Forecasting Different Types of Droughts Simultaneously Using Multivariate Standardized Precipitation Index (MSPI), MLP Neural Network, and Imperialistic Competitive Algorithm (ICA)

Table 2

Classification of the SPI’s values and corresponding probability limits [1, 46].

SPI classes	Probability limits	Description
SPI ≥ 2	≥97%	Extremely wet
2 > SPI ≥ 1.5	93.3–97.7%	Severely wet
1.5 > SPI ≥ 1	84.1–93.3%	Moderately wet
1 > SPI > −1	15.9–84.1%	Normal
−1 ≥ SPI > −1.5	6.7–15.9%	Moderately dry
−1.5 ≥ SPI > −2	2.3–6.7%	Severely dry
−2 ≥ SPI	2.3%≥	Extremely dry