ANIMATED MOVIE LOOP OF THE MCGILL RADAR DATA
DURING THE PASSAGE OF THE JULY 4-5, 1999 DERECHO
Click here to see the movie loop
EXPLANATION OF THE MOVIE LOOP
The animated movie loop displays four visualizations of the radar data from the McGill radar during a period of approximately 2 1/2 hours from 1:31 to 3:56 AM EDT on July 5, 1999. The four movie loop panels include:
1. Upper left....Movie loop of the radar reflectivity (precipitation) showing the derecho producing bow echo system moving across southern Quebec and into northern New England.
2. Upper right....Movie loop of the radar measured Doppler winds (in the same format as Fig. 5) as the derecho producing bow echo system moves across southern Quebec and into northern New England.
3. Two bottom panels....These panels are called "cross sections" and show a vertical view of the storm as it moves through the area. The vertical view is along the diagonal line shown on the upper panels with "A" at the beginning of the line and "B" at the end of the line. "A" is in the same place as the left edge of the bottom panels and "B" is in the same place as the right edge of the bottom panels. The scale for the height above the ground is on the left side of the panels and ranges from the surface to 14 km (surface to 46,000 feet). The funnel shaped gray area near the center of the bottom panels is at the location of the radar and is called the "cone of silence". It is the area above the radar where data cannot be seen by the radar.
3a. First bottom panel....This panel shows the vertical structure of the reflectivity (precipitation) as the derecho producing bow echo system moves along the diagonal line from A to B (on upper panels). The colors of yellow, red, and purple show the strong vertical bow echo thunderstorm moving to the right with the gust front. Trailing in a horizonal fashion behind the bow echo thunderstorm is a stratiform (non-convective) rain layer (green and blue colors).
3b. Second bottom panel....This panel shows the vertical structure of the Doppler winds (relative to the radar location) as the derecho producing bow echo system moves along the diagonal line from A to B (on upper panels). Note the decending severe winds slanting down from 4-5 km above the ground well behind the gust front to the surface at the gust front. This band shows up as dark blue and green to the left of the radar site and as purple to the right of the radar site. The development of this strong wind band is associated with the trailing stratiform rain layer (see 3a) and it is this slanting band of winds that brings the severe winds to the ground at the gust front.