State Climate Update for Arizona – Conditions through September 2005

 

 

September 2005                                                                                                                                                                                                                

September, typically marking the demise of the annual monsoon season across Arizona, was much drier than average across the state and symbolic of drought on the very short term. Mean monthly precipitation was of the 12th-34th percentile across Arizona, signaling an early/dry end to the monsoon season. Still, the impact of the very wet fall and winter season of 2004-05 remains evident in Palmer Drought Severity Index values across much of the state. Values through September indicate wet to very wet conditions in all regions of the state except for in southeastern Arizona (CD 7), where Index values indicate rather dry conditions. The dry conditions of September were generally not compounded by extreme heat, as mean monthly temperatures were only slightly above average except in the south-central part of the state (CD 6).

 

 

Temperature

Precipitation

PDSI

CD1

72.1%

12.6% (3)

94.6%

CD2

64.9%

19.8% (2)

89.2%

CD3

68.5%

14.4% (3)

85.6%

CD4

64.0%

34.2% (1)

65.8%

CD5

68.5%

21.6% (2)

99.1%

CD6

87.4%

23.4% (2)

89.2%

CD7

74.8%

24.3% (2)

33.3%

 

1-month percentiles of temperature, precipitation (with drought category), and Palmer Drought Severity Index for the 7 Arizona climate divisions


 

 

July 2005 – September 2005                                                                                                                                                                                          

Precipitation for the three-month period that approximately represents the monsoon season was near normal to slightly below normal across the state. The exceptions were across southwestern (CD 5) and south-central (CD 6) Arizona, where the monsoon season was slightly wetter than normal, and across southeastern (CD 7) Arizona, where the season was very dry and symbolic of “moderate drought”. Temperatures during the three months were rather high, yet mild relative to recent decades.

 

 

Temperature

Precipitation

CD1

78.4%

49.6% (0)

CD2

71.2%

27.0% (1)

CD3

80.2%

31.5% (1)

CD4

70.3%

33.3% (1)

CD5

85.6%

66.7% (0)

CD6

89.2%

60.4% (0)

CD7

80.2%

16.2% (2)

 

3-month percentiles of temperature, and precipitation (with drought category) for the 7 Arizona climate divisions


 

April 2005 – September 2005                                                                                                                                                                                         

Six-month precipitation values indicate evidence of drought conditions in southeastern Arizona (CD 7; “severe drought”), dry conditions across the northeastern (CD 2) and central (CDs 3, 4) parts of the state, and near-normal (CDs 1, 6) to slightly above normal (CD 5) elsewhere. Statewide, temperatures from spring through summer were above the long-term median, but not approaching unprecedented levels.

 

 

Temperature

Precipitation

CD1

73.0%

54.1% (0)

CD2

68.5%

36.9% (1)

CD3

82.0%

38.7% (1)

CD4

67.6%

27.9% (1)

CD5

82.0%

60.4% (0)

CD6

88.3%

53.2% (0)

CD7

85.6%

14.4% (3)

 

6-month percentiles of temperature, and precipitation (with drought category) for the 7 Arizona climate divisions


 

October 2004 – September 2005                                                                                                                                                                                   

There is no evidence of drought within the state when examining precipitation totals for the past 12-month period. Most regions were characterized by well above normal precipitation, including totals in the 90th percentile for 5 of the 7 regions, the second wettest October-September period on record for 2 of the regions (CDs 1 and 2), and the wettest on record across southwestern Arizona (CD 5). The relatively drier area continues to be across the southeast (CD 7; 60th percentile). Still, the 12-month precipitation total in that region was above the long-term median. Temperatures across the state were above normal for the past 12-month period, but again, the values were not near unprecedented levels.

 

 

Temperature

Precipitation

CD1

75.5%

99.1% (0)

CD2

82.7%

99.1% (0)

CD3

78.2%

98.2% (0)

CD4

73.6%

88.2% (0)

CD5

74.5%

100% (0)

CD6

83.6%

94.5% (0)

CD7

73.6%

60.9% (0)

 

12-month percentiles of temperature, and precipitation (with drought category) for the 7 Arizona climate divisions


               

October 2003 – September 2005                                                                                                                                                                                   

Twenty-four month precipitation values continue to indicate rather wet conditions across the state, as all regions but the southeast (CD 7) were comfortably above the long-term median value, and well above across the western portion of the state. The 2-year precipitation total was near average across southeastern Arizona (CD 7), the driest region over the past two years. Mean temperatures for the 2-year period reflect the trend toward warming over the last several decades, as temperatures were of the 81st – 94th percentile across the state.

