Chart Format Surface 850 mb 700 mb 500

Chart Format Surface 850 mb 700 mb 500 mb 300 mb NEMOC Training Department

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

Chart Basics (cont. ) z 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. z 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.

Chart Basics (cont. ) z Moisture - Areas where dew point depression is close to saturation are considered “moist”. Encompassed by green scalloping. y. Areas with plotted dew point depressions of 3, 4, or 5 are scalloped in green and the edge is shaded green. y. 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.

Jet Stream Chart Basics z Isotachs - Lines of equal wind speed. Drawn as dashed green lines. y. Drawn using 20 knot increments. Base of 50 knots. z Jet Max - A concentrated area of strong winds at upper levels. Center is shaded purple. y. More of less football/banana shaped. y. Labeled with the highest wind speed believed to be present in the max. x. Labeled speed must at least equal the highest wind reported and may not exceed the max reported wind by more than 10 knots. J 115

Jet Stream Chart Basics (Cont. ) z Jet Stream Axis - Band of maximum winds at upper levels. Drawn as solid purple line. J 115

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

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