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Public Information Notice 17-05 Updated

National Weather Service Headquarters Silver Spring MD

1000 AM EST Fri Feb 10 2017


To:       Subscribers:

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS partners and NWS employees


From:     Jon Gottschalck

          Chief, Operational Prediction Branch


Subject:  Updated: Climate Prediction Center changing to

          grid-based historical data for production of the

          Degree Day Outlook Product beginning with the

          March 16, 2017, issuance


Updated to add link to current product:


A sample of the new product (with the same valid dates as the

current product) is available at


The National Centers for Environmental Prediction (NCEP) Climate

Prediction Center (CPC) is accepting comments until March 3,

2017 on an update to the Climate Prediction Center monthly

degree day outlooks. 


The outlooks are available at


Heating and cooling degree days are derived quantities based on

daily mean temperatures that are used to estimate weather-

related energy consumption.  Seasonal and monthly degree day

totals are closely related to the seasonal mean temperature

making it possible to use the CPC seasonal temperature outlook

to produce an outlook for monthly degree day totals.  Regional

degree day totals are generally based on population-weighted

averages (rather than area-weighting) over geographic areas.

Statistics based on historical data (1961 - 2010) were used to

estimate the relationship between the monthly and seasonal mean

temperature and degree day totals.  These statistics are applied

to the CPC Probability of Exceedence temperature outlooks to

obtain a probabilistic estimate of degree day totals. 


The historical data for both temperature and degree days are

based on the climate division (CD) data from the National

Centers for Environmental Information (NCEI).  Until recently

the NCEI based its CD data on regional station averages.  The

NCEI recently developed methodology to more accurately estimate

climate division averages based on terrain adjusted gridded

analysis of station data.  The modern methodology was applied to

historical data, and the NCEI replaced the station-based CD data

with the more accurate grid-based CD data in 2014.  More

information on the NCEI data sets can be found in the following



The grid-based CD data is, in general, slightly cooler than the

station-based data, leading to substantial differences in the

30-year normals of both temperature and degree days.  This

required that the CPC degree day outlook be adjusted to be

consistent with the new population-weighted degree day outlooks

available from the NCEI. 


Beginning with the forecast issued on the third Thursday in

March 2017, the revised Degree Day Outlook based on grid-based

NCEI data will replace the current station-based degree day

product. The impact in the anomaly forecast is minor, but the

monthly degree day totals and their climatological values can be

substantially different from the existing product.


Send comments to:

   Matthew Rosencrans

   Head of Forecast Operations, Climate Prediction Center

   College Park MD 20740


For more information, please contact:

   Jon Gottschalck

   NWS NCEP CPC Operational Prediction Branch

   College Park, MD 20740


National Public Information Notices are online at: