The Hour table lists statistics for each hour of the day. The
mean annual precipitation for 10 AM is 1.59 inches. Since the source file
contains 15 minute data, the 62.7 records for 10 AM indicate an
annual average of 15.7 hours of precipitation for that hour. Average 15-minute precipitation at that hour
during hours with precipitation is 0.025", or
0.1"/hr. The maximum 15-minute precipitation over the period of record
for the 10 AM hour is 0.42" (1.68"/h intensity).
NetSTORM Intensity - Duration - Frequency Analysis
Developed by Mitch Heineman, CDM, Cambridge, Massachusetts
Input file: C:\boston\boston.15m
Statistics for station 1
ANNUALIZED TOTALS
Hour Mean Records Intensity StDev Maximum
0 1.85 69.5 0.027 ħ 0.030 0.46
1 1.84 70.6 0.026 ħ 0.029 0.87
2 1.90 73.5 0.026 ħ 0.028 0.41
3 1.88 72.7 0.026 ħ 0.030 0.53
4 1.81 71.5 0.025 ħ 0.027 0.30
5 1.84 71.0 0.026 ħ 0.027 0.32
6 1.85 73.0 0.025 ħ 0.026 0.34
7 1.67 67.3 0.025 ħ 0.030 0.58
8 1.74 65.7 0.026 ħ 0.031 0.44
9 1.61 65.2 0.025 ħ 0.025 0.37
10 1.59 62.7 0.025 ħ 0.026 0.42
11 1.62 65.2 0.025 ħ 0.027 0.41
12 1.75 66.3 0.026 ħ 0.030 0.59
13 1.81 63.9 0.028 ħ 0.036 0.68
14 1.80 65.0 0.028 ħ 0.036 0.52
15 1.88 69.4 0.027 ħ 0.034 0.68
16 1.90 72.6 0.026 ħ 0.030 0.46
17 1.82 72.4 0.025 ħ 0.027 0.47
18 1.82 71.2 0.025 ħ 0.027 0.38
19 1.71 67.5 0.025 ħ 0.028 0.41
20 1.65 66.1 0.025 ħ 0.026 0.30
21 1.69 66.7 0.025 ħ 0.026 0.34
22 1.74 68.0 0.026 ħ 0.026 0.47
23 1.77 69.9 0.025 ħ 0.025 0.35
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). The statistics
shown are comparable with those in the Hour table.
Weekday Mean Records Intensity StDev Maximum
Sun 6.50 241.8 0.027 ħ 0.032 0.68
Mon 5.95 239.3 0.025 ħ 0.026 0.41
Tue 6.02 239.0 0.025 ħ 0.027 0.68
Wed 5.56 222.9 0.025 ħ 0.027 0.46
Thu 6.00 225.8 0.027 ħ 0.030 0.87
Fri 6.28 242.4 0.026 ħ 0.028 0.47
Sat 6.24 235.5 0.027 ħ 0.031 0.59
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 Mean Records Intensity StDev Maximum Duration
Jan 3.62 168.7 0.021 ħ 0.019 0.26 15.3
Feb 3.38 152.3 0.022 ħ 0.019 0.18 15.9
March 3.97 177.2 0.022 ħ 0.019 0.30 15.6
April 3.67 156.4 0.023 ħ 0.020 0.20 15.2
May 3.35 138.9 0.024 ħ 0.024 0.36 13.9
June 3.17 106.2 0.030 ħ 0.039 0.59 11.0
July 2.82 86.4 0.033 ħ 0.041 0.68 7.6
Aug 3.43 97.5 0.035 ħ 0.050 0.87 9.5
Sep 3.45 109.7 0.031 ħ 0.038 0.53 12.3
Oct 3.52 122.3 0.029 ħ 0.031 0.46 12.8
Nov 4.17 159.2 0.026 ħ 0.026 0.39 14.9
Dec 3.99 171.8 0.023 ħ 0.021 0.22 15.2
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 Intensity StDev Maximum Duration Events Non-Events Interevent
1948 27.41 1027 0.027 ħ 0.031 0.46 12.3 32 41 130
1949 31.43 1329 0.024 ħ 0.030 0.53 11.3 42 60 162
1950 32.65 1440 0.023 ħ 0.025 0.27 15.3 35 71 162
1951 46.78 1845 0.025 ħ 0.026 0.32 13.6 52 66 153
1952 40.44 1652 0.024 ħ 0.033 0.68 15.5 42 63 129
1953 57.36 2010 0.029 ħ 0.028 0.21 14.1 50 53 118
1954 62.08 1981 0.031 ħ 0.038 0.41 13.9 49 86 144
1955 56.22 1679 0.033 ħ 0.052 0.68 14.3 42 69 129
...
