ArticleIn this particular case, the plaintiff and her party had reported rain during their approach to the crash site. Yet, the nearest recording stations just showed a trace of rain. With the application of the Doppler weather records our forensic meteorologist, Dr. Raymond Lee, was able to show that the rainfall was sufficient to have washed asphalt resurfacing products in to the adjacent lane.
Vehicle Crash, Meteorological Investigation – Expert Report
Prepared 27 September 2012
Rainfall Conditions at the Crash Site
National Weather Service (NWS) Doppler weather radar at Albuquerque, NM (station KABX) shows rain beginning to fall by 1553 MDT on US550 near the DOE crash site on 1 September 2009 (no rain was detected anywhere along this section of US550 before then). From 1553 MDT onward, the area of rain steadily expanded over the next 2 hours until it covered several miles of the southbound approach to the site. The total amount of rain that fell along this part of US550 increased throughout the late afternoon of 1 September 2009, and would have yielded measurable rain at ground level by ~1630 MDT (see Figure 1). By 1813 MDT, up to 0.3” of rain had fallen all along DOE’s route (Figure 2), with slightly more on the ground by the time that she crashed (~1830 MDT; see Figure 3).
From 1709-1817, the crash site experienced rainfall rates of at least 0.1”-0.25”/hour, with rates of up to 0.5”/hour occurring from 1726–1817 MDT. At 1817 MDT, the rainfall rate was 0.1”–0.25”/hour at the crash site and for at least 10 miles north of it. At 1830 MDT, the rainfall rate was up to 0.1”/hour at the crash site and for at least 2 miles north of it. The time sequence of KABX radar maps indicates that this rain most likely fell as irregular, spotty showers, with the result that DOE and other drivers could not be certain of the rain’s areal extent or future intensity. Ongoing showery rain in the amounts and intensities measured here will produce a thin skin of water and occasional shallow puddles on impervious road surfaces, even ones that are well drained. Because oils on road surfaces have lower density than water, any such oil will float on rainwater in very thin (but still very slippery) films of highly variable extent.
Figure 1: NWS Doppler weather radar measurements of total storm precipitation (marked in gray) by 1631 MDT on 1 September 2009 near the DOE crash site on US550 (see label and marker near bottom center of map).
Figure 2: NWS Doppler weather radar measurements of total storm precipitation (marked in transparent gray) by 1813 MDT on 1 September 2009 near the DOE crash site on US550. At this site and for several miles north of it, up to 0.3” of rain had fallen by 1813 MDT.
Figure 3: NWS Doppler weather radar measurements of total storm precipitation (marked in transparent gray) by 1830 MDT on 1 September 2009 near the DOE crash site on US550. At this site and for several miles north of it, up to 0.3” of rain had fallen by 1830 MDT.
My opinions and conclusions are based on the information available to me as of today and are accurate to within a reasonable degree of scientific certainty. If new or changed data becomes available, I would need to determine whether that data affects the conclusions given above.
Dr. Lee is an expert in the determination of weather conditions and their effect on vehicle collisions. He has spent nearly 30 years in meteorological research and education, including the last 17 years as a research professor at the U.S. Naval Academy.