FINAL REPORT Phase One FS Agreement Number: 03-JV-11222046-077 Cooperator Agreement Number: 2477 Evaluation of a New Dead Fuel Moisture Model in a Near-Real-Time Data Assimilation and Forecast Environment between Oklahoma State University (Stillwater, OK) and the Fire Sciences Laboratory, Rocky Mountain Research Station, USDA Forest Service (Missoula, MT) Dr. J. D. Carlson July 13, 2004 This final report will not repeat the earlier discussions found in the two interim progress reports of September 15, 2003 and February 10, 2004. In those reports we discussed the following: the coding and implementation of the Nelson dead fuel moisture code onto the Oklahoma Mesonet system; the problems resulting from using different time steps of weather information (15 minute vs. hourly); revising the code for rainfall rate rather than amount; testing the Nelson model against observed dead fuel moisture (DFM) from Slapout, OK from 1996-97; determining optimal model parameters for 15 minute and hourly data; the operational methodology in running the Nelson model on a real-time network of 116 weather stations; incorporation of the Nelson model into the operational Oklahoma Fire Danger Model; and initial work on running the Nelson model using 84-hour NCEP Eta model output. Details will not be repeated here. The current report summarizes and extends the analysis presented by me during a visit of Larry Bradshaw and Pat Andrews (Fire Sciences Lab, Missoula, MT) to the Oklahoma Climatological Survey in Norman, OK on May 14, 2004. During that meeting, among other things, results from an analysis for the calendar year 2003 were given, comparing Nelson model DFM values (using 15-minute Mesonet data) with those calculated by the current Oklahoma Fire Danger Model using National Fire Danger Rating System (NFDRS) algorithms. A. Introduction to the Analysis The Nelson DFM model was run for the entire calendar year 2003 using 15- minute Mesonet data and the model parameters associated with that weather-data time interval (Table 1, 2/20/04 Progress Report). Output for 1-hr, 10-hr, 100-hr, and 1000-hr DFM was produced and compared to NFDRS DFM output for the same year. For purposes of analysis, eleven Mesonet sites were selected to give wide geographical (and climatic) coverage and also to represent areas near historical fire
regions in Oklahoma. Figure 1 (below) shows the location of these 11 sites along with the 2003 rainfall at each site. Figure 1. Location of 11 Mesonet sites chosen for the analysis. Rainfall amounts for 2003 are indicated. While statistics will be shown for all 11 sites, graphs will only be presented for 3 sites for sake of brevity: Boise City (BOIS), Foraker (FORA), and Mt. Herman (MTHE). Boise City was chosen as it represents the driest portion of the state (climatologically speaking and in 2003 as well); Mt. Herman represents the humid, wet southeastern portion of Oklahoma; and Foraker, located in the tallgrass prairie region of Oklahoma, had an unusually wet year, climatologically speaking. We will proceed as follows. First, we will present graphs for NFDRS DFM at the three sites for 2003, followed by graphs for Nelson DFM at these sites. Next, we will graphically compare Nelson to NFDRS for all four DFM classes at these sites in 2003. We will then look at scatterplots of Nelson DFM versus NFDRS DFM, and present some elementary statistics comparing the Nelson and NFDRS DFM at all eleven sites. Following these discussions, we will look at some special cases: a several-day heavy rain event during the summer and a dry period as well. Finally, we will look at how Nelson compares to NFDRS at certain times of the day: 0500 CST, 1300 CST, and 1700 CST. All graphs and tables are presented in the Appendix. 2
