Potter T.D., Colman B.R. (co-chief editors). The handbook of weather, climate, and water: dynamics, climate physical meteorology, weather systems, and measurements
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One of the other data losses that resul ted from ASOS was that of the duration and
intensity of thunderstorms. Work continues on the improvement and installation of a
lightning sensor from which proximate thunder may be inferred.
This writer would be remiss if he did not mention one other major discontinuity
to climatological studies and other retrospective uses of meteorological data. That is
the conversion (on July 1, 1996) from the long-standing ‘‘airways’’ observational
codes to a modified version of the European ‘‘METAR’’ code. This transition
brought about numerous changes, but the scope of this chapter does not allow a
full treatment of all these changes. Hopefully, the listing of a few will cause the
reader to dig further before using any related data.
1. Ambient and dew-point temperatures are now recorded in Celsius (degrees
and tenths) instead of whole degrees Fahrenheit.
2. Sky cover is now reported in oktas (eighths) instead of tenths.
3. Reported weather types of which there used to be about 28 have been reduced
in number and altered in their two-letter abbreviations. Following are a few
examples of the better known ones:
Weather Type Airways Metar
Hail A GR
Rain R RA
Ice pellets IP PE
Snow S SN
Drizzle L DZ
Fog F FG
Thunderstorm T TS
4. Rounding of negative temperatures changed from arithmetically absolute (i.e.,
1.5
became 2
) to temperature absolute (i.e., 1.5
now becomes 1.0
).
This change most often affects the computation of heating degree days (HDD)
when the sum of the maximum and minimum temperat ure are odd and, when
divided by 2 to obtain the mean temperature for the day, leave a product of
whole units and tenths.
For example, Max Temp of 2
þ Min Temp of 9
¼11
2 ¼5.5
, which
used to become 6
but now becomes 5
7 SUMMARY
It is the strong recommendation of the author that anyone using meteorological and
climatological data from any source investigate its background prior to analysis for
research, publication, or use in the applied and forensic fields. Not to do so is an
abrogation of scientific integrity. Hopefully, the discussion of this chapte r wi ll cause
the reader to pause before blindly accepting the validity of any data set or value.
826 DATA VALIDITY IN THE NATIONAL ARCHIVE
BIBLIOGRAPHY
Doesken, N. J., and A. Judson, (1997). The Snow Booklet, Colorado State University, 87 pp.
Engelbrecht, H. H., and G. N. Brancato (1959). World record one minute rainfall at Unionville,
MD, Mon. Wea. Rev., 87, (8), 303–306.
Fujita, T. T. (1992). U.S. Department of Commerce, National Oceanic and Atmospheric
Administration, NCDC, Asheville, NC, Storm Data, September 1992, Vol. 34, No. 9, p. 27.
Karl, T. R., and R. G. Quayle (1988). Climate change in fact and in theory; Are we collecting
the facts? Climate Change 13, 15–17.
Karl, T. R. (1995). Long-Term Climate Monitoring by the Global Climate Observing System.
Kluwer Academic Publishers, pp. 51–56.
Schmidlin, T. W. (1990). A critique of the climate record of water equivalent of snow on the
ground in the United States. J. Appl., Meteor. 29, 1136–1141.
Schmidlin, T. W. et al. (1992). Design ground snow loads for Ohio. J. Appl. Meteor. 31, 622–
627.
Sherlock, R. H. (1947). Gust factors for the design of buildings, International Assoc. For
Bridge and Structural Engineering, Vol. 8, pp. 207–235.
Sissenwine, et al. (1973). Extreme wind speeds, gustiness, and variations with height for MIL-
STD 210B. U.S. Air Force, Cambridge Research Labs. TR-73-0560, p. 12.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1985).
Storm Data; October 1985, Vol. 27, No. 10. National Climatic Data Center, Asheville, NC,
40 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1992).
ASOS Users Guide; National Weather Service, Silver Spring, MD, 98 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1993).
Climatological Data, New York; March 1993, Vol. 105, No. 3, National Climatic Data
Center, Asheville, NC, 40 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1993).
Climatological Data, North Carolina; March 1993, Vol. 98, No. 3, National Climatic Data
Center, Asheville, NC, 36 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1994).
ASOS Progress Report—ASOS Wind Sensor, Problems Identified and Solved. National
Weather Service, Silver Spring, MD, 8 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1994).
Natural Disaster Survey Report, ‘‘Superstorm of March 1993.’’ National Weather Service,
Silver Spring, MD, 152 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1996).
National Weather Service, Observing Handbook No. 7—Surface Weather Observations and
Reports, July 1996. National Weather Service, Silver Spring, MD, 461 pp.
