^th , where 100mm is the normal total for OND.

• With 41 days (Nov 16^th – Dec 31^st) remaining, a prate of:

• ~ 1.34 mm/day is required to be at least 80% of normal

• ~ 1.83 mm/day is required to be at least 100 % of normal.

• ~ 2.31 mm/day is required to be at least 120 % of normal

 What is the probability of these prates to occur (from current to end) based on climatology?

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