Predicting hurricane landfall precipitation: optimistic and pessimistic views from the symposium on precipitation extremes

摘要

If the USWRP goal for 72-h quantitative precipitation forecasts in hurricanes is going to be achieved, it will require coordinated efforts by observationalists, modelers, and forecasters. One goal of the U.S. Weather Research Program (USWRP; Elsberry and Marks 1999) is to demonstrate the feasibility of numerical guidance that would allow 72-h quantitative precipitation forecasts (QPF) for hurricanes, thereby improving day 3 forecasts for inland flooding. This goal raises serious questions about thepredictability limit for tropical cyclone precipitation over the ocean, during landfall, and inland. The goal was thus a motivation for devoting a session of the Symposium on Precipitation Extremes to hurricane landfall precipitation. If the goal is a deterministic QPF over a small area, such as a watershed for a narrow valley, then some people are rather pessimistic about success. The National Oceanic and Atmospheric Administration (NOAA) National Weather Service Offices and River Forecast Centers issue warnings for flash floods in areas as small as 10-20 mile~2, or river floods in areas of 1000 mile~2. Clearly, rainfall has to be resolved on less than 1-mile scales for flash floods, and perhaps 5-mile scales for river floods. Furthermore, the recordrainfall rates of tropical cyclones are well known. Given this threat of flooding, what QPF guidance can be offered now, and what is necessary to improve that guidance? The USWRP's focus on hurricane landfall precipitation has already increased researchinto this topic. In addition to six invited papers and a wrapup panel with four invited presenters, 32 posters were accepted for presentation. By contrast, as recently as the 23d Conference on Hurricanes and Tropical Meteorology in 1999, only three papers were presented on this topic. This meeting summary will be a status report on the field, and will address the future requirements that were discussed at the panel session.