HR: 09:45h
AN: H21H-08    [Abstracts]
TI: The Forecast Paradigm is Changing - What Role Will the Forecaster Play?
AU: * Reynolds, D W
EM: david.reynolds@noaa.gov
AF: National Weather Service, 21 Grace Hopper Ave Stop 5, Monterey, CA 93942 United States
AB: The use of Numerical Weather Prediction (NWP) is now the fundamental starting point for all weather forecasts with valid times beyond 12 hours and in many cases 6 hours. This is a testament to the skill of numerical predictions today. Forecasters are inherently deterministic in there thinking and have been taught to provide specific forecast parameters or a small range in the forecast parameter with little emphasis as to quantifying the inherent uncertainty associated with any forecast. As such one of the main forecaster challenges today is to chose the "right" model for a given weather event. Most weather forecast offices have access to a multitude of numerical model solutions, some times dozens, especially when ensemble members are considered. For a forecaster at a Weather Forecast Office (WFO), it usually means choosing a model that has had the best track record over the most recent series of weather events. Some of the real challenges for the forecaster is maintaining an awareness of model bias since models change on the order of yearly instead of every 2 to 5 years as was true in the past. The forecaster must also be aware that depictions of mesoscale phenomena by high resolution numerical guidance may in fact simulate previously observed local phenomena but in fact be totally in error as the larger scale forcing may be in error. This is becoming a very big challenge for the WFO forecaster in the era of producing digital forecasts (Glahn and Ruth, WRF 2002). Here the forecaster is asked to produce 2.5 to 5 km sensible weather grids over their forecast area of responsibility at temporal frequencies of from 1 hour to 12-hour durations out through 7 days. There is no attempt to denote either the reliability of these forecasts or quantify the uncertainty associated with the forecasts. In fact each forecaster is required to collaborate with his/her neighboring offices to adjust the numbers to reduce incoherency of the particular forecast parameter. This philosophy flies directly in the face of two recent US Weather Research Program position papers on warm and cool season QPF studies, which proposes that probabilistic QPFs be the focus of the next 5 to 10 years and that ensembles should play a key role in this transition. We appear to have reached a plateau in our skill level in such forecasts as QPF that we may see only very minor improvements if the deterministic approach is continued. It must be recognized that if the forecast process transitions to a more probabilistic methodology, that the role of the forecaster, both at national centers and at the local office will change. In the digital forecast era, when statistical post-processing of ensemble output will provide both deterministic and reliable probabilistic forecasts, there is a question as to exactly what role, if any, the forecaster will have in producing value added sensible weather grids beyond forecast valid times of say 12 hours for use by the general public and for input to hydrologic models. This paper will try to provoke some thoughts on these issues.
DE: 3337 Numerical modeling and data assimilation
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting