NetSTORM IDF sample

NetSTORM intensity-duration-frequency analysis
Developed by Mitch Heineman, CDM Smith, 1991-2013
Input file: C:\Calcs\MetData\connecticut\bradley\063456BradleyNCDCPrc.dat

Statistics for station 069704 HARTFORD BRADLEY FLD CT                           

ANNUALIZED TOTALS

The Hour table lists statistics for each hour of the day. The mean annual precipitation for 3 AM is 1.95 inches.

Hour  Jan   Feb   March April May   June  July  Aug   Sep   Oct   Nov   Dec  Total  Records Mean      StDev     Maximum
01    0.13  0.13  0.21  0.15  0.17  0.18  0.12  0.14  0.19  0.21  0.19  0.15  1.97    31.2  6.304E-2  8.476E-2  0.890   
02    0.14  0.14  0.19  0.15  0.16  0.13  0.16  0.17  0.15  0.21  0.21  0.17  1.98    30.6  6.484E-2  9.342E-2   1.35   
03    0.14  0.13  0.17  0.14  0.12  0.15  0.15  0.16  0.18  0.21  0.21  0.17  1.95    32.1  6.061E-2  8.354E-2  0.830   
…
22    0.13  0.11  0.13  0.18  0.19  0.16  0.16  0.14  0.20  0.17  0.17  0.17  1.91    30.4  6.300E-2  8.882E-2  0.970   
23    0.14  0.11  0.15  0.16  0.17  0.15  0.11  0.15  0.17  0.18  0.16  0.17  1.83    30.1  6.071E-2  8.321E-2  0.840   
24    0.13  0.12  0.18  0.17  0.16  0.19  0.11  0.14  0.15  0.23  0.15  0.16  1.89    30.5  6.201E-2  8.856E-2   1.16

The Weekday table lists annualized statistics for each day of the week. One would not normally expect to see statistically significant variation in precipitation over the days of the week, other than meteorologic anomalies caused by anthropogenic activity (e.g. correlation of air pollution patterns with precipitation), or record-keeping anomalies (e.g. a station where data is not recorded on Sundays).

Weekday  Total  Records Mean      StDev     Maximum
Sun       6.35   100.1  6.347E-2  9.575E-2   2.38   
Mon       6.22   102.5  6.062E-2  8.786E-2   1.57   
Tue       6.18    99.8  6.188E-2  8.276E-2   1.00   
Wed       6.22   100.9  6.167E-2  9.411E-2   1.72   
Thu       6.19    98.1  6.308E-2  9.319E-2   1.64   
Fri       7.41   110.6  6.700E-2  0.108      2.33   
Sat       6.62   102.5  6.457E-2  9.510E-2   1.55

The Month table lists annualized statistics for each month. The statistics shown are comparable with those in the Hour and Weekday tables with the addition of a column for Duration. Duration indicates the average duration (hours) of storms during that month.

Month    Total  Records Mean      StDev     Maximum   Duration
Jan       3.28    71.8  4.574E-2  5.192E-2  0.500        16.3
Feb       3.03    63.7  4.761E-2  5.446E-2  0.570        17.1
March     3.76    74.8  5.028E-2  5.564E-2  0.420        17.0
…
Oct       4.00    54.5  7.342E-2  0.105      1.72        16.4
Nov       3.87    65.8  5.874E-2  6.915E-2   1.00        16.9
Dec       3.78    73.2  5.163E-2  6.031E-2  0.750        16.6

The Year table lists annual statistics. The statistics shown are comparable with those in the previous tables with the addition of columns for Events, Non-Events, and Interevent. Events indicates the number of storms exceeding the specified threshold for the year. Non-events are periods of measureable precipitation falling below the threshold. Interevent is the average time (hours) between events. Means of the annual series are listed at the end of the table.

Year     Total  Records Mean      StDev     Maximum   Duration Interevent     Histogram Bins 
                                                                         0.00 0.05 0.10 0.25 0.50 1.00 2.00
1954     19.98     301  6.638E-2  8.160E-2  0.450        15.4        205   17    7    9    3    7    3    2
1955     62.93     785  8.017E-2  0.142      1.64        16.0        167   28   13   15   19   12   10    5
1956     41.55     826  5.030E-2  6.453E-2  0.720        12.9        158   41   11   22   21   23    8    0
…
2009     47.32     768  6.161E-2  8.541E-2  0.870        12.3        151   25   13   25   24   13   14    2
2010     42.42     601  7.058E-2  0.100     0.770        18.4        204   21   10   14    9   12    9    4
2011     68.46     847  8.083E-2  0.120      1.33        15.9        139   22    6   16   15   24   15    5
2012     20.80     345  6.029E-2  0.104      1.50        11.6        245   27    3   16    7    7    5    1
___________________________________________________________________________________________________________
Mean     45.18   714.4  6.324E-2  9.440E-2   1.07        14.9        173 26.7 11.1 17.1 15.0 15.5 10.4  3.3

Dry periods exceeding the specified threshold are listed to identify droughts and possible gaps in the dataset.

