Download Collected Rules of Thumb

Collected Rules of Thumb
Edward J. Hopkins
ATM OCN 100 (2) Fall 2001
1
Rule of Thumb!
Weather Systems move:
From
West to East in
midlatitudes
From East to West in tropics
ATM OCN 100 (2) Fall 2001
2
Rules of Thumb
 Unsettled
weather (clouds and
precipitation) is typically associated
with Low pressure systems !
 Relatively tranquil weather is usually
found in the vicinity of high pressure
systems.
ATM OCN 100 (2) Fall 2001
3
Rule of Thumb
 The
tighter the packing of the
isobars, the stronger the winds!
ATM OCN 100 (2) Fall 2001
4
Rules of Thumb
Other
things being equal:
–Cloudy nights have higher
temperatures than clear nights.
–Cloudy days have lower
temperatures than clear days.
ATM OCN 100 (2) Fall 2001
5
Rule of thumb
 When:
– Air temperature falls to within 2 to
3 Fahrenheit degrees of dewpoint
and
– Winds are light
 Then:
– Fog often forms.
ATM OCN 100 (2) Fall 2001
6
Rule of thumb
 If
you can expect
– Clear skies
– Near Calm conditions
 Then:
– The afternoon dewpoint provides a
good predictor of the following
morning’s low temperature.
ATM OCN 100 (2) Fall 2001
7
Rules of Thumb
From Table 16.5 (p. 391) Moran & Morgan (1997)
 At
night, air temperatures will be lower if
the sky were clear thin if the sky were
cloud-covered.
 Clear skies, light winds and a fresh snow
cover favor extreme radiative cooling and
very low air temperature by dawn.
 Falling air pressure may indicate the
approach of stormy weather, whereas
rising air pressure suggests that fair
weather is approaching.
ATM OCN 100 (2) Fall 2001
8
Rule of Thumb!
Concerning large-scale
high pressure systems:
Highs
are typically fair-weather
systems
Winds circulate in a clockwise
outflow direction from a surface
high
ATM OCN 100 (2) Fall 2001
9
Rule of Thumb!
Concerning large-scale
low pressure systems:
Lows
are typically stormyweather systems
Winds circulate in a
counterclockwise inflow
direction into a surface low
ATM OCN 100 (2) Fall 2001
10
Rule of Thumb!
Concerning large-scale
storm systems in midlatitudes:
 Systems
typically move from west to
east in midlatitudes.
 Southern storms produce more
precipitation than northern storms.
 Weather on cold side of storm differs
from weather on warm side of storm.
ATM OCN 100 (2) Fall 2001
11
Rule of Thumb!
Concerning regional weather:
 Cooling
effects of sea (lake) breeze
during
ATM OCN 100 (2) Fall 2001
12