Latest Seasonal Assessment -
At the beginning of the period, heavy to excessive rainfall associated with Fay and its remnants will reduce
drought across parts of the Southeast. With forecasts of above median rainfall in the short- and medium-range and
the monthly outlook along with the increased odds of additional tropical systems, improvement is forecast across
the Southeast. Moderate to severe drought has recently spread into Virginia, but forecasts on most time scales
favor improvement. Although drought intensified in northern Louisiana during early August, ongoing rainfall
should alleviate drought conditions. Since late July, Colorado, Oklahoma, and Texas have experienced drought
relief and further improvement is forecast. Drought improvement is also forecast for the small areas of moderate
drought in Minnesota. Across the Great Lakes, short-term drought development is possible due to initial
conditions, but long-range forecasts are noncommittal. Therefore, no drought development is depicted on the
outlook map. A small area of drought development is forecast for northern Montana with improvement forecast for
North Dakota. Across the West, the onset of the wet season during the fall should gradually result in improvement
across northern California. However, in southern California and the Great Basin, persistence is forecast since
potential improvement is not expected until later in the winter. No changes were made to the previous outlook
regarding the Hawaiian Islands where expanding drought is forecast in some leeward areas and improvement is
expected over windward locations on the Big Island.
Discussion for the Seasonal Drought Outlook
Tools used in the Drought Outlook included the
official precipitation outlook for September 2008, the long lead forecast for September-November 2008, various medium-
and short-range forecasts and models such as the 6-10 day and 8-14 day forecasts, the soil moisture
tools based on the GFS model and the Constructed Analogue on Soil (CAS) moisture, the CFS seasonal
precipitation forecasts, and climatology.
Drought improvement across the Southeast is
weighted heavily towards the effects from Fay, the CPC medium-range forecasts, and the CPC September
precipitation outlook. Early in the period, tropical cyclone Fay or its remnant low are currently projected
to track slowly west near the Gulf Coast. Heavy to excessive rainfall will alleviate drought, but the exact
location remains unclear. The most likely areas for improvement are Alabama and southern Georgia. Additional
tropical systems could bring substantial relief, but where exactly that will occur is unknown. It should be
noted that hydrological drought indicators such as large reservoirs and groundwater will respond more slowly
than small streams, soil moisture, and pasture conditions. As water demands decrease later in the fall,
reservoir levels should show gradual improvement. Lake Okeechobee levels in Florida continue to rise.
Following Fay’s rainfall across the Florida peninsula, Okeechobee will increase further.
Confidence for the Southeast: High
In Texas, a pair of tropical cyclones, Dolly and
Edouard, along with an upper-level low have reduced drought since late July. However, extreme drought
continues in south-central Texas. Monsoonal rainfall has eliminated drought in southern New Mexico as
forecast in previous outlooks. During the remainder of August, wetter than normal conditions, as depicted in
the CPC 6-10 Day outlook, should continue in coastal Texas and Louisiana. The CPC seasonal outlook calls for
equal chances of above, below, or near normal precipitation. Improvement is expected across east Texas,
coastal Texas, and Louisiana with prospects of improvement decreasing slightly across west Texas.
Confidence for the Texas and Louisiana: Moderate
In Colorado, western Nebraska, and the western
Oklahoma panhandle, drought relief and localized flooding has occurred during the past two weeks. Monsoon
rains typically continue into September, but precipitation decreases in October and November. With expected
convective rainfall during the next five days, some improvement or improvement is forecast.
Confidence for the central and southern high Plains: Moderate
During early August, two small areas of drought
have developed in Minnesota. Forecast tools provide a mixed picture for relief prospects. With the Coupled
Forecast System leaning wet in this area for the September-November 2008 period, improvement is forecast.
Confidence for Minnesota: Low
There were a few changes to the previous outlook
for North Dakota and Montana, with improvement forecast in North Dakota and a small area of development in
northern Montana. Climatology and initial conditions favor the development area in northern Montana, while
short- and medium-range forecasts favor improvement in North Dakota.
Across the West, the beginning of the wet season
in the fall should lead towards some improvement across northern California. Although rain and mountain snow
increase later in the fall, it will take time to build a snow pack in the Sierras. Early in the period,
a series of unseasonably, deep troughs will bring moderate to locally heavy precipitation amounts to the
Pacific Northwest. Due to precipitation in the short-term and the onset of the wet season this fall,
development previously depicted in the outlook dated August 7 has been removed from the Pacific Northwest.
In southern California, persistence is predicted as precipitation typically does not significantly increase
until the winter.
Confidence for the West: High
In Hawaii, no changes were made to the previous
outlook with development forecast in some leeward areas and improvement forecast in windward sides of the
In Puerto Rico, climatology and prospects for
abundant tropical rains in coming weeks continue to suggest drought improvement.