Latest Seasonal Assessment -
July heat and dryness rapidly worsened conditions across the northern Plains and upper Midwest, resulting in drought
expansion across much of the region. The Outlook indicates that drought should largely continue in this region and
also southward into Texas as well. In contrast, the summer monsoon rains are likely to offer short-term relief to the
Southwest, Colorado, and southern Wyoming. Relief for water supplies will likely need to wait until next winterís snow
season, at the earliest, since snow melt is the major source for water in the West. Some improvement is also expected
in Wisconsin, Iowa, and Missouri, as well as the interior South. The best odds for improvement extend along the Gulf
Coast from Louisiana to northern Florida and into the southern Appalachians, as well as parts of southern Texas.
Tools used in the Drought Outlook included
the official CPC long-lead precipitation outlook for August-October, the drought termination and
amelioration probabilities for October, various medium and short-range forecasts and models such as the
6-10 day and 8-14 day forecasts and the soil moisture tools based on the GFS
model and the Constructed Analogues for the season.
Hot, dry weather resulted in major drought expansion and
intensification across the northern Plains and upper Midwest as anticipated when the Outlook was updated on July 7.
Although temperatures should tend to be above normal over parts of the northern Plains during the last half of
July, a repeat of the triple digit heat seen during the mid-July heat wave is not forecast. The 90-day temperature
outlook indicates a tendency for above-normal temperatures across the central and western states for
August-October, with equal chances for wet, dry, and normal across the central United States. Although there is no
strong signal for dry weather during August-October in the Plains states, the CAS (Constructed Analogues from Soil
moisture) suggests a tendency for dryness to persist from Texas to the Dakotas and Minnesota through the end of
October, while the CFS (Climate Forecast System) model leans toward below-normal rainfall in the southern Plains.
In short, further drought intensification and expansion may be on hold for the time being in the northern parts of
the drought region, but there are also few signs of major relief, so the odds lean toward drought continuation at
this time. Both short-term models and the CAS indicate greater odds for improvement in the western Great Lakes
region, so some drought improvement is depicted in the Wisconsin area and eastern Iowa into Missouri. In addition,
the drought amelioration probability data suggest relatively favorable odds for improvement in Wisconsin. The odds
lean slightly toward dryness for August-October in the Michigan-Indiana area, as shown in the new long-lead
seasonal precipitation outlook, but short-term moisture conditions seem sufficient to lower the risk for drought
development at this time.
The Southwest monsoon appears to be on course for normal
to above-normal rainfall this summer, based on the early start of the season, recent heavy rains, the negative
correlation with winter dryness, medium-range forecasts, and the August-October regression forecast from the
SWcast model produced at the Earth System Research Laboratory. The latter does show a signal for dryness in
southwest Arizona, so improvement is cut off for this area. No more than limited improvement is indicated in the
region due to the dependency on moisture from winter snowfall for water supplies. This means enduring drought
relief will tend to wait until next winter, at the earliest.
The first 2 weeks of the outlook period are expected to
see above-normal rainfall across the South, contributing to the improvement depicted in the Drought Outlook. Beyond
that period, there is much uncertainty, as the long-lead seasonal rainfall outlook indicates equal chances of wet
or dry outside of the Atlantic coast, which has a wet bias. Given the active Gulf of Mexico convection seen in the
near-term and the summer rainfall climate, the best odds for improvement appear to extend from Louisiana to
Florida. However, rainfall deficits for this year range up to 20 inches from southeastern Louisiana into the
Florida Panhandle, so drought eradication will be difficult absent a hurricane or tropical storm, and the path any
such storm would take is not known at this time.
The improvement shown for the Georgia to North Carolina
area is consistent with short-term forecasts for abundant rains in this area as well as some long-term models,
including the CFS. The drought amelioration probability statistics based on historical weather also support
drought improvement in Georgia, Florida, and South Carolina.
Elsewhere, Hawaii bears watching, as dry conditions have
been affecting the islands. Seasonal rainfall outlooks indicate equal chances of wet or dry, so no drought
development is indicated.