Droughts

 


DROUGHT EPISODES EXPERIENCED IN ANTIGUA (1928 - 2015)

Severe

Serious

Moderate

 Slight No.

 MAM 1928-JJA 1929

 JJA 1940 - MAM 1941 JFM 1933 - AMJ 1933 ASO 1934 - SON 1934 1
SON 1929 - AMJ 1931 JFM 1944 - MJJ 1944 ASO 1933 - JJA 1934 AMJ 1937 - JAS 1937 2
FMA 1938 - AMJ 1938 NDJ 1944 - JAS 1945 JFM 1935 - MAM 1936 FMA 1943 - MAM 1943 3
JFM 1939 - OND 1939 ASO 1964 - JFM 1967 ASO 1941 - NDJ 1941 NDJ 1945 - JFM 1946 4
JJA 1946 - ASO 1948 NDJ 1969 - MAM 1969 FMA 1950 - JJA 1950 FMA 1954 - JJA 1954 5
DJF 1952 - NDJ 1953/54 JFM 1980 - JFM 1981 ASO 1960 - JJA 1961 AMJ 1955 - JJA 1955 6
AMJ 1967 - DJF 1968/69 MJJ 1984 - SON 1984 OND 1962 - NDJ 1962 SON 1955 - JJA 1956 7
FMA 1973 - JAS 1974 AMJ 1985 - JAS 1985 FMA 1963 - AMJ 1963 SON 1956 - MAM 1958 8
JFM 1975 - NDJ 1975/76 DJF 1985 - FMA 1986 DJF 1963 - FMA 1964 SON 1959 - DJF 1959/60 9
MAM 1976 - OND 1977 JJA 1990 - DJF 1990/91 SON 1971 - NDJ 1971/72 DJF 1977 - FMA 1978 10
DJF 1976 - ASO 1977 JAS 1993 - JJA 1995 MJJ 1972 - OND 1972 MJJ 1982 - OND 1982 11
JFM 1983 - JFM 1984 NDJ 1995 - MJJ 1996 DJF 1978 - MAM 1979 DJF 1984 - JFM 1985 12
JJA 1986 - NDJ 1986/87 JAS 2009 - FMA 2010 DJF 1986 - MAM 1987 AMJ 1988 - JJA 1988 13
AMJ 2000 - OND 2001 JFM 2012 - ASO 2012 MAM 1989 - JAS 1989 JFM 1993 - MAM 1993 14
MJJ 2002 - OND 2003 NDJ 2012 - JFM 2013 OND 1989 - FMA 1990 MJJ 1998 - JAS 1998 15
  JAS 2013 - Present MAM 1991 - JFM 1992 MAM 2007 - JFM 2008 16
    ASO 1996 - OND 1996   17
    SON 1997 - FMA 1998   18
    MAM 2005 - AMJ 2005   19
    FMA 2006 - JFM 2007   20
    FMA 2009 - AMJ 2009   21
    NDJ 2010 - FMA 2011   22
         
         
         

Severe Droughts: Probability of at least one in a yr - 15.1%, at least one in 5 yrs - 56.0%, at least one in 10 yrs - 80.6%. Return Period - 6.6 years, Range - 3 to 27 seasons (average 15.2 seasons) or 5 to 29 months (average 17.2 months). These droughts normally start in the first half of the year.

Serious Droughts: Probability of at least one in a yr - 16.1%, at least one in 5 yrs - 58.5%, at least one in 10 yrs - 82.8%. Return Period - 6.2 years, Range - 3 to 24 seasons (average 9.4 seasons) or 5 to 26 months (average 11.9 months).

Moderate Droughts: Probability of at least one in a year - 22.8%, at least one in 5 yrs - 72.6%, at least one in 10 yrs - 92.5%. Return Period - 4.4 years, Range - 2 to 15 seasons (average 5.8 seasons) or 4 to 17 months (average 7.8 months).

Slight Drought: Probability of at least one in a year - 17.1%, at least one in 5 yrs - 60.9%, at least one in 10 yrs - 84.7%. Return Period - 5.8 years, Range - 2 to 19 seasons (average 5.2 seasons) or 4 to 21 months (average 7.2 months).
Serious or Severe Drought: Probability of at least one (serious or severe) in a yr - 28.9%, at least one in 5 years - 81.8%, at least one in 10 yrs - 96.7%.

Moderate or Serious or Severe Drought: Probability of at least one (moderate or serious or severe) in a yr-45.1%, at least one in 5 years - 95.0%, at least one in 10 yrs - 99.7%.

Droughts Overall: Probability of at least one (severe, serious, moderate or slight) in a year - 54.5%, Return Period - 1.8 years, Range - 2 to 27 season (average 8.5 seasons) or 4 to 29 months (average 10.5 months). 

If there is a drought - 20.9% chance it is severe, 22.4% chance it is serious (43.6% severe or serious), 32.8% chance it is moderate and 23.9%  it is slight.

Longest period between any drought is 29 seasons (31 months); longest period between a severe or serious drought is 128 seasons (10 years and 10 months).

Drought in general means water shortage and rainfall deficiency. Meteorological (climatological) drought is defined in terms of the magnitude of a precipitation shortfall/deficit and the duration of this shortfall event. This is assessed by first examining the rainfall periods of three months or more for selected places to see whether they lie below the 30th percentile (lowest 30% of the historical records). The approach used to determine the rainfall deficit is an adjusted version of the decile method developed by Gibbs and Maher (1967). An adjusted version of this method is used as the measurement of droughts within the Australian Drought Watch System.

The drought levels, based on consecutive three-month historical data, are defined as follow:

 

•    Slight: rainfall ranges from less than 30th percentile to the 20th percentile 

•    Moderate: rainfall ranges from less than the 20th percentile to the 10th percentile

•    Serious: rainfall ranges from less than the 10th percentile to the 5th percentile

•    Severe: rainfall less than the 5th percentile

 

The level of a drought period/episode (drought lasting three or more months) is described based on the maximum consecutive three-month rainfall deficit.

See our Drought and Precipitation Statement for the latest including how droughts are accessed.