U.S. Department of Commerce, Weather Bureau (1957). History of Observational Instructions
as Applied to Temperature Recordings. U.S. Government Printing Office, Washington,
D.C., 7 pp.
U.S. Department of Commerce, Weather Bureau (1958). Excessive Precipitation Techniques.
U.S. Government Printing Office, Washington, D.C., 12 pp.
BIBLIOGRAPHY 827
U.S. Department of Commerce, Weather Bureau (1963). History of Weather Bureau Precipita-
tion Measurements. U.S. Government Printing Office, Washington, D.C., 19 pp.
U.S. Department of Commerce, Weather Bureau (1963). History of Weather Bureau Wind
Measurements. U.S. Government Printing Office, Washington, D.C., 68 pp.
U.S. Department of Commerce, Weather Bureau (1968). Final Report—Test and Evaluation of
the Fischer and Porter Precipitation Gage. U.S. Government Printing Office, Washington,
D.C., 28 pp.
U.S. Department of Commerce, Weather Bureau (1969). Specification No. 450. 1016 for
Liquid in Glass Thermometers. U.S. Government Printing Office, Washington, D.C., 9 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1985).
Climatological Data, Puerto Rico and Virgin Islands; October 1985, Vol. 31, No. 10.
National Climatic Data Center, Asheville, NC, 23 pp.
U.S. Depar tment of Commerce, National Oceanic and Atmospheric Administration (1985).
Hourly Precipitation Data, Puerto Rico and Virgin Islands; October 1985, Vol. 15, No. 10.
National Climatic Data Center, Asheville, NC, 15 pp.
U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Climatic
Data Center, Asheville, NC continues to publish monthly and annual Local Climatological Data volumes
that began in 1948. They are published for about 270 cities in the United States and some of its territories.
828 DATA VALIDITY IN THE NATIONAL ARCHIVE
CHAPTER 42
DEMANDS OF FORENSIC
METEOROLOGY
W. H. HAGGARD
1 SEARCH FOR THE TRUTH
The role of the forensic meteorologist is to assist the court in the search for the truth
by presenting the most accurate description possible of the meteorological events
pertinent to the case in litigation. To fulfill this role, the forensic meteorologist must
utilize the best possible data set in his or her retrospective reconstruction of the
weather. The quality of the analysis is dependent on the availability of representative
measurements of meteorological parameters.
2 DATA NEEDED
The weather event reconstructions frequently require data and information beyond
the standardized meteorological observations collected by governmental agencies.
These frequently include eyewitness statements, field investigations, interviews, and
data from other fields (e.g., recordings of radar-deduced tracks of aircraft, ship log
books, air traffic control voice transcripts, and the like).
Handbook of Weather, Climate, and Water: Dynamics, Climate, Physical Meteorology, Weather Systems,
and Measurements, Edited by Thomas D. Potter and Bradley R. Colman.
ISBN 0-471-21490-6 # 2003 John Wiley & Sons, Inc.
829
Reliability
Legal tests of the courtroom admissibility of expert testimony have been devised at
various times. In 1923 the Frye test required that scientific evidence be of a type that
is ‘‘generally accepted’’ in the relevant scientific community. In the late 1990s the
Daubert test to eliminate ‘‘junk science’’ in the courtroom requires the proffered
scientific evidence to be ‘‘reliable and based upon scientific methodology.’’
Hindsight
Several factors impact on the reliability of the results of a retrospective meteoro-
logical analysis. There must be data available upon which to rely. The data should be
representative of the conditions of the atmosphere at the time and place of measure-
ment. The instruments, sensors, observers, radars, satellites, etc. should have the
capability of accurately sensing the requisite data. They should be properly cali-
brated, and their clocks should be set correctly. Since forensic meteorological
analyses for litigation involve retrospective reconstructions, the data utilized come
from the archives, and high quali ty of archived data is vital to proper reconstruction.
The forensic meteorologist enjoys the luxury of hindsight—usually believed to be
‘‘better’’ (or at least easier) to apply correctly than foresight. Like the forecaster,
however, he or she is limited in analytical capability by the limitations in availability,
representativeness, and quality of the available measurements pertinent to the
circumstances.
Reconstructing the bases of the cloud above a 2900-ft mountain ridge between
Nome and Koyuk, Alaska,
1
when there were no cloud base data within 100 miles
of the crash site is more difficult than reconstructing the cloud bases at Flagstaff,
Arizona
2
(where a continuously recording laser beam ceilometer record was
available) (see Fig. 1).
