<s>
The	O
history	B-Application
of	I-Application
numerical	I-Application
weather	I-Application
prediction	I-Application
considers	O
how	O
current	O
weather	O
conditions	O
as	O
input	O
into	O
mathematical	O
models	O
of	O
the	O
atmosphere	O
and	O
oceans	O
to	O
predict	O
the	O
weather	O
and	O
future	O
sea	O
state	O
(	O
the	O
process	O
of	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
)	O
has	O
changed	O
over	O
the	O
years	O
.	O
</s>
<s>
Though	O
first	O
attempted	O
manually	O
in	O
the	O
1920s	O
,	O
it	O
was	O
not	O
until	O
the	O
advent	O
of	O
the	O
computer	O
and	O
computer	B-Application
simulation	I-Application
that	O
computation	O
time	O
was	O
reduced	O
to	O
less	O
than	O
the	O
forecast	O
period	O
itself	O
.	O
</s>
<s>
ENIAC	B-Device
was	O
used	O
to	O
create	O
the	O
first	O
forecasts	O
via	O
computer	O
in	O
1950	O
,	O
and	O
over	O
the	O
years	O
more	O
powerful	O
computers	O
have	O
been	O
used	O
to	O
increase	O
the	O
size	O
of	O
initial	O
datasets	O
as	O
well	O
as	O
include	O
more	O
complicated	O
versions	O
of	O
the	O
equations	O
of	O
motion	O
.	O
</s>
<s>
The	O
development	O
of	O
global	O
forecasting	O
models	O
led	O
to	O
the	O
first	O
climate	B-Application
models	I-Application
.	O
</s>
<s>
Because	O
the	O
output	O
of	O
forecast	O
models	O
based	O
on	O
atmospheric	O
dynamics	O
requires	O
corrections	O
near	O
ground	O
level	O
,	O
model	B-Application
output	O
statistics	O
(	O
MOS	O
)	O
were	O
developed	O
in	O
the	O
1970s	O
and	O
1980s	O
for	O
individual	O
forecast	O
points	O
(	O
locations	O
)	O
.	O
</s>
<s>
This	O
technique	O
can	O
correct	O
for	O
model	B-Application
resolution	O
as	O
well	O
as	O
model	B-Application
biases	O
.	O
</s>
<s>
Even	O
with	O
the	O
increasing	O
power	O
of	O
supercomputers	O
,	O
the	O
forecast	O
skill	O
of	O
numerical	B-General_Concept
weather	I-General_Concept
models	I-General_Concept
only	O
extends	O
to	O
about	O
two	O
weeks	O
into	O
the	O
future	O
,	O
since	O
the	O
density	O
and	O
quality	O
of	O
observations	O
—	O
together	O
with	O
the	O
chaotic	O
nature	O
of	O
the	O
partial	O
differential	O
equations	O
used	O
to	O
calculate	O
the	O
forecast	O
—	O
introduce	O
errors	O
which	O
double	O
every	O
five	O
days	O
.	O
</s>
<s>
The	O
use	O
of	O
model	B-Application
ensemble	B-Application
forecasts	I-Application
since	O
the	O
1990s	O
helps	O
to	O
define	O
the	O
forecast	O
uncertainty	O
and	O
extend	O
weather	O
forecasting	O
farther	O
into	O
the	O
future	O
than	O
otherwise	O
possible	O
.	O
</s>
<s>
In	O
1904	O
,	O
Vilhelm	O
Bjerknes	O
derived	O
a	O
two-step	O
procedure	O
for	O
model-based	O
weather	O
forecasting	O
.	O
</s>
<s>
First	O
,	O
a	O
diagnostic	O
step	O
is	O
used	O
to	O
process	O
data	O
to	O
generate	O
initial	B-Algorithm
conditions	I-Algorithm
,	O
which	O
are	O
then	O
advanced	O
in	O
time	O
by	O
a	O
prognostic	O
step	O
that	O
solves	O
the	O
initial	O
value	O
problem	O
.	O
</s>
<s>
Bjerknes	O
pointed	O
out	O
that	O
equations	O
based	O
on	O
mass	O
continuity	O
,	O
conservation	O
of	O
momentum	O
,	O
the	O
first	O
and	O
second	O
laws	O
of	O
thermodynamics	O
,	O
and	O
the	O
ideal	O
gas	O
law	O
could	O
be	O
used	O
to	O
estimate	O
