A
prognostic chart
is a map displaying the likely weather forecast for a future time. Such charts generated by
atmospheric models
as output from
numerical weather prediction
and contain a variety of information such as
temperature
,
wind
,
precipitation
and
weather fronts
. They can also indicate derived atmospheric fields such as
vorticity
, stability indices,
[
clarification needed
]
or
frontogenesis
. Forecast errors need to be taken into account and can be determined either via absolute error, or by considering persistence and absolute error combined.
[
clarification needed
]
Definition
[
edit
]
The forecast map showing the state of the atmosphere at a future time is called a prognostic chart. Prognostic charts generated by computer models are sometimes referred to as machine-made forecasts.
[1]
Variety
[
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]
Surface weather prognostic charts for
mariners
indicate the positions of high and low pressure areas, as well as frontal zones, up to five days into the future. Surface wind direction and speed is also forecast on this type of chart. Wave prognostic charts show the expected sea state at some future time.
[2]
Low-level prognostic charts used by
aviators
show the forecast between the Earth's surface and 24,000 feet (7,300 m) above
sea level
over the next two days. They show areas where
visual flight rules
are in effect,
instrument flight rules
are in effect, the height of the freezing level, the location of weather features, and areas of moderate to severe turbulence.
[3]
Prognostic charts can be made of isentropic surfaces (along a certain
potential temperature
surface determined in
kelvins
) in regards to
moisture advection
, mean temperatures at the surface, mean sea level pressures, and precipitation either for a single day or multiple days.
[4]
For purposes of
severe weather
, prognostic charts can be issued to depict current
weather watches
, convective outlooks for
thunderstorms
multiple days into the future, and
fire weather
outlooks.
[5]
Manual
[
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]
A manual prognostic chart of the weather in the United States 36 hours into the future
Manual prognostic charts depict
tropical cyclones
,
turbulence
, weather fronts,
rain
and
snow
areas, precipitation type and coverage indicators, as well as centers of
high
and
low pressure
.
[6]
Within the United States, these type of maps are generated by the
Hydrometeorological Prediction Center
,
[7]
the
Storm Prediction Center
,
[5]
the
Ocean Prediction Center
,
[8]
and the
National Hurricane Center
. The
Aviation Weather Center
re-sends these maps, and also generates specialized maps for aviation.
[9]
Automated
[
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]
An automated prognostic chart of the 96-hour forecast of 850
mbar
geopotential height
and
temperature
from the
Global Forecast System
Atmospheric models are computer programs that produce
meteorological
information, including prognostic charts, for future times at given locations and altitudes.
[10]
Within any modern model is a set of equations, known as the
primitive equations
, used to predict the future state of the atmosphere.
[11]
These equations?along with the
ideal gas law
?are used to evolve the
density
,
pressure
, and
potential temperature
scalar fields
and the
velocity
vector field
of the atmosphere through time. Additional transport equations for pollutants and other
aerosols
are included in some primitive-equation mesoscale models as well.
[12]
These equations are initialized from the analysis data and rates of change are determined. These rates of change predict the state of the atmosphere a short time into the future; the time increment for this prediction is called a
time step.
This
time stepping
is repeated until the solution reaches the desired forecast time.
[13]
Time steps for global models are on the order of tens of minutes,
[14]
while time steps for regional models are between one and four minutes.
[15]
The global models are run outwards to varying times into the future. The
UKMET
Unified Model
is run six days into the future,
[16]
the
European Centre for Medium-Range Weather Forecasts
model is run out to 10 days into the future,
[17]
while the
Global Forecast System
model run by the
Environmental Modeling Center
is run 16 days into the future.
[18]
Verification
[
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]
Around 1950, a good surface prognostic chart was considered to be one whose
isobars
were in the correct location.
[19]
By 1957, it was proposed when isobars or height lines at the 500 hectopascals (15 inHg) pressure level in the atmosphere were being verified, that the degree of persistence should be considered so as to avoid getting bad forecasts for slow moving systems too much credit.