Expert Testimony
Meteorology comes into the courtroom through the testimony of expert witnesses
who are there because they possess an accumulation of education, knowledge, and
experience that qualifies them to provide weather-related testimony beyond the
normal capability of the court to obtain by other means. The qualified practitioner
of forensic meteorology is a formally educated atmospheric scientist, often with
specialized training in applied climatology, hydrometeorology, micrometeorology,
aviation meteorology, marine meteorology, and=or disaster preparedness who is
relied upon to assist legal counsel in clarifying scientific or technical issues that
relate to the weather relevant to specific cases being litigated (Falconer and Haggard,
1990).
Forensic meteorol ogists do more than a ‘‘simple’’ weather event reconstruction
(Haggard, 1980a,c, 1983, 1985, 1989; Haggard and Smutz, 1994). They may:
830 DEMANDS OF FORENSIC METEOROLOGY
Figure 1 Decoded laser beam ceilometer data, Flagstaff, Arizona, 8:45–9:20 a.m. MST, December 20, 1991,
showing values converted to heights above ground (agl) of lowest points of reflectivity (green) above ground; height of
the base of main reflectivity (red); and midpoint of recorded main reflectivity (blue). See ftp site for color image.
831
Acquire and interpret basic weather records (i.e., observations, operational
charts and analyses, archived forecasts, or advisories, etc.).
Assess the validity, representativeness, pertinence, and adequacy of the avail-
able data.
Advise engaging counsel on the meaning and appli cability of these basic
weather data to issues pending before the court.
Perform specialized meteorological analyses based on weather and other
records (e.g., topographic surveys, eyewitness repor ts, damage photos, etc.).
Prepare a comprehensive report.
Provide credible expert testimony as to the weather pertinent to the matters
under litigation.
High-quality records of measurements are essential to the accomplishment of these
functions.
3 CASE EXAMPLES
Many retrospective reconstructions are for a site- and time-specific weather event
(e.g., the collision of the Summit Venture with the Skyway Bridge, which spans the
entrance to Tampa Bay, on May 9, 1980,
3
or the crash of a ‘‘TriStar’’ airliner on
approach to Runway 17L at Dallas–Ft. Worth Airport at 6:04 pm CDT on August 2,
1985.
4
Others may involve a moderate span of time a nd an area (e.g., devastating
floods over 16 counties of western North Carolina on November 5–6, 1977,
5
affecting thousands of square miles and several days). A few will be quite dependent
on remotely sensed data (e.g., a microburst at Mayaguez, Puerto Rico
6
).
Some may involve a climatological study of decades of data (e.g., a wind study
relating to the legality of constructing a N–S runway at Anchorage International
Airport as a ‘‘crosswind runway’’—a study involving detailed analysis of 23 years of
hourly wind data
7
). The availability, adequateness, representativeness, pertinence,
and quality control of the data impacted the credibility of the analytical results in
these exemplar cases.
Visibility
Key questions in the litigation over the Summit Venture=Skyway Bridge collision
(Haggard, 1985) related to the visibility in the ship channel and speed of the vessel,
just prior to the collision with the bridge, far removed from any official weather-
reporting site. Rain was so intense the bow of the ship could not be seen from the
bridge.
Probably the most pertinent objective weather measurements relative to deter-
mination of the visibility were the rainfall rates at the ship as it traversed the channel.
The National Weather Service Weather Surveillance Radar (WSR-57) located at
Ruskin, Florida, 14 miles from the collision was in a favorable location to provide
such data.
832 DEMANDS OF FORENSIC METEOROLOGY
The collision occurred at 7:34 a.m. EDT. The radar at Ruskin was struck by
lightning at 7:13 a.m. EDT, became inoperable, and did not provide further mea-
surements until 7:43 a.m. EDT. The most potentially valuable and pertinent
measurements were not available for 21 min before and 9 min after the event.
The meteorological system producing the intense rain—which reduced visibility
to tens of feet—was sufficiently time consistent that is was possible to interpolate the
‘‘probable radar image’’ at the collision time by ‘‘bridging the gap’’ from the series
of images prior to and subsequent to the radar outage. The resultant hypothetical
image showed the ship and bridge channel spans to be within the area of the
strongest reconstr ucted radar reflectivity, consistent with nonobjective lay eyewitness
reports.
Microbursts
The principal litigation resulting from the crash of Delta Air Lines Flight
191 involved a 14-month trial in Federal District Court in Fort Worth Texas.
Dr. T. Theodore Fujita (1986) performed an intensive retrospective weather analysis
that relied on the combined meteorological measurements made by stand ard instru-
mentation, the 7-second LLWAS [low-level wind (shear)–alert system] data at
sensors near and on the airport, weather satellite and radar imagery, the parametric
data measured by the digital flight data recorder on the a ccident aircraft, and on-site
physical evidence. This artful combination of all available pertinent data permitted a
reconstruction of the interaction of aircraft and the atmosphere and led to a detailed
reconstruction of the dynamics of the microburst that the aircraft penetrated.
