Surface

1
Chart Format

• Surface
• 850 mb
• 700 mb
• 500 mb
• 300 mb
• NEMOC Training Department

2
Chart Basics

• Isobars - Lines of equal pressure. Drawn on
  constant height charts as solid black lines.
• Contours - Lines of equal height. Drawn on
  constant pressure charts as solid black lines.
• Isotherms - Lines of equal air temperature.
  Drawn as dashed red lines every 5oC.
  Base 0oC.
  
  Note - 0oC on 850 mb chart is dashed blue.

3
Chart Basics (cont.)

• Trough Axes - An elongated area of relatively low
  pressure on a constant height chart or low height
  on a constant pressure chart. Depicted as dashed
  brown lines on the surface and solid black lines
  aloft.
• Ridge Axes - An elongated area of relatively high
  pressure on a constant height chart or high
  height on a constant pressure chart. Depicted as
  zig-zag black lines.

4
Chart Basics (cont.)

• Moisture - Areas where dew point depression is
  close to saturation are considered moist.
  Encompassed by green scalloping.
• Areas with plotted dew point depressions of 3, 4,
  or 5 are scalloped in green and the edge is
  shaded green.
• Areas with plotted dew point depressions of 0, 1,
  or 2 are scalloped in green and shaded solid
  green, using a darker shade of green than above.

5
Jet Stream Chart Basics

• Isotachs - Lines of equal wind speed. Drawn as
  dashed green lines.
• Drawn using 20 knot increments. Base of 50
  knots.
• Jet Max - A concentrated area of strong winds at
  upper levels. Center is shaded purple.
• More of less football/banana shaped.
• Labeled with the highest wind speed believed to
  be present in the max.
• Labeled speed must at least equal the highest
  wind reported and may not exceed the max reported
  wind by more than 10 knots.

6
Jet Stream Chart Basics (Cont.)

• Jet Stream Axis - Band of maximum winds at upper
  levels. Drawn as solid purple line.

7
Intervals

• Constant Height Chart - Isobars drawn using...
• Surface - 4 mb increments. Base of 1000 mb.
• Constant Pressure Charts - Contours drawn
  using...
• 850 mb - 3 dam increments. Base of 150 dam.
  
• 700 mb - 3 dam increments. Base of 300 dam.
• 500 mb - 6 dam increments. Base of 558 dam.
• 300 mb - 12 dam increments. Base of 912 dam.
• 250 mb - 12 dam increments. Base of 912 dam.
• Note 1 decameter (dam) 10 meters

8
Review

• The 700 mb Chart is normally labeled every _____
  meters.
• 30
• Isotachs are drawn at what intervals?
• 20 knots
• What color is past history on a surface chart?
• Yellow
• What is the interval and color of isotherms on
  upper air charts?
• 5oC - Red