[20]
See also
[
edit
]
References
[
edit
]
- ^
Ahrens, C. Donald (2008).
Essentials of meteorology: an invitation to the atmosphere
. Cengage Learning. p. 244.
ISBN
978-0-495-11558-8
.
- ^
Kotsch, William J. (1983).
Weather For th Mariner
. Naval Institute Press. pp. 236?239.
ISBN
978-0-87021-756-2
.
- ^
United States Naval Air Training Command (April 2003).
Aviation Weather Student Guide
(PDF)
.
Corpus Christi, Texas
Naval Air Station. pp. 2?5, 2?6
. Retrieved
2011-02-26
.
- ^
United States Department of Agriculture
(1941).
Climate and Man: Part Two
. The Minerva Group, Inc. pp. 647?651.
ISBN
978-1-4102-1539-0
.
- ^
a
b
Storm Prediction Center
(2011).
"Forecast Products"
.
National Centers for Environmental Prediction
. Retrieved
2011-02-27
.
- ^
Federal Aviation Administration
(2007).
Gliding Flyer Handbook
. Skyhorse Publishing, Inc. pp. 9?30, 9?31.
ISBN
978-1-60239-061-4
.
- ^
Hydrometeorological Prediction Center
(2011).
"Short Range Forecasts"
.
National Centers for Environmental Prediction
. Retrieved
2011-02-26
.
- ^
Ocean Prediction Center
(2011),
Atlantic Offshore
,
National Centers for Environmental Prediction
- ^
Aviation Weather Center
(2011).
"Analysis and forecast surface conditions (prog charts)"
.
National Centers for Environmental Prediction
. Retrieved
2011-02-26
.
- ^
Ahrens, C. Donald (2008).
Essentials of meteorology: an invitation to the atmosphere
. Cengage Learning. p. 244.
ISBN
978-0-495-11558-8
.
- ^
Pielke, Roger A. (2002).
Mesoscale Meteorological Modeling
.
Academic Press
. pp.
48
?49.
ISBN
0-12-554766-8
.
- ^
Pielke, Roger A. (2002).
Mesoscale Meteorological Modeling
.
Academic Press
. pp.
18
?19.
ISBN
0-12-554766-8
.
- ^
Pielke, Roger A. (2002).
Mesoscale Meteorological Modeling
.
Academic Press
. pp.
285
?287.
ISBN
0-12-554766-8
.
- ^
Sunderam, V. S.; van Albada, G. Dick; Peter, M. A.; Sloot, J. J. Dongarra (2005).
Computational Science ? ICCS 2005: 5th International Conference, Atlanta, GA, USA, May 22?25, 2005, Proceedings, Part 1
. Springer. p. 132.
ISBN
978-3-540-26032-5
.
- ^
Zwieflhofer, Walter; Kreitz, Norbert; European Centre for Medium Range Weather Forecasts (2001).
Developments in teracomputing: proceedings of the ninth ECMWF Workshop on the Use of High Performance Computing in Meteorology
. World Scientific. p. 276.
ISBN
978-981-02-4761-4
.
- ^
Chan, Johnny C. L. & Jeffrey D. Kepert (2010).
Global Perspectives on Tropical Cyclones: From Science to Mitigation
. World Scientific. pp. 295?296.
ISBN
978-981-4293-47-1
.
- ^
Holton, James R. (2004).
An introduction to dynamic meteorology, Volume 1
. Academic Press. p. 480.
ISBN
978-0-12-354015-7
.
- ^
Brown, Molly E. (2008).
Famine early warning systems and remote sensing data
. Springer. p. 121.
ISBN
978-3-540-75367-4
.
- ^
Eugenia Kalnay
(2003).
Atmospheric Modeling, Data Assimilation and Predictability
(PDF)
. Cambridge University Press. p. 7.
ISBN
0-521-79179-0
. Retrieved
2011-02-27
.
- ^