CORRECT!

2). On a Surface Analysis Chart, the solid lines that depict sea level pressure patterns are called

a). millibars.
b). isogons.
c). isobars.
The answer is:
c). isobars.

Let's take a look at today's Surface Analysis Chart (May 14, 2009). The national view indicates that there are three distinct high pressure areas existing: one over New England extending into the southeast states, one centered over the midwest, and one pushing its way east from the west coast. There are low pressure areas also appearing, indicated by the red 'L's on the chart.

Isobars are the gray lines on the chart labeled with numbers indicating the atmospheric pressure along the line in millibars (mb). When pilots consult these charts during their weather self-brief, it is helpful to consider the pressure differences in order to determine where the strongest winds are likely to be. Isobars indicate areas of equal pressure, and where there is a lot of pressure change over a short distance (such as over New England in this example), the winds in that area are likely to be quite strong. Indeed, the METAR (Aviation Routine Weather Report) for Bangor international Airport in Bangor, ME (KGBR) for 3:53pm today, local time, is reproduced here:

METAR KBGR 19:53Z 05/14/09
KBGR 141953Z 18023G36KT 10SM FEW030 BKN046
OVC080 13/06 A3024 RMK AO2 PK WND 19037/1943
SLP240 T01280061

Note that the winds reported in the METAR are from the south at 23 knots gusting to 36 knots (18023G36KT). This METAR confirms for us that the winds in the areas of steep pressure gradients are of special interest to pilots operating in those areas.

back

back