the 700 mb forecast chart, the 70% relative humidity line usually
encloses areas that are likely to have clouds
On the 700
mb forecast chart, the
90% relative humidity line often encloses areas
where precipitation is likely. If upward
velocities are present, the chance of measurable
precipitation in enhanced.
On the 850 mb forecast chart, snow is likely north of the -5 degree
Celsius isotherm, whereas rain is likely south of this line.
The 5400 1000-500 mb thickness line
is also used during the cool season east of the Rockies to forecast
- For the storm to intensify
(deepen), an area of upper-level divergence must
be over the cyclonic storm. On a 500 mb forecast
chart that shows vorticity, look for a vorticity
maximum (vort max) and remember that to the east
of an area of positive vorticity we usually find
upper-level divergence, upward air motions, and
cyclonic storm motion
from Meteorology Today by C. D.
QUESTIONS FOR THOUGHT:
You are in Calgary, Canada, 100 km east of the Rockies. The
current wind is from the north. Looking at a prog for tomorrow,
you see that the wind will be from the west. Will tomorrow's
temperature be warmer or cooler than today? Explain.
What type of weather would you expect if the 700 hPa relative
humidity is 95% and the 1000-500 hPa thickness is 5000 meters?