Discussion for the Seasonal Drought Outlook
Tools used in the Drought Outlook
included the official precipitation outlook for October 2008, the long lead forecast for October-December
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, evaluation of expected tropical
system activity, the CFS seasonal forecast of precipitation anomalies over the U.S. for Oct-Nov-Dec, and
The tropical weather systems that effected the CONUS have chipped away at the
edges of the drought areas over Texas and the southeast. Unfortunately the heaviest
precipitation from the tropical systems missed the core drought areas for both
of these regions. Currently the tropics have become much quieter and this is the main
reason the new drought outlook is much more pessimistic for improvement over the southeast.
Global models and MJO considerations suggest that the tropics will again become active
in about a week to ten days so this will have to be closely monitored. In the short range,
strong high pressure over the northwest Atlantic in combination with disturbances forming
on a frontal system off the southeast coast will cause anomalous easterly flow and
precipitation along coastal North Carolina. This is the main reason improvement is shown
over a small area of coastal North Carolina. The idea that tropical activity may once again
increase in the Atlantic over the next two weeks is a primary reason why areas of South Carolina,
Gerogia and Alabama are depicted as showing some improvement. The drought areas of eastern Tennessee,
southwest North Carolina, southeast Kentucky, and Southwest Virginia are less likley to be
impacted by tropical systems and are forecast to have drought persist.
Confidence for the Southeast and mid-Atlantic: Moderate
Rainfall associated with a frontal system and the remnants of Pacific Tropical Storm Lowell
brought some relief to western Texas while rainfall associated with Hurricane Ike did the same
for eastern Texas. Recently global models have suggested tropical system development in the
western Gulf of Mexico, although the very latest runs have backed off of this idea.
Even in the absence of an organized tropical system anomalous easterly flow suggests that
coastal sections of southeast Texas would receive beneficial rainfall to alleviate drought.
For this reason an area of improvement is indicated over southeast coastal Texas. Further
inland, HPC forecasts no rain over the area in the 1-5 day period. Medium and longer range
forecasts have near normal or equal chances over interior Texas, and soil moisture anomaly change
tools show worsening conditions. For these reasons the drought area over interior Texas is forecast
Confidence for Texas: Moderate
Over the mid-West, the patchy areas of drought saw some relief from precipitation associated with the
remnants of hurricane Ike. Light precipitation is expected over these areas in the 1-5 day period. Medium
range forecasts indicate near to above normal precipitation for the region while longer range forecasts
have equal chances for this region. Soil moisture anomaly changes show worsening conditions while
the seasonal CFS precipitation forecast for Oct-Nov-Dec indicates wet as the most likely category for the region.
For these reasons areas of some improvement are indicated over the mid-West.
Confidence for the mid-West: Moderate
In Colorado recent rains have eliminated the drought area near Denver. Drought is ongoing
over eastern Colorado/southwestern Kansas. Little rain is expected for days 1-5 while medium and longer
range forecasts show near normal precipitation or equal chances for above/below. Soil moisture anomaly
change indicators are mixed and weak. The seasonal CFS precipitation forecast for Oct-Nov-Dec shows a slight tilt of
the odds towards drier than normal. For these reasons an area of some improvement is indicated.
Confidence for eastern Colorado/southwest Kansas: Moderate
The Northern Plains has received some beneficial rains over the last 30 days. Light precipitation is
forecast over the area in the 1-5 day period. Above median precipitation is forecast over the area
for the 6-10 day and 8-14 day periods. Current 30 day and 90 day forecast have equal chances for
above or below normal precipitation. Soil moisture change charts show a mixed signal with some
suggestion of worsening conditions. The seasonal CFS precipitation forecast for Oct-Nov-Dec shows near to above normal as the
most likely categories for precipitation for the region. For these reasons the current drought area indicates some
improvement over the area.
Confidence for the Northern Plains: High
Over the west little precipitation has fallen recently as this is climatologically a dry time
of year. Some precipitation is forecast over Northern California during the 1-5 day period. The 6-10 day
forecast indicates near normal precipitation over Northern California while the 8-14 day forecast shows
above normal precipitation. Medium and longer range forecasts generally show warmer and drier than normal
conditions for Southern California. Palmer drought indicator probability forecasts show a high probability of
improvement for Northern California. For these reasons an area of improvement is indicated over Northern California,
an area of some improvment is shown for central California and an area of persist is progged for Southern
California and Southern Nevada.
Confidence for the west: Moderate
In Hawaii, the eastern section of the Big Island and all of Lanai are now in D1 drought. The current forecast
indicates that these areas will persist.
In Puerto Rico, recent rains associated with tropical systems have eliminated the drought region for the island.