the	O
state	O
of	O
the	O
atmosphere	O
in	O
the	O
future	O
through	O
numerical	B-General_Concept
methods	I-General_Concept
.	O
</s>
<s>
With	O
the	O
exception	O
of	O
the	O
second	O
law	O
of	O
thermodynamics	O
,	O
these	O
equations	O
form	O
the	O
basis	O
of	O
the	O
primitive	O
equations	O
used	O
in	O
present-day	O
weather	B-General_Concept
models	I-General_Concept
.	O
</s>
<s>
In	O
1922	O
,	O
Lewis	O
Fry	O
Richardson	O
published	O
the	O
first	O
attempt	O
at	O
forecasting	O
the	O
weather	O
numerically	B-General_Concept
.	O
</s>
<s>
The	O
large	O
error	O
was	O
caused	O
by	O
an	O
imbalance	O
in	O
the	O
pressure	O
and	O
wind	O
velocity	O
fields	O
used	O
as	O
the	O
initial	B-Algorithm
conditions	I-Algorithm
in	O
his	O
analysis	O
.	O
</s>
<s>
The	O
first	O
successful	O
numerical	O
prediction	O
was	O
performed	O
using	O
the	O
ENIAC	B-Device
digital	O
computer	O
in	O
1950	O
by	O
a	O
team	O
led	O
by	O
American	O
meteorologist	O
Jule	O
Charney	O
.	O
</s>
<s>
When	O
news	O
of	O
the	O
first	O
weather	O
forecast	O
by	O
ENIAC	B-Device
was	O
received	O
by	O
Richardson	O
in	O
1950	O
,	O
he	O
remarked	O
that	O
the	O
results	O
were	O
an	O
"	O
enormous	O
scientific	O
advance.	O
"	O
</s>
<s>
The	O
first	O
calculations	O
for	O
a	O
24‑hour	O
forecast	O
took	O
ENIAC	B-Device
nearly	O
24hours	O
to	O
produce	O
,	O
but	O
Charney	O
's	O
group	O
noted	O
that	O
most	O
of	O
that	O
time	O
was	O
spent	O
in	O
"	O
manual	O
operations	O
"	O
,	O
and	O
expressed	O
hope	O
that	O
forecasts	O
of	O
the	O
weather	O
before	O
it	O
occurs	O
would	O
soon	O
be	O
realized	O
.	O
</s>
<s>
In	O
the	O
United	O
Kingdom	O
the	O
Meteorological	O
Office	O
first	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
was	O
completed	O
by	O
F	O
.	O
H	O
.	O
Bushby	O
and	O
Mavis	O
Hinds	O
in	O
1952	O
under	O
the	O
guidance	O
of	O
John	O
Sawyer	O
.	O
</s>
<s>
These	O
experimental	O
forecasts	O
were	O
generated	O
using	O
a	O
12	O
×	O
8	O
grid	O
with	O
a	O
grid	O
spacing	O
of	O
260km	O
,	O
a	O
one-hour	O
time-step	O
,	O
and	O
required	O
four	O
hours	O
of	O
computing	O
time	O
for	O
a	O
24-hour	O
forecast	O
on	O
the	O
EDSAC	B-Device
computer	O
at	O
the	O
University	O
of	O
Cambridge	O
and	O
the	O
LEO	B-Device
computer	I-Device
developed	O
by	O
J	O
.	O
Lyons	O
and	O
Co	O
.	O
</s>
<s>
Following	O
these	O
initial	O
experiments	O
,	O
work	O
moved	O
to	O
the	O
Ferranti	B-Device
Mark	I-Device
1	I-Device
computer	O
at	O
the	O
Manchester	O
University	O
Department	O
of	O
Electrical	O
Engineering	O
and	O
in	O
1959	O
a	O
Ferranti	B-Device
Mercury	I-Device
computer	O
,	O
known	O
as	O
'	O
Meteor	O
 '	O
,	O
was	O
installed	O
at	O
the	O
Met	O
Office	O
.	O
</s>
<s>
Operational	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
in	O
the	O
United	O
States	O
began	O
in	O
1955	O
under	O
the	O
Joint	O
Numerical	B-General_Concept
Weather	I-General_Concept
Prediction	I-General_Concept
Unit	O
(	O
JNWPU	O
)	O
,	O
a	O
joint	O
project	O
by	O
the	O
U.S.	O
Air	O
Force	O
,	O
Navy	O
,	O
and	O
Weather	O
Bureau	O
.	O
</s>
<s>
The	O
JNWPU	O
model	B-Application
was	O
originally	O
a	O
three-layer	O
barotropic	O
model	B-Application
,	O
also	O
developed	O
