Modified U.S. Drought Outlooks to begin June 20

The Climate Prediction Center (CPC) submitted modifications in late March 2013 for the U.S. Drought Outlooks (DOs) to NWS Headquarters that were approved and will become operational after the standard 75-day review process. Major changes involve the replacement of the updated Seasonal Drought Outlook (SDO) with a new Monthly Drought Outlook (MDO), and the clarification of the drought outlook categories (e.g. Some Improvement and Improvement). The initial SDO, released the third Thursday of each month, will continue with the new drought outlook categories. The modified SDO and new MDO will become operational in mid-June, starting with the July-September 2013 SDO (released June 20) and the July 2013 MDO (released June 30).

The modifications to the DOs, particularly the MDO, were possible due to the improved skills of short- to medium-term forecasts (e.g. 6-10 day, 8-14 day, week 3) and dynamical models (e.g. NMME, IMME, CFSv2, etc.), along with the fact that droughts can develop and intensify on shorter time scales than 3-months, such as the 2012 Midwest Flash Drought. By producing a MDO at the end of each month instead of an updated SDO, it could be beneficial for short-term agricultural purposes, especially during the growing season. The initial SDO will still be disseminated on the third Thursday of the month, but there will no longer be an updated SDO released the following first Thursday of next month. Lastly, this new DO schedule mirrors the release of CPC’s 1- and 3-month Temperature and Precipitation Outlooks.

Changes were also made to the drought outlook categories. For the DOs, drought is defined as D1 or worse (based upon the U.S. Drought Monitor [USDM] categories of D0 – abnormally dry, to D4 – exceptional drought). Since the category of Some Improvement could be interpreted as either improvement or persistence (or a buffer zone between Persistence and Improvement) and therefore not scored in the verification of the SDO, it was replaced with Persistence, Improvement, or Removal. The new Removal category implies that drought (D1 or worse) will end (D0 or none) by the last day of the outlook period. The modified Improvement category implies at least a one category improvement in the USDM levels by the end of the period although drought still remains. The Persistence, Development, and No Drought categories remain unchanged.

Verification and skill scores of the new DOs will be made available on the CPC web page in the near future. The old initial and updated SDOs have been verified and skill scored using objective GIS techniques since late 2009 as compared to the USDM drought categories at the end of the DO period. For the location of the current SDO (either initial or updated) and additional SDO information on the CPC web page, refer to: http://www.cpc.ncep.noaa.gov/products/expert_assessment/seasonal_drought.html

The first map example depicts the new MDO produced on January 31, 2013 for February 2013, and the second map example shows the modified SDO produced on January 17, 2013, for the January 17-April 30, 2013 period. Both maps have the modified drought outlook categories incorporated.