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Drought Termination and Amelioration

Ending a hydrological drought requires that recharge, demand, and runoff moisture levels have been brought back to normal or above normal.

Many factors affect the amount of precipitation required to end (terminate) or reduce the severity of (ameliorate) a drought:

  • Climatology: The typical conditions that a region experiences during each month and season of the year are a factor. Given a drought of equal magnitude in a dry and wet climate, the wetter region requires more precipitation to end the drought.
  • Season: The season in which the precipitation falls can also greatly influence the quantity of precipitation required to end a drought. During a typically moist month (such as those experienced in the winter and spring along the West Coast) more precipitation may be required to end a drought than during the typically dry months of the summer.
  • Soil Moisture: Because soil moisture conditions are generally lower in the dry months, the precipitation needed to bring soil conditions back to normal may be less than that required to return soil moisture conditions to normal during a generally wetter season.
  • Duration: Regardless of a region's climate, over a sufficiently long period of time, near-normal precipitation is often sufficient for ending a drought with moisture conditions gradually returning to normal.

Source: National Centers for Environmental Information
 

Drought Recovery – Valid June 2019

Next update scheduled for September 2019Map showing the precipitation needed to end Drought Conditions in 1 Month: 9-13 inches in the Pacific Northwest, 5 inches in western New Mexico, 5 inches in northern North Dakota, 7 inches in eastern Georgia and southern South Carolina, and 15 inches along the coastline of eastern Florida.

  • As of the end of May 2019, much of the United States does not require any additional precipitation to end a drought – owing to the general lack of drought east of the Rocky Mountains.
  • In the western U.S., parts of Oregon and Washington states were most in need of precipitation, with most areas needing 5-10” of rain in the next month to end the current drought.
  • Parts of South Carolina and eastern Georgia are also in drought and would need 15-20” of rain during the summer months to end the drought.
  • Long-term climatology suggests low probabilities for ending the western drought in the next three months, with odds at less than 1% of reaching these rainfall amounts in all areas. Meanwhile, probabilities are around 25% for eliminating the drought in the eastern U.S. by the end of August 2019.

 

Drought Outlook – Valid for June - September 2019

Next update scheduled for September 2019

  • Drought is expected to persist and perhaps worsen over far northwestern Washington and Oregon states through the period. Coastal Carolina’s are also expected to remain dry.
  • Some drought development is possible on the Big Island of Hawaii through September 2019, with drought removal likely across the four corners region and into northern New Mexico.
  • Much of the central U.S. corn belt region is expected to remain wetter than normal through the summer 2019 season. A broad wet signal also extends along the Ohio River into the Mid-Atlantic states.
  • Reduced evaporative demand is favored for much of the Great Plains, from the Dakota’s south to Texas. Southern Gulf Coast states may see enhanced evaporative demand through August.

Projected PHDI for September 30, 2019. The northwest and southeast should negative (dry) values while the midwest and northeast show positive (wet) values. 1-month EDDI map for June 18, 2019 showing wetness categories in the Plains and Great Lakes regions, while the Northwest, Mid-Atlantic, and Southeast regions are in drought categories.

 

Drought Termination and Amelioration Tools

Thumbnail of Current Drought Reduction Tool
Maps and data of precipitation, associated probabilities, and percent of normal precipitation needed to end or ameliorate drought as it currently exists across the Contiguous U.S.
Thumbnail of the Projected PHDI Map
Maps of Projected Palmer Hydrological Drought Index (PHDI) created by calculating when a drought will end based on precipitation needed by using a ratio of moisture received to moisture required to end a drought.
Thumbnail of a Evaporative Demand Drought Index map
The Evaporative Demand Drought Index (EDDI) is an experimental drought monitoring and early warning guidance tool. It assesses the "thirst" of the atmosphere utilizing physically-based evaporative demand driven by near-surface temperature, wind speed, humidity, and solar radiation.