by	O
Charney	O
.	O
</s>
<s>
In	O
1956	O
,	O
the	O
JNWPU	O
switched	O
to	O
a	O
two-layer	O
thermotropic	O
model	B-Application
developed	O
by	O
Thompson	O
and	O
Gates	O
.	O
</s>
<s>
The	O
main	O
assumption	O
made	O
by	O
the	O
thermotropic	O
model	B-Application
is	O
that	O
while	O
the	O
magnitude	O
of	O
the	O
thermal	O
wind	O
may	O
change	O
,	O
its	O
direction	O
does	O
not	O
change	O
with	O
respect	O
to	O
height	O
,	O
and	O
thus	O
the	O
baroclinicity	O
in	O
the	O
atmosphere	O
can	O
be	O
simulated	O
using	O
the	O
and	O
geopotential	O
height	O
surfaces	O
and	O
the	O
average	O
thermal	O
wind	O
between	O
them	O
.	O
</s>
<s>
However	O
,	O
due	O
to	O
the	O
low	O
skill	O
showed	O
by	O
the	O
thermotropic	O
model	B-Application
,	O
the	O
JNWPU	O
reverted	O
to	O
the	O
single-layer	O
barotropic	O
model	B-Application
in	O
1958	O
.	O
</s>
<s>
The	O
Japanese	O
Meteorological	O
Agency	O
became	O
the	O
third	O
organization	O
to	O
initiate	O
operational	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
in	O
1959	O
.	O
</s>
<s>
The	O
first	O
real-time	O
forecasts	O
made	O
by	O
Australia	O
's	O
Bureau	O
of	O
Meteorology	O
in	O
1969	O
for	O
portions	O
of	O
the	O
Southern	O
Hemisphere	O
were	O
also	O
based	O
on	O
the	O
single-layer	O
barotropic	O
model	B-Application
.	O
</s>
<s>
Hinkelmann	O
did	O
so	O
by	O
removing	O
small	O
oscillations	O
from	O
the	O
numerical	B-Application
model	I-Application
during	O
initialization	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
solar	O
radiation	O
effects	O
were	O
added	O
to	O
the	O
primitive	O
equation	O
model	B-Application
in	O
1967	O
;	O
moisture	O
effects	O
and	O
latent	O
heat	O
were	O
added	O
in	O
1968	O
;	O
and	O
feedback	O
effects	O
from	O
rain	O
on	O
convection	O
were	O
incorporated	O
in	O
1971	O
.	O
</s>
<s>
Three	O
years	O
later	O
,	O
the	O
first	O
global	O
forecast	O
model	B-Application
was	O
introduced	O
.	O
</s>
<s>
Efforts	O
to	O
involve	O
sea	O
surface	O
temperature	O
in	O
model	B-Application
initialization	O
began	O
in	O
1972	O
due	O
to	O
its	O
role	O
in	O
modulating	O
weather	O
in	O
higher	O
latitudes	O
of	O
the	O
Pacific	O
.	O
</s>
<s>
A	O
global	O
forecast	O
model	B-Application
is	O
a	O
weather	O
forecasting	O
model	B-Application
which	O
initializes	O
and	O
forecasts	O
the	O
weather	O
throughout	O
the	O
Earth	O
's	O
troposphere	O
.	O
</s>
<s>
Within	O
any	O
modern	O
model	B-Application
is	O
a	O
set	O
of	O
equations	O
,	O
known	O
as	O
the	O
primitive	O
equations	O
,	O
used	O
to	O
predict	O
the	O
future	O
state	O
of	O
the	O
atmosphere	O
.	O
</s>
<s>
Therefore	O
,	O
numerical	B-General_Concept
methods	I-General_Concept
obtain	O
approximate	O
solutions	O
.	O
</s>
<s>
Different	O
models	O
use	O
different	O
solution	O
methods	O
:	O
some	O
global	O
models	O
and	O
almost	O
all	O
regional	O
models	O
use	O
finite	B-Algorithm
difference	I-Algorithm
methods	I-Algorithm
for	O
all	O
three	O
spatial	O
dimensions	O
,	O
while	O
other	O
global	O
models	O
and	O
a	O
few	O
regional	O
models	O
use	O
spectral	B-Algorithm
methods	I-Algorithm
for	O
the	O
horizontal	O
dimensions	O
and	O
finite-difference	B-Algorithm
methods	I-Algorithm