B. NFDRS Dead Fuel Moisture in 2003 Figure A1 in the Appendix presents three graphs of NFDRS dead fuel moisture in 2003 at the three sites BOIS, FORA, and MTHE. One-hr DFM is depicted in brown, 10- hr in orange, 100-hr in light green, and 1000-hr in dark green. Dead fuel moisture is in % on the y-axis and hour of the year (GMT) on the x-axis. Hourly DFM is plotted. In the Oklahoma Fire Danger Model, NFDRS dead fuel moistures are updated hourly for 1-hr and 10-hr fuels, while 100-hr and 1000-hr DFM are updated once a day at 2200 GMT (1600 CST). As would be expected, note how DFM for 1-hr fuels is the most dynamic, changing in direct response to weather conditions, followed by 10-hr, then 100-hr and 1000-hr. Note how 1-hr and 10-hr fuels are confined between about 1% and 27%, never going higher even during rain events (not shown). These algorithms were developed for dry conditions and rainfall is not a variable for these size fuels. This stands in contrast to the Nelson model, where rainfall permits DFM values to climb much higher for both sizes of fuels. At the FORA and MTHE sites, 100-hr and 1000-hr DFMs actually rise higher than 1- and 10-hr DFM during certain times of the year - to values at or above 30%. Finally, note how the 1000-hr DFM generally lies above the 100-hr DFM at all three sites, although the amplitude of its changes is generally less than that of the 100-hr DFM. C. Nelson Model Dead Fuel Moisture in 2003 The Nelson model was run for 2003 using 15-minute Mesonet data. DFM values for each size fuel were initialized on January 1, 2003 with the DFM values given by the Oklahoma Fire Danger Model (NFDRS algorithms). Figure A2 shows the DFM behavior of the four timelag fuels at the three Mesonet sites. The same color scheme is used as in Figure A1. As with NFDRS, the 1-hr fuels are more dynamic, followed by 10-hr, 100-hr, and then 1000-hr. However, in contrast to NFDRS, the 1-hr and 10-hr fuels are allowed to reach much higher DFM values during wet periods (not shown). The Nelson model has a built-in maximum of 85% for 1-hr fuels and 60% for 10-hr fuels, which one can see on the graphs are values often reached (such high values are confirmed by actual observed DFM at Slapout during 1996-97). Occasionally 100-hr values reach 30% or higher as with NFDRS, but 1000-hr values generally are lower than those of NFDRS and the 1000-hr DFM trace is generally at the lower end of the 100-hr DFM trace, in contrast to NFDRS where it is usually higher than the 100-hr trace. 3
D. Nelson Model versus NFDRS Dead Fuel Moisture in 2003 In this section we will compare the Nelson DFM behavior with that of NFDRS for each timelag fuel class. We ll start with 1-hour and conclude with 1000-hr. Figure A3 presents the comparisons between Nelson and NFDRS for 1-hour timelag fuels at the three Mesonet sites. The left vertical axis and x-axis are the same as before, but in addition, hourly rainfall (mm) is added, which is shown on the right vertical axis. Nelson DFM appears in green, NFDRS DFM in orange, and rainfall in blue. Hourly values for both Nelson and NFDRS are plotted. Even though the daily resolution is poor, one can easily pick out the wet periods when the Nelson 1-hr DFM often soars to 85%, while the NFDRS stays around 20-25%. On the low end of DFM, the Nelson model appears to track the NFDRS quite well, although the Nelson model sometimes (e.g., first 1000 hours at FORA and MTHE) does not appear to capture the lowest values of DFM. Of course, without measured DFM values to validate either model, one does not know which one is more accurate in these instances. Figure A4 presents the comparisons for 10-hr timelag fuels. Again, during the wet periods, the Nelson 10-hr DFM soars to much higher values (up to 60%) in contrast to NFDRS which stays around 20-25%. Similar to the 1-hr behavior, but more frequent, the NFDRS 10-hr DFM appears to capture the lowest values better than Nelson (e.g., the BOIS plot). But again, with no observed DFM to compare, it s hard to say which model is the more accurate at those low DFM values. The 100-hr behavior of the two models is shown in Figure A5. For these fuels the NFDRS appears to capture higher values of DFM at certain times, while at other times, Nelson gives higher DFM. Nelson appears