19th Conference on Climate Variability and Change
AMS Forum: Climate Change Manifested by Changes in Weather


NCEP global ensemble based anomaly forecast

Yuejian Zhu, NOAA/NWS/NCEP/EMC, Camp Springs, MD; and Z. Toth

An NCEP Global Ensemble Forecast System (GEFS) was recently implemented to improve probabilistic forecasts. More importantly, the North American Ensemble Forecast System (NAEFS) has operationally generated products since 1200 UTC on May 30, 2006. Anomaly forecast by percentile is one of the NAEFS products made after a bias correction from the current analysis. Based on the NCEP/NCAR 40-year reanalysis, a daily climatological distribution (PDF) has been built up for 19 atmospheric variables such as height, temperature, winds, etc.. This anomaly uncertainty information allows users to create climatological percentiles that correspond to any percentile forecast value, such as 5 or 10 (low extreme), 50 (medium), and 90 or 95 (high extreme) bias corrected values. For example, a low extreme (5%) of the ensemble 2 meter temperature forecast could be much above climatological normals (or a high percentile), which indicates high probability of a high temperature extreme. This could be a heat wave in the Northern Hemisphere summer season if combined with high humidity. If downscaled from the current one by one degree forecast to 5 kilometer resolution by applying local climatology, this product could be a future part of the NDGD (National Digital Guidance Database) uncertainty information for users.

Joint Poster Session 2, Model Diagnostics and General Climate Variability (Joint with Climate Change Manifested by Changes in Weather and 19th Conference on Climate Variability and Change)
Monday, 15 January 2007, 2:30 PM-4:00 PM, Exhibit Hall C

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