in	O
the	O
vertical	O
.	O
</s>
<s>
The	O
National	O
Meteorological	O
Center	O
's	O
Global	O
Spectral	O
Model	B-Application
was	O
introduced	O
during	O
August	O
1980	O
.	O
</s>
<s>
The	O
European	O
Centre	O
for	O
Medium-Range	O
Weather	O
Forecasts	O
model	B-Application
debuted	O
on	O
May	O
1	O
,	O
1985	O
.	O
</s>
<s>
The	O
United	O
Kingdom	O
Met	O
Office	O
has	O
been	O
running	O
their	O
global	O
model	B-Application
since	O
the	O
late	O
1980s	O
,	O
adding	O
a	O
3D-Var	O
data	O
assimilation	O
scheme	O
in	O
mid-1999	O
.	O
</s>
<s>
The	O
Canadian	O
Meteorological	O
Centre	O
has	O
been	O
running	O
a	O
global	O
model	B-Application
since	O
1991	O
.	O
</s>
<s>
The	O
United	O
States	O
ran	O
the	O
Nested	B-Application
Grid	I-Application
Model	I-Application
(	O
NGM	B-Application
)	O
from	O
1987	O
to	O
2000	O
,	O
with	O
some	O
features	O
lasting	O
as	O
late	O
as	O
2009	O
.	O
</s>
<s>
Between	O
2000	O
and	O
2002	O
,	O
the	O
Environmental	B-Application
Modeling	I-Application
Center	I-Application
ran	O
the	O
Aviation	O
(	O
AVN	O
)	O
model	B-Application
for	O
shorter	O
range	O
forecasts	O
and	O
the	O
Medium	O
Range	O
Forecast	O
(	O
MRF	O
)	O
model	B-Application
at	O
longer	O
time	O
ranges	O
.	O
</s>
<s>
During	O
this	O
time	O
,	O
the	O
AVN	O
model	B-Application
was	O
extended	O
to	O
the	O
end	O
of	O
the	O
forecast	O
period	O
,	O
eliminating	O
the	O
need	O
of	O
the	O
MRF	O
and	O
thereby	O
replacing	O
it	O
.	O
</s>
<s>
In	O
late	O
2002	O
,	O
the	O
AVN	O
model	B-Application
was	O
renamed	O
the	O
Global	O
Forecast	O
System	O
(	O
GFS	O
)	O
.	O
</s>
<s>
The	O
German	O
Weather	O
Service	O
has	O
been	O
running	O
their	O
global	O
hydrostatic	O
model	B-Application
,	O
the	B-Application
GME	I-Application
,	O
using	O
a	O
hexagonal	O
icosahedral	O
grid	O
since	O
2002	O
.	O
</s>
<s>
The	O
GFS	O
is	O
slated	O
to	O
eventually	O
be	O
supplanted	O
by	O
the	O
Flow-following	B-Application
,	I-Application
finite-volume	I-Application
Icosahedral	I-Application
Model	I-Application
(	O
FIM	O
)	O
,	O
which	O
like	O
the	B-Application
GME	I-Application
is	O
gridded	O
on	O
a	O
truncated	O
icosahedron	O
,	O
in	O
the	O
mid-2010s	O
.	O
</s>
<s>
In	O
1956	O
,	O
Norman	O
A	O
.	O
Phillips	O
developed	O
a	O
mathematical	O
model	B-Application
which	O
could	O
realistically	O
depict	O
monthly	O
and	O
seasonal	O
patterns	O
in	O
the	O
troposphere	O
,	O
which	O
became	O
the	O
first	O
successful	O
climate	B-Application
model	I-Application
.	O
</s>
<s>
Following	O
Phillips	O
's	O
work	O
,	O
several	O
groups	O
began	O
working	O
to	O
create	O
general	B-Application
circulation	I-Application
models	I-Application
.	O
</s>
<s>
The	O
first	O
general	O
circulation	O
climate	B-Application
model	I-Application
that	O
combined	O
both	O
oceanic	O
and	O
atmospheric	O
processes	O
was	O
developed	O
in	O
the	O
late	O
1960s	O
at	O
the	O
NOAA	O
Geophysical	O
Fluid	O
Dynamics	O
Laboratory	O
.	O
</s>
<s>
By	O
the	O
early	O
1980s	O
,	O
the	O
United	O
States	O
 '	O
National	O
Center	O
for	O
Atmospheric	O
Research	O
had	O
developed	O
the	O
Community	O
Atmosphere	O
Model	B-Application
;	O
this	O
model	B-Application
has	O
been	O
continuously	O
