Investigation SURFACE AIR PRESSURE PATTERNS

1A - 8
Continue drawing and labeling isobars of the series where they existed within the data
pattern. For example, the next higher isobar value to the north and west of the 1024-mb
isobar just completed is the 1028-mb isobar, which will be an unclosed loop. Be sure to label
your isobars with their values when their ends extend beyond the data field. Look for regions
where there are closed isobars. Where the isobars enclose lower pressures, draw a bold L
where the lowest pressure is located. Where higher pressures are enclosed, place a bold H to
mark the location of the highest pressure.
9. Figure 3 is the analyzed surface pressure map from the course website produced by
the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for
Environmental Prediction (NCEP) for 12Z 29 NOV 2011. The Figure 3 map shows the
location of isobars, air pressure system centers and fronts. Color-coded shadings indicate
where a national network of weather radars detected varying intensities of precipitation at
map time. The Figure 3 map [(is)(is not)] the same time and date as the Figure 2 map of
pressures you have just analyzed.
Compare your isobar pattern with that drawn on the Figure 3 map. The Figure 3 map of
isobars is constructed by a computer based on a much more complete set of pressure values.
(This may account for some of the variations between your analysis and that by the computer.
The more extensive data set is also the source of several additional plotted Hs and Ls
denoting locally minimally higher or lower pressure centers, respectively.)
By analyzing the pressure values reported on weather maps to find pressure patterns, one
can locate the centers of locally highest and lowest pressures. We will see that these pressure
centers often mark the centers of major weathermakers, either regions of fair weather or
stormy conditions, respectively.
For assistance in locating states and cities of the United States mentioned in this and
subsequent investigations, one good source is Google maps, http://maps.google.com/maps.
By using the directional arrows and scale to the left of the map area, you can move and zoom
in (+) or out (–) to pinpoint locations. You may wish to bookmark this (or another favorite)
map page for reference as we proceed through the course.
Unless otherwise stated, all maps are from the course website. These maps, text data and
satellite views are produced by the National Centers for Environmental Prediction (NCEP)
of the National Weather Service (NWS), an office of the National Oceanic and Atmospheric
Administration (NOAA).
Weather Studies: Investigations Manual 2012-2013 & Summer 2013