Another microburs t-related accident occ urred at Mayaguez, on the western coast
of Puerto Rico, on June 7, 1992, killing crew and passengers of a commuter plane
attempting to land. The detailed weather reconstruction (Fujita et al., 1992) was
largely dependent on a sequential analysis of satellite and radar measurements made
remotely. The growth and collapse of thunderstorms augmented by the topography
and sea breezes of the island were remotely sensed. The results of analyses of those
measurements were integrated with multiple witness statements from both airborne
and ground-based persons closer to the event. Finally the dynamics of the aircraft
and its track were fitted into the meteorological analysis to locate the point of
impact of the microburst relative to the trajectory of the plane immediately prior
to impact (see Fig. 2). The coordinated use of remotely sensed meteorological
measurements, their augmentation by anecdotal local witness statements, and their
combination with tracked and timed aircraft positions were essential to the recon-
struction of the weather scenario.
Winds
Measurement validity was an element of dispute in the litigation over construction of
the ‘‘crosswind’’ north–south runway at Anchorage International Airport (Ha ggard,
1980b). The Federal Aviation Administration (FAA) conducted a study of winds
relative to the existing east–west runway. Though 23 years of wind data existed, they
3 CASE EXAMPLES 833
Figure 2 Motion and collapse of San Juan observed radar echo over Mayaguez, Puerto Rico, on June 7, 1992.
Curved black line shows center of reflectivity at 1810, 1820, 1832, and 1842 UTC; echo outlines at 1832, and
1842 are shown in black; interpolated echo outline at 1834:47 is shown in blue; aircraft track is shown in red;
and probable microburst encounter is depicted in blue (times are shown in Atlantic Standard Time ¼AST;
AST ¼UTC minus 4 h, such that 1820 UTC ¼1420 AST ¼2:20 pm AST). See ftp site for color image.
834
were not compatible. Some were observed at 16 compass points, others at 36
compass directions; some were recorded in miles per hour, others in knots; some
were digitized at hourly intervals, others only at 3-h times; the ‘‘official wind obser-
vations’’ were made at 12 different consecutive sites over the 23 years of available
‘‘on airport’’ measurements. The life span of the various sites ranged from 11
months to 10 years, averaging 5.2 years.
In its design study, the FAA used the latest 7 years of compatible 36 point, 3-h
wind data, which yielded a qualifying (for cross-wind runway construction) cross
wind of 15 knots or g reater 5.88% of the time (5.0% is required for a cross-wind
runway).
An affected property owner had a 17-year wind study made and determined the
qualifying cross winds were apparen tly present less than 5% of the time. A federal
judge stopped the $33 million construction project and ordered a wind study
utilizing ‘‘all available data.’’
In the undertaking of this complex task, utilizing separate analyses for the differ-
ing periods of noncompatible data units, it was discovered that all data from one
anemometer location (3=21=61 to 1=17=64) yielded strikingly low cross-wind
components compared to prior and subsequent data. Wind speeds were compatible
with earlier and later records, but the direction appeared anomalous. A statistical (F )
test showed the data from that nearly 3-year sample to be statistically from a different
population than the remaining data.
Adjusting the wind data of this sample by 30
(the difference between true and
magnetic north at Anchorage) removed the statistical ‘‘bias’’ and made the sample
compatible with the prior and subsequent data, suggesting the wind vane directional
calibration might have been based on magnetic rather than true north during that
sampling period.
Clouds
In aviation meteorology, the sky condition is a key element, deter mining whether
aircraft operations may be conducted under visual flight rules (VFR) or instrument
flight rules (IFR). While most scheduled commercial aviation flights are conducted
under IFR, regardless of the observed conditions, a large percent age of ‘‘general
aviation’’ flights are conducted under VFR conditions, and many pilots are
not ‘‘IFR qualified and equipped.’’ To them the accuracy of the ‘‘measurement’’
of sky condition is vital for a determination of whether they can legally operate
their aircraft under visual flight rules.
The measurement of sky condition has historically been made by human observers
viewing the sky and recording the percentage (in oktas or tenths) of the sky obscured by
clouds. Recently, this task has been increasingly taken over by the Automated Surface
Observing System (ASOS), vertically scanning laser ceilometer beams that substitute
percentage of time clouds are sensed at various heights in the atmosphere below
12,000 ft above the ground level for the areal estimates formerly made by human
observers.
3 CASE EXAMPLES 835