refined	O
into	O
the	O
2000s	O
.	O
</s>
<s>
In	O
1986	O
,	O
efforts	O
began	O
to	O
initialize	O
and	O
model	B-Application
soil	O
and	O
vegetation	O
types	O
,	O
which	O
led	O
to	O
more	O
realistic	O
forecasts	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
Center	O
for	O
Ocean-Land	O
Atmosphere	O
Studies	O
(	O
COLA	O
)	O
model	B-Application
showed	O
a	O
warm	O
temperature	O
bias	O
of	O
2	O
–	O
4°C	O
(	O
4	O
–	O
7°F	O
)	O
and	O
a	O
low	O
precipitation	O
bias	O
due	O
to	O
incorrect	O
parameterization	O
of	O
crop	O
and	O
vegetation	O
type	O
across	O
the	O
central	O
United	O
States	O
.	O
</s>
<s>
Coupled	O
ocean-atmosphere	O
climate	B-Application
models	I-Application
such	O
as	O
the	O
Hadley	O
Centre	O
for	O
Climate	O
Prediction	O
and	O
Research	O
's	O
HadCM3	B-Application
model	B-Application
are	O
currently	O
being	O
used	O
as	O
inputs	O
for	O
climate	O
change	O
studies	O
.	O
</s>
<s>
Now	O
,	O
gravity	O
waves	O
are	O
required	O
within	O
global	B-Application
climate	I-Application
models	I-Application
in	O
order	O
to	O
properly	O
simulate	O
regional	O
and	O
global	O
scale	O
circulations	O
,	O
though	O
their	O
broad	B-Algorithm
spectrum	I-Algorithm
makes	O
their	O
incorporation	O
complicated	O
.	O
</s>
<s>
The	O
Climate	B-Application
System	I-Application
Model	I-Application
(	O
CSM	O
)	O
was	O
developed	O
at	O
the	O
National	O
Center	O
for	O
Atmospheric	O
Research	O
in	O
January	O
1994	O
.	O
</s>
<s>
The	O
horizontal	O
domain	O
of	O
a	O
model	B-Application
is	O
either	O
global	O
,	O
covering	O
the	O
entire	O
Earth	O
,	O
or	O
regional	O
,	O
covering	O
only	O
part	O
of	O
the	O
Earth	O
.	O
</s>
<s>
This	O
allows	O
regional	O
models	O
to	O
resolve	O
explicitly	O
smaller-scale	O
meteorological	O
phenomena	O
that	O
cannot	O
be	O
represented	O
on	O
the	O
coarser	O
grid	O
of	O
a	O
global	O
model	B-Application
.	O
</s>
<s>
Regional	O
models	O
use	O
a	O
global	O
model	B-Application
for	O
initial	B-Algorithm
conditions	I-Algorithm
of	O
the	O
edge	O
of	O
their	O
domain	O
in	O
order	O
to	O
allow	O
systems	O
from	O
outside	O
the	O
regional	O
model	B-Application
domain	O
to	O
move	O
into	O
its	O
area	O
.	O
</s>
<s>
Uncertainty	O
and	O
errors	O
within	O
regional	O
models	O
are	O
introduced	O
by	O
the	O
global	O
model	B-Application
used	O
for	O
the	O
boundary	O
conditions	O
of	O
the	O
edge	O
of	O
the	O
regional	O
model	B-Application
,	O
as	O
well	O
as	O
errors	O
attributable	O
to	O
the	O
regional	O
model	B-Application
itself	O
.	O
</s>
<s>
In	O
the	O
United	O
States	O
,	O
the	O
first	O
operational	O
regional	O
model	B-Application
,	O
the	O
limited-area	O
fine-mesh	O
(	O
LFM	O
)	O
model	B-Application
,	O
was	O
introduced	O
in	O
1971	O
.	O
</s>
<s>
The	O
NGM	B-Application
debuted	O
in	O
1987	O
and	O
was	O
also	O
used	O
to	O
create	O
model	B-Application
output	O
statistics	O
for	O
the	O
United	O
States	O
.	O
</s>
<s>
The	O
ETA	O
model	B-Application
was	O
implemented	O
for	O
the	O
United	O
States	O
in	O
1993	O
and	O
in	O
turn	O
was	O
upgraded	O
to	O
the	O
NAM	B-Application
in	O
2006	O
.	O
</s>
<s>
The	O
U.S.	O
also	O
offers	O
the	O
Rapid	B-Application
Refresh	I-Application
