89th American Meteorological Society Annual Meeting

Sunday, 11 January 2009
QPF Verification for the Alaska-Pacific River Forecast Center
Phoenix Convention Center
Richard, C. Lam, University of Oklahoma, Norman, OK
The Alaska-Pacific River Forecast Center (APRFC) produces 6-hourly QPF for the state of Alaska from May 1 to October 31 every day. In 2009, the APRFC plan on to automate the QPF process. Thus, it is important to evaluate the quality of the APRFC forecasters. Data from 2003 to 2007 are used to verify QPF for seven locations (Anchorage, Fairbanks, Homer, Juneau, Seward, Talkeetna, and Yakutat) in the state for the first 48 hours. In addition, bias and skill of the QPF produced by the APRFC forecasters are evaluated.

In general, forecasters have smaller forecast bias models. Most models and the APRFC forecasters tend to overestimate precipitation in Homer. On the other hand, they have a considerable negative bias for QPF in Yakutat. During the dry season in May, June, July, and October, QPF forecasts are likely to be overdone. In the wet season of August and September, however, QPF forecasts are likely to be underdone.

In summary, the APRFC staffs do provide additional values to the QPF forecasts. Forecasters are able to reduce the error by 20% to 35% in Anchorage and Homer. Error reduction of about 15% can be found in Fairbanks, Juneau, Seward, Talkeetna, and Yakutat. Selected individual models, such as the GFS and NGM, can further reduce the QPF error. This project will help the APRFC staffs to improve the forecast skills when they start to automate the QPF process in the summer of 2009.

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