Tools used in the Drought Outlook included the
official CPC precipitation outlook for March 2009 and the long lead forecast for March – May 2009,
the four-month Palmer drought termination and amelioration probabilities, 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 Climate Forecast System
seasonal precipitation forecasts, and climatology.
The recent Pacific storms brought beneficial
moisture to drought-affected California, and more relief is on the way. The storm forecast for the first
weekend of the valid period (February 21-22) should bring over 2 inches of precipitation to the Sierra and
northwestern parts of the state. The previous storm delivered widespread 2 to 7 inches, boosting streamflows
and mountain snow pack. The official 6-10 day and 8-14 day forecasts indicate above-normal precipitation for
much of the state. The Drought Outlook shows improvement where the expected precipitation amounts in the
first two weeks of the forecast period are highest, and where the seasonal forecast models show less chance
of a return to drier weather during March-May. Nevertheless, it is important to point out that the expected
improvement is unlikely to end the hydrological drought affecting the state. The largest reservoirs showed
storage levels on February 17 ranging from 44 to 83 percent of normal, and just 30 to 49 percent of capacity.
With the major reservoirs less than half full, it would be difficult to get enough moisture before the dry
season begins to fill the reservoirs. Another concern is the March-May precipitation forecast, as the
majority of the dynamic models indicate below-normal precipitation across the southern half of the state.
This is one reason for depicting persisting drought across southern California.
Forecast confidence for California: Moderate
Improvement elsewhere in the West could be more
difficult, although the water supply situation is not as serious as in California. The expected storm track
during the first 2 weeks is sufficient to bring at least some improvement for the northern Great Basin, but
the official CPC 3-month precipitation outlook tilts the odds toward below-normal totals from eastern Nevada
toward the southern Plains.
Confidence for the Great Basin and Intermountain region: Low
The small drought area in southeastern Colorado is
switched from some improvement to persist because the forecasts for all time periods from 5 days to 3 months
are dry. In the same vein, forecasts from short term to seasonal time periods indicate below-normal rainfall
for Texas and New Mexico, so the Outlook continues to depict drought expansion westward into New Mexico.
Expansion into the Texas Panhandle is more muted because both recent moisture and heavy rain in August and
October make it more difficult for drought to develop, as indicated by the University of Washington Ensemble
Streamflow Prediction models, which show relatively low odds for development in the Panhandle. Despite some
indicators not showing imminent drought, winter wheat is in poor condition. Given the continuing La Niña into
late winter or early spring and warm and dry forecasts, the area from Texas northward into western Kansas
needs to be monitored.
Confidence for the southern Plains: High
Medium-range forecasts and climatology favor
improvement for the small drought areas in Montana and the long-term drought in northern Wisconsin and
adjacent Michigan. The area shown as some improvement in the prior Outlook changed to straight improvement
in this forecast due mainly to the expected storm track and the spring climatology. The NCDC Palmer drought
amelioration maps indicate better than a 60 percent chance for amelioration by the end of May.
Confidence for the Upper Midwest: Moderate
The latest CPC monthly and seasonal forecasts show
the odds tending toward dry for the South and Southeast, and persistence is indicated for the scattered
drought areas in those regions. Near-normal rainfall is forecast for the first 2 weeks of the period, so
there may be temporary improvement.
Confidence for the South and Southeast outside of Florida: Moderate
The long-term drought in the northern
Georgia-western Carolinas area has not gone away despite some beneficial moisture this winter. Short,
medium, and long range forecast models show a wet-to-dry transition from the Ohio Valley toward the South
Atlantic coastal plain. Improvement is shown for eastern Tennessee to reflect these forecasts, with more
limited improvement in the western Carolinas and northeast Georgia.
Confidence for the Appalachians: Moderate
Florida has seen some periods of rain in recent
weeks, but the overall trend has been toward increasing dryness, especially in the southern Peninsula, where
impressive dry season rainfall deficits have developed. With medium range, monthly, and seasonal forecasts
all pointing toward below-normal rainfall, the Outlook continues to depict persisting and expanding drought
across the Peninsula and into southeastern Georgia. Wildfire danger could become a major concern before the
onset of the wet season if these forecasts are correct.
Confidence for Florida: High
In Hawaii, the Outlook continues to indicate
improvement due to seasonal forecasts and climatology. A few seasonal dynamic models show below-normal
rainfall over the southern islands, and this decreases the confidence levels to some extent.
Confidence for Hawaii: Moderate