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Climate Prediction Center

 
 
 

November 2008 - January 2009

 

Latest Seasonal Assessment - During the next few months, northern portions of the country are more likely to experience significant drought relief compared to southern portions of the country. In the West, improvement continues to be indicated for northern California, even though in the short-term Pacific storms are likely to be steered into Washington and Oregon. Drought is forecast to develop across west-central parts of Arizona, as well as over southern Texas and northern peninsular Florida. The persistent drought over south-central Texas is expected to continue, though significant rains should fall just east of this area. In the Southeast, some improvement is indicated for a large area, though it is unclear as to how much rain may fall over southern portions of this area. The expectation of several troughs moving through the region in the short-term makes it very risky not to go with at least some drought relief for central Georgia and central South Carolina. In the longer term, however, there is a pronounced tilt in the odds for drier than average conditions across the Southeast US, as indicated by CPC's long-range forecasts. At least a one-category improvement is expected across the upper Midwest/Great Lakes region due to the proximity of the climatological storm track, and significant short-term precipitation is also anticipated over western North Dakota extending into eastern Montana. In Hawaii, the latest seasonal forecasts from CPC show EC (equal chances) for below-, near-, and above average precipitation, and we are entering a wetter time of the year for the Islands. Therefore, some improvement is now indicated for this area.

 
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 southern Nevada.
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.

 

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Page Author: Climate Prediction Center Internet Team
Page last modified: October 2, 2008
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