to keep track with NFDRS on the low end of DFM, and additionally, frequently models lower values than NFDRS. Figure A6 shows the 1000-hr behavior of the two models. Here we find big differences. It is clear that for all except the first 1000 hours or so, the Nelson model yields lower DFM values than NFDRS. The amplitude changes in DFM of each model throughout the year are of the same order of magnitude (which is encouraging), but it is clear that on the average Nelson DFM values are 5-10% lower than NFDRS (at MTHE in the early part of the year, Nelson underpredicts by about 15%). However, looking at the rainfall patterns, there is no apparent physical reason why NFDRS DFM should increase so greatly in the period of time before Hour 2000. Thus, it may be that Nelson is more accurate (but without observed DFM one does not know). A word of encouragement, however, for the 1000-hr Nelson model should be given at this point. We did conduct an analysis of NFDRS vs. Nelson for all four fuel sizes using an observed DFM data set from Slapout, OK from March 1996 through December 1997. This was the subject of our paper at the Fifth Symposium on Fire and Forest Meteorology in Orlando last November. This paper was written before the final parameters were selected, so current results should be even better. 4
In that analysis, we showed that the r2 values between the Nelson DFM and the observed were consistently higher for all size fuels than the r2 between NFDRS and the observed. The values were as follows: 1-hr (Nelson r2 = 0.65; NFDRS r2 = 0.55); 10- hr (Nelson r2 = 0.78; NFDRS r2 = 0.58); 100-hr (Nelson r2 = 0.77; NFDRS r2 = 0.51); 1000-hr (Nelson r2 = 0.50; NFDRS r2 = 0.39). Figure A7 shows the behavior of the Nelson 1000-hr model and the NFDRS 1000-hr values versus observed Slapout 1000-hr DFM for 1996 and 1997. It is clear that the Nelson 1000-hr model is superior to the NFDRS. The Nelson model more closely tracks the observed data, especially on the low end of the DFM scale, which is critical for fire management concerns. Here, as in the examples just shown (Figure A6), NFDRS predicts higher values than Nelson (and most of the observed) by 5-10%. We now turn our attention to scatterplots of Nelson versus NFDRS DFM for each timelag fuel class. These plots show where the two models are similar and where they diverge. In particular, we plot on the y-axis the difference (Nelson DFM - NFDRS DFM) and on the x-axis, Nelson DFM. Figure A8 shows the scatterplots for 1-hour fuels. In the range of DFM up to 20% or so (x-axis), the distribution is centered about 0 on the y-axis, indicating that Nelson and NFDRS are similar (close r2) in value, although one can see that Nelson tends to predict slightly higher values even in this range (as seen in Fig. A3). Above 20% Nelson predicts increasingly higher values than NFDRS, which is to be expected since Nelson 1-hr DFM can go as high as 85%, while NFDRS only goes as high as 25-30%. Figure A9 shows similar scatterplots for 10-hour fuels. For DFM values up to about 20% (x-axis), the distribution is centered about 0 on the y-axis, indicating Nelson is as likely to predict DFM values greater than NFDRS as it is to predict values under NFDRS. Above 20% Nelson predicts increasingly higher values than NFDRS, since Nelson 10-hr DFM can go as high as 60% while NFDRS is capped at about 25-30%. Figure A10 gives the scatterplots for 100-hour fuels. Below about 20% DFM, Nelson predicts lower values than NFDRS (the distribution is centered about the -3% value on the y-axis), while above about 20% Nelson predicts higher values on average than NFDRS. The 1000-hour scatterplots are shown in Figure A11. Here the results are telling and consistent with what has been discussed earlier. It is clear that NFDRS, except at the highest levels of DFM, predicts much higher DFM values than Nelson. Depending on the site, the distribution is centered between -4% and -8%. Some simple statistics for the Nelson and NFDRS dead fuel moisture values are given in Tables 1-4 in the Appendix. Hourly values throughout the calendar years are included in this analysis. The maximum DFM, minimum DFM, average DFM, range in DFM, and standard deviation (SDev) in DFM are listed for both models, with a separate table for each timelag fuel. 5
