Weather Forecasting:
This is a guided tour through weather forecasting intended to help you better understand weather
forecasting.
Methods List six methods of Weather Forecasting listed in the Forecasting Methods section of
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/home.rxml . For each method describe the method
in your own words well enough so you can tell the difference between each Method.
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Notes on how to navigate through this online meteorology guide.
For each section of this module work through the section using the
button near the bottom of the
page. When you are through with the section you will see a
and can either advance to the next
section by using this arrow or advance to the next section by going back to the main page at
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fcst/home.rxml .
Advance to the section on Surface Features and work through this complete section to answer the
questions below.
What is an anticyclone?
How does air circulate around an anticyclone in the Northern Hemisphere? Clockwise or counterclockwise?
With air moving away from the anticyclone region, air must sink from above to replace it. This sinking
motion leads to generally ____________ skies and ____________ precipitation near the high.
Northerly winds associated with an approaching high are likely to result in _____________temperatures
while southerly winds found on the backside of a high, or once a high has passed through, typically result in
a _____________ trend.
What is a cyclone?
In what direction does wind circulate around a cyclone? Clockwise or counterclockwise?
Air converges into a low pressure center which causes air to _____________
The____________________ may produce clouds and precipitation.
As a cyclone approaches, the likelihood of clouds and precipitation _______________.
Southerly winds associated with an approaching cyclone are likely to result in ___________ temperatures
while northerly winds found on the backside of a low, or once a low has passed through, typically result in
______________________ trend.
A cold front is defined as the transition zone where a ____________ air mass is replacing a ______________
air mass.
The air mass behind a cold front is likely to be ________________ than the air mass before the front.
The air cool air rises and the moisture condenses to produce clouds and precipitation
__________________________the cold front. In contrast to lifting along a warm front , upward motions
along a cold front are typically ___________________, producing ________________ and
____________________ bands of showers and thunderstorms. However, these bands are often quite
narrow (a couple hundred kilometers across) and move rapidly just ahead of the cold front.
What is a warm front?
Warm air rides up and over the cold air mass, cooling as it rises, producing clouds and precipitation in
advance of the surface warm front. Because the lifting is ________________ and steady, generally
______________________________________ precipitation develops ahead of a warm front.
What is a stationary front?
If a stationary front is nearby and ___________________ is approaching along the front,
______________________ amounts of precipitation are possible.
What is an occluded front?
What is a dry line?
If a dry-line is approaching your region, predict that air will be much _________________ after the boundary
moves through. Storms are possible as the dry-line approaches. The temperature may rise after the dry-line
passes through, since dry air heats up more quickly than moist air.
Advance to the section on Temperatures and work through this complete section to answer the questions
below.
Forecast Tip:
When forecasting daytime temperatures, if cloudy skies are expected, forecast __________________
temperatures than you would predict if clear skies were expected.
Forecast Tip:
When forecasting nighttime temperatures, if cloudy skies are expected, forecast ___________________
temperatures than you would predict if clear skies were expected.
Forecast Tip:
If a city is expected to be located west of a high pressure center then _______________ temperatures are
likely. However, if the city is expected to be in the northerly winds of a high pressure center, then forecast
____________________ temperatures. Cities under the influence of high pressure centers can expect
generally fair weather with little or no precipitation.
Forecast Tip:
If a city is expected to be located west of a low pressure center then _________________ temperatures are
likely. However, if the city is expected to be in the southerly winds of either a high or low pressure center,
then forecast __________________ temperatures. Cities under the influence of low pressure centers can
expect generally ______________ with ___________________
What is temperature advection?
Forecast Tip:
When forecasting temperatures, look at the temperatures upstream from the station for which you making
a forecast. If they are warmer, that means ____________________ air is being transported towards your
station and the temperature should ____________. Put in another way, if there is warm advection
occurring at a given station, expect the temperatures to increase. In contrast, if cold advection is occurring
at a given station, expect the temperatures to drop..
Forecast Tip:
When snow cover is present, forecast ________________________ daytime temperatures than you would
normally predict if there was no snow cover. At night, snow on the ground readily gives off heat. This
causes rapid cooling. Forecast the overnight temperature to be __________________ than you would
predict if there was no snow cover.
Forecast Tip:
On a calm night, the maximum surface cooling can take place. But on a windy night, some warmer air is
mixed downward to the surface, which prevents the temperatures from dropping as quickly as they would
on a clear night. Therefore, forecast _________________________ temperatures for a windy night than for
a calm night.
Advance to the section on Precipitation and work through this complete section to answer the questions
below.
Forecast Tip:
If there is sufficient moisture in the air (dew point near air temp)and a forcing mechanism like a cold front
(for example) is approaching the area, then there is an increased probability that _____________________
will occur.
Most precipitation that reaches the ground actually begins as ________________high in the atmosphere.
Forecast Tip:
When forecasting precipitation type, if temperatures are expected to be above freezing, then _________ is
most likely. If temperatures are expected to be below freezing, then forecast for _________. Snow can
actually survive falling through 1000 ft of above freezing temperatures without melting. The reason for this
is as evaporation takes place from the snow flake, the snow flake is cooled. This loss of heat from
evaporation offsets the heat gained by the environment.
The Low pressure system (middle latitude cyclone) is moving towards the North East. The dash lines show
the fronts 6 hr ago.
The 12 hr forecast for position 1 is: Cloudy and cold this morning with snow this afternoon and tonight.
The 12 hr forecast for position 2 is: Partly Cloudy and continues warm through this afternoon.
The 12 hr forecast for position 3 is: “Cloudy with possible showers today, turning colder by tonight.
The 12 hr forecast for position 4 is: Clearing and colder today with continued rising pressure.
Forecast Practice (Test your understanding) Answers are at the end. Try to answer the
questions without looking.
Multiple Choice
Identify the choice that best completes the statement or answers the question.
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1. Suppose it is warm and raining, and a cold front is moving toward your location. Directly behind the cold
front, it is cold and snowing. Still further behind the front, the weather is cold and clearing. If the front is
scheduled to pass your area in 6 hours, a persistence forecast for your area for 12 hours from now would be:
a. cold and snowing.
b. cold and clearing.
c. cold and cloudy.
d. warm and raining.
e. not enough information on which to base a forecast.
2. A persistence forecast could be quite accurate when:
a. a frontal system approaches your location at constant speed.
b. you are positioned in the middle of a large, stationary air mass.
c. the weather has been unusually cold for several days.
d. upper level winds blow straight from west to east.
3. Predicting the weather by weather types employs which forecasting method?
a. probability
b. steady-state
c. analogue
d. persistence
e. guess
4. Suppose that where you live, the middle of January is typically several degrees warmer than the rest of the
month. If you forecast this "January thaw" for the middle of next January, you would have made a:
a. forecast based on the analogue method.
b. persistence forecast.
c. forecast based on weather types.
d. probability forecast.
e. climatological forecast.
5. A prog is:
a. a chart that interprets the current state of the atmosphere.
b. an instrument that draws lines on an upper-level chart.
c. a new method of forecasting the weather.
d. a forecast chart that shows the atmosphere at some future time.
e. another name for a probability forecast.
6. The greatest improvement in forecasting skill during the past 30 years has been made in forecasting:
a. snowstorms along the eastern seaboard.
b. the development of middle latitude cyclones in the Pacific Ocean.
c. severe storm warnings for hurricanes and tornadoes.
d. the movement of warm and cold fronts.
e. maximum and minimum temperature 6 to 10 days into the future.
ForcastPractice
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
D
B
C
E
D
C
PTS:
PTS:
PTS:
PTS:
PTS:
PTS:
1
1
1
1
1
1