(	O
which	O
replaced	O
the	O
RUC	B-Architecture
in	O
2012	O
)	O
for	O
short-range	O
and	O
high-resolution	O
applications	O
;	O
both	O
the	O
Rapid	B-Application
Refresh	I-Application
and	O
NAM	B-Application
are	O
built	O
on	O
the	O
same	O
framework	O
,	O
the	O
WRF	B-Application
.	O
</s>
<s>
Météo-France	O
has	O
been	O
running	O
their	O
Action	O
de	O
Recherche	O
Petite	O
Échelle	O
Grande	O
Échelle	O
(	O
ALADIN	O
)	O
mesoscale	O
model	B-Application
for	O
France	O
,	O
based	O
upon	O
the	O
ECMWF	O
global	O
model	B-Application
,	O
since	O
1995	O
.	O
</s>
<s>
The	O
Canadian	O
Regional	O
Finite-Elements	O
model	B-Application
(	O
RFE	O
)	O
went	O
into	O
operational	O
use	O
on	O
April	O
22	O
,	O
1986	O
.	O
</s>
<s>
It	O
was	O
followed	O
by	O
the	O
Canadian	O
Global	O
Environmental	O
Multiscale	O
Model	B-Application
(	O
GEM	O
)	O
mesoscale	O
model	B-Application
on	O
February	O
24	O
,	O
1997	O
.	O
</s>
<s>
The	O
German	O
Weather	O
Service	O
developed	O
the	O
High	O
Resolution	O
Regional	O
Model	B-Application
(	O
HRM	O
)	O
in	O
1999	O
,	O
which	O
is	O
widely	O
run	O
within	O
the	O
operational	O
and	O
research	O
meteorological	O
communities	O
and	O
run	O
with	O
hydrostatic	O
assumptions	O
.	O
</s>
<s>
The	O
Japan	O
Meteorological	O
Agency	O
has	O
run	O
a	O
high-resolution	O
,	O
non-hydrostatic	O
mesoscale	O
model	B-Application
since	O
September	O
2004	O
.	O
</s>
<s>
The	O
Urban	O
Airshed	O
Model	B-Application
,	O
a	O
regional	O
forecast	O
model	B-Application
for	O
the	O
effects	O
of	O
air	O
pollution	O
and	O
acid	O
rain	O
,	O
was	O
developed	O
by	O
a	O
private	O
company	O
in	O
the	O
US	O
in	O
1970	O
.	O
</s>
<s>
Development	O
of	O
this	O
model	B-Application
was	O
taken	O
over	O
by	O
the	O
Environmental	O
Protection	O
Agency	O
and	O
improved	O
in	O
the	O
mid	O
to	O
late	O
1970s	O
using	O
results	O
from	O
a	O
regional	O
air	O
pollution	O
study	O
.	O
</s>
<s>
While	O
developed	O
in	O
California	O
,	O
this	O
model	B-Application
was	O
later	O
used	O
in	O
other	O
areas	O
of	O
North	O
America	O
,	O
Europe	O
and	O
Asia	O
during	O
the	O
1980s	O
.	O
</s>
<s>
The	O
Community	O
Multiscale	O
Air	O
Quality	O
model	B-Application
(	O
CMAQ	O
)	O
is	O
an	O
open	B-License
source	I-License
air	O
quality	O
model	B-Application
run	O
within	O
the	O
United	O
States	O
in	O
conjunction	O
with	O
the	O
NAM	B-Application
mesoscale	O
model	B-Application
since	O
2004	O
.	O
</s>
<s>
The	O
first	O
operational	O
air	O
quality	O
model	B-Application
in	O
Canada	O
,	O
Canadian	O
Hemispheric	O
and	O
Regional	O
Ozone	O
and	O
NOx	O
System	O
(	O
CHRONOS	O
)	O
,	O
began	O
to	O
be	O
run	O
in	O
2001	O
.	O
</s>
<s>
It	O
was	O
replaced	O
with	O
the	O
Global	O
Environmental	O
Multiscale	O
model	B-Application
–	O
Modelling	O
Air	O
quality	O
and	O
Chemistry	O
(	O
GEM-MACH	O
)	O
model	B-Application
in	O
November	O
2009	O
.	O
</s>
<s>
During	O
1972	O
,	O
the	O
first	O
model	B-Application
to	O
forecast	O
storm	O
surge	O
along	O
the	O
continental	O
shelf	O
was	O
developed	O
,	O
known	O
as	O
the	O
Special	O
Program	O
to	O
List	O
the	O
Amplitude	O
of	O
Surges	O
from	O
Hurricanes	O
(	O
SPLASH	O
)	O
.	O
</s>
<s>
In	O
