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|As the year began,
moderate to extreme drought covered one-third* of the contiguous
United States including much of the eastern seaboard and
northwestern U.S. The combination of generally warmer- and
drier-than-average conditions led to an increase in the areal
coverage to slightly more than 50 percent during the summer months,
largely due to a rapid intensification of drought in the Southwest.
This value fell to 35 percent by the end of December as
precipitation from landfalling tropical systems and a more active
storm track helped alleviate drought in much of the eastern part of
- *This drought statistic is based on the Palmer Drought
Index, a widely used measure of drought. The Palmer Drought Index
uses numerical values derived from weather and climate data to
classify moisture conditions throughout the contiguous United
States and includes drought categories on a scale from mild to
moderate, severe and extreme.
The most extensive national drought coverage during the past 100
years (the period of instrumental record) occurred in July 1934
when 80 percent of the contiguous U.S. was in moderate to extreme
drought. Although the current drought and others of the 20th
century have been widespread and of lengthy duration, tree ring
records indicate that the severity of these droughts was likely
surpassed by other droughts including that of the 1570s and 1580s
over much of the western U.S. and northern Mexico.
||On a national scale,
long-term drought (as measured by the Palmer Drought Index) rapidly
expanded during the first half of 2002 to reach a peak area
coverage of about 39% of the country in the severe to extreme
categories by July. Heavy rains from tropical systems and frontal
storms fell over some of the drought areas during the late summer
and fall, resulting in a decrease in the drought area to about 22%
of the contiguous U.S. by the end of December.
The percent of the country in the severe to extreme wet spell
categories (as measured by the Palmer Drought Index) fluctuated
between 0 and 4% during most of the year, eventually rising to
about 7% by the end of December.
|The 2002 national
drought had its origins in late 1999. At its peak
in July 2002 this drought, when compared to other droughts of
the 20th Century, was as extensive as the major droughts of the
last 40 years, but not as large as the "dust bowl" droughts of the
1930s and 1950s. The duration of the current national drought
(about 37 months) is longer than the duration of the 1970s drought
and about as long as the late 1980s drought.
|The 2002 national
drought was focused in several areas during the year. Abnormal
dryness, which plagued the parts of the Southwest since mid-2001,
worsened in that region in 2002 and spread into the central Plains
during the spring
(March-May). Record dry conditions from 2001 continued into
early 2002 in the eastern U.S., peaking in February
and contributing to the
fourth driest February, nationally, in the 108-year record. The
2001-2002 rainy season in the West
region (California and Nevada) dried out beginning in January,
with the drier than normal conditions continuing
through October. Drier than normal weather which developed in
the Pacific Northwest during the spring persisted
through November. Areas of severe short-term drought developed
in the Ohio Valley and southern Great Lakes during the summer
(June-August) and late
The drought severely impacted many areas of the country. Drought
emergencies were declared and water restrictions implemented in
many cities and counties. The impacts included depleted reservoirs,
dry wells, and desiccated crops and pastures. Dust storms roared in
Montana, Colorado, and Kansas, bringing back memories of the 1930s.
The largest wildfires in state history occurred in Colorado, Arizona, and Oregon this year.
|The 2001-2002 rainy
season (November-March) for the West
region started out wet, but it turned dry in January. The
region experienced below normal precipitation consistently for the
next ten months, resulting in the driest January-October in the
|In the Pacific
Northwest the 2001-2002 rainy season (October-April) was
generally wet, giving the region overall a near
average hydrologic year (October-September). Subnormal rainfall
fell starting with the 2002 dry season, however, resulting in the
driest May-October in the 108-year record.
||During late 2001 and
early 2002, extreme dryness afflicted almost the entire eastern
seaboard. This was the latest dry episode in a long-term drought
which started, generally, in
July 1998 for the Northeast
May 1998 for the Southeast.
September 2001-February 2002 ranked as the second driest such six-month period
for the Northeast. A four-month wet spell followed, but short-term
drought struck again during the following two months giving the
third driest July-August in the 108-year record.
|In the Southeast,
October 2001-May 2002 ranked as the seventh driest October-May in the
108-year record. Precipitation deficits in this region have been
much below the long-term mean for the last four years.
||On a statewide basis,
the Carolinas were the epicenter
of the 2002 drought in the Southeast. The states from Virginia to
Georgia had their driest August-July on record this year. The
extreme dryness of this period, coupled with the persistent dryness
of much of the last four years, resulted in a near-record dry
statewide Palmer Hydrological Drought Index for both North and South Carolina.
||Nebraska was the epicenter
of drought in the central Plains. Precipitation shut off over much
of the state beginning in December 2001, resulting in the driest
December-July in the 108-year record. In the southern Plains, Texas
was dogged by drought
in the Trans-Pecos region and
in Deep South Texas. While
other parts of the Lone Star State received abundant rainfall, Deep
South Texas (climate division 10) had the
driest September-August on record in 2002. The Trans Pecos
region (climate division 5) has been experiencing drought for much
last five years.
|The western United
States suffered from drought for much of the year. In north central Montana (climate
division 3), several years of subnormal precipitation culminated in
a Palmer Hydrological Drought Index that, by early 2002, had
reached the lowest levels seen in the last 100 years. With
duststorms swirling, local experts were comparing the parched
landscape to the Dust Bowl years of the 1930s.
||Dry conditions have
persisted in Wyoming since
1999. This prolonged dryness, coupled with record dry conditions
August 2001-July 2002, gave the state the driest Palmer
Hydrological Drought Index in the last 100 years.
|Colorado was another western state
hit hard by drought this year. The persistent dryness from
September 2001 to August 2002, aggregated across the state, was so
severe that, not only did it set a new record for September-August,
it broke the old record by a huge margin. Numerous seasonal records were set for the
state, including the driest
December-August. The unprecedented moisture deficits resulted
in a statewide Palmer Hydrological Drought Index that rapidly
reached record drought intensity.
occurred in the intermountain basin this year. On a statewide
basis, Utah received below
normal precipitation each of the first eight months of 2002, giving
the state the driest January-August in the 108-year record. This is
a marked departure from the unusually wet conditions that have
characterized much of the last two decades.