Discussion for the Seasonal Drought Outlook
Tools used in the Drought Outlook included the
official precipitation outlook for November-January, 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, and climatology.
The Drought Outlook calls for limited improvement over the
interior Southeast, especially within the next two weeks, as several upper-level troughs approach
this region from the west. Beneficial showers will help offset low streamflow
values and groundwater levels. The official CPC November-January 2008/09
precipitation forecast calls for below average rainfall across this region in
the longer term. Drought is expected to develop across northern portions of
peninsular Florida during the next several months. In stark contrast, the CAS
soil moisture tool indicates wetter than normal conditions for northern parts
of peninsular Florida, with relative dryness over Alabama, and the middle
Atlantic coast, but this solution appears to be the outlier. Improving drought
conditions are also forecast across the Ohio/Tennessee Valley area, with this
region being within the mean storm track.
Confidence for the Southeast: Moderate
In south-central Texas, rainfall has been on the light side for
the past 30 days, with more significant rainfall totals recorded over the northern half of the state. The drought is
expected to persist across south-central Texas, which is consistent with CPC's official November-January 2008-09 seasonal
precipitation forecast, and CPC's 30-day forecast for November in this area. Drought may expand even further south into
Texas. Improvement is expected further north however, for central Oklahoma and the southeast corner of Colorado.
Confidence for south-central Texas: Moderate
In North Dakota, predicted precipitation amounts range from 2.5
inches in eastern parts of the state to about half an inch near the Montana border, according to the latest HPC 5-day QPF
forecasts. This is attributed to passing low pressure systems and their associated fronts. Observations during the past 30
days show that western North Dakota has received between 1.0 and 2.5 inches of precipitation, with the heavier amounts as
expected over the eastern half of the state. The Drought Outlook now calls for improvement over this drought area, given the
short-term forecast and the wet November-January forecast from the CFS.
Confidence for North Dakota: Moderate
The proximity of the upper Great Lakes region to the climatological
storm track should result in significant drought improvement across that area. Much of the expected improvement is likely
during the first few days of the Outlook, as a deep low pressure system moves across the area.
Confidence for upper Great
Lakes region: High
In the West, with the wet season well underway, continued
improvement is anticipated across northern California, even though in the next two weeks the main storm track and associated
jet stream will be further north across Washington and Oregon. Some improvement is forecast over the central third of
California and northwestern Nevada, while drought is likely to persist from southern California northeastward across much
of central and eastern Nevada. Drought may expand into west-central Arizona during the period. The updated CPC November
monthly precipitation forecast made at the end of October shows a tilt in the odds for above average along the West coast
from Washington through northern California, and below average rainfall for the southern third of California and extreme
Confidence for Western US: High
For the Hawaiian Islands, some improvement in the drought is
expected during the November-January 2008/09 period. With the climatologically wet time of year approaching for this area,
it seems reasonable to improve the drought conditions from persistence to at least some improvement.