1978	O
,	O
the	O
first	O
hurricane-tracking	B-Application
model	I-Application
based	O
on	O
atmospheric	O
dynamics	O
–	O
the	O
movable	O
fine-mesh	O
(	O
MFM	O
)	O
model	B-Application
–	O
began	O
operating	O
.	O
</s>
<s>
Within	O
the	O
field	O
of	O
tropical	B-Application
cyclone	I-Application
track	I-Application
forecasting	I-Application
,	O
despite	O
the	O
ever-improving	O
dynamical	O
model	B-Application
guidance	O
which	O
occurred	O
with	O
increased	O
computational	O
power	O
,	O
it	O
was	O
not	O
until	O
the	O
decade	O
of	O
the	O
1980s	O
when	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
showed	O
skill	O
,	O
and	O
until	O
the	O
1990s	O
when	O
it	O
consistently	O
outperformed	O
statistical	O
or	O
simple	O
dynamical	O
models	O
.	O
</s>
<s>
The	O
Geophysical	O
Fluid	O
Dynamics	O
Laboratory	O
(	O
GFDL	O
)	O
hurricane	O
model	B-Application
was	O
used	O
for	O
research	O
purposes	O
between	O
1973	O
and	O
the	O
mid-1980s	O
.	O
</s>
<s>
Once	O
it	O
was	O
determined	O
that	O
it	O
could	O
show	O
skill	O
in	O
hurricane	O
prediction	O
,	O
a	O
multi-year	O
transition	O
transformed	O
the	O
research	O
model	B-Application
into	O
an	O
operational	O
model	B-Application
which	O
could	O
be	O
used	O
by	O
the	O
National	O
Weather	O
Service	O
in	O
1995	O
.	O
</s>
<s>
The	O
Hurricane	B-Application
Weather	I-Application
Research	I-Application
and	I-Application
Forecasting	I-Application
(	O
HWRF	B-Application
)	O
model	B-Application
is	O
a	O
specialized	O
version	O
of	O
the	O
Weather	B-Application
Research	I-Application
and	I-Application
Forecasting	I-Application
(	O
WRF	B-Application
)	O
model	B-Application
and	O
is	O
used	O
to	O
forecast	O
the	O
track	O
and	O
intensity	O
of	O
tropical	O
cyclones	O
.	O
</s>
<s>
The	O
model	B-Application
was	O
developed	O
by	O
the	O
National	O
Oceanic	O
and	O
Atmospheric	O
Administration	O
(	O
NOAA	O
)	O
,	O
the	O
U.S.	O
</s>
<s>
Despite	O
improvements	O
in	O
track	O
forecasting	O
,	O
predictions	O
of	O
the	O
intensity	O
of	O
a	O
tropical	O
cyclone	O
based	O
on	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
continue	O
to	O
be	O
a	O
challenge	O
,	O
since	O
statiscal	O
methods	O
continue	O
to	O
show	O
higher	O
skill	O
over	O
dynamical	O
guidance	O
.	O
</s>
<s>
A	O
second	O
generation	O
of	O
models	O
was	O
developed	O
in	O
the	O
1980s	O
,	O
but	O
they	O
could	O
not	O
realistically	O
model	B-Application
swell	O
nor	O
depict	O
wind-driven	O
waves	O
(	O
also	O
known	O
as	O
wind	O
waves	O
)	O
caused	O
by	O
rapidly	O
changing	O
wind	O
fields	O
,	O
such	O
as	O
those	O
within	O
tropical	O
cyclones	O
.	O
</s>
<s>
Since	O
surface	O
winds	O
are	O
the	O
primary	O
forcing	O
mechanism	O
in	O
the	O
spectral	O
wave	O
transport	O
equation	O
,	O
ocean	O
wave	O
models	O
use	O
information	O
produced	O
by	O
numerical	B-General_Concept
weather	I-General_Concept
prediction	I-General_Concept
models	O
as	O
inputs	O
to	O
determine	O
how	O
much	O
energy	O
is	O
transferred	O
from	O
the	O
atmosphere	O
into	O
the	O
layer	O
at	O
the	O
surface	O
of	O
the	O
ocean	O
.	O
</s>
<s>
Along	O
with	O
dissipation	O
of	O
energy	O
through	O
whitecaps	O
and	O
resonance	B-Application
