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<br /> <br />- 4- <br /> <br /> <br />John Henz, HDR - we maximize all storms used in this study. He mentioned that not all storms that are the e <br />'worst case' have been generated yet (ex: Big Thompson where surface dew points were extremely high). <br />The point was that the PMP employed a maximization of surface dew points that have been observed in the <br />recorded history of Eastern Colorado. He mentioned that the numerical forecast models can handle' general <br />precipitation' but there are difficulties encountered when thunderstorm-related precipitation is involved. Henz <br />also acknowledged that some improvements have been made in large storm modeling. <br /> <br />Ed Tomlinson, A W A - In response to John Liou stated that the defmition is not theoretical for PMP studies. <br />We need to go from a definition to a value to give to the engineers to get a PMF output. There is no model to <br />compute the theoretical PMP number. Assumptions need to be made and are made by the A W A, the NWS <br />and the World Meteorological Organization alike. If there are good storms on record for a region we can <br />analyze those storms, maxhnize those storms with more moisture available. We are conservative and we make <br />the worst assumptions with dew points; then we take that to increase the rainfall. We have to stick with the <br />accepted methodologies. If the procedure works and we get a bigger storm next week to add to the historical <br />list; we will most likely get a value near the theoretical PMP value; if we have a bigger storm tomorrow, the <br />previous maximum factor may be lower, but we may still get a number similar to the calculated PMP. <br /> <br />Lou Sclireiner, BOR - The NWS follows what Tomlinson is saying, but the NWS goes beyond to include all <br />generalized storms. We feel this is appropriate and we are probably more conservative. Both methodologies <br />are still storm based with storms that have occurred in the past. There are limits to what storms we use, like <br />A W A using local storms and the NWS using storms from across the eastern US. In the late 40s, the NWS was <br />commissioned to develop numbers that hydrologic engineers could use. Over the years, the NWS believes <br />that the best methodology is to go to the generalized reports. The Bureau, in the 50s - 70s, we went back to a <br />procedure similar to the A W A method, but in the 80s, we adopted the generalize reports because we thought <br />they were superior to the site-specific studies; the generalized report will give a more conservative values in a <br />the end. Mr. Schreiner added comments that all storms (spatially) applied by the NWS also goes through a ., <br />theoretical adjustment as well. In addition, he also mentions 'how much' data is 'realistic' in arriving at a <br />theoretical value as well. Over the years he believes that the best and most consistent methodology is to go <br />through 'general reports' . <br /> <br />Ed Tomlinson, A W A - there are models like the MM5 and the RAMs model that can produce rain on the <br />ground, but they are not certified and not totally consistent yet. <br /> <br />John Henz, HDR - We find the highest dew point values for a storm and don't assume another storm is <br />feeding off of that dew point between the storm and the dew point location. We use the highest dew points to <br />get the most maximum rainfall on the ground. We can use higher dew points and higher feeding winds; <br /> <br />Jack Byers, DWR - You mentioned other models that are being use; how do those compare and how far are <br />these models from being useful in this study? How do the 'new' models that simulate weather compare with <br />reality and how far are they from being useful? <br /> <br />Ed Tomlinson, A W A - The models aren't being run for this purpose at this time because there is no funding <br />right now; we would like to make that comparison. In Iowa some MM5 runs have shown that their procedures <br />might not be working well, but is that due to the model not being perfected yet. <br /> <br />Larry Lang, CWCB - The NWS has said they could start working on a theoretical model in about ten years <br />if they had the funding and the personnel. <br /> <br />John Henz, HDR - with this last snow storm, it was forecasted very well by the models, three days in _ <br />advance, we knew that we were going to get hit with heavy storm, but it was a general storm, local storms ., <br />cannot be modeled as well; the new models can get within 10% of reality for general storms; <br /> <br />Flood Protection? Water Project Planning and Finance? Stream and Lake Protection <br />Water Supply Protection 7 Conservation Planning <br /> <br />