These statistics confirm what has been discussed and shown previously. In addition, some other interesting points can be made. Note how the minimum DFMs (for both models) generally increase as one moves west to east across the state (down the table) toward the more humid and wetter part of the state. Even the maximum DFMs (for both models) generally increase as one moves west to east. Correspondingly, the average DFM for all four timelag fuels increases from west to east. Standard deviations are of the same order of magnitude between Nelson and NFDRS for 100- and 1000-hr fuels, but as would be expected, are higher in the Nelson model for 10-hr and, especially, 1-hr fuels. Ranges in DFM, as would be expected, are significantly higher in the Nelson model for 1-hr and 10-hr fuels as compared to NFDRS, slightly higher in the Nelson model for 100-hr fuels, and similar or slightly higher in the Nelson model for 1000-hr fuels. E. Nelson Model versus NFDRS Dead Fuel Moisture during Wet and Dry Periods Here we look at the behavior of the Nelson and NFDRS DFM over two periods of time ranging from about a week to one month, the first during a heavy rain event and the second during a hot dry period. The heavy rain event is from August 29 to September 1, 2003 at Foraker, OK. The hot dry period is from the month of July 2003 at Slapout, OK. Figures A12 and A13 present the Nelson and NFDRS DFM during a heavy rain event at Foraker, OK over a four-day period from August 29 through September 1, 2003. During that period 8.13" of rain fell, most of it in the first three days. The 1-hr and 10-hr DFM are depicted in Figure A12. One can see the superiority of the Nelson model in predicting the high fuel moistures associated with each rainfall period; the NFDRS DFM values are hardly affected at all, showing the same amplitude of increase as associated with the diurnal cycle during dry periods. The 100-hr and 1000-hr DFMs are shown in Figure A13. Here the behavior between the two models is similar, although Nelson, being based on 15-minute data, is more dynamic, responding to each individual rainfall episode, while NFDRS DFM, since it only is updated once daily for 100-hr and 1000-hr fuels, shows only a general increase or decrease. In contrast to August, July 2003 was a hot dry month across Oklahoma. Figures A14 and A15 present the Nelson and NFDRS DFM during the month of July at Slapout, OK. Daily highs were in the 100s and high 90s, with the average high for the month being 97F. There was only 0.12" of rain during the month, rain which fell during the last four days of the month. The 1-hr and 10-hr DFM are depicted in Figure A14. Note how closely Nelson and NFDRS track each other, capturing the diurnal cycle. Only during the rain event at the end of the month (and the end of June, which is also shown) does Nelson predict higher DFM values, as it should. The 100-hr and 1000-hr DFM are shown in Figure A15. Nelson, being based on 15-minute data, is able to capture the small diurnal DFM changes while gradually trending downward for the month, while NFDRS only trends downward until the rain event at the end of the month. It s encouraging to see that the general slopes of DFM throughout the month are similar for both systems. The 100-hr DFMs track a lot closer than do the 1000-hr, which, as we 6