Dry preceding 07/05/1958 for  1.2 months
Dry preceding 11/26/2000 for  1.3 months

Longest drought      =     38 days preceding 11/26/2000        
Period of record     =  57.75 years
Period missing       =   0.21 years
Number of records    =  41438
Mean                 =  6.324E-2
Mean event depth     =  0.906   (greater than or equal to  0.25 units)
Annual event depth   =   41.1   (greater than or equal to  0.25 units)
Mean event duration  =  15.86 hours
Interevent coeff.var.=   0.85 (excluding periods exceeding  35 dry days)
Interevent time      =      9 hours
Plotting position    =   0.40

NOTES:
Sub-events excluded from frequency analyses
0.2-year missing period excluded from IDF analysis. Check that this does not include droughts

The Largest Events table identifies events with the greatest total precipitation over the period of record. Storm duration is determined using the interevent time criterion. Each storm is assigned a sequential Event number. Duration is given in hours. Records indicates the number of non-zero entries for the storm. MaxDepth indicates the largest individual entry for the storm. The 9/22/75 storm has a recurrence interval of 24 years, is the 956th storm in the record, lasted 102 hours, has 85 records, and had a maximum 1-hour accumulation of 1.07".

LARGEST EVENTS
Recurr	Rank	Depth   	Date	            Event	Percentile	EventHrs	Records	Maximum
128.69	   1	  13.97   	08/18/1955  4:00	   48	 100.0	   36.00	     34	    1.64
 23.76	   2	  7.730   	09/22/1975 22:00	  956	 100.0	  102.00	     85	    1.07
 22.56	   3	  7.600   	10/11/2005 17:00	 2287	  99.9	   93.00	     66	    1.16
 21.66	   4	  7.500   	06/04/1982 18:00	 1239	  99.9	   71.00	     50	    0.53
 21.39	   5	  7.470   	05/28/1984  9:00	 1336	  99.8	   80.00	     73	    0.40

The Largest N Hour Totals tables identify events with the greatest precipitation at selected durations over the period of record. Durations are user-specified. Recurrences shown are based on the GEV distribution for return periods exceeding one year.


LARGEST   1.00 HOUR DURATION TOTALS
Recurr	Rank	Total   	Date            	Event	Percentile
 67.85	   1	  2.380   	08/11/1985 19:00	 1382	 100.0
 61.22	   2	  2.330   	07/15/2005 20:00	 2277	  99.9
 18.52	   3	  1.820   	08/17/1962 16:00	  362	  99.9
 14.11	   4	  1.720   	10/03/1979 15:00	 1136	  99.8
 11.24	   5	  1.640   	08/18/1955 10:00	   48	  99.8


LARGEST   6.00 HOUR DURATION TOTALS
Recurr	Rank	Total   	Date            	Event	Percentile
 50.17	   1	  4.900   	08/19/1955  2:00	   48	 100.0
 43.85	   2	  4.710   	09/06/2008 18:00	 2436	 100.0
 25.79	   3	  4.050   	10/14/2005 19:00	 2287	  99.9
 20.42	   4	  3.800   	05/24/1989  1:00	 1547	  99.9
 17.57	   5	  3.650   	09/08/2011  2:00	 2579	  99.9


LARGEST  24.00 HOUR DURATION TOTALS
Recurr	Rank	Total   	Date            	Event	Percentile
175.39	   1	  12.05   	08/18/1955 10:00	   48	 100.0
 23.92	   2	  6.140   	06/05/1982  6:00	 1239	  99.9
 19.85	   3	  5.810   	10/14/2005 14:00	 2287	  99.9
 16.94	   4	  5.550   	09/16/1999  2:00	 2025	  99.8
 14.19	   5	  5.280   	09/11/1960 18:00	  276	  99.7


LARGEST  96.00 HOUR DURATION TOTALS
Recurr	Rank	Total   	Date            	Event	Percentile
154.14	   1	  14.40   	08/17/1955 12:00	   47	 100.0
 20.69	   2	  7.810   	06/02/1982  1:00	 1238	  99.9
 19.06	   3	  7.630   	09/23/1975  3:00	  956	  99.9
 18.80	   4	  7.600   	10/11/2005 17:00	 2287	  99.9
 17.68	   5	  7.470   	05/28/1984  9:00	 1336	  99.9

The Frequency Estimates table summarizes statistics for all reported durations. xi, alpha, and kappa can be used to plot the distributions in spreadsheets or elsewhere.


FREQUENCY ESTIMATES
Duration                                         Average recurrence interval (years)
(Hours) 1-wk     2-wk     1-mo     3-mo     6-mo     1-yr
       0.019    0.038    0.083     0.25      0.5        1      2        5       10       25       50      100       xi         alpha      kappa
 Event <0.25    0.580     1.09     1.85     2.37     3.00     3.70     4.80     5.88     7.86     9.94     12.7      3.440     0.6454    -0.4280      
  1.00 <0.25    <0.25    0.300    0.520    0.680    0.850     1.10     1.38     1.60     1.94     2.23     2.58      1.028     0.1977    -0.2144      
  6.00 <0.25    0.430    0.760     1.20     1.48     1.86     2.17     2.68     3.16     4.02     4.90     6.05      2.051     0.3048    -0.3968      
 24.00 <0.25    0.570     1.08     1.73     2.18     2.73     3.28     4.04     4.80     6.22     7.75     9.82      3.107     0.4343    -0.4516      
 96.00 <0.25    0.560     1.29     2.17     2.82     3.36     4.17     5.31     6.38     8.24     10.1     12.5      3.898     0.7041    -0.3743      

Empirical results for periods from 1 week to 1 year
GEV distribution fitted using L-moments for 2 - 100 years
Processing time: 9 seconds

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