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Climate of 2002 - June Colorado Drought National Climatic Data Center, 15 July 2002 |
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| June marked the seventh consecutive month with below-normal precipitation, statewide, for Colorado. While June 2002 was only the 15th driest June on record, the dryness has been so severe for most of the last year that all seasons from May-June 2002 back to July 2001-June 2002 ranked as the driest such season on record (see table below). The extreme short-term dryness resulted in a rapid intensification of long-term drought, as measured by the Palmer Hydrological Drought Index, with the statewide PHDI reaching levels (in magnitude, but not in duration) comparable to the worst drought episode of the 1930s. Several wildfires broke out during June, including the Hayman Fire -- the largest wildfire in Colorado history. According to the USDA, 84% of Colorado's pasture and range land was rated in the poor to very poor category by early July. Based on July 2 USGS observations as summarized by the National Weather Service, 42% of 99 streamflow sites in the state set new all-time record lows for streamflow. |
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| As noted by the Colorado State Climatologist, Dr. Roger Pielke Sr., while the last year (i.e., July 2001-June 2002) has seen record dryness, the previous two years were only slightly drier than average and seven of the previous nine years were much wetter than average. This is illustrated by State Climate Office data for Fort Collins, which is in climate division 4 (the Platte Drainage Basin) in northeast Colorado. |
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As seen in the graph above left, the last two years at Fort Collins were dry, but not nearly as dry as the droughts of the late 19th and mid-20th centuries. Much of the 1990s was characterized by unusually wet conditions. This is reflected in the accumulated precipitation deficit graph above right. This graph shows how the droughts of the 1930s and 1950s resulted in a deepening precipitation deficit (more negative on the precipitation axis) and how the wetness of the last two decades brought the deficit back to zero. The 48-month Standarized Precipitation Index (SPI) value for December 2001 is also near zero (see graph to right), reflecting the balance between the dryness of 2000-2001 and the wet conditions of 1998-1999.
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| Data for Colorado climate division 4 are shown below. |
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| The last three months (April-June) have been very dry for the Platte Drainage Basin (division 4). But the dryness was not as severe in prior months, and 2001 averaged near the long-term mean. The Standardized Precipitation Index (SPI) shows this especially well. |
| The graph to the right shows the June 2002 SPI for seven time scales: one month (June 2002 SPI), two months (May-June 2002 SPI), three months (April-June 2002), six months (January-June 2002), nine months (October 2001-June 2002), 12 months (July 2001-June 2002), and 24 months (July 2000-June 2002). The Colorado division 4 SPI reaches its driest (most negative) value at three months and is still quite dry (less than -2.0) at six and nine months. The SPI is not as dry at 12 and 24 months. |
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| This is also seen in plots of the 102-year history of the SPI at these seven time scales (see graphs below). The one-month to nine-month 2002 SPI's (for June, May-June, April-June, January-June, and October 2001-June 2002) are quite dry, but the 12-month (July 2001-June 2002) and 24-month (July 2000-June 2002) SPI's don't come anywhere near the severity of the mid-20th Century SPI's. |
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