have seen before, are typically significantly higher for NFDRS. Note again, however, that the 1996-97 Slapout comparison with actual observed 1000-hr DFMs has shown the Nelson model to be more accurate. F. Nelson Model versus NFDRS Dead Fuel Moisture at Specific Times of Day We also compared the Nelson vs. NFDRS DFM values at three times of the day throughout 2003. In some sense, we only should have included days when no rain occurred, since the 1- and 10-hr NFDRS algorithms were not constructed for rainy periods. However, since 100-h and 1000-h NFDRS DFM do include rainfall (duration) in their calculations, and since the purpose is to compare NFDRS in its current state with Nelson, we decided to use all days of 2003 in our database. Table 5 gives the r2 values between the Nelson and NFDRS DFM values at three specific times of the day: 0500 CST, 1300 CST, and 1700 CST. The table is grouped according to timelag fuel, with the 1-hr fuels at the three sites listed first, followed by 10-hr and so on. Since NFDRS values are calculated hourly for 1-hr and 10-hr fuels, hourly Nelson values are utilized in the comparison. However, since only 24-hr average information is utilized in calculating 100-hr and 1000-hr NFDRS values, we utilized 24-hr average DFM values from the Nelson model in these comparisons. For 1- and 10-hr fuels, r2 values at all three sites increase as one goes from 0500 (5 a.m.) to the afternoon hours of peak heating. Except at MTHE for 1-hr fuels, the highest r2 for these timelag fuels occur at the 1700 hour. This is especially apparent at the two eastern sites FORA and MTHE, which feature more humidity and rainfall. Since the 1-hr and 10-hr NFDRS DFM algorithms were developed for the peak heating hours, it makes sense that there would be a better correlation with Nelson DFMs during this time of day. The NFDRS algorithms for 1- and 10-hr fuels do not perform as well in the early morning hours when conditions are generally wetter than in the afternoon. For 100-hr fuels the highest r2 values at all three sites typically occur at the 1700 hour, followed closely by the 0500 hour, and then the 1300 hour. However, since the NFDRS values are only updated daily at 1600 CST using the past 24-hr weather, only the 1700 comparison is truly valid, since the 0500 and 1300 NFDRS values are the same as those calculated at 1600 the day before. 1000-hr r2 values are of the same order of magnitude for a given station no matter which time of day, with Boise City showing the highest r2 values, probably because it is located in the driest part of the state and thus experiences weather conditions more similar to those for which the NFDRS algorithm was developed. Scatterplots, similar to Figures A8 - A11, showing Nelson vs. NFDRS DFM at each time of day are available, but are not shown in the Appendix due to the extra volume they would require. 7
G. Future Work Due to unexpected delays during the first year (Phase One) of this project, the forecast analysis portion of the project was not completed, but will be done during Phase Two. The Eta forecast ingest, interpolation to Mesonet sites, and integration of the forecast component into the Nelson model have been completed, but several months of Eta forecasts need to be run and analyzed per the original Plan of Work. 8
APPENDIX Analysis of Nelson Model Performance in 2003 versus NFDRS Dead Fuel Moisture 9
Figure A1. NFDRS dead fuel moisture behavior at three Mesonet sites in 2003. 10
Figure A2. Nelson model DFM behavior at three Mesonet sites in 2003. 11
Figure A3. Nelson vs. NFDRS DFM for 1-hr timelag fuels. 12
Figure A4. Nelson vs. NFDRS DFM for 10-hr timelag fuels. 13
Figure A5. Nelson vs. NFDRS DFM for 100-hr timelag fuels. 14
Figure A6. Nelson vs. NFDRS DFM for 1000-hr timelag fuels. 15
Figure A7. Nelson vs. NFDRS DFM for 1000-hr timelag fuels as compared against observed 1000-hr DFM at Slapout, Oklahoma. 16
Figure A8. Scatterplots of Nelson vs. NFDRS DFM for 1-hr timelag fuels. 17
Figure A9. Scatterplots of Nelson vs. NFDRS DFM for 10-hr timelag fuels. 18
Figure A10. Scatterplots of Nelson vs. NFDRS DFM for 100-hr timelag fuels. 19
Figure A11. Scatterplots of Nelson vs. NFDRS DFM for 1000-hr timelag fuels. 20