between	O
waves	O
,	O
surface	O
winds	O
from	O
numerical	B-General_Concept
weather	I-General_Concept
models	I-General_Concept
allow	O
for	O
more	O
accurate	O
predictions	O
of	O
the	O
state	O
of	O
the	O
sea	O
surface	O
.	O
</s>
<s>
Statistical	O
models	O
were	O
created	O
based	O
upon	O
the	O
three-dimensional	O
fields	O
produced	O
by	O
numerical	B-General_Concept
weather	I-General_Concept
models	I-General_Concept
,	O
surface	O
observations	O
,	O
and	O
the	O
climatological	O
conditions	O
for	O
specific	O
locations	O
.	O
</s>
<s>
These	O
statistical	O
models	O
are	O
collectively	O
referred	O
to	O
as	O
model	B-Application
output	O
statistics	O
(	O
MOS	O
)	O
,	O
and	O
were	O
developed	O
by	O
the	O
National	O
Weather	O
Service	O
for	O
their	O
suite	O
of	O
weather	B-Application
forecasting	I-Application
models	I-Application
by	O
1976	O
.	O
</s>
<s>
The	O
United	O
States	O
Air	O
Force	O
developed	O
its	O
own	O
set	O
of	O
MOS	O
based	O
upon	O
their	O
dynamical	O
weather	B-General_Concept
model	I-General_Concept
by	O
1983	O
.	O
</s>
<s>
Extremely	O
small	O
errors	O
in	O
temperature	O
,	O
winds	O
,	O
or	O
other	O
initial	O
inputs	O
given	O
to	O
numerical	B-Application
models	I-Application
will	O
amplify	O
and	O
double	O
every	O
five	O
days	O
.	O
</s>
<s>
While	O
a	O
set	O
of	O
equations	O
,	O
known	O
as	O
the	O
Liouville	O
equations	O
,	O
exists	O
to	O
determine	O
the	O
initial	O
uncertainty	O
in	O
the	O
model	B-Application
initialization	O
,	O
the	O
equations	O
are	O
too	O
complex	O
to	O
run	O
in	O
real-time	O
,	O
even	O
with	O
the	O
use	O
of	O
supercomputers	O
.	O
</s>
<s>
These	O
uncertainties	O
limit	O
forecast	O
model	B-Application
accuracy	O
to	O
about	O
six	O
days	O
into	O
the	O
future	O
.	O
</s>
<s>
Edward	O
Epstein	O
recognized	O
in	O
1969	O
that	O
the	O
atmosphere	O
could	O
not	O
be	O
completely	O
described	O
with	O
a	O
single	O
forecast	O
run	O
due	O
to	O
inherent	O
uncertainty	O
,	O
and	O
proposed	O
a	O
stochastic	O
dynamic	O
model	B-Application
that	O
produced	O
means	O
and	O
variances	O
for	O
the	O
state	O
of	O
the	O
atmosphere	O
.	O
</s>
<s>
While	O
these	O
Monte	B-Algorithm
Carlo	I-Algorithm
simulations	I-Algorithm
showed	O
skill	O
,	O
in	O
1974	O
Cecil	O
Leith	O
revealed	O
that	O
they	O
produced	O
adequate	O
forecasts	O
only	O
when	O
the	O
ensemble	O
probability	O
distribution	O
was	O
a	O
representative	O
sample	O
of	O
the	O
probability	O
distribution	O
in	O
the	O
atmosphere	O
.	O
</s>
<s>
It	O
was	O
not	O
until	O
1992	O
that	O
ensemble	B-Application
forecasts	I-Application
began	O
being	O
prepared	O
by	O
the	O
European	O
Centre	O
for	O
Medium-Range	O
Weather	O
Forecasts	O
,	O
the	O
Canadian	O
Meteorological	O
Centre	O
,	O
and	O
the	O
National	O
Centers	O
for	O
Environmental	O
Prediction	O
.	O
</s>
<s>
The	O
ECMWF	O
model	B-Application
,	O
the	O
Ensemble	O
Prediction	O
System	O
,	O
uses	O
singular	O
vectors	O
to	O
simulate	O
the	O
initial	O
probability	O
density	O
,	O
while	O
the	O
NCEP	O
ensemble	O
,	O
the	O
Global	O
Ensemble	B-Application
Forecasting	I-Application
System	O
,	O
uses	O
a	O
technique	O
known	O
as	O
vector	O
breeding	O
.	O
</s>
