87th AMS Annual Meeting

Wednesday, 17 January 2007
Forecast Performance of the New Local Three Month Temperature Outlook
Exhibit Hall C (Henry B. Gonzalez Convention Center)
Marina Timofeyeva, NOAA/NWS, Silver Spring, MD; and A. Bair, A. Hollingshead, R. E. Livezey, D. Unger, and H. C. Hartmann
NOAA's National Weather Service (NWS) introduced a new experimental local temperature outlook, in July 2006. This product, called the Local 3-Month Temperature Outlook (L3MTO), is the first in a series of local climate products planned for release by the NWS over the next 2 to 3 years. The product is available for 1160 locations nationwide and can be accessed via any NWS Weather Forecast Office (WFO) climate website (under the “Climate Prediction” tab, or the NWS Climate website http://www.nws.noaa.gov/climate/l3mto.php ).

The L3MTO is an extension of the national 3-month temperature outlook that NOAA's Climate Prediction Center (CPC) issues on the third Thursday of each month (http://www.cpc.ncep.noaa.gov/products/predictions/90day/ ), to a specific site. The L3MTO features the same information as the national 3-month temperature outlook, meaning the outlooks are provided for 3 categories (below, near, and above normal), and for the probability of exceedance. The difference is the L3MTO extracts more spatial detail, includes multiple presentation formats and supportive text for easier interpretation.

Forecast performance evaluation is essential to 1) guide the ongoing improvement in forecasting procedures, and 2) to guide users in assessing the potential usability of this product. To accomplish the first purpose, an extensive study was conducted on the overall L3MTO performance that included analysis using Continuous Ranked Probability Skill Scores (CRPSS), modified Heidke Skill Scores, and reliability diagrams. To accomplish the second purpose a forecast evaluation tool (http://fet.hwr.arizona.edu/ForecastEvaluationTool/), developed at the University of Arizona, is available via the L3MTO webpage. This user defined forecast evaluation tool provides multiple verification statistics for both national and local 3-month temperature outlooks. The analysis is available for user defined selection of any combination of 3-month periods and/or years during 1994 to the present. Overall, the study identified locations and 3-month periods with satisfactory forecast performance, and their spatial and temporal variability.

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