1996 48.53 1820 0.027 ħ 0.027 0.26 13.2 52 56 141
1997 30.12 1351 0.022 ħ 0.021 0.22 12.8 35 77 135
1998 52.89 1687 0.031 ħ 0.038 0.45 14.3 45 55 150
1999 37.61 1289 0.029 ħ 0.036 0.47 11.6 43 50 158
2000 44.31 1559 0.028 ħ 0.030 0.33 12.7 46 59 180
2001 29.55 1148 0.026 ħ 0.031 0.41 10.5 33 66 141
2002 39.69 1666 0.024 ħ 0.024 0.39 13.8 47 65 150
2003 40.57 1572 0.026 ħ 0.030 0.41 12.0 41 76 137
2004 43.90 1551 0.028 ħ 0.031 0.27 14.9 38 81 156
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Mean 42.54 1646.7 0.026 ħ 0.029 0.36 13.4 44 65 145
Dry periods exceeding the specified threshold are listed to identify
droughts and possible gaps in the dataset.
Dry preceding 10/28/1963 for 25 days
Dry preceding 07/10/1975 for 23 days
Dry preceding 07/01/1999 for 38 days
Dry preceding 02/01/2003 for 22 days
Longest drought = 38 days preceding 07/01/1999
Period of record = 56.67 years
Number of records = 93311
Mean event depth = 0.86 (>= 0.25 inches)
Annual event depth = 37.82 (>= 0.25 inches)
Mean event duration = 14.75 hours
Interevent coeff.var.= 0.81 (periods of > 21 dry days excluded)
Interevent time = 6 hours
Plotting position = 0.40
Sub-events excluded from interval analyses
The Largest Storms 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 Oct. 20, 1996 storm has a
plotting position of 35 years, is the 2154th storm in the
record, lasted 33 hours, has 116 records (29 hours with precipitation),
and had a maximum 15-minute accumulation of 0.26" (1.04"/h intensity).
LARGEST STORMS
Return Rank Depth Date Event Duration Records MaxDepth
94.78 1 11.90 08/18/1955 5:15 327 40.50 118 0.52
35.54 2 7.12 10/20/1996 3:00 2154 33.00 116 0.26
21.87 3 6.97 10/05/1962 7:45 662 61.50 163 0.26
15.80 4 6.75 06/12/1998 15:45 2220 43.00 93 0.45
12.36 5 6.74 06/04/1982 16:15 1514 83.25 199 0.13
LARGEST 0.25 HOUR INTERVAL TOTALS
Return Rank Depth Date Event
94.78 1 0.87 08/01/1985 1:30 1658
35.54 2 0.68 07/10/1955 15:15 324
21.87 3 0.68 08/05/1952 13:30 191
15.80 4 0.59 06/04/1960 12:15 570
12.36 5 0.58 08/06/1967 7:15 853
LARGEST 1.00 HOUR INTERVAL TOTALS
Return Rank Depth Date Event
94.78 1 2.11 08/01/1985 1:15 1658
35.54 2 1.76 07/10/1955 14:45 324
21.87 3 1.71 08/06/1967 6:45 853
15.80 4 1.63 08/05/1952 13:00 191
12.36 5 1.58 09/01/1949 3:00 61
LARGEST 24.00 HOUR INTERVAL TOTALS
Return Rank Depth Date Event
94.78 1 8.33 08/18/1955 12:00 327
35.54 2 5.88 10/20/1996 4:00 2154
21.87 3 5.88 06/13/1998 7:15 2220
15.80 4 5.73 05/15/1954 19:30 271
12.36 5 5.63 09/10/1954 18:30 288
LARGEST 48.00 HOUR INTERVAL TOTALS
Return Rank Depth Date Event
94.78 1 11.90 08/18/1955 5:15 327
35.54 2 7.12 10/20/1996 3:00 2154
21.87 3 6.75 06/12/1998 15:45 2220
15.80 4 6.70 10/05/1962 13:30 662
12.36 5 5.98 03/31/2004 10:30 2457
FREQUENCY ANALYSIS
Interval
(Hours) 1-wk 2-wk 1-mo 3-mo 6-mo 1-yr Return Period (years)
0.019 0.038 0.083 0.25 0.5 1 2 5 10 25 50 100 xi alpha kappa Station
Storm <0.25 0.52 0.99 1.79 2.29 2.77 3.57 4.70 5.74 7.49 9.21 11.37 3.2818 0.7266 -0.3406 1
0.25 <0.25 <0.25 <0.25 <0.25 <0.25 0.29 0.36 0.45 0.52 0.63 0.74 0.87 0.3409 0.0564 -0.2825 1
1.00 <0.25 <0.25 0.31 0.49 0.61 0.78 0.98 1.18 1.36 1.66 1.95 2.30 0.9220 0.1371 -0.3040 1
24.00 <0.25 0.54 0.99 1.71 2.16 2.64 3.19 3.98 4.71 5.93 7.14 8.67 2.9950 0.5027 -0.3456 1
48.00 <0.25 0.55 1.06 1.88 2.43 2.91 3.69 4.68 5.60 7.18 8.75 10.76 3.4457 0.6227 -0.3593 1
Empirical results for periods from 1 week to 1 year
GEV distribution fitted using L-moments for 2 - 100 years
Analysis begun : 07/05/2005 12:04:35
Analysis completed: 07/05/2005 12:05:52