 

 

Temperature

Precipitation

CD1

81.7%

93.6% (0)

CD2

89.9%

84.4% (0)

CD3

89.0%

86.2% (0)

CD4

94.5%

66.1% (0)

CD5

89.0%

97.3% (0)

CD6

90.8%

83.5% (0)

CD7

82.6%

40.4% (0)

 

24-month percentiles of temperature, and precipitation (with drought category) for the 7 Arizona climate divisions


 

October 2002 – September 2005                                                                                                                                                                                   

Precipitation totals for the longer 3-year period indicate conditions that are not as wet when considering the past two years, as a portion of the very dry year of 2002 enters the timeframe. Rather dry conditions are evident across the southeastern portion of the state (CD 7; 22nd percentile), where the total precipitation for the period is suggestive of “moderate drought” conditions. Elsewhere, precipitation was either near or above the long-term median for the 3-year period. Temperatures for the period were well above the historical median; however, the longer 3-year time period likely illustrates the more general climatic changes of the past several decades rather than shorter term anomalies.

 

 

Temperature

Precipitation

CD1

85.2%

86.1% (0)

CD2

91.7%

68.5% (0)

CD3

93.5%

75.0% (0)

CD4

97.2%

46.3% (0)

CD5

92.6%

92.6% (0)

CD6

94.4%

75.0% (0)

CD7

86.1%

22.2% (2)

 

36-month percentiles of temperature, and precipitation (with drought category) for the 7 Arizona climate divisions


October 2001 – September 2005                                                                                                                                                                                   

Forty eight-month precipitation values indicate clear evidence of longer-term drought conditions across two areas of the state, with abnormally dry conditions across another three areas. All regions within the state, except for the southwest (CD 5), have been characterized by less than average precipitation over the 4-year period. Precipitation totals for the period indicate “abnormally dry” conditions across the northeastern (CD 2), west-central (CD 3), and south-central (CD 6) portions of the state. Long-term conditions suggestive of “severe drought” exist across southeastern (CD 7) and east-central (CD 4) Arizona, as both are characterized by 48-month precipitation that is in the 8th-11th percentile range. Temperatures for the 4-year period are near unprecedented highs but, again, this is likely to be a reflection of longer-term trends rather than shorter-term anomalies.

 

 

Temperature

Precipitation

CD1

88.8%

45.8% (0)

CD2

93.5%

38.3% (1)

CD3

97.2%

30.8% (1)

CD4

98.1%

8.4% (3)

CD5

92.5%

72.0% (0)

CD6

96.3%

34.6% (1)

CD7

96.3%

11.2% (3)

 

48-month percentiles of temperature, and precipitation (with drought category) for the 7 Arizona climate divisions


 

 

  

 

 



 

Summary                                                                                                                                                                                                                             

Corresponding with the end of the annual monsoon season, September 2005 was characterized by unusually low rainfall across the state. However, the wet fall and winter conditions of 2004-05 were still reflected in high (wet) Palmer Drought Index Values for much of the state. Problematic has been the re-emergence of dry conditions across southeastern Arizona over the past 3-6 months, associated with dry spring and summer seasons. There exists little or no evidence of drought across Arizona over the past 12-to-24 months with generally much greater precipitation than normal during the period. However, long-term drought is evident on the 36-month time frame across southeastern Arizona, and dryness and drought is evident across much of the state on the 48-month time frame. The most critical areas of dryness over the past 4 years are located across southeastern and east-central Arizona. In these areas, precipitation was of an amount suggestive of “severe drought”. Included within the 4-year period is the very dry year of 2002, which is certain to have a significant influence. Overall, short-term conditions indicate a shift from the unusual wetness of fall and winter to a rather dry spring and summer. The impacts of the wetness earlier in the year have persisted such that the Palmer Drought Severity Index values continue to indicate unusual wetness across most of the state; the increased precipitation of fall and winter has clearly provided relief to the longer-term drought condition. Still, the southeastern and east-central regions continue to struggle with long-term precipitation totals suggestive of drought, and southeastern Arizona has shown recent signs of re-emerging dry conditions on the short-term.