Climate Prediction Center - Outlooks: Palmer Drought Outlook Explanation

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HOME > Outlooks > Special Outlooks Products > Palmer Drought > Outlook Explanation

THE PROBABILITIES ARE OBTAINED BY RUNNING THE CURRENT PALMER DROUGHT DATA FOR EACH CLIMATE DIVISION 4 MONTHS AHEAD USING THE WEATHER SCENARIOS (TEMPERATURE AND PRECIPITATION) OF ALL THE PAST YEARS SINCE AND INCLUDING 1931. THE PROBABILITY IN PERCENT FOR A GIVEN CATEGORY IS THE NUMBER OF TIMES THE PROJECTED PDI FELL IN A GIVEN DROUGHT CATEGORY DIVIDED BY THE NUMBER OF YEARS SINCE 1931 TIMES 100. THE PDI VALUES FOR THE 7 CATEGORIES ARE:

EXTREME OR SEVERE DROUGHT	LESS THAN OR EQUAL -3.0
MODERATE DROUGHT	GREATER THAN -3.0 AND LESS THAN OR EQUAL -2.0
MILD DROUGHT	GREATER THAN -2.0 AND LESS THAN OR EQUAL -1.0
NEAR NORMAL OR INCIPIENT	GREATER THAN -1.0 AND LESS THAN CONDITIONS +1.0
MOIST SPELL	GREATER THAN OR EQUAL +1.0 AND LESS THAN +2.0
UNUSUAL MOIST SPELL	GREATER THAN OR EQUAL +2.0 AND LESS THAN +3.0
VERY OR EXTREME MOIST	GREATER THAN OR EQUAL +3.0 SPELL


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