for the most part available freely online, but finding it and more importantly inter- preting it are tasks best left for the forensic meteorologist.
A variety of analysis techniques may be employed to ascertain weather conditions. One of the most important includes spa- tial and temporal interpretation. For exam- ple, there are only around fifty weather sta- tions (Fig. 1) recording hourly temperatures in Vermont, and with area coverage over 9,000 square miles, that’s only an average of one station for every 180 square miles. But with the right approaches, air tempera- tures can be interpolated to an accuracy of a few degrees Fahrenheit at all locations. Reconstructing cloud conditions and pres- ent weather (rain, snow, fog), is more chal- lenging, but careful analysis using addition- al datasets such as satellite imagery can, in most cases, produce useful results. Skilled forensic meteorologists can pro- vide value-added analysis to a variety of weather-related incidents. These include:
1. Determine rainfall amounts, cover- age, timing, intensity within a thun- derstorm;
2. Determine historical significant of heavy rainfall event (e.g., Tropical Storm Irene);
3. Verify storm damage from high winds, flooding, hail, and/or light- ning strikes;
4. Estimate observed maximum wind gusts and timing with a land-falling hurricane;
5. Describe likely road surface charac- teristics during a winter car accident or slip and fall;
6. Describe weather forecast infor- mation and storm watch/warnings available surrounding a period in question;
7. Recreate sun-angle and sky condi- tions surrounding an accident;
8. Reconstruct air path trajectories to determine plume sources—who is responsible for air pollution;
9. Estimate wind and wave conditions for admiralty cases;
10. Provide cloud base, visibility, and related weather information for air- craft incidents.
Severe Thunderstorm Example: The Indiana State Fair Incident
On the night of August 13, 2011, a se-
vere thunderstorm moved through the In- diana State Fairgrounds as a large crowd was watching an outdoor music perfor-
mance. The outflow boundary, or lead- ing edge of cold air at the thunderstorm’s edge, arrived by 9:00 PM producing winds around 60 MPH. This resulted in the struc- tural failure of staging equipment, which collapsed, killing four people and injuring scores more. From the author’s perspective, this event should have been prevented given the clear storm radar signatures. This incident high- lights apparent flaws in the decision sup- port process of getting the right weather information to the right persons, and hav- ing those persons take the right protective actions. But of more concern for the pres- ent discussion is the demonstration of how weather radar data and National Weather Service warning information can be incor- porated into reconstructing a severe thun- derstorm. Figure 2 shows the National Weather Service radar base reflectivity from 8:15 to 9:00 PM Eastern Daylight Time; the in- cident location is shown by the white star. Warmer colors, such as orange and red show more intense rainfall, while greens and blues show less intense rainfall. Ap- proximately forty-five minutes prior to the incident, a line of strong thunderstorms was located approximately
thirty miles to the northwest. By 8:30 PM, this line of
Figure 2. Base radar reflectivity from Indianapolis, IN, National Weather Service Doppler radar. Courtesy Iowa State University:
http://mesonet.agron.iastate.edu/archive/.
18 THE VERMONT BAR JOURNAL • WINTER 2012
www.vtbar.org
The Forensic Meteorologist—“Reconstructing Weather”
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