TABLE 1. Statistics (in %) of Nelson vs. NFDRS DFM for 1-hr timelag fuels. All eleven Mesonet sites are listed, in general order from west to east. Station Nelson NFDRS Max Min Avg Range SDev Max Min Avg Range SDev BOIS 85.0 2.2 14.3 82.8 9.9 26.7 1.3 11.6 25.4 6.2 SLAP 85.0 2.2 15.4 82.8 10.9 26.2 1.4 12.3 24.7 5.9 CHEY 85.0 2.2 15.2 82.8 10.1 26.6 1.3 12.3 25.3 5.8 MAYR 85.0 3.0 16.2 82.0 11.6 26.8 2.2 12.8 24.6 6.0 MEDI 85.0 2.8 15.5 82.2 10.7 27.1 2.0 12.5 25.1 5.7 GUTH 85.0 3.6 17.1 81.4 11.5 27.2 2.7 13.8 24.4 5.8 SULP 85.0 4.6 17.5 80.4 11.3 27.0 3.3 14.3 23.7 5.6 FORA 85.0 4.5 18.9 80.5 13.4 27.6 3.6 14.8 24.0 6.0 WILB 85.0 5.0 19.6 80.0 12.6 27.7 3.5 15.8 24.2 6.3 TAHL 85.0 5.4 18.7 79.6 11.4 26.8 4.2 15.1 22.5 5.6 MTHE 85.0 4.7 20.3 80.3 13.3 26.8 3.3 16.1 23.5 5.9 TABLE 2. Statistics (in %) of Nelson vs. NFDRS DFM for 10-hr timelag fuels. All eleven Mesonet sites are listed, in general order from west to east. Station Nelson NFDRS Max Min Avg Range SDev Max Min Avg Range SDev BOIS 55.1 3.5 12.0 51.6 5.5 25.2 2.1 11.6 23.1 5.4 SLAP 59.8 4.1 13.3 55.7 6.6 25.5 2.1 12.4 23.3 5.2 CHEY 55.6 4.7 13.4 50.9 5.9 25.3 2.2 12.4 23.1 5.1 MAYR 60.0 4.1 13.8 55.9 6.7 25.5 3.2 12.9 22.4 5.3 MEDI 60.0 4.7 13.9 55.3 6.3 26.1 3.6 12.6 22.6 5.0 GUTH 60.0 4.7 15.1 55.3 6.9 26.2 4.0 13.9 22.2 5.1 SULP 56.7 6.3 15.7 50.4 6.5 25.1 4.6 14.4 20.5 4.9 FORA 60.0 6.1 16.0 53.9 7.8 26.4 4.8 15.0 21.5 5.2 WILB 60.0 6.4 16.8 53.6 7.4 27.5 5.1 15.9 22.4 5.4 TAHL 59.0 6.6 16.4 52.4 7.0 26.7 5.4 15.2 21.2 4.9 MTHE 60.0 7.2 17.8 52.8 8.1 26.4 4.9 16.2 21.5 5.1 21
TABLE 3. Statistics (in %) of Nelson vs. NFDRS DFM for 100-hr timelag fuels. All eleven Mesonet sites are listed, in general order from west to east. Station Nelson NFDRS Max Min Avg Range SDev Max Min Avg Range SDev BOIS 30.3 4.7 11.2 25.6 3.3 21.9 5.5 11.8 16.4 3.4 SLAP 30.3 5.1 12.1 25.3 3.7 26.8 5.5 12.7 21.3 3.7 CHEY 26.2 5.6 12.1 20.6 3.2 21.1 6.1 12.6 15.0 3.5 MAYR 31.5 5.2 12.6 26.2 3.8 29.0 6.1 13.3 22.8 4.0 MEDI 26.1 6.1 12.7 20.0 3.4 22.9 6.8 12.9 16.1 3.4 GUTH 31.7 5.6 13.6 26.1 3.8 24.9 6.9 14.4 18.0 3.7 SULP 30.3 7.3 14.1 22.9 3.8 24.8 9.1 14.8 15.7 3.2 FORA 35.0 8.2 14.5 26.8 4.0 30.8 8.6 15.7 22.3 3.7 WILB 34.1 8.3 14.9 25.8 3.9 27.9 10.0 16.4 17.9 3.3 TAHL 32.3 8.4 14.6 23.8 3.5 27.0 9.6 15.8 17.4 3.2 MTHE 34.0 9.2 15.9 24.8 4.2 32.3 10.1 16.9 22.2 3.4 TABLE 4. Statistics (in %) of Nelson vs. NFDRS DFM for 1000-hr timelag fuels. All eleven Mesonet sites are listed, in general order from west to east. Station Nelson NFDRS Max Min Avg Range SDev Max Min Avg Range SDev BOIS 16.7 5.1 9.9 11.5 2.4 17.1 8.8 13.0 8.3 1.9 SLAP 15.4 5.2 10.0 10.2 2.1 19.6 10.0 14.3 9.6 2.3 CHEY 16.1 4.7 9.3 11.4 2.7 18.5 9.9 13.9 8.6 2.0 MAYR 16.4 5.1 10.7 11.3 2.3 24.1 9.7 15.1 14.4 2.5 MEDI 17.1 4.9 10.5 12.2 2.4 18.5 10.6 14.4 7.9 1.8 GUTH 20.6 5.1 11.3 15.5 3.1 22.7 10.6 16.4 12.1 2.6 SULP 20.4 5.2 11.9 15.2 2.9 22.7 12.5 16.9 10.2 2.2 FORA 19.8 6.7 12.6 13.1 2.5 26.3 13.4 18.2 12.9 2.6 WILB 23.4 7.3 13.0 16.1 2.8 25.8 13.5 18.7 12.3 2.4 TAHL 23.5 6.6 12.8 16.9 3.1 26.8 13.8 18.0 13.0 2.4 MTHE 22.4 9.4 13.9 13.0 2.4 30.2 14.7 19.8 15.4 2.7 22
Figure A12. Nelson vs. NFDRS 1-hr and 10-hr DFM during a heavy rain event (Aug. 29- Sep. 1, 2003) at Foraker, OK. 23
Figure A13. Nelson vs. NFDRS 100-hr and 1000-hr DFM during a heavy rain event (Aug. 29 - Sep. 1, 2003) at Foraker, OK. 24
Figure A14. Nelson vs. NFDRS 1-hr and 10-hr DFM during a hot dry period (July 2003) at Slapout, OK. 25
Figure A15. Nelson vs. NFDRS 100-hr and 1000-hr DFM during a hot dry period (July 2003) at Slapout, OK. 26
TABLE 5. R2 values for Nelson vs. NFDRS DFM for 1-, 10-, 100-, and 1000-hr Fuels at 0500 CST, 1300 CST, and 1700 CST. Hourly values from the Nelson model are compared to hourly NFDRS values for 1-hr and 10-hr fuels, while 24-hr average Nelson values are compared to 24-hr average NFDRS values for 100-hr and 1000-hr fuels. r2 0500 CST 1300 CST 1700 CST BOIS 1-hr 0.41 0.45 0.50 FORA 1-hr 0.29 0.49 0.58 MTHE 1-hr 0.29 0.57 0.51 BOIS 10-hr 0.44 0.50 0.61 FORA 10-hr 0.27 0.55 0.58 MTHE 10-hr 0.23 0.61 0.63 BOIS 100-hr 0.62 0.57 0.62 FORA 100-hr 0.63 0.55 0.66 MTHE 100-hr 0.55 0.47 0.58 BOIS 1000-hr 0.47 0.46 0.47 FORA 1000-hr 0.11 0.11 0.12 MTHE 1000-hr 0.12 0.11 0.13 27