Weather Depiction Chart Radar Summary Chart (SD) A detailed explanation of a station model is depicted in the  previous discussion of surface analysis charts. A weather depiction chart details surface conditions as  derived from METAR and other surface observations. It  is prepared and transmitted by computer every 3 hours  beginning at 0100 Zulu time (0100Z), and is valid at the time  of the plotted data. Designed to be used for flight planning,  it gives an overall picture of the weather across the United  States.  [Figure 4-30] A radar summary chart  [Figure 4-31]  is a computer-generated  graphical display of a collection of automated radar weather  reports (SDs). The chart is published hourly, 35 minutes  past the hour. It displays areas of precipitation as well as  information regarding the characteristics of the precipitation.  An SD chart includes: The weather depiction typically displays major fronts or  areas of high and low pressure. It also provides a graphic  display of Instrument Flight Rules (IFR), VFR, and marginal  VFR (MVFR) weather. Areas of IFR conditions (ceilings  less than 1,000 feet and visibility less than 3 miles) are  shown by a hatched area outlined by a smooth line. MVFR  regions (ceilings 1,000 to 3,000 feet, visibility 3 to 5 miles)  are shown by a non-hatched area outlined by a smooth line.  Areas of VFR (no ceiling or ceiling greater than 3,000 feet  and visibility greater than 5 miles) are not outlined. Weather  depiction charts show a modified station model that provides  sky conditions in the form of total sky cover, cloud height or  ceiling, weather, and obstructions to visibility, but does not  include winds or pressure readings like the surface analysis  chart. A bracket ( ] ) symbol to the right of the station  indicates the observation was made by an automated station.  •  No information—if information is not reported, the  chart will read “NA.” If no echoes are detected, the  chart will read “NE.” •  Precipitation intensity contours—intensity can be  described as one of six levels and is shown on the  chart by three contour intervals. •  Height of tops—the heights of the echo tops are given  in hundreds of feet MSL. •  Movement of cells—individual cell movement is  indicated by an arrow pointing in the direction of  movement. The speed of movement in knots is the  number at the top of the arrow head. “LM” indicates  little movement. $_{Figure 4-30.}$  Weather depiction chart. 4-31