A New Look at the 2004 Baltimore Water Taxi Accident

During the afternoon of 6 March 2004, the "Lady D", a water taxi servicing the Baltimore Harbor, was capsized in a strong convective windstorm, resulting in five deaths. A cluster of convective storms developed over north-central Maryland during the afternoon, and then tracked rapidly eastward through the Baltimore Harbor and upper Chesapeake Bay between 2050 and 2120 UTC. Radar wind velocity measurements from Dover AFB NEXRAD between 35 and 45 knots were associated with a cluster of downbursts as the convective storm complex approached the Baltimore Harbor. About two hours prior to the water taxi accident, the GOES imager microburst product, derived from 1847 UTC sounder data, indicated output BTD 35 to 36K over western Baltimore City in proximity to the location of the generation of the downbursts. Previous validation has identified that BTD greater than 35K corresponds to wind gust potential greater than 35 knots. According to news reports, the Lady D capsized between 2050 and 2100 UTC (see Baltimore Sun article).


Figure 1. GOES imager microburst product derived from 1847 UTC 6 March 2004 sounder data. Radar reflectivity and velocity imagery from DOVER AFB NEXRAD at 2048 UTC are overlying the microburst product image.

Figure 1 shows the 1847 UTC GOES microburst product with overlying radar imagery from Dover AFB NEXRAD. Figure 1 displays several features associated with high downburst wind gust potential: Output BTD greater than 35K (orange shading) over western Baltimore City, and radar wind velocity of 35 to 45 knots (green shading) surrounding a high reflectivity (red shading) convective storm over downtown Baltimore near the inner harbor. Between 2050 and 2100 UTC, the Lady D capsized in the Baltimore Harbor due to the strong convective winds. The cluster of convective storms then continued to track rapidly southeastward over the Chesapeake Bay, moving over the Eastern Shore at Tolchester Beach, Maryland. Although the high winds were not verified in surface observations in proximity to the Baltimore Harbor, an NOS PORTS station recorded a wind gust of 48 knots at Tolchester Beach about 20 minutes later at 2118 UTC. This high wind report was the result of a downburst, clearly marked in a wind histogram from Tolchester Beach PORTS station in Figure 2.



Figure 2. Wind histogram from Tolchester Beach PORTS station on 6 March 2004 (top) and GOES imager microburst product at 1946 UTC with overlying radar reflectivity from Dover AFB NEXRAD at 2117 UTC.

The 1946 UTC microburst product indicated high risk values downstream of the convective storm over Tolchester at 2117 UTC. Maximum output BTD over the Delmarva Peninsula of 35 to 37K indicated wind gust potential of 35 to 37 knots. The measured wind gust of 48 knots at Tolchester signifies that the rapid forward motion of the storm as well as precipitation loading, with radar reflectivity greater than 55 dBZ, were also factors in the magnitude of the wind gust associated with the downburst at Tolchester Beach. Based on radar velocity and the measured wind gust at Tolchester, wind gusts of 35 to 45 knots were likely with the convective storm complex as it moved over the Baltimore Harbor. The GOES imager microburst product two hours prior to the event would have been useful in assessing convective wind gust potential and, perhaps, may have provided guidance in issuing more timely warnings.