Climate of 2005 - May
U.S. Regional Drought Watch

Regional Overview

The May precipitation pattern at the primary stations in Alaska was mixed and mostly drier than average for Hawaii. In Puerto Rico, the precipitation signal was mixed during May, based on National Weather Service radar estimates of precipitation. May streamflow averaged near normal for Puerto Rico and dry for the Hawaiian Islands.

Long-term moisture deficits persisted in many areas. Six-month dryness was evident for parts of the Northwest, South and Southeast. The Pacific Northwest has experienced a dry winter followed by a wet spring, though spring excesses did not significantly ease six to seven years of precipitation deficits.

The southwestern U.S. has been very wet during the winter and spring though long-term deficits remain across parts of the Southwest and West, and much of the central to northern Plains. These are reflected in the end of May U.S. Drought Monitor map. The Southwest has recovered at the 12 to 24 month timescales, but still shows dryness in some parts at the 36 to 60 month timescales.

Parts of the central U.S. have been persistently dry for the spring, with states from Texas to Pennsylvania showing dryness at the 3-month timescale. Both Michigan and Illinois ranked 3rd driest on record for the spring.

Some regional highlights:

• Seven states had the tenth driest, or drier, spring (March-May) on record.
• Six states had the tenth driest, or drier, May on record.
• End-of-month and month-averaged soil moisture conditions were drier than normal across parts of the northern Rockies and northern High Plains, the central Plains, the Pacific Northwest, and the Lower Mississippi Valley, based on model computations (CPC-1, CPC-2, MRCC). The models also indicated dry soil moisture conditions in eastern Alaska and near the surface and at depth across parts of the central Plains to the Great Lakes.
• Streamflow levels were below seasonal norms across northern parts of the Pacific Northwest, northern Rockies, and parts of the Lower Mississippi Valley and southern Plains, both as computed by models and based on USGS observations.

These overall conditions are evident in the following indicators:

• Palmer Drought Indices,
• Standardized Precipitation Index,
• long-term (36 to 60 month) percent of normal precipitation maps,
• airport station percent of normal precipitation maps,
• statewide precipitation rank maps,
• Cooperative station percent of normal precipitation maps,
• satellite-based observations of vegetative health,
• National Weather Service model calculations of
  • soil moisture,
  • runoff,
  • evaporation,
• National Weather Service model calculations of soil moisture using the Leaky Bucket Model,
• Midwest Regional Climate Center model calculations of soil moisture,
• percent of average maps for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center
  • hydrologic year precipitation
  • snow water equivalent of snowpack,
• streamflow maps maintained by the USGS.

A detailed review of drought and moisture conditions is available for all contiguous U.S. states and the nine climatological regions:

REGIONS:

• In contrast to the sharp north-south gradient in moisture receipt during the winter for the West, the spring saw above-average precipitation fall across much of the western U.S. However, snow water content in the Northwest still reflected the lack of winter precipitation. Basin-averaged end-of-May snowpacks in parts of central California and Utah remained above average, contrasting with snowpacks in Oregon, Washington, Idaho, Montana and Wyoming. This pattern is also apparent in basin-averaged water-year-to-date precipitation anomalies.

Additional Contacts:

For additional information on current and past wildfire seasons please see the National Interagency Fire Center web site or the U.S. Forest Service Fire and Aviation web site.

NCDC's Drought Recovery Page shows the precipitation required to end or ameliorate droughts and the probability of receiving the required precipitation.

Additional climate monitoring graphics can be found at the Climate Prediction Center's monitoring pages:

• Weekly, Monthly, 3-Month, 12-Month Monitoring
• El Nino, Drought, Snow Cover, and Degree Day Monitoring
• Weekly Drought Monitoring
• Soil Moisture Monitoring

Precipitation and modeled soil moisture anomaly maps for the Midwest U.S. can be found at the Midwest Regional Climate Center's monitoring page.

Drought conditions on the Canadian prairies can be found at the Agriculture and Agri-Food Canada Drought Watch page.

• For all climate questions other than questions concerning this report, please contact the National Climatic Data Center's Climate Services Division:
  Climate Services Division
  NOAA/National Climatic Data Center
  151 Patton Avenue
  Asheville, NC 28801-5001
  fax: 828-271-4876
  phone: 828-271-4800
  email: ncdc.info@noaa.gov
  
  
  
• For further information on the historical climate perspective presented in this report, contact:
  Richard Heim
  NOAA/National Climatic Data Center
  151 Patton Avenue
  Asheville, NC 28801-5001
  fax: 828-271-4328
  email: Richard.Heim@noaa.gov
  
  
  -or-
  
  
  Jay Lawrimore
  NOAA/National Climatic Data Center
  151 Patton Avenue
  Asheville, NC 28801-5001
  fax: 828-271-4328
  email: Jay.Lawrimore@noaa.gov