Here is a check-list that you can refer to when making
your forecasts.
Print it and/or refer to it often.
- Will cloud cover play an important role in your
temperature forecast? (more
info...)
Cloudiness during the day blocks sunshine and
tends to keep temperatures cool. Nighttime cloudiness
keeps surface heat from escaping into the atmosphere,
which makes overnight temperatures warmer. The
thicker the clouds, the more effect it will have.( Close)
- Will temperature advection play an important role
in your temperature forecast? (more
info...)
If the winds at the surface or at 850 mb are blowing
from an area with much warmer or cooler temperatures
(across the contour lines on a temperature map),
then it will help to move that airmass into your
location. If the winds are strong enough (greater
than 10 or 15 knots), this could have a significant
warming or cooling effect on your temperatures.
( Close)
- Will fronts play an important role in your temperature
forecast? (more
info...)
If a cold front moves through your location, you
can expect cooler temperatures behind it. Any
precipitation will usually occur in close vicinity
of the front. If a warm front moves through, expect
warmer air behind it. Any precipitation will occur
only on the north side of the front, but over
a large area. Stationary fronts can sometimes
cause precipitation, but they will not affect
your temperature forecast unless they are very
close to your location. ( Close)
- Is there sufficient moisture (from surface to
850 mb) for precipitation to occur? (more
info...)
- If there is moisture available,
is there a forcing mechanism to lift it?
Dew point is a good indicator for the amount of
moisture in the atmosphere. If there is less than
a 10 degree Celsius difference (about 18 degrees
Fahrenheit) between the air temperature and the
dew point temperature, then you would consider
there to be sufficient moisture for precipitation.
Relative humidity (RH) may also be used. In order
for precipitation to occur, however, this air
has to be lifted for the moisture to condense.
Good forcing mechanisms include but are not limited
to fronts, vorticity, divergence in the upper
atmosphere, and convergence near the surface.
( Close)
- Is there vorticity at 500 mb? (more
info...)
Vorticity refers to a type of rotating motion
in the atmosphere. The movement of high and low
areas of vorticity at 500 mb can be a good indicator
for where upward and downward motion will occur.
If an area of high vorticity will moving into
your location in the next 12 hours or so, then
you can expect upward motion to occur ahead of
it. Conversely, if an area of low vorticity is
approaching, then you will experience downward
motion. ( Close)
- Are there any short waves at 700 mb? (more
info...)
Short waves can be observed as small "kinks" in
the flow of the atmosphere (look at the contour
lines to find where they are). You can expect
upward motion to occur in areas where these are
located. ( Close)
- Is the jet stream at 300 mb positioned for development?
(more
info...)
If you divide the area of highest winds in the
jet stream into four quadrants, the left front
and right rear sections are the most favorable
areas for upward motion and precipitation to occur.
The right front and left rear sections support
downward motion and are not good for precipitation.
( Close)
Starred * links
are particularly useful at the beginning of the semester.
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Page originally designed by Meteorology Alum Heather Moser
Last modified
Monday, January 14, 2008 6:11 PM
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